power - Penton

power - Penton
$129
T
N
E
M
E
G
A
N
A
M
S A M D AV I S
POWER
SUPPLIES
SYSTEMS
APPLICATIONS
COMPONENTS
SEMICONDUCTORS
Copyright © 2016 by Penton Media,Inc. All rights reserved.
POWER ELECTRONICS LIBRARY
TABLE OF CONTENTS
ID
VGS
VD
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
0V
-1V
-1.5V
-2V
-2.5V
-3.3V
MANAGEMENT
BY SAM DAVIS
VDD
BP6
BOOT
BP3
VIN
Linear
Regulators
Driver
Control
SYNC/RESET_B
Ramp
+
RESET_VOUT
S Q
R Q
COMP
BP6
+
Reference
DAC
PWM
OC Event
Average IOUT
Fault
VREF for
Soft-Start and
VOUT_COMMAND
VOUT Sense
OV/UV Detection
DIFFO
AGND
20.0
GND
Current
Sense,
OC
Detection
OC Threshold
-20.0
-40.0
-60.0
CLK
DATA
-80.0
-100.0
ADC, PMBus Commands,
IC Interface, EEPROM
-2.0
-1.0
CNTL
0.0
VD
1.0
2.0
3.0
Courtesy of Efficient Power Conversion
ADDR0
INTRODUCTION........................................................
2
750 kΩ
Temperature
ADDR1
Sensing
PGOOD
PART 1: THE POWER SUPPLY
PGND
POWER SUPPLY FUNDAMENTALS............ 3
CHAPTER 1:
-3.0
SMBALERT
PMBus Engine
VSET
5V
4V
3V
2V
1V
0V
40.0
ID 00.0
LSFET
Error Amplifier
FB
SW
Pre-Bias
Oscillator
VGS
80.0
60.0
Anti-CrossConduction
RT
100.0
HSFET
VOUTS+ VOUTS– TSNS/SS
PART 4: POWER APPLICATIONS
CHAPTER 12: WIRELESS POWER TRANSFER................ 98
CHAPTER 13: ENERGY HARVESTING........................ 104
CHAPTER 2:
POWER SUPPLY CHARACTERISTICS.......... 6
CHAPTER 14: CIRCUIT PROTECTION DEVICES........... 108
CHAPTER 3:
POWER SUPPLIES – MAKE OR BUY?....... 14
CHAPTER 15: PHOTOVOLTAIC SYSTEMS................... 115
CHAPTER 4:
POWER SUPPLY PACKAGES................... 17
CHAPTER 16: WIND POWER SYSTEMS..................... 124
POWER MANAGEMENT
REGULATORY STANDARDS.................... 24
CHAPTER 17: ENERGY STORAGE............................. 129
CHAPTER 6: POWER SUPPLY SYSTEM
CONSIDERATIONS............................... 27
CHAPTER 19: MOTION SYSTEM POWER
MANAGEMENT................................. 141
CHAPTER 5:
PART 2: SEMICONDUCTORS
CHAPTER 18: ELECTRONIC LIGHTING SYSTEMS........ 134
CHAPTER 20: COMPONENTS AND METHODS
FOR CURRENT MEASUREMENT........... 146
CHAPTER 7:
VOLTAGE REGULATOR ICS.................... 31
CHAPTER 21: THERMOELECTRIC GENERATORS......... 151
CHAPTER 8:
POWER MANAGEMENT ICS................. 51
CHAPTER 22: FUEL CELLS......................................... 156
CHAPTER 9:
BATTERY POWER MANAGEMENT ICS.... 68
CHAPTER 23:
PART 3: SEMICONDUCTOR SWITCHES
SILICON POWER MANAGEMENT
POWER SEMICONDUCTORS................. 77
CHAPTER 10:
CHAPTER 11:
POWER MANAGEMENT OF
TRANSPORTATION SYSTEMS............... 162
CHAPTER 24: POWER MANAGEMENT TEST
AND MEASUREMENT............................. 4
CHAPTER 25: DATACENTER POWER............................. 4
WIDE BANDGAP SEMICONDUCTORS... 91
☞ LEARN MORE @ electronicdesign.com/powermanagement | 1
POWER ELECTRONICS LIBRARY
INTRODUCTION TO
POWER
MANAGEMENT
SAM DAVIS
powerelectronics.com
P
ower management technology plays a major role in virtually all electronic systems,
including analog, digital, and mixed-signal systems. It doesn’t matter whether it is
consumer, industrial, computer, or transportation electronics, power management
technology plays a pivotal role. Regardless of the application, power management
technology regulates, controls, and distributes power throughout the system.
Therefore, power management affects the reliability, performance, cost, and time-to-market
for electronic systems. An analogy would be that power management functions in a manner
similar to the body’s blood vessels that supply the proper nutrients to keep the body alive.
Likewise, power management supplies and controls the power that keeps an electronic
system alive.
Designing system power management is much more complicated now than it was a decade
ago. Today, designers must cope with ICs that operate below 1 V, or others that may consume
over 100 A. In addition, there is a trend toward mixed-signal systems employing analog and
digital circuits. Plus, processors of different types are now part of some power management
functions. And, there are also system-oriented functions that require application-specific ICs
to perform specific power management tasks.
The primary power management device is the power supply that accepts an ac or dc input
and produces a regulated dc output that powers the electronic system. The key component
of the power supply is the voltage regulator that is usually an integrated circuit (IC), with
several different types that provide specific characteristics. Other important components are
the power semiconductors and the various power management ICs that perform a variety of
functions.
This book covers power management components and systems, with an emphasis on their
application. The book also includes updated information for articles that appeared in Power
Electronics Technology magazine. There is also new material that has not appeared before.
All the important information about power management is contained in one book. There are
25 chapters that describe the components and systems associated with power management.
☞ LEARN MORE @ electronicdesign.com/powermanagement | 2
POWER ELECTRONICS LIBRARY
PART 1. POWER SUPPLIES
CHAPTER 1:
POWER SUPPLY
FUNDAMENTALS
T
he key component of the dc power management system is the power supply that provides dc power for the associated system.
The specific type of dc power management
depends on its power input, which includes:
• AC input—A power supply that accepts an
ac utility power input, rectifies and filters it, then applies the resulting dc voltage to a regulator circuit that
provides a constant dc output voltage. There is a wide
variety of ac-dc supplies that can have an output voltage
from less than 1V to thousands of volts. This dc power
management system usually employs a switch-mode
power supply, although some linear supplies are available.
• DC input—A power supply that accepts a dc voltage
input, typically 5 V, 12V, 24V, or 48 V and produces a dc
output voltage. At the low end, a supply of this type can
produce less than 1Vdc, whereas other dc-dc supplies
can produce thousands of volts dc. Here, power management usually employs a switch-mode power supply.
• Battery input (for portable equipment)—Because of size
and weight restrictions of portable equipment, this power
management function is usually integrated with the rest
of the electronic system. Some of these systems also
include an ac adapter, which is a small
power unit that plugs into the ac wall
outlet and provides a dc output voltage.
Figure 1-1.
Usually, the ac adapter is used to power
Basic AC-DC
the unit and can also recharge the sysLinear Power
tem battery.
Supply
• Ultralow voltage input (energy harvesting)—Energy harvesting can provide the
power to charge, supplement, or replace
batteries. A key component in energy
harvesting is a power converter that can
operate with ultralow voltage inputs. In
operation, this power converter captures
a minute amount of energy, accumulates it, stores it, and
then maintains the stored energy as a power source.
Low-voltage inputs can come from solar power, thermal
energy, wind energy, or kinetic energy.
Linear vs. Switch-Mode Power Supplies
There are two basic power supply configurations
used with dc power management subsystems: linear
and switch-mode. Linear power supplies always conduct
current. Switch-mode supplies convert dc to a switched
signal that is then rectified to produce a dc output. Differences between these two configurations include size and
weight, power-handling capability, EMI, and regulation.
The linear regulator’s main components are a pass
transistor, error amplifier, and voltage reference, as seen
in Fig. 1-1. The linear regulator maintains a constant
output voltage by using the error amplifier to compare a
portion of the output voltage with a stable voltage reference. If the output voltage tends to increase, feedback
causes the pass transistor to lower the output voltage
and vice versa. OEM linear supplies can handle several
amperes of current. They are usually bulky benchtop or
rack-mounted supplies.
In most applications, older, high-current linear supplies have been superseded by switch-mode supplies.
110 VAC
Bridge
Rectifier
Pass
Transistor
VOUT
R1
Error
Amplifier VREF
☞ LEARN MORE @ electronicdesign.com/powermanagement | 3
Voltage
Reference
COUT
R2
Ground
CHAPTER 1: POWER SUPPLY FUNDAMENTALS
POWER ELECTRONICS LIBRARY
Shown in Fig. 1-2 is a typical isolated
switch-mode supply. Here, the ac input
voltage is rectified and filtered to obtain a dc
voltage for the other power-supply components. One widely used approach uses the
on and off times pulse-width modulation
Bridge
(PWM) to control the power-switch output
110 VAC
Rectifier
voltage. The ratio of on time to the switching
period time is the duty cycle. The higher the
duty cycle, the higher the power output from
the power semiconductor switch.
The error amp compares a portion of
the output voltage feedback with a stable
voltage reference to produce the drive for
PWM circuit. The resulting drive for the PWM
controls the duty cycle of the pulsed signal
applied to the power switch, which in turn
controls the power-supply dc output voltFigure 1-2.
age. If the output voltage tends to rise or fall,
Typical Isolated
the PWM changes the duty cycle so that the
AC-DC Switchdc output voltage remains constant.
Mode Power
An isolation circuit is required to maintain
Supply
isolation between the output ground and the
power supplied to the power supply’s components. Usually, an optocoupler provides
the isolation while permitting the feedback
voltage to control the supply’s output.
The inductor-capacitor low-pass output
filter converts the switched voltage from the
switching transformer to a dc voltage. The
filter is not perfect, so there is always some
residual output noise called “ripple.” The
amount of ripple depends on the effectiveness of the low-pass filter at the switching
frequency. Power-supply switching frequencies can range between 100kHz to over
1MHz. Higher switching frequencies allow
the use of smaller-size, lower-value inductors
and capacitors in the output low-pass filter.
TABLE 1-1. LINEAR VS. SWITCH-MODE
Parameter
Linear Power Supply
Switch-Mode Power Supply
Size
Can be twice the size
Half the size
Weight
Heavier because of ac
input power transformer
Higher frequency, lower weight
switching transformer
Efficiency
50-70%
80-90+%
Design Complexity
Simpler
More Complex
EMI
“Quiet” (None)
More (depends on switching frequency and layout)
L1
D1
VCC
VOUT
Low-Pass
Filter
R1
Load
C1
R2
Clock
ON
PWM
Controller
OFF
Power
Switch
Isolation
Circuit
VCC
Error
Amplifier
VOUT Feedback
VCC
Voltage
Reference
However, higher frequencies can also increase
power semiconductor losses, which reduces
power-supply efficiency.
The power switch is a key component in the
power supply in terms of power dissipation. The
switch is usually a power MOSFET that operates
in only two states—on and off. In the off state,
the power switch draws very little current and
dissipates very little power. In the on state, the
power switch draws the maximum amount of
current, but its on-resistance is low, so in most
cases its power dissipation is minimal. In the
transition from the on state to the off state and off
to on, the power switch goes through its linear
region so it can consume a moderate amount
of power. The total losses for the power switch
are therefore the sum of the on and off state
plus the transition through its linear regions. The
actual losses depend on the power switch and
its operating characteristics. Table 1-1 compares
the characteristics of isolated, ac-dc linear and
switch-mode power supplies.
