Texas Instruments | DC/DC Buck Converters With Ultra-Low IQ for Industrial Battery-Pack Applications | Application notes | Texas Instruments DC/DC Buck Converters With Ultra-Low IQ for Industrial Battery-Pack Applications Application notes

Texas Instruments DC/DC Buck Converters With Ultra-Low IQ for Industrial Battery-Pack Applications Application notes
Using DC/DC Buck Converters With Ultra-Low Quiescent
Current for Industrial Battery-Pack Applications
Gautam Hari
E-bikes, drones, and hand-held power electronic
applications such as vacuum cleaners and power
tools, are powered using high cell count Lithium-ion
stack battery packs. The voltages for these battery
packs can be as high as 20S (~72 V) and in some
cases, even higher due to charging and transients
generated in the system. Consumer electronics with
battery packs are built with a viewpoint to improve user
experience that, in one way, is achieved by extended
battery life. The auxiliary power supply requires a
unique design to ensure high transient voltage and low
quiescent current requirements are satisfied.
Selecting a highly efficient, wide VIN range DC/DC
converter with low IQ can help provide outstanding user
experience in the form of longer battery life with fewer
charge and discharge cycles. This application note
describes industrial battery pack architectures and
their requirements while highlighting the benefits of
using the LM5163 (0.5-A) and LM5164 (1-A) family of
synchronous buck converters for these applications.
Understanding Industrial Battery-pack Systems
Figure 1 is a system-level block diagram of a batterypack application with protection, gauge, and
communication functionality. The auxiliary power
supply block, highlighted in red, consists of a lowdropout linear regulator (LDO) and a buck DC/DC
converter to power various sub-systems integrated
within the battery pack, such as communications and
battery management sub-systems.
Innovative industrial battery packs often require:
• Reliable indication of real-time battery capacity and
state-of-health
• Robust and complete protection for overvoltage,
excessive temperature, and overcurrent
• Low idle and standby current consumption during
transportation and storage
There are typically two modes of operation for the
battery pack system associated with maximizing
battery life:
• Idle Mode: The system is being shipped and all
integrated chips are turned off.
• Standby Mode: Diagnostic circuits are always
powered on with the load currents extremely low.
SNVA867 – June 2019
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Figure 1. High-cell Battery-pack System Block
Diagram
Auxiliary Power Supply Requirements
The auxiliary power supply, built to support up to 5 W
output power, is used to facilitate the idle and standby
modes of operation while the main power supply (not
included in Figure 1) is used to provide power in the
full-load mode. To facilitate its operation in idle and
standby modes, it is imperative to choose the right
DC/DC converter for the auxiliary power supply.
Standby mode requires always-on state-of-health
(SOH) diagnostics where internal circuits are always
powered on to ensure battery health and proper
functionality. The system could also be in idle mode
when in transportation and all internal circuits are
turned off. In both cases, the system must ensure
minimal current consumption from the battery to
ensure its long lifetime and improve user experience.
An efficient way to accomplish this task is to use a
DC/DC converter with low shutdown and standby
currents and high efficiency that can sustain a wide VIN
range when connected directly to the battery.
Auxiliary Power Supply Solution
The LM5163 and LM5164 family of synchronous buck
DC/DC converters provide innovative solutions for
high-cell count battery applications. Based on the
schematic of Figure 2, the converters are designed to
regulate over a wide input voltage range up to 100 V.
Using DC/DC Buck Converters With Ultra-Low Quiescent Current for
Industrial Battery-Pack Applications Gautam Hari
Copyright © 2019, Texas Instruments Incorporated
1
www.ti.com
LO
68 µH
VIN = 6 V...100 V
VIN
EN
BST
RON
GND
VOUT = 12 V
IOUT = 1 A
0
0
RFB2
49.9 k:
PGOOD
100
90
80
70
60
50
VIN = 14V
VIN = 24V
VIN = 48V
VIN = 72V
0.1
20
30
40
50
60
Input Voltage (V)
70
80
90
100
D006
High-Cell Battery-Pack System Implementation
As shown in Figure 3, a synchronous switching
converter like the LM5163 and LM5164 in high
conversion ratio applications offers a larger light-load
efficiency (above 80%) relative to the higher power
dissipation of the external diode with a nonsynchronous converter.