Voltage Regulator ICs
Regulating the output voltage of virtually all
power supplies is dependent on voltage regulator ICs. These ICs obtain a DC input from
rectified AC or a battery. In operation, the
voltage regulator feeds back a percentage of its
output voltage that is compared with a stable
reference voltage. If the output voltage tends to
rise or fall compared with the reference, the
☞ LEARN MORE @ electronicdesign.com/powermanagement | 4
CHAPTER 1: POWER SUPPLY FUNDAMENTALS
POWER ELECTRONICS LIBRARY
feedback causes the output to remain the same. Chapter
7 provides the details of voltage regulator ICs. Also, there
are lab kits to help engineers understand voltage regulator IC operation.
Related Articles
1. Sam Davis, Component Power Analysis Supports Design
of 94% Efficient 200 W AC-DC Supply, powerelectronics.com,
December, 2013.
2. Michael O’Loughlin, Voltage/Current Sensing Technique Cuts
Flyback Converter Costs, powerelectronics.com, November,
2012.
3. Don Knowles, The AC-DC Power Supply: Make It Or Buy It?,
powerelectronics.com, August, 2012.
4. Steve Sandler, Measuring Stability: Stability and Why It
Matters, powerelectronics.com, December, 2014.
5. Sam Davis, Digitally-Controlled AC-DC Supply,
powerelectronics.com, January, 2012.
6. Sam Davis, Bi-Directional Controller IC Employs
Supercapacitors for dc Power Backup, powerelectronics.com,
May, 2014.
7. Sam Davis, DC-DC Converter Design Considerations for
Wearable Devices, powerelectronics.com, February, 2014.
8. Steve Sandler, Five Things Every Engineer Should Know
about Bode Plots, powerelectronics.com, January, 2014.
9. Viral Vaidya, High-Voltage Synchronous Regulators Address
Industrial Power Dilemma, powerelectronics.com, December,
2013.
10. am Davis, Power-Management IC Supports Automotive
Instrument Cluster Design, powerelectronics.com, March, 2014.
11. Ernie Wittenbreder, Topology Selection by the Numbers Part
One, powerelectronics.com, March, 2006.
12. Ernie Wittenbreder, Topology Selection By the Numbers
Part Two, powerelectronics.com, April, 2006.
13. Bramble, Simon, Digital Feedback Controls Supply Voltage
Accurately, powerelectronics.com, January, 2006.
14. Sam Davis, Power Supply Characteristics FAQs,
powerelectronics.com, April, 2014.
15. Christophe Basso, Why is it Important to Plot a Power
Stage Small-Signal Response?, powerelectronics.com,
September, 2013.
16. Power-Management Lab Kits for Young and Old Engineers
powerelectronics.com, July 13, 2016.
☞
BACK TO TABLE OF CONTENTS
Featured Power Supply Assets
Sponsored by
Power Topologies Quick
Reference Guide
☞ Download Now
Power Management
Lab Kit-Reinforcing
Power Supply Knowledge
Comprehensive collection
of Power Supply Design
white papers
☞
☞
View Lab Kit
Download
White Paper
☞ LEARN MORE @ electronicdesign.com/powermanagement | 5
POWER ELECTRONICS LIBRARY
PART 1. POWER SUPPLIES
CHAPTER 1:
POWER SUPPLY
CHARACTERISTICS
Protecting the Supply
There are several other characteristics that impact power-supply
operation. Among these are those
employed to protect the supply,
which are listed below.
Overcurrent: A failure mode
caused by output load current that
is greater than specified. It is limited
by the maximum current capability
of the power supply and controlled by internal protection
circuits. It can also damage the power supply in some
cases. Short circuits between the power-supply output
and ground can create currents within the system that
are limited only by the maximum current capability and
internal impedance of the power supply. Without limiting,
this high current can cause overheating and damage the
power supply as well as the load and its interconnects
(printed circuit board traces, cables). Therefore, most
power supplies should have current limiting (overcurrent
protection) that activates if the output current exceeds a
specified maximum.
Overtemperature: A temperature that is above the power
supply’s specified value must be prevented or it can
cause power-supply failure. Excessive operating temperature can damage a power supply and the circuits connected to it. Therefore, many supplies employ a temperature sensor and associated circuits to disable the supply
if its operating temperature exceeds a specific value. In
95%
90%
36VIN
85%
75VIN
Efficiency
E
fficiency is one of the most important power
supply characteristics. It determines the
thermal and electrical losses in the system,
as well as the amount of cooling required.
Also, it determines the physical package
sizes of both the power supply and the final
system. Plus, it determines the system component operating temperatures and the resultant system reliability.
These factors contribute to the determination of the total
system cost, both hardware and field support. Power-supply data sheets usually include a plot of efficiency versus
output current, as shown in Fig. 2-1. This plot shows that
efficiency varies with the power supply’s applied voltage
as well as the output load current.
Efficiency, reliability, and operating temperature are
interrelated. Power-supply data sheets usually include
specific airflow and heat-sink requirements. For example,
the ambient operating temperature affects the output load
current that the power supply can handle reliably. Derating curves for the power supply (Fig.
2-2) indicate its reliable operating
2-1. Typical
current versus temperature. Derating efficiency plot for a
shows how much current the supply power supply.
can be safely handle if it is operating
with natural convection, or 200 LFM
and 400 LFM.
80%
75%
70%
65%
60%
1.0
2.0
3.0
Output Current (A)
☞ LEARN MORE @ electronicdesign.com/powermanagement | 6
4.0
5.0
CHAPTER 2: POWER SUPPLY CHARACTERISTICS
POWER ELECTRONICS LIBRARY
turns the supply off if the output voltage
exceeds a specified amount. Another
200 LFM
11.0
approach is a crowbar zener diode that
10.0
conducts enough current at the over400 LFM
9.0
voltage threshold so that it activates
8.0
the power-supply current limiting and it
7.0
shuts down.
6.0
Natural Convection
Soft Start: Inrush current limitation
5.0
may
be needed when power is first
4.0
applied
or when new boards are hot
3.0
plugged. Typically, this is achieved by a
2.0
soft-start circuit that slows the initial rise
1.0
of current and then allows normal oper0
10
20
30
40
50
60
70
80 85
ation. If left untreated, the inrush current
Ambient Temperature °C
can generate a high peak charging curparticular, semiconductors
used
in the
are vulnerrent that impacts the output voltage. If this is an important
Figure 2-2. Typical Derating
Curves
for a supply
Power Supply
able to temperatures beyond their specified limits. Many
consideration, select a supply with this feature.
supplies include overtemperature protection that turns off
Undervoltage Lockout: Known as UVLO, it turns the
the supply if the temperature exceeds the specified limit.
supply on when it reaches a high enough input voltage
Overvoltage: This failure mode occurs if the output voltand turns off the supply if the input voltage falls below a
age goes above the specified dc value, which can impose certain value. This feature is used for supplies operating
excessive dc voltage that damages the load circuits. Typfrom utility power as well as battery power. When operatically, electronic system loads can withstand up to 20%
ed from battery-based power UVLO disables the power
overvoltage without incurring any permanent damage. If
supply (as well as the system) if the battery discharges so
this is a consideration, select a supply that minimizes this
much that it drops supply’s input voltage too low to permit
risk. Many supplies include overvoltage protection that
reliable operation.
Electromagnetic Compatibility (EMC):
Involves design techniques that minimize
electromagnetic interference (EMI). In
Power Supply:
switch-mode power supplies, a dc voltage
Bus Slave
is converted to a chopped or a pulsed
CLK
DATA
waveform. This causes the power supply
CNTL
to generate narrow-band noise (EMI) at the
SMBALRT
fundamental of the switching frequency and
its associated harmonics. To contain the
Write Protect
Address 1
noise, manufacturers must minimize radiatCentral Control Unit:
ed or conducted emissions.
System Host/Bus Master
Power Supply:
Power-supply manufacturers minimize
Bus Slave
CLK
EMI radiation by enclosing the supply in a
DATA
metal box or spray coating the case with a
CNTL
metallic material. Manufacturers also need
SMBALRT
to pay attention to the internal layout of the
2-3. PMBus
supply and the wiring that goes in and out
Write Protect
Address 2
conceptual diagram.
of the supply, which can generate noise.
Most of the conducted interference on the
Power Supply:
Bus Slave
power line is the result of the main switching
CLK
transistor or output rectifiers. With powDATA
er-factor correction and proper transformer
CNTL
SMBALRT
design, connection of the heat sink, and
filter design, the power-supply manufacturer can reduce conducted interference so
Write Protect
Address 3
2-2. Typical
derating curves
for a power
supply.
Output Current (A)
12.0
☞ LEARN MORE @ electronicdesign.com/powermanagement | 7
POWER ELECTRONICS LIBRARY
CHAPTER 2: POWER SUPPLY CHARACTERISTICS
dynamic currents with fast ramp rates
on the power supply. To accommodate
Current
Power Stage
Sense
the microprocessor, the supply’s output
Error Amplifier
Output
And Pulse-Width
voltage must ramp up or down within a
Power
Reference
Modulator
specified time interval, but without excessive overshoot.
Efficiency: Ratio of output-to-input power
Voltage
(in percent), measured at a given load
Current Sense
Sense
current with nominal line conditions (Pout/
PMBus Interface
Voltage Sense
Pin).
Non Volatile
Holdup time: Time during which a power
Memory
supply’s output voltage remains within
specification following the loss of input
CLK
DATA
PMBus to
2-4. Block diagram of power.
SMBALRT
System
typical non-isolated
Inrush current: Peak instantaneous input
CNTL
Host
PMBus converter.
current drawn by a power supply at turnthat the supply can achieve EMI regulatory agency
on.
approvals without incurring excessive filter cost.
International standards: Specify a power
Always check to see that the power-supply manusupply’s safety requirements and allowfacturer meets the requirement of the regulatory EMI
able EMI (electromagnetic interference)
standards.
levels.
There are several power-supply characteristics that
Isolation: Electrical separation between
affect their operation:
the input and output of a power supply
Drift: The variation in dc output voltage as a funcmeasured in volts. A non-isolated has a
tion of time at constant line voltage, load, and ambidc path between the input and output of
ent temperature.
supply, whereas an isolated power supply
Dynamic response: A power supply may be ememploys a transformer to eliminate the dc
ployed in a system where there is a requirement to
path between input and output.
provide fast dynamic response to a change in load
Line regulation: Change in value of dc
power. That can be the case for the load of highoutput voltage resulting from a change in
speed microprocessors with power-management
2-5. Block diagram
ac input voltage, specified as the change
functions. In this case, the microprocessor may be of typical isolated
in ± mV or ± %.
in a standby state and upon command it must start PMBus converter.
Load regulation: Change in value of dc
up or turn off immediately, which imposes high
output voltage resulting from a change in
load from open-circuit to maximum-rated
Input
output current, specified as the change in
Current
Power
Sense
± mV or ± %.
Isolation
Isolation
Output noise: This can occur in the
Error Amplifier Isolation
Output
power supply in the form of short bursts
And Pulse-Width
Reference
Power of high frequency energy. The noise is
Modulator
caused by charging and discharging of
Power Stage
parasitic capacitances within the power supply during its operating cycle. Its
Voltage
Current Sense
amplitude is variable and can depend on
Sense
PMBus Interface
the load impedance, external filtering, and
Voltage Sense
how it is measurement.
Non Volatile
Output voltage trim: Most power supMemory
plies have the ability to “trim” the output
CLK
voltage, whose adjustment range does
DATA
PMBus to
SMBALRT
not need to be large, usually about ±10%.
System
CNTL
Host
One common usage is to compensate for
Input
Power
☞ LEARN MORE @ electronicdesign.com/powermanagement | 8
CHAPTER 2: POWER SUPPLY CHARACTERISTICS
POWER ELECTRONICS LIBRARY
VIN
VIN
CIN
VOUT
VDD
ENABLE
VSENP
EN
PG
VR5
10 μF
10 μF
VR6
VSENN
ISL8273M
VR
VR55
VDRV
VCC
SCL
VDRV1
100 kΩ
SDA
2 × 10 μF
SALRT
VMON
6.65 kΩ
SGND
PGND
2-6. ISL8273M is compatible with PMBus Power System
Protocol Specification Parts I and II version 1.2.
the dc distribution voltage drop within the system. Trimming can either be upward or downward from the nominal
setting using an external resistor or potentiometer.
Periodic and random deviation (PARD): Unwanted
periodic (ripple) or aperiodic (noise) deviation of the
power-supply output voltage from its nominal value. PARD
is expressed in mV peak-to-peak or rms, at a specified
bandwidth.
Peak current: The maximum current that a power supply
can provide for brief periods.
Peak power: The absolute maximum output power that a
power supply can produce without damage. It is typically
well beyond the continuous reliable output power capability and should only be used infrequently.
Power-supply sequencing: Sequential turn-on and off of
power supplies may be required in systems with multiple
operating voltages. That is, voltages must be applied
in a specific sequence, otherwise the system can be
damaged. For example, after applying the first voltage
and it reaches a specific value, a second voltage can be
ramped up, and so on. Sequencing works in reverse when
power is removed, although speed is not usually as much
of a problem as turn-on.
Remote on/off : This is preferred over switches to turn
power supplies on and off. Power-supply data-sheet specifications usually detail the dc parameters for remote on/
off, listing the on and off logic levels required.
Remote sense: A typical power supply monitors its
output voltage and feeds a portion of it back to the supply
to provide voltage regulation. In this way, if the output
tends to rise or fall, the feedback regulates the supply’s
output voltage. However, to maintain a constant output at
the load, the power supply should actually
monitor the voltage at the load. But, connections from a power supply’s output to its
COUT
load have resistance and current flowing
through them that produces a voltage drop
that creates a voltage difference between
the supply’s output and the actual load.
For the optimal regulation, the voltage fed
back to the power supply should be the
PMBUS
actual load voltage. The supply’s two (plus
INTERFACE
and minus) remote sense connections
monitor the actual load voltage, a portion
of which is then fed back to the supply with
very little voltage drop because the current
through the two remote sense connections
is very low. As a consequence, the voltage
Management
applied to the load is regulated.
Ripple: Rectifying and filtering a switching power supply’s output results in an ac
component (ripple) that rides on its dc output. Ripple frequency is some integral multiple of the converter’s switching frequency, which depends on the converter topology.
Ripple is relatively unaffected by load current, but can be
decreased by external capacitor filtering.
Tracking: When using multiple output power supplies
whereby one or more outputs follow another with changes
in line, load, and temperature, so that each maintains the
same proportional output voltage, within specified tracking tolerance, with respect to a common value.
VOUT
PMBus
The PMBus specification describes the addition of
digital control for a power supply over a specified physical
bus, communications protocol, and command language.
A conceptual diagram of PMBus-capable power supplies
controlled from a central location is shown in Fig. 2-3.
It contains a bus master and three slaves. Figures 2-4
and 2-5, respectively, show the block diagrams of typical
non-isolated and isolated converters that might be found
in the system shown in Fig. 2-3.
A typical system employing a PMBus will have a central control unit and at least one PMBus-enabled power
supply attached to it. The connected power supplies are
always slaves, and the central control unit is always the
master. The central control unit initiates all communication
on the bus, and the slave power supplies respond to the
master when they are addressed.
The PMBus specification only dictates the way the central control unit and the slave power supplies communicate with each other. It does not put constraints on power-supply architecture, form factor, pinout, power input,
☞ LEARN MORE @ electronicdesign.com/powermanagement | 9
CHAPTER 2: POWER SUPPLY CHARACTERISTICS
POWER ELECTRONICS LIBRARY
power output, or any other characteristics of the supply.
The specification is also divided into two parts.
Part I: Physical implementation and electrical specifications.
Part II: Protocol, communication, and command language.
To be PMBus-compliant, a power supply must:
•M
eet all requirements of Part I of the PMBus specification.
• Implement at least one of the PMBus commands that is
not a manufacturer-specific command.
• If a PMBus command is supported, execute that command as specified in Part II of the PMBus specification.
• If a PMBus command is not supported, respond as
described in the “Fault Management and Reporting”
section of Part II of the PMBus specification.
In addition, the device must be capable of starting up
unassisted and without any communication with or connection to the PMBus. This behavior may be overridden
by programming new defaults for the device, but the
capability to start up unassisted must be present. This implies that the PMBus device must be able to store operating defaults for its configurable parameters on the device
itself in some form of nonvolatile storage.
Doing so can significantly decrease the amount of time
required for the system to start up, since no communication is required to configure the device for its operating
parameters. If the central control unit gets power from
a PMBus device that it is controlling, then that PMBus
device must obviously be set to start up automatically, or
the central control unit would never start and the system
would not function.
To get the latest and most complete specification for
PMBus, download it from the PMBus Web site at http://
pmbus.org/specs.html. The PMBus is derived from the
System Management Bus (SMBus) Specification Version
1.1, which is an improvement over the I2C bus. I2C is a
simple two-line, synchronous serial communication bus
originally designed to allow communication between two
or more integrated circuits that are in close proximity to
each other. SMBus extensions and improvements over I2C
include host notification via the SMBALRT bus line and
packet error checking (PEC) to help prevent erroneous
operation from noise issues.
There are several differences between the PMBus and
SMBus specifications. Those most notable from a system-design perspective are the optional host notify protocol and the group command protocol.
Host notification is required for SMBus compliance, but
is optional for PMBus compliance. However, most PMBus
devices will support this feature, since it tells the host that
a problem exists so it can take appropriate action without
having to continually poll each slave device to check for
problems. This lightens the load on both the host and
the bus itself, providing greater system capability. Host
notification is done using a single line (SMBALRT) that is
passively pulled high.
When a slave has information that the host is likely to
need, the slave pulls the SMBALRT line low. The host can
then poll each device individually or use the protocol described in the “SMBus Host Notify Protocol” section of the
SMBus 2.0 specification.
The group command protocol is designed to allow several PMBus-compliant devices to simultaneously execute
commands. For more specific information on this feature,
refer to Part I,
Section 5.2 of the PMBus Specification.
You can group PMBus commands into several categories; a partial list of the actual commands is listed below:
•
On, off, and margin testing
•
OPERATION
•
ON_OFF_CONFIG
•
VOUT_MARGIN_HIGH
•
VOUT_MARGIN_LOW
•
Output-voltage related
•
VOUT_COMMAND
•
VOUT_TRIM
•
VOUT_CAL_OFFSET
•
VOUT_SCALE_LOOP
•
VOUT_SCALE_MONITOR
•
Addressing, memory, communication, and capability
•
STORE_DEFAULT_ALL
•
RESTORE_DEFAULT_ALL
•
STORE_DEFAULT_CODE,
•
RESTORE_DEFAULT_CODE
•
WRITE_PROTECT
•
PAGE
•
PHASE
•
QUERY
•
Fault management
•
IOUT_OC_FAULT_LIMIT
•
IOUT_OC_FAULT_RESPONSE
•
IOUT_OC_WARN_LIMIT
•
OT_WARN_LIMIT
•
OT_FAULT_LIMIT
•
OT_FAULT_RESPONSE
•
VIN_UV_WARN_LIMIT
•
VIN_UV_FAULT_LIMIT
•
VIN_UV_FAULT_RESPONSE
•
CLEAR_FAULTS
•
Sequencing
•
TON_DELAY
☞ LEARN MORE @ electronicdesign.com/powermanagement | 10
CHAPTER 2: POWER SUPPLY CHARACTERISTICS
POWER ELECTRONICS LIBRARY
VDD
BP6
BOOT
BP3
VIN
Linear
Regulators
HSFET
Driver
Control
Anti-CrossConduction
RT
Pre-Bias
Oscillator
SYNC/RESET_B
Ramp
+
RESET_VOUT
COMP
S Q
R Q
LSFET
PWM
OC Event
Average IOUT
Error Amplifier
FB
+
Reference
DAC
SW
BP6
Fault
VREF for
Soft-Start and
VOUT_COMMAND
GND
Current
Sense,
OC
Detection
OC Threshold
PMBus Engine
VSET
VOUT Sense
OV/UV Detection
ADC, PMBus Commands,
IC Interface, EEPROM
CLK
DATA
SMBALERT
CNTL
ADDR0
ADDR1
DIFFO
Temperature
Sensing
AGND
750 kΩ
PGOOD
PGND
VOUTS+ VOUTS– TSNS/SS
2-7. TPS544C25 synchronous buck converter with PMBus and frequency
synchronization.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
TON_RISE
TOFF_DELAY
TOFF_FALL
Status
STATUS_BYTE,
STATUS_WORD
STATUS_VOUT
STATUS_IOUT
STATUS_CML
Telemetry
READ_VIN
READ_VOUT
READ_IIN
READ_IOUT
READ_TEMPERATURE
READ_DUTY_CYCLE
READ_PIN
READ_POUT
Other
FREQUENCY_SWITCH
VIN_ON
•
VIN_OFF
•
POUT_MAX
Version 1.3 of PMBus was added in
2014. The major new addition to PMBus is the AVSBus, which is an interface
designed to facilitate and expedite communication between an ASIC, FPGA, or
processor and a POL control device on a
system, for the purpose of adaptive voltage scaling. When integrated with PMBus,
AVSBus is available for allowing independent control and monitoring of multiple
rails within one slave.
•The AVSBus is behaviorally and electrically similar to SPI bus without chip select
lines. AVS_MData and AVS_SData are
equivalent to MOSI and MISO. AVS_Clock
is equivalent to CLK of the SPI bus. Maximum bus speed is 50 MHz.
•A
VSBus is an application-specific protocol to allow a powered device such as
an ASIC, FPGA, or Processor to control
its own voltage for power savings.
•T
he combination of these protocols in a
slave device is an efficient and effective
solution for systems containing loads that
need to adapt the operating voltage.
ISL8273M
Intersil’s ISL8273M provides a PMBus
digital interface that enables the user to configure all
aspects of the module operation as well as monitor the
input and output parameters (Fig. 2-6). The ISL8273M
can be used with any SMBus host device. In addition, the
module is compatible with PMBus Power System Management Protocol Specification Parts I and II version 1.2.
The ISL8273M accepts most standard PMBus commands.
When configuring the device using PMBus commands, it
is recommended that the enable pin is tied to SGND.
The SMBus device address is the only parameter that
must be set by the external pins. All other device parameters can be set using PMBus commands.
The ISL8273M can operate without the PMBus in pinstrap mode with configurations programmed by pin-strap
resistors, such as output voltage, switching frequency,
device SMBus address, input UVLO, soft-start/stop, and
current sharing.
The TPS544x25 from Texas Instruments are PMBus 1.2
compliant, non-isolated synchronous buck converters
with integrated FETs, capable of high-frequency operation and 20-A or 30-A from a 5 mm × 7 mm package (Fig.