40
10
Figure 4. LM5164 Typical IQ vs. VIN
Figure 2. LM5164 Converter Typical Schematic
1
Load (A)
With a well-designed auxiliary power supply that
incorporates a high efficiency, low IQ DC/DC buck
converter, Texas Instruments' Accurate Gauging and
50 μA Standby Current, 13S, 48-V Li-ion Battery Pack
Reference Design achieves 50-μA standby and 15-μA
"ship" mode current consumption, saving more energy
and allowing longer ship time and idle time.
This reference design enables high state-of-charge
(SOC) gauging accuracy using a 13S, 48-V Li-ion
battery pack. It monitors each cell voltage, peak
current, and temperature with high accuracy and
protects the Li-ion battery pack against overvoltage,
undervoltage, overtemperature, and overcurrent
situations. Based on the BQ34z100-G1, the SOC
gauging takes advantage of an impedance-tracking
algorithm and achieves as high as 2% accuracy at
room temperature.
The reference design uses a low-cost, 2-layer PCB
and supports an optimized firmware that enables
reduced product development time.
Figure 3. LM5164 Converter Efficiency, VOUT = 12 V
An ultra-low shutdown current specification of 6 μA at
48-V input (see Figure 4) enables extended battery life
when in idle mode, and its low operating quiescent
current specification of 10 μA ensures minimum
battery discharge when diagnostics are active. Even
though an LDO can provide the same low IQ
performance, it cannot deliver high efficiency (above
75%) at light loads or support ultra-high efficiency
(above 85%) at heavier loads.
Placed in a popular low pin count (8-pin) SOIC leaded
package, the LM5163 and LM5164 converters require
few external components and can be designed with
reduced system complexity and solution cost.
2
10
5
FB
0.01
15
COUT
47 µF
* VOUT tracks VIN if VIN < 12 V
Efficiency (%)
Sleep
Shutdown
20
CBST
2.2 nF RFB1
448 k:
RRON
105 k:
30
0.001
25
SW
LM5164
CIN
2.2 µF
The SOIC leaded package pin-pitch is 1.27 mm and
satisfies the 1-mm spacing requirement dictated by
IPC-9592B for high-voltage designs up to 100 V.
Quiescent Current (PA)
This alleviates the need for transient suppression
when motor-generated back-EMF returns energy to
the input bus that results in transient spikes at the
input of the DC/DC converter. With a minimum
controllable on-time of 50 ns, the LM5163 and LM5164
converters enable the direct step-down from a high
cell-count battery pack to low-voltage rails.
Table 1. Buck Converter Recommendations
Device
VIN Range,
Rated IOUT
Performance
Feature
Package
LM5163
6 V to 100 V, 0.5 A
Wide VIN, low IQ
SO-8
LM5164
6 V to 100 V, 1 A
Wide VIN, low IQ
SO-8
LMR36006
4.2 V to 60 V, 0.6 A
Low EMI, low IQ
VQFN-12
LM5166
3.5 V to 65 V, 0.5 A
Low EMI, low IQ
VSON-10
Table 2. Related TI Application Notes
SNVA804
IC Package Features Lead to Higher Reliability in
Automotive and Communications Equipment Systems
SNVA806 Powering Drones With a Wide VIN DC/DC Converter
Using DC/DC Buck Converters With Ultra-Low Quiescent Current for
Industrial Battery-Pack Applications Gautam Hari
Copyright © 2019, Texas Instruments Incorporated
SNVA867 – June 2019
Submit Documentation Feedback
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