☞ LEARN MORE @ electronicdesign.com/powermanagement | 11
CHAPTER 1: POWER SUPPLY CHARACTERISTICS
POWER ELECTRONICS LIBRARY
provides real-time, precision
monitoring of voltage, current,
and temperature, and allows full
programmability of the iJA parameters. Function-setting pins make
them easy to use in applications
where PMBus communication is
not implemented. A GUI (graphical user interface) and evaluation
boards are available for development support.
Operating from an 8 to 14VDC
input, the iJA series can provide
output voltages from 0.6 to 3.3V,
with a precision set-point accuracy of 1%. The series is designed to meet a wide range of
applications, including servers, routers, and other Information & Communication Technology (ICT) equipment,
semiconductor manufacturing equipment, measuring
equipment, and general industrial equipment.
The surface-mount converters occupy only 0.45 square
inch of board space, representing an ultra-high power
density of 580 Watts per cubic inch. Overall dimensions
are 22.9mm × 12.7mm × 9.7mm with a weight of just 6.5g.
Optimization of components using digital control enables
a high current output in high-temperature, low-airflow
environments. The iJA power module has a typical efficiency of 94% with a 3.3V output, 12V input, and 80%
loading.
2-8. TDK-Lambda’s
35A iJA series of
POL non-isolated
dc-dc converters are
PMBus compliant.
2-7). High-frequency, low-loss switching, provided by
an integrated NexFET power stage and optimized drivers, allows for very high-density power solutions. These
devices implement the industry standard fixed-switching
frequency, voltage-mode control with input feed-forward
topology that responds instantly to input voltage change.
These devices can be synchronized to the external clock
to eliminate beat noise and reduce EMI/EMC.
The PMBus interface enables the Adaptive Voltage
Scaling (AVS) through NexFET Power Stage VOUT_COMMAND, flexible converter configuration, as well as key
parameter monitoring including output voltage, current,
and an optional external temperature. Response to fault
conditions can be set to either restart, latch-off, or ignore
depending on system requirements. Two on-board linear
regulators provide suitable power for the internal circuits.
Features
• Input voltage: 4.5V to 18V
• Output voltage: 0.5V to 5.5V
• Single thermal pad
• 500mV to 1500 mV reference for AVS and margining
through PMBus
• 0.5% reference accuracy at 600mV and above
• Lossless low-side MOSFET current sensing
• Voltage mode control with input feed-forward
• Differential remote sensing
• Thermal shutdown
iJA Series
TDK-Lambda’s 35A iJA series of POL (point-of-load)
non-isolated dc-dc converters are PMBus compliant and
feature digital control (Fig. 2-8). These converters provide
better dynamic performance and improved system stability, as well as allow a great deal of flexibility and customization to the end application’s needs.
The PMBus read-write functionality of the converter
Related Articles
1. Christophe Basso, Compensating the RHPZ in the CCM
Boost Converter: The Analytical Way, powerelectronics.com,
April 2014.
2. Christophe Basso, Compensating the RHPZ in the CCM
Boost Converter: Using a Simulator, powerelectronics.com,
April 2014.
3. Steve Sandler, How Can I Measure PSRR Using an
Oscilloscope?, powerelectronics.com, August 2013.
4. Sam Davis, Back to Basics: Voltage Regulator ICs Part 1,
powerelectronics.com, June 2013.
5. Deisch, Cecil, Slope Compensation with Negative
Resistance Improves PWM Operation, powerelectronics.com,
June, 2009.
6. Tom Skopal, Power-Supply Failures Are Mostly Preventable,
powerelectronics.com, August 2008.
7. Dodson, Stephen, Top-Down Approach Simplifies AC-DC
Power Supply Selection, powerelectronics.com, May 2010.
8. Hsu, Jhih-Da, Design Concepts: AC Adapters for Notebook
Computers—Part 1, powerelectronics.com, November 2009.
9. Hsu, Jhih-Da, Highly Integrated Solution for AC Adapters—
☞ LEARN MORE @ electronicdesign.com/powermanagement | 12
CHAPTER 2: POWER SUPPLY CHARACTERISTICS
POWER ELECTRONICS LIBRARY
Part 2: Experimental Results, powerelectronics.com, January
2010.
10. Gary Raposa, What’s the Difference Between Watts and
Volt-Amperes?, powerelectronics.com, December 2010.
11. Steve Sandler, Evaluate Feedback Stability When There’s
No Test Point, powerelectronics.com, May 2012.
12. Hegarty, Timothy, Peak Current-Mode DC-DC Converter
Stability Analysis, powerelectronics.com, June 2010.
13. Arun Ananthampalayam, Back-to-Basics: Power Factor and
the Need for Power Factor Correction, powerelectronics.com,
August 2013.
14. Peter Blyth, Understanding Efficiency: Looking for the
Worst-Case Scenario, powerelectronics.com, January 2015.
15. Sam Davis, Digital Compensation Simplifies Power Supply
Design, Improves Performance, powerelectronics.com, April
2014.
☞
BACK TO TABLE OF CONTENTS
Featured Power Supply Assets
Sponsored by
Power Topologies Quick
Reference Guide
☞ Download Now
Power Management
Lab Kit-Reinforcing
Power Supply Knowledge
Comprehensive collection
of Power Supply Design
white papers
☞
☞
View Lab Kit
Download
White Paper
☞ LEARN MORE @ electronicdesign.com/powermanagement | 13
POWER ELECTRONICS LIBRARY
PART 1. POWER SUPPLIES
CHAPTER 3:
POWER SUPPLIES-
MAKE OR BUY?
P
ower supplies are necessary in virtually every
piece of electronic equipment. Therefore,
equipment manufacturers are confronted with
the task of deciding whether to make or buy
a power supply for their system. DC power
management employs a power supply that
can either be bought or made by the equipment manufacturer. The make-or-buy decision for power supplies can
have a major impact on the cost and time-to-market for the
end-item electronic equipment.
The equipment manufacturer has several challenges
to consider before making a power supply in-house:
• Can they make it cheaper than a purchased power
supply?
• Is time-to-market a consideration?
• Are the necessary people and resources available to
make the power supplies, including design and production facilities?
• Does the design and production include the time,
costs, and fees associated with getting agency certifications specific to power supplies?
Unless the equipment manufacturer can meet these
challenges, it most likely will buy the power supplies
and then implement the power management subsystem.
Among the reasons for an equipment manufacturer to
make the power supply in-house are:
• They can’t install a commercial power supply because
there is not enough room, such as in a battery-based
portable system.
• They must meet unique safety and EMC (electromagnetic compatibility) requirements that are not available
in commercial units, such as found in military and aerospace systems.
• They want the equipment to be proprietary.
• They think they can make it cheaper.
There are other factors to consider when deciding between making and buying the power supplies:
• Overall budget.
• Time-to-market for the end-item equipment.
• Finding and employing “safety critical” components for
the power- supply section.
• Time, costs, and fees associated with getting agency
certifications specific to power supplies.
• Will your competitors have an advantage if they purchase a technically superior standard power supply?
If the equipment manufacturer’s decision is to buy the
power supplies, the first step is to find a manufacturer
certified to meet the required reliability, safety, and EMC
specifications. This usually means an investigation into
the proposed manufacturer and development of the appropriate specification for the power supplies. Also, this
usually requires a means for the equipment manufacturer
to inspect the incoming power supply to ensure it meets
its specifications. Plus, the equipment manufacturer may
want to establish multiple sources to ensure delivery of
enough products. In addition, the power-supply manufacturer should provide documentation and technical
support, if it is required. The power-supply company
should also be able to support the return of failed units.
Involve the power-supply manufacturer early on in
the design stage for architectural, product, and cooling
discussions. Traditionally, power supplies have been
subject to the tailpipe syndrome (i.e., remembering them
when the project is nearly complete and having little time
to select them).
If the equipment manufacturer decides to make the
power supplies, it will start with a paper design, followed
by a prototype, design review, and then a decision on
whether to go ahead with production. Given the goahead, the purchasing department can order all the components, which usually includes qualified components
from qualified vendors. As long as there are no long leadtime components, production can start. Allow sufficient
time for relevant safety agency approvals.
☞ LEARN MORE @ electronicdesign.com/powermanagement | 14
CHAPTER 3: POWER SUPPLIES– MAKE OR BUY?
POWER ELECTRONICS LIBRARY
There are alternatives to making and manufacturing
and multiple-output voltages).
the power supplies. For example, one alternative is to
3. Encapsulated dc-dc converters (single- and multisubcontract the design phase. In addition, the producple-output voltages).
tion can also be subcontracted. The cost of subcontract4. Bus dc-dc converters.
ing should be compared with doing everything in-house.
5. Point-of-load (POL) converters (non-isolated).
When the first units are completed they will have to be 6. Power over Ethernet power (PoE) supplies.
tested for safety, EMC, and reliability over the required
7. High-voltage dc-dc converters.
temperature range. This depends on the appropriate
It is a good idea to select a power supply that prostandards that must be met, which might vary for some
vides a safety margin for the future. Too often, electronic
countries. If the manufacturer doesn’t have this facility in- systems expand from their initial requirements and need
house, the units can be sent to a testing laboratory.
additional current, power, and sometimes even a new
The equipment manufacturer should check the supoutput voltage. A new output voltage requires an adply’s reliability. They can send one or two supplies to a
ditional power supply or one with an adjustable output
facility that performs HALT (Highly Accelerated Life Test)
voltage, although most supplies can accommodate a
or ALT (Accelerated Life Test).
10% variation in output voltage.
• HALT is the process of determining the reliability of a
The OEM power supply must provide the necessary
product by gradually increasing stresses until the prod- output voltage, current, and power. With such a broad
uct fails. This is usually performed on entire systems,
range of standard products, you should see what type of
but can be performed on individual assemblies as well. power supply can meet your requirements. One way to
• ALT is the process of determining the reliability of a
start is to understand the characteristics of the available
product in a short period of time by accelerating stress- power supplies. If you can’t find a standard supply to
es (usually temperature) on the product. This is also
meet your requirements, you will probably need to buy a
good for finding dominant failure mechanisms. ALTs are custom-designed supply that is more expensive than a
usually performed on individual assemblies rather than
standard unit. An economic alternative to a custom powfull systems.
er supply is the wide range of “modular power supplies”
• Calculate the electrolytic capacitor life
using measured temperature data
Power Supply Requirements
The equipment manufacturer may
AC Input Voltage Range
Line Frequency
Hz
also want to check each power supply
DC Input Voltage Range
by “burning them in.” This is usually done
by powering each supply for a given
Power Factor Correction? Yes
No
RoHS Compliant? Yes
No
period (for example, 24 hours) and then
°C
Operating Temperature Range
checking them to see if they are operating
Volts
(V)
Peak
Current
(A) Regulation (±)
Current
(A)
properly. Often, this is done by putting
Output
#1
several supplies on a burn-in rack at the
same time.
Output #2
What OEM ac-dc power supplies can
be purchased?
1. AC adapters.
2. Front-end power supplies for Distributed Power Architecture (DPA).
3. Centralized power supplies (singleand multiple-output voltages).
4. AC-DC brick power supplies.
5. High-voltage power supplies.
What OEM dc-dc converters can be
purchased?
1. DC-DC brick dc-dc converters (singleand multiple-output voltages)
2. Non-brick dc-dc converters (single-
Output #3
Output #4
Output #5
Output #6
Agency Safety Approvals
Package
Enclosed
Open Frame
PCB Mount
Cooling Integral Fan
Price Target
DIN Rail
System Fan
Surface Mount
Convection-Cooled
Estimated Annual Usage
3-1. Power-supply requirements worksheet.
☞ LEARN MORE @ electronicdesign.com/powermanagement | 15
SIP
DIP
CHAPTER 3: POWER SUPPLIES– MAKE OR BUY?
POWER ELECTRONICS LIBRARY
on the market today that can be tailored to your needs
without the NRE and delays associated with a custom
design.
One of the best ways to find the optimum power
supply for your application is to fill out a form similar to
that in Fig. 3-1. This allows you to list your requirements
and then leave it up to the power-supply vendor to give
you the answer. The completed form also allows you to
use the same information if you are looking for a second
source.
Related Articles
1. Don Knowles, The AC-DC Power Supply: Make It or Buy It?,
powerelectronics.com, August 2012.
2. Bonnie C. Baker, Tackling the Challenges of Power
Dissipation, powerelectronics.com, April 2004.
3. David Morrison, Modeling DC-DC Converter Transient
Response, powerelectronics.com, August 2004.
4. Daly, Brendan, Automatic Routine Speeds Power-Supply
Calibration, powerelectronics.com, March 2005.
5. Tom Skopal, Power-Supply Failures Are Mostly Preventable,
powerelectronics.com, August 2008.
6. Sandler, Steve, A New Technique for Testing Regulator
Stability Non-Invasively, powerelectronics.com, September
2011.
7. Davis, Sam, Controller IC Employs Real-Time Adaptive Loop
Compensation, PMBus, powerelectronics.com, January 2012.
8. Steve Sandler, Evaluate Feedback Stability When There’s No
Test Point, powerelectronics.com, May 2012.
9. Steve Sandler, When Bode Plots Fail Us, powerelectronics.
com, May 2012.
10. Steve Sandler, Five Things Every Engineer Should Know
about Bode Plots, powerelectronics.com, January 2014.
11. Joe Chong, Managing Multiple Supply Voltages,
powerelectronics.com, August 2004.
12. Brian Narveson, Why Is My DC-DC Converter Too Hot?,
powerelectronics.com, June 2006.
☞
BACK TO TABLE OF CONTENTS
Featured Power Supply Assets
Sponsored by
Power Topologies Quick
Reference Guide
☞ Download Now
Power Management
Lab Kit-Reinforcing
Power Supply Knowledge
Comprehensive collection
of Power Supply Design
white papers
☞
☞
View Lab Kit
Download
White Paper
☞ LEARN MORE @ electronicdesign.com/powermanagement | 16
POWER ELECTRONICS LIBRARY
PART 1. POWER SUPPLIES
CHAPTER 4:
POWER SUPPLY
PACKAGES
P
ower-supply packages will influence the performance, cost, and size of the power supply
used in the power-management subsystem.
Therefore, the selection process for purchasing
a power supply should take the package style
into account. Package styles can range from
the open-frame type without an enclosure to the completely enclosed type, like the standard brick.
The quest for multiple source dc-dc converter modules has led to a family of standard “brick” sizes. There
are now “16th-brick” and “eighth-brick” sizes to go
along with the full-bricks, half-bricks, and quarter-bricks.
And, power densities have gone beyond 50W/in.3 Many
of these modules are interchangeable with those of
many manufacturers, which ensures multiple sources.
In addition, pinouts of the brick converters are now a
de facto standard, allowing interchangeability between
different manufacturers’ products. Currently, distributed
power architecture (DPA) system bricks can dissipate
hundreds of watts. Table 4-1 lists the size for each of the
brick sizes. Generally, the larger the size, the higher the
maximum power output.
Modular brick dc-dc converters supplied by the
front-end supply provide electrical isolation, increased
load transient performance, and a modular upgrade
path (Fig. 4-1). Their lower output voltage draws a larger
current (for a given power level) and has less tolerance
TABLE 4-1. SIZE OF BRICK DC-DC CONVERTERS
Type
Length
Width
Height
1/16 brick
1.65
0.8
0.5
1/8 brick
2.28
0.9
0.5
1/4 brick
2.28
1.45
0.5
1/2 brick
2.40
2.28
0.5
3/4 brick
3.45
2.40
0.5
Full brick
4.60
2.40
0.5
4-1. TDK-Lambda’s CN-A Series of dc-dc converters
have a 60V to 160VDC input range with output voltages
from 5V to 24VDC (adjustable ±10%). Output power
ratings are 30W, 50W, and 100W. These isolated power
modules are in the industry-standard quarter-brick
footprint.
for deviations in its voltage caused by voltage drops on
the lines between the converter output and its load.
There are also ac-dc bricks. Initially, these bricks
required two modules. One module for the ac input rectification and power factor correction (PFC), and another
for the dc-dc isolation and low voltage conversion. Now,
these two functions are available in a single brick, thus
eliminating module interconnects and saving 25% or
more printed circuit board space.
An example of a single module ac-dc brick with
PFC is TDK-Lambda’s 1000W PFE1000F series that is
available with 12V, 28V, and 48V nominal outputs that
are adjustable to ±20%. The series can operate with a
baseplate temperature range from -40°C up to +100°C.
Line and load regulation is 0.4% max and efficiency is in
the range of 82% to 86% depending on output voltage.
☞ LEARN MORE @ electronicdesign.com/powermanagement | 17
CHAPTER 4: POWER SUPPLY PACKAGES
POWER ELECTRONICS LIBRARY
4-2. Gresham Power Electronics’ (M)WLP75 AC/DC
converter. This open-frame series is the fourth addition
to the EOS low-profile, high-efficiency (M)WLP series.
Available in medical and industrial versions, (M)WLP75
features include: 75W convection rating; efficiencies
up to 93%; -40 to 70°C operation; standby power
< 0.3 Watt; weight 150g; dual fusing; and Class II
Option available for medical applications and RoHS
compliance.
These models accept an 85Vac to 265Vac input
at 47-63Hz and have active power-factor correction
(PFC), an input-to-output isolation of 3kVAC, and an
input-to-baseplate rating of 2.5kVAC with application
circuitry. In addition, overvoltage, overcurrent, and overtemperature protections are included.
The PFE1000F comes in a 6.3 × 3.94 × 0.53-in. package that is larger than a dc-dc full-brick, but its construction resembles its dc-dc cousins. Other members
of the PFE series are rated at 300W, 500W, and 700W
and are housed in a full-brick package the same size as
the dc-dc full-brick. These full-brick ac-dc supplies also
have PFC.
An advantage of the DPA approach with multiple dcdc converter brick modules is that the heat produced by
each of the modules is spread throughout a system. In
contrast, most of the heat associated with a centralized
power system is in the single power supply.
Use of a dc bus voltage, typically 48V, also means
cables with lower current are bused throughout the
system. Higher current requirements are handled by the
dc-dc converter modules that are located close to their
loads, which minimizes distribution losses and enables
smaller, less expensive conductors to be used for the
cables that bus the secondary voltage.
From a reliability standpoint, each element in a DPA
has its own power supply, so failure of a single dc-dc
converter module will only affect a single function or
printed circuit board, which aids the design of fault-tolerant systems.
DC-DC converter brick modules are a key ingredient
in DPA systems. The performance of these converters
is directly related to the IC operating voltage requirements that are dropping from the historic standard of 5V
to 1.5V, with projections of less than 1.0V over the next
decade. Besides the 5V and 3.3V outputs, some converters now provide 2.5V, 1.8V, and 1.2V, and some can
supply 0.8V.
“Off-the-shelf” standard brick converters can lower
system development costs and also shorten design
cycles because if they have already been tested and are
available from multiple sources. If the system’s powering
requirements change, it is relatively simple to replace
one converter module with another, that is, no major
redesign is usually required.
The majority of packaged dc-dc converter brick
modules are mounted on p.c. boards holding associated
digital circuits. Therefore, the converter module’s size
impacts a board’s circuit density. This includes the converter’s footprint area that determines how much circuitry
can be placed on the board. Converter module height
is also important because it affects spacing between
boards within the system. Eliminating the need for a heat
sink also allows tighter board-to-board spacing.
To operate without a heat sink and provide more power output, the brick dc-dc converter must be efficient,
particularly at the new lower semiconductor operating
voltages. Therefore, the converter must minimize its
internal power loss and the operating temperature of its
components. Achieving higher efficiency also reduces
the system’s input power and cooling requirements.
Plus, it influences system manufacturing and operating
costs.
Minimizing internal power loss lowers the converter’s
case temperature, which may eliminate the need to employ forced-air cooling. Most converters have maximum
case temperature ratings less than 100°C.
One approach to reducing internal power loss and
improving converter efficiency is to employ synchronous
rectifiers consisting of power MOSFETs. This higher
efficiency obtained by synchronous rectifiers means
the converter dissipates less heat and may no longer
require a heat sink.
Non-Brick Power Supplies
Non-brick dc-dc power supplies are available in both
single- and multiple-output versions. They come in openframe, such as these from Gresham Power Electronics
☞ LEARN MORE @ electronicdesign.com/powermanagement | 18
CHAPTER 4: POWER SUPPLY PACKAGES
POWER ELECTRONICS LIBRARY
4-3. Astrodyne’s modular 3.8 kW Mercury-Flex is hotswappable, enabling maximum uptime. For applications
that require higher power, you can connect the modules
in parallel current sharing groups through a four-module
shelf assembly. This enables designs of upwards to 228
kW in a single universal 19-in. rack (30U).
(Fig. 4-2). Most of these modules deliver from 20W to
500W, which is somewhat less than their larger brick
cousins. They may be rack-mounted, DIN-Rail mounted,
or packaged within an electronic system. Some of these
power supplies have a high enough isolation voltage to
allow them to be certified for use in medical systems.
The physical size of these power supplies varies over
a wide range, from a length of 0.65 in. to 21.2 in. Some
packages employ SMT, DIP, or SIP connections, whereas some use through-hole pins and others use screw
terminals.
Non-brick supplies with multiple outputs include
those employed with Compact PCI systems that employ
5V, 3.3V, and ±12V.
Astrodyne TDI digitally programmable ac/dc power
supply provides 3,800 W of regulated power and can
operate as either a current or voltage source up to 400
V or 170 A (Fig. 4-3). Intended for industrial applications that require a flexible, digitally controlled industrial
power supply with a universal voltage range of 90 VAC
to 264 VAC and a 50/60 Hz single-phase input, the
Astrodyne TDI Mercury-Flex is offered in a variety of
adjustable dc output voltage range models including
0-28V, 0-56V, 0-85V, 0-125V, and 0-400V. This reliable
unit delivers efficiency up to 93%, with a power factor of
4-4. CUI’s PFR-2100 is a 2,000 W front-end supply in an
enclosed package.
0.97 or better, helping to lower energy requirements and
heat dissipation. Its 14 VDC auxiliary output is useful for
powering miscellaneous user circuits.
CUI Inc.’s PFR-2100 is a 2000 W front-end ac-dc
power supply in an enclosed package (Fig. 4-4). The
PFR-2100 series is a blind-mate rectifier with a programmable output voltage range of 100~410 Vdc. Key
features include a hot-swap blind-docking capability
implemented through the use of a single connector that
integrates ac, dc, and I/O signals. The PFR-2100 delivers high efficiency up to 93% in a package measuring
11.5 × 5.2 × 2.5 in. (292.1 × 132.08 × 63.5 mm). The
series is ideally suited for use in data-center high-voltage dc bus power systems, broadcast amplifiers, and
EV battery-charging systems.
The programmable dc output voltage delivers a constant current up to 5.125 A with droop current sharing
for paralleling up to 12 units. Additional features include
power-factor correction, remote on/off control, power
good signal, and front-panel LED indicators. The PFR
2100 series complies with all applicable EMC require-
4-5. The BMR466’s unique LGA (Line Grid Array)
footprint is 0.98 × 0.55 in. and has an exceptionally low
profile of 0.276 in., which facilitates compact system
design.
☞ LEARN MORE @ electronicdesign.com/powermanagement | 19
POWER ELECTRONICS LIBRARY
CHAPTER 4: POWER SUPPLY PACKAGES
4-6. MinMax AAF-05 Series features: ultra compact
size (1.0 × 1.0 × 0.64 in.); fully encapsulated plastic
case for PCB and chassis mounting version; Universal
Input 85—264VAC, 47~440Hz; Protection Class II as
per IEC/EN 60536; and I/O Isolation 3000VAC with
reinforced insulation.
1.2V, but can be adjusted from 0.6V to 1.8V either via a
pin-strap resistor or PMBus commands. The BMR466
powertrain guarantees high efficiency and reliability and
ments to accommodate worldwide applications and
offers 60950-1 safety approvals. Protections for overvolt- is built from the latest generation of power-transistor
semiconductors, enabling the module to deliver up to
age, overcurrent, and overtemperature are also provid94.9% with a 5V input and a 1.8V output, at half load.
ed.
Through software control, the BMR466 uses
class-leading
adaptive compensation of the PWM conBMR466
trol loop and advanced energy-optimization algorithms
Ericsson’s BMR466 is a 60A digital point-of-load
to reduce energy consumption and deliver a stable and
(POL) dc/dc power module for powering microprocessecure power supply with fast transient performance
sors, FPGAs, ASICs, and other digital ICs on complex
over a wide range of operating conditions. In multi-modboards. The BMR466’s unique LGA footprint is 0.98 ×
ule systems, two or more of the single-phase BMR466
0.55 in. and has an exceptionally low profile of 0.276
POL converters can be synchronized with an external
in., which facilitates compact system design (Fig. 4-5).
Spreading the placement of the 60A units across printed clock to enable phase spreading, which means the
reduction of input ripple current and corresponding cacircuit boards means that heat dissipation can be dispacitance requirements and efficiency losses. The ripple
tributed, optimizing the use of multi-layer board technolcurrent can be estimated using the Ericsogy and simplifying cooling arrangements.
son Power Designer (EPD) software tool,
In addition, the use of a surface-mount
which enables easy capacitor selection.
LGA package with symmetric contact
The BMR466 is also fully compliant with
layout offers superior mechanical contact
PMBus commands and has been integratand high reliability after soldering. The
ed into the EPD software, which makes it
elimination of connecting leads results
in lower inductance, enabling excellent
easy for power system architects to simunoise, and EMI characteristics. This is
late and configure complete multi-module
further enhanced because a high number
and multi-phase systems prior to impleof the LGA contacts are ground pins.
4-7. Aimtec’s 1 watt
mentation. This cuts time-to-market.
Up to eight of the fully regulated 60A
dc-dc converter series
Suited for deployment in distributed
(maximum) POL converters can be conis available in a compact
power and intermediate bus voltage arnected in parallel to deliver up to 480A in
single-inline SIP4.
chitectures within the ICT (Information and
Communication Technology), telecom,
multi-module and multi-phase systems.
and industrial sectors, the module targets
This produces an economical, efficient,
high-power and high-performance use in products such
and scalable power solution with a small footprint, high
stability, advanced-loop compensation, and class-leadas networking and telecommunications equipment, serving thermal characteristics.
ers, and data-storage applications, as well as industrial
Operating from a 4.5V to 14V input, the BMR466
equipment.
is ideally suited to operation across a range of intermediate bus voltages and complies with the Dynamic
Encapsulated Power Supplies
Bus Voltage scheme to reduce power dissipation and
Encapsulated/sealed dc-dc power supplies are
save energy. The factory default output voltage is set to
available in both single- and multiple-output versions,
☞ LEARN MORE @ electronicdesign.com/powermanagement | 20
CHAPTER 4: POWER SUPPLY PACKAGES
POWER ELECTRONICS LIBRARY
µModule
4-8. The LTM4650
µModule is housed in a
conventional ball-grid
array (BGA) package.
like these from MinMax (Fig. 4-6). They come in SIP,
DIP, SMT, and through-hole pin packages. Most of these
modules deliver from less than 1W to over 300W, which
is somewhat less than other non-brick packages. They
are usually mounted directly on a printed circuit board.
A typical single-output plastic-encapsulated supply
of this type rated at 1W. The Series accepts nominal
input of either 3.3V, 5V, 12V, 15V, or 24V and produces
outputs of 3.3V, 5V, 9V, 12V, 15V, or 24V. Isolation options
are 1,000V or 3,000V. A five-pin SMD package measures
0.5 × 0.32 × 0.29 in.
Another plastic-encapsulated type is housed in a SIP
package rated at 3W. Its nominal input voltages are either 5V, 12V, 24V, or 48V. Output voltages are either 3.3V,
5V, 9V, 12V, or 15V. The SIP package measures 0.86 ×
0.36 × 0.44 in.
A sealed dc-dc power supply for COTS (commercial
off-the-shelf for military applications) measures 2.4 × 2.3
× 0.5 in. It accepts a nominal 270V dc input and delivers either 3.3V, 5V, 12V, 15V, or 28V, with up to a 200W
output rating. It has a mu-metal shield for low radiated
emissions.
Aimtec’s AM1SS-NZ series of unregulated 1 Watt
DC-DC converters provides continuous short-circuit protection with auto recovery restart (Fig. 4-7). The restart
feature will work continuously until the short-circuit condition is cleared, protecting the converter, the load, and
the converter’s input circuit from extremely high currents
a short circuit can cause.
Supported input voltages of 3.3, 5, 12, 15, and
24VDC convert to single output voltages of 3.3, 5, 9, 12,
15, and 24VDC. Operating within an ambient temperature range of -40°C to +105°C (derating at 85°C), the
AM1SS-NZ series is designed for versatility and can be
integrated into a multitude of applications, such as digital circuits, low-frequency analog, or relay-drive circuits.
Available in a compact, single-inline SIP4 package
(11.60 × 10.10 × 6.00 mm), the AM1SS-NZ is offered
with an input-output isolation upgraded to 1500VDC for
easy integration in industrial, telecommunication, and
computer applications.
Power-supply packages continue to shrink by using
semiconductor industry manufacturing techniques. The
result is the μModule (power module) regulator that integrates switching controllers, power FETs, inductors, and
all supporting components in a conventional ball-grid
array (BGA) package (Fig. 4-8). The circuit requires only
a few input and output capacitors.
The LTM4650 is a dual 25A or single 50A output
switching mode step-down dc/dc converter. Operating from a 4.5V to 15V input, the LTM4650 supports
two outputs each with an output voltage range of 0.6V
4-9. Phihong’s energy-efficient 10W wall-mount adapter
series is available in 5- and 9VDC outputs. The PSC12x
Series consists of five versions: A, E, K, S, and C,
each of which features a country-specific fixed-outlet
plug. PSC12A adapters are equipped for use in the
United States, Europe, United Kingdom, Australia, New
Zealand, and China. PSC12x Series adapters are rated
for operation from 0ºC to +40ºC.
4-10. Spellman Bertan High-Voltage Power Supply
PMT30CN-1features: 500V to 7.5kV @ 1.9 to 4 Watts;
modular design; stability and regulation; low noise and
ripple; arc and short-circuit protected; and CE listed, UL
recognized and RoHS compliant.
☞ LEARN MORE @ electronicdesign.com/powermanagement | 21
CHAPTER 4: POWER SUPPLY PACKAGES
POWER ELECTRONICS LIBRARY
to 1.8V, each set by a single external resistor. Its high
efficiency design delivers up to 25A continuous current
for each output. The LTM4650 is pin-compatible with the
LTM4620 (dual 13A, single 26A) and the LTM4630 (dual
18A, single 36A).
This μModule supports frequency synchronization,
multiphase operation, burst-mode operation and output
voltage tracking for supply-rail sequencing and has an
onboard temperature diode for device-temperature monitoring. High switching frequency and a current-mode
architecture enable a very fast transient response to
line and load changes without sacrificing stability. Fault
protection features include overvoltage and overcurrent
protection.
The LTM4650 is housed in a 16mm × 16mm ×
5.01mm BGA package.
AC Adapters
AC adapters are a cost-effective and relatively fast
way to provide a power source for computer peripherals
such as these from Phihong (Fig. 4-10). There are two
types of dc output adapters: linear and switch-mode.
The switch-mode adapter provides greater efficiency and smaller size, whereas the linear power supply
adapter is less efficient and larger, but could be “quieter,” that is, less radiated or conducted EMI. However,
there are several adapters using the switch-mode topology that meet the FCC’s EMI requirements
It is important to obtain an adapter that has high
efficiency, which minimizes heat dissipation, resulting in
an adapter that is small and reliable. Without this high
efficiency, the resulting internal temperature rise would
be potentially hazardous and a major reliability limiter. In
many applications, the adapter may be placed in a confined space, or it may be buried under a pile of cable, so
minimizing heat is essential.
AC adapters are a cost-effective power source to
charge portable system batteries because the OEM
does not have to design and qualify the supply. Typically, these adapters can power the unit as well as charge
the associated battery.
The switch-mode adapter provides greater efficiency and smaller size, whereas the linear power supply
adapter is less efficient and larger, but produces less
radiated or conducted EMI. A high efficiency adapter
minimizes heat dissipation, resulting in a smaller and
reliable unit.
The California Energy Commission approved new
energy saving standards in order to slow down the
demand for electricity throughout the state. According
to the CEC, the energy savings from the new standards
over the next 10 years will enable the state to avoid
building three large power plants.
On average, ENERGY STAR-approved models are
35% more efficient than conventional designs, and often
are lighter and smaller in size. Many adapters have
safety approvals from cUL/UL, TUV, SAA, CE, C-Tick,
and CCC (except for 48V). Some provide no-load power
consumption of less than 0.5W, as well as low leakage
current with a maximum of 0.25mA.
High-Voltage Power Supplies
High voltage ac-dc power supplies offer regulated
outputs for bench top or OEM use (Fig. 4-11). Typical
applications include: spectrometers, detectors, imaging, electron beam systems, projection television, X-ray
systems, capacitor charging, laser systems, and cathode-ray tubes.
Available high-voltage ac-dc power supplies have
many circuit and system variations. There are single-phase supplies with switch-selectable 115/230Vac,
three-phase 208V inputs, and most include power-factor
correction (PFC).
The method for generating the high voltage is either
with a conventional switch-mode power converter, or a
resonant high-frequency inverter.
Power-supply enclosures are usually fully metal-enclosed units, 19-in. enclosed metal rack panels, or
smaller modules intended for embedded applications.
High-voltage power-supply outputs can range from
1kV to over 100kV, from fractions of a milliamp to amperes, and output power from watts to kilowatts. Output
polarity may be a fixed positive voltage, fixed negative
voltage, or a reversible positive or negative voltage
output. The output interface may be a high-voltage
connector, or a captive high-voltage cable. The output
voltage adjustment may be provided by a local internal
potentiometer, or a ground-referenced signal for remote operation. Output monitors on some units monitor
voltage or current, or both. Output ripple is usually rated
in peak-to-peak in mV or peak-to-peak as a percent of
output voltage.
Most supplies offer protection against arcs or output
short circuits. Among the miscellaneous features found
in these supplies are local and remote programming,
fault indicators with safety interlock, overload protection,
and an enable voltage signal input for remote control.
Related Articles
1. Mario Battello, Rectifier ICs and Thermal Packaging Enhance
SMPS, powerelectronics.com, May 2006.
2. John Mookken, Modular Approach Simplifies Power-System
☞ LEARN MORE @ electronicdesign.com/powermanagement | 22
CHAPTER 4: POWER SUPPLY PACKAGES
POWER ELECTRONICS LIBRARY
Design, powerelectronics.com, May 2006.
3. Lily Hsiu-shih Chu, Better Power Packages Make Better
Circuits, powerelectronics.com, May 2007.
4. Sam Davis, New Breed of MCMs Optimize System
Performance and Cost, powerelectronics.com, October 2009.
5. Sam Davis, Innovative Packaging Shrinks 600 mA and 6 A
Power Supplies, powerelectronics.com, January 2011.
6. Sam Davis, 25 A POL Regulator Shrinks PCB Size by 20%,
powerelectronics.com, May 2013.
7. Wolfgang Peinhopf, Chip-Embedded Packaging Contributes
to New Performance Benchmark for DrMOS, powerelectronics.
com, April 2013.
8. Sam Davis, Ultra-Small Packages Shrink Power Management
ICs, powerelectronics.com, November 2013.
9. Gary Gill, New Thermal Design Options Drive Power Density,
powerelectronics.com, August 2013.
10. Jason Sun, Optimizing Power Supply Adapter Design,
powerelectronics.com, July 2010.
☞
BACK TO TABLE OF CONTENTS
Featured Power Supply Assets
Sponsored by
Power Topologies Quick
Reference Guide
☞ Download Now
Power Management
Lab Kit-Reinforcing
Power Supply Knowledge
Comprehensive collection
of Power Supply Design
white papers
☞
☞
View Lab Kit
Download
White Paper
☞ LEARN MORE @ electronicdesign.com/powermanagement | 23
POWER ELECTRONICS LIBRARY
PART 1. POWER SUPPLIES
CHAPTER 5:
POWER-MANAGEMENT
REGULATORY
STANDARDS
R
egulatory standards must be met because
international and domestic standards are
required for the power-management section
of the end-item equipment. These standards
vary from one country to another, so the power
subsystem manufacturer and the end-item
system manufacturer must adhere to these standards
where the system will be sold. Design engineers must
understand these standards even though they may not
perform standards certification. Understanding these regulatory standards usually poses problems for power-management subsystem designers.
• Many standards are technically complex, requiring an
expert to be able to decipher them.
• Often, standards are written in a form that is difficult for
the uninitiated to interpret because there are usually
exemptions and exclusions that are not clear.
• Several different agencies may be involved, so some
may be specific to one country or group of countries
and not others.
• Standard requirements vary and sometimes conflict
from one jurisdiction to another.
• Standards are continually evolving, with new ones introduced periodically, so it is difficult to keep pace with
them.
What standards agencies are encountered at the product and system level?
ANSI: The American National Standards Institute oversees the creation, promulgation, and use of norms and
guidelines that directly impact businesses, including
energy distribution.
EC (European Community) Directives: Companies responsible for the product intended for use in the European Community must design and manufacture it in accordance with the requirements in the relevant directives.
EN (European Norm): Standard directives for the European community.
IEC (International Electrotechnical Commission): Generates standards for electrical and electronic systems.
UL (Underwriter’s Laboratory): Safety approvals for electrical and electronics products within the United States. A
UL approval can also be obtained through the CSA.
CSA (Canadian Standards Association): Safety approval
required to use an electrical or electronic product within
Canada. A CSA approval can also be obtained through
the UL.
Telcordia: Standards for telecom equipment in the United
States.
ETSI (European Telecommunications Standards Institute):
Standards for telecom equipment.
Required safety standards for power supplies include
EN60950 and UL60950 “Safety of Information Technology Equipment” based on IEC60950, containing requirements to prevent injury or damage due to hazards such
as: electric shock, energy, fire, mechanical, heat, radiation, and chemicals. As of January 1997, the EC Low
Voltage Directive (LVD) 73/23/EEC and the amending
directive 93/68/EEC requires the manufacturer to make a
declaration of conformity if the product is intended to be
sold in the European Community.
Specific standards power-supply acoustics define
maximum audible noise levels that may be produced by
☞ LEARN MORE @ electronicdesign.com/powermanagement | 24
CHAPTER 5: POWER MANAGEMENT REGULATORY STANDARDS
POWER ELECTRONICS LIBRARY
the product. The main contributor to the acoustic noise is
usually the fan in a power supply with an internal fan.
ESD (Electrostatic Discharge) standards include
EN61000-4-2 that tests immunity to the effects of
high-voltage low-energy discharges, such as the static
charge built up on operating personnel.
Power-Line Standards for Power Supplies
EN61000-3: Limits voltage changes the power supply
under test can impose on the input power source (flicker
test).
EN61000-4: Tests the effects of transients and determines the ability of the power supply to survive without
damage or operate through temporary variations in main
voltage. These transients can be in either direction (undervoltage or overvoltage).
EN61000-3-2: Limits the harmonic currents that the power supply generates onto the power line. The standard
applies to power supplies rated at 75 W with an input line
current up to 16A/phase.
EN61000-4-11: Checks the effect of input voltage dips on
the ac input power supplies.
EMC Standards for Power Supplies
The most commonly used international standard for
emissions is C.I.S.P.R. 22 “Limits and Methods for Measurement of Emissions from ITE.” Most of the immunity
standards are contained in various sections of EN61000.
As of January1996, EC Directive 89/336/ EEC on EMC
requires the manufacturer to make a declaration of conformity if the product is sold in the European Community.
Sections of EN61000 for EMC include:
EN61204-3: This covers the EMC requirements for power
supplies with a dc output up to 200V at power levels up
to 30kW, and operating from ac or dc sources up to 600
V.
EN61000-2-12: Compatibility levels for low-frequency
conducted disturbances and signaling in public medium-voltage power supply systems
EN61000-3-12: Limits for harmonic currents produced by
equipment connected to public low-voltage systems with
input current >16A and < 75A per phase
EN61000-3-2: Limits harmonic currents injected into the
public supply system. It specifies limits of harmonic components of the input current, which may be produced by
equipment tested under specified conditions
EN61000-4-1: Test and measurement techniques for
electric and electronic equipment (apparatus and systems) in its electromagnetic environment.
EN61000-4-11: Measurement techniques for voltage
dips, short interruptions, and voltage variations immunity
tests.
EN61000-4-12: Testing for non-repetitive damped oscillatory transients (ring waves) occurring in low-voltage
power, control, and signal lines supplied by public and
non-public networks.
EN61000-4-3: Testing and measurement techniques for
immunity requirements of electrical and electronic equipment to radiated electromagnetic energy. It establishes
test levels and the required test procedures.
EN61000-4-4: Testing and measurement techniques for
electrical fast transient/burst immunity test.
EN61000-4-5: Recommended test levels for equipment
to unidirectional surges caused by overvoltage from
switching and lightning transients. Several test levels are
defined that relate to different environment and installation conditions.
EN61000-6-1: Electromagnetic compatibility (EMC)
immunity for residential, commercial, and light-industrial
environments
EN61000-6-2: Generic standards for EMC immunity in
industrial environments
EN61000-6-3: Electromagnetic compatibility (EMC) emission requirements for electrical and electronic apparatus
intended for use in residential, commercial, and light-industrial environments.
EN61000-6-4: Generic EMC standards for industrial environments intended for use by test laboratories, industrial/medical product designers, system designers, and
system installers.
Restriction of Hazardous Substances (RoHS) Affects
Power Supplies
RoHS is a directive that restricts use of hazardous
substances in electrical and electronic equipment.
Designated 2002/95/EC, it is commonly referred to as
the Restriction of Hazardous Substances Directive. This
RoHS directive took effect in July 2006, and includes
power supplies. Often referred to as the lead-free directive, RoHS restricts the use of: lead; mercury; cadmium;
hexavalent chromium (Cr6+); polybrominated biphenyls
(PBB) (flame retardant); and polybrominated diphenyl
ether (PBDE) (flame retardant).
Electronic Waste Directives
RoHS is closely linked to the Waste and Electronic Equipment Directive (WEEE). Designated 2002/96/
EC, it makes power-supply manufacturers responsible
for the disposal of their waste electrical and electronic
equipment. Companies are compelled to use the collected waste in an ecologically friendly manner, either
☞ LEARN MORE @ electronicdesign.com/powermanagement | 25
CHAPTER 5: POWER MANAGEMENT REGULATORY STANDARDS
POWER ELECTRONICS LIBRARY
by ecological disposal or by reuse/refurbishment of the
collected WEEE.
Directives for Disposal of Batteries
Batteries are not included within the scope of RoHS.
However, in Europe, batteries are under the European
Commission’s 1991 Battery Directive (91/157/EEC),
which was recently increased in scope and approved in
the form of the new battery directive, version 2003/0282
COD, which will be official when submitted to and published in the EU’s Official Journal. This new directive
explicitly highlights improving and protecting the environment from the negative effects of the waste contained in
batteries.
Related Articles
1. Peter Blyth, Converters Address Medical Equipment
Compliance, powerelectronics.com, March 2006.
2. Lesley Kao, MOV and PPTC Devices Enable IEC 61000-4-5
Compliance, powerelectronics.com, July 2006.
3. Peter Resca, Evolving Standards Reshape Medical Power
Supplies, powerelectronics.com, April 2007.
4. Ed Fink, REACH: The Shot (to be) Heard Around the World,
powerelectronics.com, November 2008.
5. Peter Resca, New Energy Star Requirements Impact
Powering of Solid-State Lighting, powerelectronics.com,
February 2009.
6. Sam Davis, DirectFET 2 Power MOSFETs Meet AEC-Q101,
powerelectronics.com, February 2010.
7. UL, UL Developing First-Edition Standard for Wireless
Charging Devices for Use with Low-Energy Products,
powerelectronics.com, July 2010.
8. Don Tuite, Conforming with Worldwide Safety and EMC/EMI
Standards, powerelectronics.com, November 2010.
9. Alberto Guerra, Safety Standards in Appliance Motion
Control Made Easier with Digital Control, powerelectronics.
com, March 2012.
10. Swati Umbrajkar, Lithium (Ion) Battery Safety and Required
Regulatory Testing, powerelectronics.com, July 2012.
☞
BACK TO TABLE OF CONTENTS
Featured Power Supply Assets
Sponsored by
Power Topologies Quick
Reference Guide
☞ Download Now
Power Management
Lab Kit-Reinforcing
Power Supply Knowledge
Comprehensive collection
of Power Supply Design
white papers
☞
☞
View Lab Kit
Download
White Paper
☞ LEARN MORE @ electronicdesign.com/powermanagement | 26
POWER ELECTRONICS LIBRARY
PART 1. POWER SUPPLIES
CHAPTER 6:
POWER
SUPPLY
SYSTEM CONSIDERATIONS
O
verall design of the power-management
tronic system. They are powered from the ac power line
subsystem involves several system-orient- and produce a dc voltage output. They may provide one
ed issues. Adequate space must be avail- or multiple output voltages. These outputs then provide
power to the specific circuits that require the various
able for the selected power supply. Make
voltages. For most small, relatively low-power systems,
sure the power supply will fit in the space
centralized power distribution is usually the most costprovided for it. Therefore, make sure the
and performance-effective.
package type you want, such as open-frame, enclosed,
A typical centralized system is the type employed in
brick, encapsulated, etc., will fit in the allocated space.
desktop
computers; that is, a single supply provides all
In addition, make sure there is enough room adjacent to
the required voltages: +5V, ±12V. (Note: 3V is replacing
the power supply to allow it to cool if you are using natural
5V on many computers as the main
convection cooling. If you are using
logic voltage.) However, the cenforced air cooling, make sure that
+5V
Centralized
tralized approach can suffer from
you have sufficient air movement
+12V Electronic
power
system
lack of flexibility.
around the supply.
–12V
supply
+15V
If the system requires an
One aspect of space availadditional low voltage, the power
ability is the standards for size
management subsystem must be
of rack-mounted power systems,
6-1. Centralized Power Supply Can
redesigned by replacing the entire
such as 1U, 2U, 3U, etc. The term
Produce Multiple Voltage Outputs
centralized supply or adding a
1U defines one rack unit of height
voltage regulator derived from an existing output. If any
that equals 1.75 in. of rack height. A 2U rack mount
height would be 2 x 1.75 in., or 3.5 in. high, and so on.
existing supply voltage requires a higher current capabilThe 1U, 2U, and 3U heights are maximum dimensions.
ity, the centralized supply must be replaced.
Individual rack-mounted power supplies must be a
An advantage for the centralized power supply is the
bit shorter than the equipment’s overall height to allow
cost associated with powering a small to moderate size
for the top and bottom covers. So a 1U-high enclosystem. A single supply with multiple outputs can be
sure-mountable power supply needs to be shorter than
more cost-effective than a distributed supply with multi1.75 in.; a 2U enclosure-mountable supply needs to be
ple dc-dc converters.
shorter than 3.5 in., and so forth.
To minimize power distribution losses, the centralized
supplies should be located near the load. For safety and
Power Distribution
EMI reasons, it should be located as close as possible to
Distributing power in the end-item system depends on the ac entry point, which is often a problematic tradeoff.
the type of power supply used. Five different distribution
Although centralized power works well for many applicamethods are possible:
tions, it is usually unsuitable for distributing high power at
Centralized Power Architecture (Fig. 6-1) accepts an low voltages.
ac power line input and produces one or up to five output
A drawback of the centralized supply is its transient
voltages. As implied, centralized supplies operate from
response, which is the ability to react quickly to rapidly
a central location and supply all the power for an elecchanging loads. Centralized power systems may have
☞ LEARN MORE @ electronicdesign.com/powermanagement | 27
CHAPTER 6: POWER SUPPLY SYSTEM CONSIDERATIONS
POWER ELECTRONICS LIBRARY
difficulty responding to transient loads and handling
resistive voltage drops. Another potential problem is its
characteristic of concentrating heat in one specific area.
Distributed Power Architecture (DPA) (Fig. 6-2) converts the incoming ac power to a secondary dc bus voltage, using a front-end supply. This dc bus voltage can
be 12V, 24V, or 48V and is usually less than 60V. This bus
voltage is distributed throughout the system, connecting
to dc-dc converter modules associated with specific
subsystems or circuit cards
The most popular DPA voltage is 48V used by telecommunication systems. The secondary voltage is
bused throughout the system, connecting to dc-dc converter modules associated with specific subsystems or
circuit cards. You can locate the front-end supply either
in a card cage or in a convenient place within the system. For non-telephone applications, the trend is to use
lower intermediate bus voltages, ranging from 7V to 12V.
This is because as the speed and complexity of the digital circuits and microprocessors increase, their internal
spacings decrease, resulting in reduced input voltages
for these devices. Therefore, the secondary buses power
local dc-dc converters that output lower voltages. Higher-speed devices use lower voltages.
One common characteristic for front-end supplies is
power-factor correction (PFC) that lowers the peak currents drawn from the ac line. This reduces the harmonic
content fed back into the power line, which might otherwise interfere with other equipment connected to the
same power line.
Among the features of most front-end supplies is the
ability to work over a broad ac input voltage range, for
example, 85 to 265Vac. Some front-end supplies may be
paralleled to increase the available power. Some paralleled supplies may be combined in a 19-in. rack. Models
usually include protection features for overvoltage, overcurrent, short-circuit, and overtemperature.
Optional on-board intelligence on some front-end supplies is the ability to communicate with the host computer. Transmitted data can include operational status, such
as temperature, current limit, and installation location
identification.
Intermediate Bus Architecture (IBA) inserts another
level of power distribution between a front-end power
supply and POL. An IBA (Fig. 6-3) employs an isolated
bus converter that delivers an unregulated 9.6V to 14V
to power to the non-isolated POL converters. As shown
in Fig. 6-3, a typical bus converter delivers an unregulated, stepped-down voltage of 9.6 to 14V with a nominal
2000Vdc input output isolation. This converter is ideal for
a loosely regulated 12Vdc Intermediate Bus Architecture
110 Vac
Front-end
power
supply
48V
dc
Secondary
dc bus
voltage
NI=Non-isolated
POL=Point-of-load converter
NI
POL
P.C. board
NI
POL
P.C. board
NI
POL
P.C. board
6-2. Distributed Power Architecture Employs Front-End
Power Supply for Multiple POL Mounted on System P.C.
Boards
to power a variety of downstream non isolated, point of
load regulators. These modules are suited for computer
servers, enterprise networking equipment, and other
applications that use a 48V (+10%) input bus.
Cost savings can be achieved in many applications
by replacing multiple 48V in isolated dc-dc converters
with low-cost, non isolated POL modules or embedded
converters that are fed from the 12V bus converter rail.
Implementing one central point of isolation eliminates
the need for individual isolation at each point of load,
allowing reduced costs, greater flexibility, and savings on
board space.
Bus converters achieve high efficiency by limiting
the input range and essentially optimizing for a single
input voltage. Bus converters are designed for efficienPOL
System
dc-dc
converter
p.c. board
(non-isolated)
Front-end
power
supply
(isolated)
48V
bus
Bus
converter
(isolated)
12V
(Nominal)
POL
System
dc-dc
converter
p.c. board
(non-isolated)
POL
System
dc-dc
converter
p.c. board
(non-isolated)
6-3. Intermediate Bus Architecture Adds an Isolated
Bus Converter
☞ LEARN MORE @ electronicdesign.com/powermanagement | 28
CHAPTER 6: POWER SUPPLY SYSTEM CONSIDERATIONS
POWER ELECTRONICS LIBRARY
efficiency, which minimizes heat dissipation, resulting in
an adapter that is small and reliable. Without this high
efficiency, the resulting internal temperature rise would
be potentially hazardous and a major reliability limiter. In
many applications, the adapter may be placed in a confined space, or it may be buried under a pile of cable, so
minimizing heat is essential.
Battery-Based Power Distribution requires virtually all
circuits designed “from the ground up.” The power
management subsystem design involves voltage regulation circuits operating from a battery whose output
voltage naturally decreases with use.
Related Articles
6-4. TDK-Lambda’s medically certified DTM65-C8
external power supplies offer a class II input and do
not require an earth ground connection and meets the
stringent Level VI DoE standards for efficiency. It is
housed in a rugged, vent-free IP21 rated enclosure,
measuring 106 x 60 x 31mm. AC is applied using a
standard IEC60320-C8 cable and DC provided through
a four pin Power-DIN connector.
cy. Removing the entire feedback path (reference, error
amp, optocoupler, etc.) liberates board area and power.
Additional parallel MOSFETs may be added to lower
on resistances. MOSFET duty cycles in the power train
are set and maintained at 50%, and all components are
optimized for the voltages they will actually experience
and not the voltages they may experience. Also, for high
efficiency most bus converters employ synchronous
rectifier outputs.
Bus converter packages come in many sizes, from
SIPs and SMTs to quarter-brick, eigth-brick and sixteenth
brick modules.
AC Adapter’s distribute power external to the enditem system. They plug into an ac power outlet to provide dc power via a cable and connector that plugs into
the end item system. One of the widely used ac input
power supplies (Fig. 6-4). They are a cost effective and
relatively fast way to obtain a power source for computer
peripherals and other electronic devices without going
through power supply safety and EMI qualification tests.
All the OEM has to do is provide the appropriate connector within the associated equipment. Typically, many
printers and scanners operate from these adapters that
supply a regulated dc voltage. Laptop computers and
other portable equipment use these adapters to power
the unit as well as charge their battery.
It is important to obtain an adapter that has high
1. Sam Davis, 850W, Quarter Brick Bus Converter is 98%
Efficient, Works with Online Power Simulation Tool, PET, May,
2012.
2. Sullivan, Joe, Bus Converter Maximizes System Efficiency,
Minimizes Heat Losses, PET, March, 2011.
TABLE 6-1. COMPARISON OF POWER DISTRIBUTION
APPROACHES FOR ELECTRONIC SYSTEMS
Power
Distribution
Remarks
Centralized Power
Architecture
•Usually most cost- and performance-effective
for small, low-power systems.
• Most of the heat is centralized in a single power supply.
• Lacks design flexibility for adding voltages or
current requirements.
Distributed Power
Architecture (DPA)
• Changing load current or voltage usually
requires only a POL change.
• Failure of a single POL usually only affects a
single function or p. c. board.
• Heat is spread throughout the system.
Intermediate Bus
Architecture (IBA)
• Achieves high efficiency by limiting input voltage range and usually operating open-loop,
• Power train duty cycles usually maintained at
50%
• All components are optimized for load voltage/
current.
AC Adapter Power
Distribution
• Does not require power supply safety and EMI
qualification tests, which have been certified by
its manufacturer.
• Two types: linear and switch-mode. The switchmode adapter provides greater efficiency and
smaller size, whereas the linear power supply
adapter is less efficient and larger, but could
be “quieter,” that is, less radiated or conducted
EMI.
• Usually limited 100 W, or less.
Battery-based
Power Distribution
• Operates from Li-ion, NiCd or NiMH battery
packs.
• Provides high efficiency for maximum battery
run time
• Must have light weight, small physical size
power supplies
• Must be thermally efficient to prevent
overheating.
☞ LEARN MORE @ electronicdesign.com/powermanagement | 29
CHAPTER 6: POWER SUPPLY SYSTEM CONSIDERATIONS
POWER ELECTRONICS LIBRARY
3. David Morrison, Distributed Power Architectures Evolve and
Reconfigure, PET, December, 2004.
4. Steve Sandler, Assessing POL Regulators Using NonInvasive Techniques, PET, October, 2012.
5. Davis, Sam, Automatically Compensated POL Controller IC
Integrates PMBus Compatibility, PET, November, 2011.
6. David Morrison, POL Breaks New Ground with Integrated
Magnetics, PET, October, 2004.
7. David Morrison, Design Technique Models POL Performance,
PET, April, 2004.
8. Sam Davis, Power Integrity: Measuring, Optimizing, and
Troubleshooting Power Related Parameters in Electronics
Systems, PET, July, 2014.
9. Sam Davis, Digital Power Supply Controller Enables “On the
fly” Firmware Upgrades, PET, May, 2013.
10. Bell, Bob, Topology Key to Power Density in Isolated DCDC Converters, PET, February, 2011.
☞
BACK TO TABLE OF CONTENTS
Featured Power Supply Assets
Sponsored by
Power Topologies Quick
Reference Guide
☞ Download Now
Power Management
Lab Kit-Reinforcing
Power Supply Knowledge
Comprehensive collection
of Power Supply Design
white papers
☞
☞
View Lab Kit
Download
White Paper
☞ LEARN MORE @ electronicdesign.com/powermanagement | 30
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement