AC/DC Switch Mode Power Supply
Design Guide
www.fairchildsemi.com
AC/DC Switch Mode Power Supply Design Guide
Table Of Contents
Product Information
Total Solutions.........................................................................................................................................3
Fairchild Power Switch (FPS™) ...............................................................................................................4-5
Pulse Width Modulator (PWM) Controllers .................................................................................................6
Power Factor Correction (PFC) Controllers..................................................................................................7
Optocoupler Solutions .............................................................................................................................8
Voltage References and Shunt Regulators ...................................................................................................9
High Voltage Switching Technologies.......................................................................................................10
Switch Mode Power Supply IGBTs...........................................................................................................10
High-Voltage MOSFETs ..........................................................................................................................11
Additional Discrete Components .............................................................................................................12
Design Examples
Examples of Typical Application Circuits .............................................................................................13-22
1W Power Supply with less than 100mW Standby Power using FSD210 ..........................................13
Dual Negative Output Non-Isolated Flyback using FSD200...............................................................14
10W Single Output Isolated Flyback using FSDM0265RN and Zener Diode .....................................15
10W Multiple Output Isolated Flyback using FSD210 with Primary Side Regulation ...........................16
2.5W Single Output Isolated Flyback using FSD200 with KA431 Reference......................................17
180W-200W Quasi-Resonant Flyback with Input Power Factor Correction using KA5Q1265RF,
FAN7527B, and FQP13N50C ....................................................................................................18-19
16W Multiple Output Isolated Flyback Converter using FSDM0265RN .............................................20
40W Isolated Flyback Power Supply using FSDM07652R ................................................................21
24W Flyback Converter using 1500V IGBT and FAN7554 ..............................................................22
Design Ideas
250W to 450W Desktop PC Forward Switch Mode Power Supply.......................................................23
500W Telecom/Server Double Switch Forward Switch Mode Power Supply..........................................24
500W Telecom/Server ZVS Phase-Shift Full Bridge Switch Mode Power Supply .....................................25
Application Note Highlights
Design Guidelines for Off-Line Flyback Converters using Fairchild Power Switch (FPS) – AN-4137 ............26-27
Power Factor Correction (PFC) Basics – AN-42047...................................................................................28
Choosing Power Switching Devices for SMPS Designs – AN-7010........................................................29-30
Global Power Resources™
Design Support .....................................................................................................................................31
www.fairchildsemi.com/acdc
1
2
AC/DC Switch Mode Power Supply Design Guide
Total Solutions
Fairchild is the only semiconductor supplier that provides a complete portfolio for AC/DC switch mode power supplies.
Whether your design is 1W or 1200W, Fairchild's solutions help achieve increased efficiency, reduce stand-by power,
and support the industry's 1W initiatives. These solutions include: SuperFET™ technology that achieves world-class
RDS(ON) and provides higher power density, reducing heat sink size, Green Fairchild Power Switch (FPS) that offers
state-of-the-art stand-by power supporting the industry's initiatives targeting less than 1W, and Power Factor Correction
ICs that decrease cost and increase system efficiency.
SMPS IGBTs
High Voltage MOSFETs
• Increase output power
• Reduce system cost
• Stealth™ Diode Co-Pack enhances
recovery time
•
•
•
•
25% lower A * RDS(ON) minimizes system size
100% Avalanche tested
Voltage ranges from 60V to 1000V
SuperFET offers best in class FOM
Power Factor Correction (PFC) Controllers
Additional Discrete Components
Voltage References/Shunt Regulators
• Increase efficiency
• Increase usable PFC bandwidth and
simplifiy compensation
• Reduce ripple voltage and output
capacitor size
• Reduce EMI and system noise
• Low-Voltage MOSFETs
• MOSFET and Schottky Combos
• Diodes and Rectifiers
• Bipolar Transistors and JFETs
•
•
•
•
PFC Controller
or PFC/PWM
Controller
AC
Input
Input
Filter
MOSFET/
IGBT
Switch
MOSFET
Switch
Bridge
Rectifier
PWM Controller
Transformer
Fairchild
Power Switch
Output
Rectifier
or MOSFET
Optocoupler
Programmable output voltages
Temperature compensated
Low output noise
Fast turn-on time
Output
Filter
Load
Voltage
Reference
Optically Isolated
Error Amplifier
PWM Controller
• Gr een c u r r en t m o d e r ed u c es p o w er
c o n s u m p t i o n w i t h b u r s t m o d e o p er at i o n
• In t er n al s t ar t -u p s w i t c h
• Pr o g r am m ab l e s o f t s t ar t
• Ov er Vo l t ag e Pr o t ec t i o n (OVP)
Optically Isolated Error Amplifier
Fairchild Power Switch (FPS)
• Green FPS reduces power consumption with
burst mode operation
• Avalanche rated SenseFET™
• Frequency modulation reduces EMI
• Built in soft start
www.fairchildsemi.com/acdc
3
• Single component solution vs. 2 components
• High isolation, 5,000V RMS
• Low tolerance results in easier design, fewer
components
• Save board space
Optocoupler
• MICROCOUPLER™ offers stable CTR up to 125°C
• Narrow Current Transfer Ratio (CTR)
• Multiple package types for ease of use
AC/DC Switch Mode Power Supply Design Guide
Fairchild Power Switch (FPS)
Fairchild's FPS products are highly integrated off-line power switches with a fully avalanche rated SenseFET and a
current mode PWM IC (see Burst Mode Operation figure below). The Green FPS products help reduce the system's
stand-by power to below 1Watt with the burst mode operation.
• Advanced burst mode operation supports 1W standby power regulations
• Integrated frequency modulation reduces EMI emissions
FPS Parallel Dice Solution
(Side-by-Side)
Ipk
FB
Vcc
GND
FPS Single Die Solution
(BCDMOS)
VFB
GND
GND
GND
Drain
Vstr
• Various protection and control functions reduce Bill-of-Material costs
PWM
IC
SenseFET
Burst Mode Operation Reduces Stand-By
Power to Less than 1W
Vstr
Drain
Drain
Drain
Vcc
Burst
Operation
Feedback
Waveform
Normal Operation
VBURSTH
VBURSTL
Current
Waveform
Not
Switching
Not
Switching
Frequency Modulation Reduces Overall
Electromagnetic Interference (EMI)
Peak Level Limit
Peak Level Limit
Peak Waveform
Quasi Peak Waveform
100kHz
100kHz Fixed
FixedFrequency
Frequency
FSDH0165
FSDH0165
134kHz
Modulation
134kHzwith
withFrequency
Frequency
Modulation
FSD210
FSD210
EMI reduction can be accomplished by modulating the switching frequency of a SMPS.
Frequency modulation can reduce EMI by spreading the energy over a wider frequency range.
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4
AC/DC Switch Mode Power Supply Design Guide
Fairchild Power Switch (FPS)
Green FPS
Part
Number
Application
PO(max) (W)
85-265VAC
PO(max) (W)
230VAC ±15%
Peak Current HV-FET Rating
Limit (A)
(V)
RDS(ON) max (Ω)
Switching
Frequency (V)
Frequency
Mod. (kHz)
Package
TO220-5L
FSCM0565RC
STB, LCD Monitor
70
85
2.5
650
2.2
66
Yes
FSCM0565RD
STB, LCD Monitor
50
65
2.5
650
2.2
66
Yes
D2PAK-5L
FSCM0765RC
STB, LCD Monitor
85
95
3
650
1.6
66
Yes
TO220-5L
FSCM0765RD
STB, LCD Monitor
60
70
3
650
1.6
66
Yes
D2PAK-5L
FSCQ0765RT
CTV, DVD, Audio Electronics
85
100
5
650
1.6
QRC
No
TO220F-5L
FSCQ1265RT
CTV, DVD, Audio Electronics
140
170
7
650
0.9
QRC
No
TO220F-5L
FSCQ1565RP
CTV, DVD, Audio Electronics
210
250
11.5
650
0.65
QRC
No
TO3PF-7L
FSCQ1565RT
CTV, DVD, Audio Electronics
170
210
8
650
0.65
QRC
No
TO220F-5L
FSD1000
PC Main + Aux , LCD
12
13.6
Adjustable
700
9
70
No
DIPH-12
FSD200B
Charger, Aux Power
5
7
0.3
700
32
134
Yes
LSOP-7
FSD200BM
Charger, Aux Power
5
7
0.3
700
32
134
Yes
DIP-7
FSD210B
Charger, Aux Power
5
7
0.3
700
32
134
Yes
DIP-7
FSD210BM
Charger, Aux Power
5
7
0.3
700
32
134
Yes
LSOP-7
FSDH0265RL
DVDP, STB, Fax, Printer,
Scanner, Adapters
20
27
1.5
650
6
100
Yes
LSOP-8
FSDH0265RN
DVDP, STB, Fax, Printer,
Scanner, Adapters
20
27
1.5
650
6
100
Yes
DIP-8
PC Aux, STB, DVD,
12
17
0.7
650
19
100
Yes
DIP-8
PC Aux, STB, DVD,
Adapters
12
17
0.7
650
19
100
Yes
LSOP-8
FSDL0165RL
DVDP, STB, Printer, Fax,
Scanner, Adapters
12
23
1.2
650
10
50
Yes
LSOP-8
FSDL0165RN
DVDP, STB, Printer, Fax,
Scanner, Adapters
12
23
1.2
650
10
50
Yes
DIP-8
FSDL0365RL
DVDP, STB, Printer, Fax,
24
30
2.15
650
4.5
50
Yes
LSOP-8
24
30
2.15
650
4.5
50
Yes
DIP-8
12
17
0.7
650
19
50
Yes
DIP-8
12
17
0.7
650
19
50
Yes
LSOP-8
FSDM0265RNB DVDP, STB, Fax, Printer,
Scanner, Adapters
20
27
1.5
650
6
67
Yes
DIP-8
FSDM0365RL
DVDP, STB, Fax, Printer,
Scanner, Adapters
24
30
2.15
650
4.5
67
Yes
LSOP-8
FSDM0365RNB DVDP, STB, Fax, Printer,
Scanner, Adapters
24
30
2.15
650
4.5
67
Yes
DIP-8
FSDH321
Adapters
FSDH321L
Scanner, Adapters
FSDL0365RNB
DVDP, STB, Printer, Fax,
Scanner, Adapters
FSDL321
PC Aux, STB, DVD,
Adapters
FSDL321L
PC Aux, STB, DVD,
Adapters
FSDM0565RB
LCD ,STB, Adapters
48
56
2.3
650
2.2
66
No
TO220F-6L
FSDM07652RB
LCD ,STB, Adapters
56
64
2.5
650
1.6
66
No
TO220F-6L
FSDM311
Aux Power, Adapters
12
20
0.55
650
19
70
No
DIP-8
FSDM311L
Aux Power, Adapters
12
20
0.55
650
19
70
No
LSOP-8
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5
AC/DC Switch Mode Power Supply Design Guide
Pulse Width Modulator (PWM) Controllers
Similarly to Green FPS, the FAN7601, FAN7602, and 7610 are green PWM controllers, offering burst mode operation
during stand-by mode allowing the design to meet the International Energy Agency's (IEA) "1-Watt Initiative".
• Burst mode operation
• Operating frequency of up to 300kHz
• Operating current 4mA (max)
• Programmable soft start 20mS
Burst Mode Operation Diagram
VO
Burst mode operation: In order to minimize the power dissipation
in standby mode, the Green PWMs implement burst mode
functionality. As the load decreases, the feedback voltage
decreases. As shown in the figure, the device automatically enters
burst mode when the feedback voltage drops below VBURL. At this
point switching stops and the output voltages start to drop at a
rate dependent on standby current load. This causes the feedback
voltage to rise. Once it passes VBURH switching starts again. The
feedback voltage falls and the process repeats. Burst mode operation
alternately enables and disables switching of the power MOSFET
thereby reducing switching loss in standby mode.
VFH
VBURH
VBURL
Ids
Vds
Time
PWM Controllers
Part
Number
Number of
Outputs
Control
Mode
Switching
Frequency (kHz)
Supply Voltage
Max (V)
Output Current
Max (A)
Duty
Ratio (%)
FAN7554
1
Current
500
FAN7601*
1
Current
300
FAN7602*
1
Current
FAN7610*
1
Current
KA3524
–
Voltage
KA3525A
2
Voltage
Startup
Current (µA)
30
1
98
200
SO-8
20
0.25
98
Internal Switch
DIP-8, SO-8, SSOP-10
65
20
0.25
75
Internal Switch
DIP-8, SO-8, SSOP-10
QRC
20
0.5
–
Internal Switch
DIP-14, SO-14
350
40
0.1
–
8000
DIP-16
-
40
0.5
–
8000
DIP-16
Package
KA3842A
1
Current
500
30
1
100
200
DIP-8, SO-14
KA3842B
1
Current
500
30
1
100
450
DIP-8, SO-14
KA3843A
1
Current
500
30
1
100
200
DIP-8, SO-14
KA3843B
1
Current
500
30
1
100
450
DIP-8, SO-14
KA3844B
1
Current
500
30
1
50
450
DIP-8, SO-14
KA3845
1
Current
500
30
1
50
450
DIP-16
KA3846
2
Current
500
40
0.5
100
200
DIP-16
KA3882E
1
Current
500
30
1
100
200
SO-8
KA7500C
2
Voltage
300
42
0.25
–
1000
DIP-16, SO-16
KA7552A
1
Voltage
600
30
1.5
74
150
DIP-8
KA7553A
1
Voltage
600
30
1.5
49
150
DIP-8
KA7577
1
Voltage
208
31
0.5
53
150
DIP-16
ML4823
1
Voltage
1000
30
–
80
1100
DIP-16, SO-16
NOTE: FAN7602 and FAN7610 under development
*Burst Mode Operation reduces system standby power to 1W or less
www.fairchildsemi.com/acdc
6
AC/DC Switch Mode Power Supply Design Guide
Power Factor Correction (PFC) Standalone and PFC/PWM Combo Controllers
Fairchild’s full line of both stand alone PFC controllers and PFC/PWM combo controllers offer crucial cost-and energysaving solutions that address the demanding requirements of a diverse range of medium-and high-power Switch Mode
Power Supply (SMPS) designs.
• Offerings include both continuous/discontinuous devices
• Current fed gain modulator for improved noise immunity
• Synchronized clock output to reduce system noise and to synchronize to downstream converter
• Patented one-pin voltage error amplifier with advanced input
180
9
8
160
8
7
140
120
6
120
6
100
5
100
5
80
4
80
4
3
60
3
40
2
40
2
20
1
20
0
0
0
60
VIN
IIN
7
VIN
1
IIN
Before Power Factor Corrected
Current
Voltage
140
Current
9
VCAP
160
Voltage
180
0
After Power Factor Corrected
Simplified Application Circuits
DC VOUT
AC VIN
AC VIN
DC VOUT
FPS
PFC
PFC/PWM
Combo
PMW
Optocoupler
Reference
Optocoupler
Reference
Stand-Alone PFC Controllers
PFC/PWM Combo Controllers
Power Factor Correction Stand-Alone Controllers
Part
Number
PFC Control
Operating Current
(mA)
Startup Current
(µA)
Package
FAN7527B
Discontinuous Mode
3
60
DIP-8, SOP-8
FAN7528
Discontinuous Mode
2.5
40
DIP-8, SOP-8
KA7524B
Discontinuous Mode
6
250
DIP-8, SOP-8
KA7525B
Discontinuous Mode
4
200
DIP-8, SOP-8
KA7526
Discontinuous Mode
4
300
DIP-8, SOP-8
ML4821
Average Current Mode
26
600
DIP-18, SOIC-20
FAN4810
Average Current Mode
5.5
200
DIP-16, SOIC-16
FAN4822
Average Current Mode
22
700
DIP-14, SOIC-16
Fpwm Over
Fpfc
Operating Current
(mA)
PWM Duty Cycle
Max (%)
Power Factor Correction Combo Controllers
Part
Number
FAN4800
PFC Control
Startup Current
(µA)
Package
Average Current Mode
1
5.5
49
200
DIP-16, SOIC-16
FAN4803-1
Input Current
Shaping Mode
1
2.5
50
200
DIP-8, SOIC-8
FAN4803-2
Input Current
Shaping Mode
2
2.5
50
200
DIP-8, SOIC-8
ML4824-1
Average Current Mode
1
16
50
700
DIP-16, SOIC-16
ML4824-2
Average Current Mode
2
16
45
700
DIP-16, SOIC-16
ML4826
Average Current Mode
2
22
50
700
DIP-20
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7
AC/DC Switch Mode Power Supply Design Guide
Optocoupler Solutions
The MICROCOUPLER™ package platform of optocouplers reduces board space and offers stable CTR up to 125°C,
while offering high input to output isolation voltages.
• High Current Transfer Ratio, CTR at low IF
• Operating Temperature Range, Topr: -40°C to +125°C
• Ultra small packaging – low profile 1.2mm
• Applicable to Pb-free IR reflow soldering profile: 260°C peak
Normalized CTR @ 25°C
1.2
1
0.8
0.6
0.4
0
-40
BGA Package
MICROCOUPLER™
4-Pin DIP Package
0.2
0
26
40
56
NOTE: under devlopement
70
110
90
125
Temperature (°C)
For a complete listing of Fairchild’s Optocouplers please visit:
www.fairchildsemi.com/products/opto
Optically Isolated Error Amplifiers
Fairchild's FOD27XX series optically isolated error amplifiers offer designers a comprehensive selection of reference voltages,
tolerances, isolation voltages and package sizes to optimize their specific power design.
Shunt
Reference
FOD27XX
Transistor
Optocoupler
FOD27XX
VCC
+
_
=
To Primary
+
Comp
From Secondary
NOTE: FOD2743 is a reverse pin-out
Optical Amplifiers
Part
Number
VREF (V)
Tolerance (%)
Isolation (kV)
Package
Operating
Temperature (°C)
CTR* (%)
Bandwidth (kHz)
30
FOD2711
1.24
1
5.0
DIP-8
-40 to +85
100 – 200
FOD2741
2.5
0.5 – 2.0
5.0
DIP-8
-25 to +85
100 – 200
30
FOD2743
2.5
0.5 – 2.0
5.0
DIP-8
-25 to +85
50 – 100
50
* CTR is specified at ILED = 1mA
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8
AC/DC Switch Mode Power Supply Design Guide
Voltage References and Shunt Regulators
Fairchild's suite of voltage references/shunt regulators offer flexible output voltages, space saving packages, and
multiple voltage tolerances to meet the challenges of a SMPS design.
• Programmable output voltages
• Temperature compensated
• Low output noise
• Fast turn-on time
Regulators
Part
Number
Preset Output
Voltage (V)
Adj. Output
Adj. Output
Voltage (Min) (V) Voltage (Max) (V)
Tolerance (V)
Max
Current (mA)
Package
FAN4041CI
Adjustable
1.22
12
0.5
30
SOT-23
FAN4041DI
Adjustable
1.22
12
1
30
SOT-23
FAN431
2.5 Adjustable
2.5
3
2
100
TO-92
KA431S
2.5 Adjustable
2.5
37
2
100
SOT-23F
LM336Bx5
5 Adjustable
4
6
2
15
TO-92
LM336x25
2.5
2.5
37
2
15
TO-92
LM336x5
5 Adjustable
4
6
4
15
TO-92
LM431A
2.5 Adjustable
2.5
37
2
100
SOIC-8, TO-92
LM431B
2.5 Adjustable
2.5
37
1
100
SOIC-8, TO-92
LM431C
2.5 Adjustable
2.5
37
0.5
100
SOIC-8, TO-92
LM431SA
2.5 Adjustable
2.5
37
2
100
SOT-23F, SOT-89
LM431SB
2.5 Adjustable
2.5
37
1
100
SOT-23F, SOT-89
LM431SC
2.5 Adjustable
2.5
37
0.5
100
SOT-23F, SOT-89
RC431A
Adjustable
1.24
12
1.5
20
SOT-23, TO-92
TL431A
2.5 Adjustable
2.5
37
1
100
SOIC-8, TO-92
TL431CP
2.5 Adjustable
2.5
37
2
100
DIP-8
www.fairchildsemi.com/acdc
9
AC/DC Switch Mode Power Supply Design Guide
High Voltage Switching Technologies
Fairchild offers an array of switching solutions for each application
Switch
QFET
IGBT
SMPS IGBT
SuperFET™
Higher
Switching Frequency
Lower
Lower
Wattage
Higher
Switch Mode Power Supply IGBTs
Fairchild's SMPS IGBTs are optimized for switch mode power supply designs offering better VSAT/EOFF. Additionally,
this control smooths the switching waveforms for less EMI. SMPS IGBTs are manufactured using stepper based technology
which offers better control and repeatability of the top side structure, thereby providing tighter specifications.
SMPS IGBTs vs. MOSFETs
• Reduce conduction losses due to low saturation voltage
• Reduce current tail, reduces switching losses
• Improve transistor and system reliability
• IGBT advantage in current density facilitates higher output power
Reduce System Cost
• Smaller die size for higher voltages reduces overall costs
• May often eliminate components
• Increase operating frequency and reduce transformer/filter cost
• Fastest switching IGBTs in the market today
Stealth™ Diode Co-Pack
Diode Recovery Comparative Data
• Avalanche energy rated
• Offers soft recovery switching (S = tb/ta>1) at rated current, high
TJ = 125°C, IF = 13.5A,
di/dt = 90A/µs, VR = 400V
switching di/dt, and hot junction temperature (125°C)
charge (QRR) and reduced Irrm
Current
Irrm (Stealth)
• Maximize IGBTs efficiency with the improved lower reverse recovery
0
VCE = 100V/div
• Reduces switching transistor turn-on losses in hard switched applications
• Reduces EMI
Irrm (Competitor)
ICE = 5A/div
• Offers reverse recovery times (trr) as low as 25ns – superior to fast
Time = 25ns/div
recovery diode MOSFETs
• Elimination of snubber circuit becomes possible
• Improved device efficiency with the improved lower reverse recovery charge (QRR) and reduced Irrm
• Reduces switching transistor turn-on losses in hard switched applications
www.fairchildsemi.com/acdc
10
AC/DC Switch Mode Power Supply Design Guide
High-Voltage MOSFETs
SuperFET and QFET technologies are high voltage MOSFETs from Fairchild with outstanding low on-resistance and low
gate charge performance, a result of proprietary technology utilizing advanced charge balance mechanisms.
• Ultra-low RDS(ON) (0.32Ω), typical
Packages
• Best-in-class di/dt (1430A/µs, max)
• Low output capacitance (Coss = 35pF, typical)
TO-3P
Fairchild MOSFET Technology Comparison
FOM (FOM = RDS(on) x Qg)
50
D2-PAK
45
FQP8N60C
RDS(ON) 0.975
Qg
27.0 nC
40
35
30
25
20
15
10
FQP7N60
R DS(ON) 0.80 Ω
Qg
29.0 nC
FQP5N50C
RDS(ON) 1.072 Ω
18.0 nC
Qg
FQP19N20C
RDS(ON) 0.135 Ω
40.5 nC
Qg
FQP11N40C
RDS(ON) 0.43 Ω
28.0 nC
Qg
FQP19N20
R DS(ON) 0.12 Ω
Qg
31.0 nC
FQP11N40
RDS(ON) 0.38 Ω
Qg
27.0 nC
FQP7N80
RDS(ON) 1.20
Qg
40.0 nC
FQP7N80C
RDS(ON) 1.59 Ω
27.0 nC
Qg
FQP5N50
RDS(ON) 1.36 Ω
Qg
13.0 nC
D-PAK
TO-126
TO-247
FQP18N20V2
R DS(ON) 0.12 Ω
Qg
20.0 nC
QFET
QFET C-series
FCP11N60
R DS(ON) 0.32 Ω
40.0 nC
Qg
FQP18N50V2
R DS(ON) 0.23 Ω
Qg
42.0 nC
5
QFET V2-series
SuperFET
TO-92
0
200
400
500
600
800
TO-220
Voltage
MOSFET Selection Table
VDSS
Specification
200V
RDS(ON), typ (Ω)
RDS(ON), max (Ω)
8-SOP
QFET™
C-Series
V2-Series
FQP19N20
FQP19N20C
FQP18N20V2
0.12
0.135
0.12
SuperFET™
–
0.15
0.017
0.14
–
Qg, typ (nC)
31.00
40.50
20.00
–
Qgd, typ (nC)
13.50
22.50
10.00
–
–
400V
FQP11N20
FQP11N40C
RDS(ON), typ (Ω)
0.38
0.43
–
–
RDS(ON), max (Ω)
0.48
0.53
–
–
Qg, typ (nC)
27.00
28.00
–
–
Qgd, typ (nC)
12.30
15.00
–
–
FQP5N50
FQP5N50C
FQP18N50V2
RDS(ON), typ (Ω)
1.36
1.072
0.23
–
RDS(ON), max (Ω)
1.80
1.40
0.265
–
13.00
18.00
42.00
–
500V
Qg, typ (nC)
Qgd, typ (nC)
6.40
9.70
14.00
–
FQP7N60
FQP8N60C
–
FCP11N60
RDS(ON), typ (Ω)
0.8
0.975
–
0.32
600V
RDS(ON), max (Ω)
1.00Ω
1.2Ω
–
0.38
Qg, typ (nC)
29.00
28.00
–
40.00
Qgd, typ (nC)
14.50
12.00
–
21.00
–
800V
FQP7N80
FQP7N80C
–
RDS(ON), typ (Ω)
1.2
1.59
–
–
RDS(ON), max (Ω)
1.5
1.9
–
–
Qg, typ (nC)
40.00
27.00
–
–
Qgd, typ (nC)
20.00
10.60
–
–
www.fairchildsemi.com/acdc
11
TO-3PF
I2-PAK
I-PAK
8-DIP
TO-264
TO-92L
TO-220F
SOT-223
AC/DC Switch Mode Power Supply Design Guide
Additional Discrete Components
Fairchild is a leading supplier of discrete components providing a broad portfolio in an array of packages and functions
to meet each design need, including:
Discrete BGA
Packaging
• Low-voltage MOSFETs
• Low-voltage MOSFET and Schottky combos
• Diodes and rectifiers
– Schottky
– Bridge
Discrete FLMP
Packaging
– Small signal
– Zener
• Bipolar transistors and JFETs
Low-voltage MOSFET BGAs combine small footprint, low profile, low RDS(ON), and low thermal resistance to effectively
address the needs of space-sensitive, performance-oriented load management and power conversion applications.
For additional information on Fairchild’s BGA packaging and product selection, visit www.fairchildsemi/products/
discrete/power_bga.html
Fairchild’s patented FLMP packaging eliminates conventional wire-bonds and also provides an extremely low thermal
resistance path between the PCB and the MOSFET die (drain connection). This can greatly improve performance
compared to many other MOSFET packages by reducing both the electrical and the thermal constraints. For additional
information on Fairchild’s FLMP packaging and product selection, visit www.fairchildsemi/products/discrete/flmp.html
Package Impedance Comparisons
Package
Description
Ldd (nH)
Lss (nH)
Lgg (nH)
Rd (mΩ)
Rs (mΩ)
Rg (mΩ)
2 x 2.5mm BGA
0.056
0.011
0.032
0.05
0.16
0.79
4 x 3.5mm BGA
0.064
0.006
0.034
0.02
0.06
0.95
5 x 5.5mm BGA
0.048
0.006
0.041
0.01
0.04
0.78
FLMP (Large 3s)
0.000
0.744
0.943
0.002
0.245
2.046
FLMP (Large 7s)
0.000
0.194
0.921
0.002
0.137
2.038
SO-8
0.457
0.901
1.849
0.12
2.04
20.15
1.77
SO-8 Wireless
0.601
0.709
0.932
0.16
0.23
IPAK (TO-251)
2.920
3.490
4.630
0.25
0.74
8.18
DPAK (TO-252)
0.026
3.730
4.870
0.00
0.77
8.21
D2PAK (TO-263)
0.000
7.760
9.840
0.00
0.96
12.59
www.fairchildsemi.com/acdc
12
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
1W Power Supply with less than 100mW Standby Power using FSD210
Typical Application – Small home or factory automation appliances
Lp = 1200µH 94/9/2 EF13 (on Vogt Fi324 core)
T1
EF13 VOGT 6PIN
L100
1
D103
P6KE150A
Pm = 600W
D101
1N4007
FS1
230V/250mA
9V/100mA output
6
D201
1
2
3
4
5
3
4
EGP10D
CONN2
B4B-XH-A
D102
UF4007
5
R105
10R
0.125W
VCC
DRAIN
7
D105
VSTR
+ C101
10µF
400V
8
+ C100
10µF
400V
R100
FDLL4148
D202
BZX84C9
0.35W
+ C201
220µF
25V
VFB
R201
100R
0.125W
fsw=134kHz
4
GND
GND
3
2
1
GND
IC1
FSD210M
1
2
R101
L101
+ C104
47µF
50V
C103
4.7µF
63V
Q1
BC847B
R202
470R
0.125W
CONN1
B2P3-VH
85V-265VAC input
This compact non-isolated flyback solution draws less than 100mW standby power over the whole input voltage range. This example
shows a 9V output system. Here the FSD210 is powered from an auxiliary winding rather than directly from the high voltage bus.
For output voltages of 12V and over, the device may be powered directly from the output winding. A low cost Zener diode circuit
provides the regulation reference.
• Less than 100mW standby power
– Ideal for applications permanently connected to an AC supply
• Overload protection circuit distinguishes between temporary and permanent overload
– Device does not shut down during load surge conditions
– Inherent short circuit protection
• Frequency modulation reduces EMI reduction circuitry
– Low cost, compact solution possible
Fairchild Devices
FSD210M
P6KE150A
EGP10D
BZX84C9
UF4007
1N4007
FDLL4148
BC847B
Description
Fairchild Power Switch (0.3A/134kHz)
Transient Voltage Suppressor (600W/150V)
Fast Recovery Diode (1A/200V)
Zener Diode (9V)
Fast Recovery Diode (1A/1000V)
General Purpose Diode (1A/1000V)
General Purpose Diode (10mA/100V)
General Purpose Transistor
www.fairchildsemi.com/acdc
13
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
Dual Negative Output Non-Isolated Flyback using FSD200
Typical Application – Home appliance control board power supply
Lp = 1500µH 100/11/10 EF13 (on Vogt Fi324 core)
T1
EF13 VOGT 6PIN
L100
FS1
230V/250mA
1
D101
D100
1N4007 1N4007
D103
P6KE150A
6
D211
EGP10D
-5V/300mA, -12V/100mA output
3
2
1
5
3
D201
EGP10D
Pin 3: Mains Ground
Pin 2: -5V/300mA
Pin 1: -12V/100mA
5
7
VCC
DRAIN
VSTR
D202
BZX84C5V1
0.35W
VFB
fsw = 134kHz
Q1
BC847B
4
GND
3
GND
2
1
GND
IC1
FSD200M
D106
FDLL4148
1
2
R101
L101
C103
47nF
63V
+ C104
1µF
50V
R201
100R
0.125W
+
+ C101
10µF
400V
C201
220µF
25V
+
+ C100
10µF
400V
8
D102
UF4007
R100
CONN2
B3P-VH
4
C211
220µF
25V
R202
470R
0.125W
CONN1
B2P3-VH
85V-265VAC from appliance
input filter stage
A dual non-isolated flyback is used to generate voltages which are negative with respect to the neutral power line. This is used in
applications where triacs are driven, such as in household appliances. A Zener diode, a bipolar transistor and a diode allow the
negative voltage to be regulated by the FPS. The dual input diode helps to protect against line transients.
• Generation of two negative outputs referred to the input line
– Useful for applications using triacs
• High switching frequency reduces the required inductance
– More compact, lower cost core
• Frequency modulation reduces EMI reduction circuitry
– Split 400V input capacitor and input inductor sufficient in most cases
Fairchild Devices
FSD200M
P6KE150A
EGP10D
BZX84C5V1
UF4007
1N4007
FDLL4148
BC847B
Description
Fairchild Power Switch (0.3A/134kHz)
Transient Voltage Suppressor (600W/150V)
Fast Recovery Diode (1A/200V)
Zener Diode (5.1V)
Fast Recovery Diode (1A/1000V)
General Purpose Diode (1A/1000V)
General Purpose Diode (10mA/100V)
General Purpose Transistor
www.fairchildsemi.com/acdc
14
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
10W Single Output Isolated Flyback using FSDM0265RN and Zener Diode
Typical Application – Power bricks and single-phase frequency inverters
Lp = 2400µH 114/9/4 EF20 (on Vogt Fi324)
C300
Y1
FS101
230V/3A
T1
VOGT EF20
L100
D101
1N4007
R102
100k
2W
C103
2.2nF
1000V
4
8
3
6
L201
2.7µH
2
D102
1N4007
1
R101
D103
1N4007
85V-265VAC input
7
6
Drain
8
VStr
GND
5
Drain
Drain
1
+ C102
22µF
400V
Vcc
Ipk
+ C101
22µF
400V
2
VFB
+ C201
220µF
50V
R103
10R
0.6W
IC1
FSDM0265RN
fsw = 70kHz
+ C202
220µF
50V
1
2
3
4
5V/2A output
D202
BZX84C3V9
0.5W
D106
1N4148
2
3
C105
1µF
50V
4
CONN101
B2P3-VH
1
D105
UF4007
CONN201
B4P-VH
D201
SB540
R104
4.7K
0.6W
L101
C104
100nF
50V
IC2
H11A817A.W
4
1
3
2
R201
120R
0.6W
D104
1N4007
The FSDM0265RN contains a PWM controller and a MOSFET on two different chips. The 650V MOSFET is fully avalanche rated
and tested which leads to increased system reliability. This application shows a cost reduced feedback circuit using a Zener diode.
R104 is used to reduce the current limit. Higher power parts in the green FPS family have a higher current limit and a lower RDS(ON)
than the lower power parts. Using a lower RDS(ON) part increases the efficiency, particularly at low input voltages. So replacing a
low power part with a high power part increases the efficiency but also the current limit. If it were not possible to reduce the current
limit, the flyback transformer would have to be rated at the higher current limit, making it more expensive.
• FSDM0265RN has a fully avalanche rated MOSFET
– Robust performance under transient conditions
• Overload protection circuit distinguishes between temporary and permanent overload
– Device does not shut down during load surge conditions
– Inherent short circuit protection
• Current limit may be lowered using an external resistor
– Increased flexibility in choice of range of FPS parts
Fairchild Devices
FSDM0265RN
BZX84C3V9
H11A817A
SB540
UF4007
1N4007
1N4148
Description
Fairchild Power Switch (1.5A/70kHz)
Zener Diode (3.9V)
Transistor Optocoupler
Schottky Diode (5A/40V)
Fast Recovery Diode (1A/1000V)
General Purpose Diode (1A/1000V)
General Purpose Diode (10mA/100V)
www.fairchildsemi.com/acdc
15
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
10W Multiple Output Isolated Flyback using FSD210 with Primary Side Regulation
Typical Application – Set top boxes, decoders and small DVD players
Lp = 2200µH EF20 (on Epcos N67 core)
FS1
230V/1A
TR1
0
8
12
R1
D2
1N4007
D3
P6KE200
100R
11
D5
BA159
D6
1N4007
D8
1N4148
FL1/VFD
1
-22V/50mA
2
5
7
4
9
C8
1µF
50V
D12
10V
0.5W
C10
33nF
50V
1
2
D15
1N4007
C11
22nF
50V
Q4
BC546B
D4
1N4935
5
-12VA/50mA
R11
560R
Primary 81 turns
Vcc 7 turns
5V 3 turns
3.3V 2 turns
12V 9 turns
22V 11 turns
VFD 2 turns
R10
120R
R101
R2
100R
+ C2
22µF
35V
EF20 EPCOS 12Pin
D14
1N4007
L2
2.2mH
0.09A
0
C5
10µF
50V
D17
12V
C14
100nF
50V
C15
10µF
16V
6
D9
1N4148
Vcc
VFB
4
GND
3
8
VSTR
1
DRAIN
+
GND
C7
4.7µF
400V
GND
+
2
C6
4.7µF
400V
D10
1N4935
0
10
fsw = 134kHz
IC1
FSD210M
FL2/VFD
7
3
R3
68R
D1
1N4935
+
L1
2.2mH
0.09A
+
C1
2.2nF
Y1
0
0
+12VA/50mA
+12V/50mA
C3
100nF
50V
D7
12V
+ C4
10µF
16V
0
+3.3V/0.5A
D13
SB140
+ C9
100µF
16V
0
L3
FERRITE BEAD
+5V/0.5A
D16
SB140
+ C12
100µF
16V
+ C13
100µF
16V
10W output
0
PL3
B2P3-VH
195V-265VAC input
Multiple output flyback converters are used in applications where power is supplied to diverse sub-systems such as drives, tuners,
audio stages and complex processor and logic circuits. Primary side regulation is used in this circuit to reduce the total cost. For this
power level and above it is more cost effective to use four diodes in a full bridge configuration than a single diode with a larger
capacitor. For high current outputs it is recommended to use a Schottky diode on the secondary side.
• Primary side regulation reduces system cost
– Cross regulation is good, total regulation worse than with an optocoupler solution
• Frequency modulation approach minimizes EMI circuitry
– Common-mode choke can be replaced by a simple dual capacitor, dual low cost inductor circuit
• Overload protection circuit distinguishes between temporary and permanent overload
– Device does not shut down during load surge conditions from drive unit
– Inherent short circuit protection
Fairchild Devices
FSD210M
BZX84Cxx
P6KE200
SB140
1N4935
1N4937
UF4007
1N4007
1N4148
BC546B
Description
Fairchild Power Switch (0.3A/134kHz)
Zener Diodes (10V, 12V)
Transient Voltage Suppressor (600W/200V)
Schottky Diode (1A/40V)
Fast Recovery Diode (1A/200V)
Fast Recovery Diode (1A/600V)
Fast Recovery Diode (1A/1000V)
General Purpose Diode (1A/1000V)
General Purpose Diode (10mA/100V)
General Purpose Transistor
www.fairchildsemi.com/acdc
16
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
2.5W Single Output Isolated Flyback using FSD200 with KA431 Reference
Typical Application – Isolated main or standby power supplies for household appliances
Lp = 2400µH 114/9/4 EF20 (on Vogt Fi324)
C300
Y1
FS101
230V/3A
T1
VOGT EF20
L100
D101
1N4007
R102
100k
2W
C103
2.2nF
1000V
4
8
3
6
L201
2.7µH
2
D102
1N4007
1
R101
D103
1N4007
85V-265VAC input
6
7
VStr
GND
5
Drain
8
Drain
1
Drain
2
+ C102
22µF
400V
Vcc
Ipk
+ C101
22µF
400V
VFB
+ C201
220µF
50V
R103
10R
0.6W
IC1
FSDM0265RN
fsw = 70kHz
+ C202
220µF
50V
1
2
3
4
5V/2A output
D202
BZX84C3V9
0.5W
D106
1N4148
2
3
C105
1µF
50V
4
CONN101
B2P3-VH
1
D105
UF4007
CONN201
B4P-VH
D201
SB540
R104
4.7K
0.6W
L101
C104
100nF
50V
IC2
H11A817A.W
4
1
3
2
R201
120R
0.6W
D104
1N4007
In this converter, isolation is provided by the transformer and the H11A817A optocoupler. Output accuracy is improved using the
KA431 voltage reference. The values R201, R203, C206, R204 and C104 set the closed loop control parameters and performance.
Using a Schottky diode is a cost-effective method of improving efficiency where needed.
• Feedback circuit using KA431 reference and H11A817A optocoupler
– More accurate regulation over line, load and temperature than with a Zener diode
• Schottky diode used in output stage
– Cost-effective means of improving efficiency
• Integrated soft start function
– Prevents power surges during switch-on time
Fairchild Devices
FSD200M
KA431
H11A817A
SB180
UF4007
1N4007
Description
Fairchild Power Switch (0.3A/134kHz)
2.5V Reference (2.5V)
Transistor Optocoupler
Schottky Diode (1A/80V)
Fast Recovery Diode (1A/1000V)
General Purpose Diode (1A/1000V)
www.fairchildsemi.com/acdc
17
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
180W-200W Quasi-Resonant Flyback with Input Power Factor Correction using KA5Q1265RF,
FAN7527B, and FQP13N50C
Typical Application – Color Televisions
NTC100
2R
11
14
3
C114
630V
R302
20K
0.25W
C309
1nF
25V
R110
S10K275
Q301
FQP13N50C
FAN7527B
R306
10R
0.25W
+ C201
1000µF
50V
C210
470pF
1000V
+ C101
220µF
450V
R309
6K
0.25W
R307
0.3R
0.6W
D211
EGP20D
D304
8V2
0.5W
VR301
10K
18V/1A
+ C212
1000µF
50V
+ C211
1000µF
50V
CONN2
B9P-VH
L221
10µH
5A
D221
FYPF0545
Lp = 530µH
Np/Ns = 0.8
45V/0.01A
+ C202
1000µF
50V
L211
10µH
5A
C220
470pF
1000V
D303
1N4148
LF100
L201
10µH
5A
D201
EGP20D
R318
470K
0.25W
C307
1µF MLCC
50V
R305
22K
0.6W
4
3
2
1
-
BD100
R311
1M
0.25W
C113
630V
C200
470pF
1000V
R308
470K
0.25W
5
6
7
8
+
12V/2A
+ C222
1000µF
50V
+ C221
1000µF
50V
1
2
3
4
5
6
7
8
9
T1
EF42 VOGT
D103
1N4937
1
22
21
C110
250V
D108
1N4007
R108
68K
0.5W
R118
68K
0.5W
20
3
19
18
C230
470pF
1000V
17
R103
10R
0.25W
FS1
230V/3A
7
16
9
15
D231
EGP20K
1
D10
1N49376
Sync
Vcc
C104
47nF
50V
5
GND
FB
4
3
Drain
C107
680pF
1600V
+
2
1
C103
47µF
50V
D241
FYPF0545
D105
1N4937
C105
3.3nF
50V
R105
470R
0.25W
IC2
H11A817A
4
1
3
2
R201
1K
0.25W
C400
R204
IC3
KA431LZ
+ C232
100µF
200V
+ C241
1000µF
50V
CONN3
B2P-VH
1
2
8.5V/1A
+ C242
1000µF
50V
180W-200W Output
R204
250K
0.25W
R202
1K
0.25W
R203
140V/0.9A
L241
10µH
5A
R106
600R
0.25W
F
195V-265VAC input
+ C231
100µF
200V
C240
470pF
1000V
IC1
KA5Q1265RFYDTU
CONN1
B2P3-VH
L231
10µH
5A
14
13
BEAD101
FERRITE BEAD
2
C112
630V
T301
VOGT EF25 PFC
6
R301
1M2
0.25W
C305
470nF
630V
C111
630V
D302
EGP30J
Lp = 600µH, 3A, 58T/4T EF25 (on Vogt Fi324 core)
C206
39K 100nF
0.25W 100V
High/Low
VR201
30K
R206
4K7
0.25W
www.fairchildsemi.com/acdc
18
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
180W-200W Quasi-Resonant Flyback with Input Power Factor Correction using KA5Q1265RF,
FAN7527B, and FQP13N50C (Continued)
Typical Application – Color Televisions
The circuit shown consists of a PFC stage built around the FAN7527B/FQP13N50C/EGP30J circuit and the quasi-resonant PWM
stage built around the KA5Q1265RF/T1 circuit. This circuit is suited for input voltages in the range from around 195V to 265V.
The transition mode PFC stage generates a DC bus voltage of around 400V. The purpose of the stage is to reduce the harmonic content of the input current drawn from the AC supply as required by the EN61000-3-2 standard. An additional benefit is that the input
power factor is very high.
The KA5Q1265RF circuit generates the required output voltages using a multiple output flyback configuration. The device operates in
discontinuous mode and detects the point where the secondary current has dropped to zero. The device then switches on after a
delay set by the circuit around C105. As the delay is chosen to be at the first minimum of the primary side voltage ring as it
changes from Vin + nVo to Vin - nVo the device is switched on at a low voltage, which reduces the switching loss. The switching
frequency is therefore asynchronous and varies with the load. This reduces the visible effect of switching noise on the television
screen. Fixed frequency switching noise would be seen as diagonal lines on the screen. The turns ratio is chosen to be unusually low
for a standard flyback because the output voltage on the main winding is exceptionally high. This keeps the reflected voltage nVo low.
If the load on a quasi-resonant flyback circuit is reduced, the switching frequency increases which causes a reduction in efficiency.
The KA5Q series has a burst mode of operation. In normal operation the High/Low signal is High. When this signal which is typically
supplied by a microcontroller is Low, the current increases through the optocoupler, the feedback voltage goes to ground and the
device enters burst mode. In this case the output voltages drop until the voltage supplied to the chip through the auxiliary winding
drops to around 12V. The device remains in hysteretic burst mode until the feedback voltage increases. In this low power mode, the
PFC chip is deactivated via D304. In normal operation, the auxiliary winding voltage is around 24V, so there is sufficient voltage to
power up the PFC chip. In burst mode, the FPS voltage is between 11V and 12V, so the FAN7527B chip is deactivated, as its supply
voltage is around 8V lower than this.
• Complete PFC and PWM solution for a color television power supply
– High efficiency (typically 90% at full load)
– High power factor and low input current harmonics
• Quasi-resonant mode ideal for TV applications
– High efficiency due to lower voltage switching
– Asynchronous switching is not at constant frequency
– Slower dV/dt causes lower internal radiated interference
• Supports low power standby
– Hysteretic burst mode for KA5Q1265RF device
– FAN7527B PFC controller deactivated at low power
Fairchild Devices
KA5Q1265RF
FAN7527B
FQP13N50C
EGP30J
1N4937
GBU4M
BZX85C8V2
Description
Fairchild Power Switch (8A/quasi resonant)
Transition mode PFC controller
High Voltage MOSFET (13A/500V)
Fast Recovery Diode (3A/600V)
Fast Recovery Diode (1A/600V)
Bridge Rectifier (4A/1000V)
Zener Diode (8.2V)
Fairchild Devices
KA431
H11A817A
EGP20D
EGP20K
FYPF0545
1N4007
1N4148
www.fairchildsemi.com/acdc
19
Description
2.5V Reference (2.5V)
Transistor Optocoupler
Fast Recovery Diode (1A/200V)
Fast Recovery Diode (1A/600V)
Fast Recovery Diode (5A/45V)
Fast Recovery Diode (1A/1000V)
General Purpose Diode (10mA/100V)
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
16W Multiple Output Isolated Flyback Converter using FSDM0265RN
Typical Application – Set top boxes, decoders, and small DVD players
Industrial and communications applications using FPGAs and complex logic chips
Lp = 1000µH EF25 (on Vogt Fi324 core)
T1
1
6
8
D102
UF4007
5
R103
22R
0.6W
DF10M
BR101
10
R105
2.2k
0.6W
0V
IC2
H11A817A
4
3
+ C103
10µF
50V
2
2
1
85V-265VAC input
L4
56µH
0V
C104
33µF
50V
Primary 80 turns
Vcc 14 turns
5V 6 turns
3.3V 4 turns
6.6V 8 turns
12V 14 turns
3
C300
250V
C9
100nF
63V
0V
3
R202
1K
0.6W
2
1
2
2.5V
C5
100nF
63V
0V
0V
VIN
VOUT
0V
0V
R201
220R
0.6W
VOUT
3.3V/1.2A
(incl 1.2V load)
+ C14
220µF
16V
IC4 0V
FAN1112D
+ C16
2200µF
16V
0V
D13
SB330
CONN1
B2P3-VH
VIN
C2
100nF
63V
C110
275V
FS1
230V/3A
0V
IC5
FAN1616AS25
1
3
3
5V/1.2A
(incl 2.5V load)
+ C11
220µF
16V
+ C12
2200µF
16V
D12
SB360
1
7
6
VFB
2
L3
56µH
0V
2
1.2V
C10
100nF
63V
1
1
IC1
FSDM0265RN
Vcc
6.6V/0.7A
+ C7
1000µF
16V
D14
SB360
4
D103
1N4148
Drain
8
VStr
GND
5
Drain
Drain
R110
T3
0V
9
0V
ILim
~ -
+ C101
47µF
400V
4
~ +
12V/100mA
+ C15
47µF
25V
D15
SB180
7
GND
3
GND
C102
10nF
1000V
R102
10k
2W
R204
1.2K
0.6W
C206
100nF
100V
R203
2.2K
0.6W
0V
16W output
R205
5.6K
0.6W
IC3
KA431LZ
0V
The isolated, multiple output application shown is suited to applications requiring all of the common logic supply voltages: 5V, 3.3V,
2.5V and 1.2V. The flyback architecture is easily expandable: two additional outputs at 12V and 6.6V are shown in this application.
The design is scalable to higher power levels by changing the size of the FPS device and the transformer. The FSDM0265RN uses
current mode control which provides excellent response to line and load transient conditions. The flexible overload protection can
distinguish between a temporary current surge and a longer term overload condition. The over current latch is a current limit which
is active even during the blanking time. This provides additional system robustness against a secondary diode short circuit condition.
• FSDM0265RN has a fully avalanche rated MOSFET with overcurrent latch
– Robust performance under transient conditions
– Device switches off if there is a secondary diode short
• Overload protection circuit distinguishes between temporary and permanent overload
– Device does not shut down during load surge conditions
– Inherent short circuit protection
• Current limit may be lowered using an external resistor
– Increased flexibility in choice of range of FPS parts
Fairchild Devices
FSDM0265RN
FAN1112D
FAN1616AS25
H11A817A
KA431
DF10M
Description
Fairchild Power Switch (1.5A/70kHz)
Voltage Regulator (1.2V/1A)
Voltage Regulator (2.5A/0.5A)
Transistor Optocoupler
2.5V Reference (2.5V)
Bridge Rectifier
Fairchild Devices
SB180
SB330
SB360
UF4007
1N4148
Description
Schottky Diode (1A/80V)
Schottky Diode (3A/30V)
Schottky Diode (3A/60V)
Fast Recovery Diode (1A/1000V)
General Purpose Diode (10mA/100V)
www.fairchildsemi.com/acdc
20
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
40W Isolated Flyback Power Supply using FSDM07652R
Typical Application – AC Input Industrial Control, LCD Monitor
Lp = 520µH EER3016
T1:EER 3016
DB101
2KBP06
+ 2
1
1
3
+ C103
100µF
400V
R102
40K
1W
C104
100µF
400V
D201
MBRF10100
12V
C201
1000µF
25V
R206
56K
2W
L201
10
+ C202
1000µF
25V
+
8
2
4-
2
R105
40K
1W
D101
UF4007
40W output
3
C102
R104
5R
220nF
275VAC
6
5
4
LF101:23mH
3
R101
C101
ZD101
22V
220nF
275VAC
2
Vstr
Drain
NC
GND
4
1
5
2
+ C105
22µF
50V
F101
FUSE
1
L202
7
5V
C203
1000µF
10V
C204
1000µF
10V
+
+
6
Vfb
C301
Vcc
IC101
FSDM07652R
560K/1W
RT101
D202
MBRF1045
D102
1N4148
4.7nF
YCAP
C106
47nF
50V
R201
1K
IC301
H11A817A
Primary 36 turns
Vcc 8 turns
5V 3 turns
12V 7 turns
R204
5.6K
R202
1.2K
R203
10K
C205
47nF
50V
IC201
KA431
R205
5.6K
85V-265VAC Input
CONN1
B2P3-VH
This shows a higher power isolated flyback application, sharing the same features as many of the lower power applications. A
lower inductance value is used to ensure that the associated leakage inductance is also kept low in this application, remembering
that snubber losses are proportional to the leakage inductance and to the square of the current.
• FPS containing PWM IC with co-packaged MOSFET solution is very robust and improves system reliability
– Fully avalanche rated switch
– Over current protection for secondary diode short circuit
– Over voltage protection
• Current mode control gives excellent line and load regulation
– Better regulation
• Overload protection distinguishes between temporary and permanent overload
• Internal soft start reduces inrush current and output overshoot on turn on
Fairchild Devices
FSDM07652R
H11A817A
KA431
1N4007
1N4148
KBP06M
Description
Fairchild Power Switch (2.5A/70kHz)
Optocoupler
2.5V Reference (2.5V)
General Purpose Diode (1A/1000V)
General Purpose Diode (10mA/100V)
Bridge Rectifier Diode (1.5A/600V)
www.fairchildsemi.com/acdc
21
AC/DC Switch Mode Power Supply Design Guide
Examples of Typical Application Circuits
24W Flyback Converter using 1500V IGBT and FAN7554
Typical Application – Motor Drives, Uninterruptible Power Supplies, 3-Phase Input Systems
D1
D2
D3
1N4007
1N4007
1N4007
R102
33k
1W
R121
150k
1W
C102
10nF
1000V
UF4007
R122
150k
1W
4
+
C203
1000µF
50V
D202
EGP20D
2
3
R126
4.7K
0.25W
R105
110k
0.6W
+
C202
220µF
50V
CONN2
B2P-VH
1
2
R103
10R
0.6W
Q1
SGF5N150UFTU
EF35
R206
0R
0.6W
CONN3
B2P-VH
R207
N.C.
0.6W
1
2
D103
5
6
R201
1K8
0.6W
GND
R123
10K
0.25W
OUT
VREF
C206
100nF
25V
RT/CT
R203
39K
0.6W
4
1
R107
110k
0.6W
R205
1K5
0.6W
IC2
H11A817A.W
+
C122
1µF
50V
C123
1nF
25V
R127
330
0.25W
R128
0.8R
2W
C104
47nF
63V
4
1
3
2
IC3
3
C21
5.6nF
25V
R204
13K
0.6W
R202
1K8
0.6W
IC1
FAN7554
+
IS
+ C103
22µF
50V
7
1N4148
FB
C106
47µF
400V
C201
1000µF
50V
10
9
8
1
+
R106
110k
0.6W
+
7
R125
22
0.25W
8
C105
47µF
400V
R104
110k
0.6W
3
1N4007
VCC
D6
1N4007
SS
D5
1N4007
24V/1A output
L201 22µH
14
13
12
6
2
D4
D201
EGP20D
T1
1
D102
1
KA431LZ
2
Note: EMI components removed from circuit for clarity
1
2
3
4
3 phase input
CONN1
B4P-VH
This inventive flyback solution uses a cost-effective 1500V IGBT as the main switching element, offering a more robust design. The
alternative option for the switch would be a MOSFET with a rated voltage exceeding 1000V, which is a more expensive solution. The
FAN7554 PWM controller provides the PWM regulation. Frequency compensation comes from the standard KA431
reference circuit.
• Flyback converter with cost-effective 1500V IGBT
– Ensures high robustness against external voltage transients at a reasonable cost
• Complete, tested sub-system solution from Fairchild's Global Power Resource with test circuit data
– Fairchild Semiconductor offers all semiconductor components in the circuit
– Efficiency exceeds 78% for 24W output, 600V input, 20kHz switching frequency
– Efficiency exceeds 74% for 24W output, 600V input 40kHz switching frequency
– IGBT temperature rises less than 40°C in test circuit
Fairchild Devices
SGF5N150UFTU
FAN7554
EGP20D
H11A817A.W
KA431LZ
1N4007
UF4007
1N4148
Description
1500V, 5A IGBT
PWM Controller
Fast Recovery Diode (1A/200V)
Transistor Optocoupler
2.5V Reference (2.5V)
Diode (1A/1000V)
Fast Recovery Diode (1A/1000V)
General Purpose Diode (10mA/100V
www.fairchildsemi.com/acdc
22
AC/DC Switch Mode Power Supply Design Guide
Design Ideas
250W to 450W Desktop PC Forward Switch Mode Power Supply
Boost Diode
Rectifier
PFC
(Power
Factor
Correction)
Transformer
PWM
(Pulse Width
Modulator)
Optocoupler
Suggested Products
Bridge Rectifier
2KBP10M
PFC IC
ML4821
PFC MOSFET
FCP20N60
Boost Diode
PWM IC
FFP05U60DN
KA384X
KA3525
PWM MOSFET
FQP8N80C
Rectifier
H11A817
MOC819
GBU4M
FAN4810
FQP18N50V2
RHRP860
FQP9N90C
12V FFPF10U20DN
GBU6M
FAN4822
FDH27N50
FFP10U60DN
FQA10N80C
12V FFAF10U20DN
FCP11N60
IRL9R860
FQA11N90
KBL10
5V FYAF3004DN
3.3V FYP1504DN
3.3V FYP2004DN
3.3V FYAF3004DN
www.fairchildsemi.com/acdc
23
Optocoupler
12V FPF06U20DN
AC/DC Switch Mode Power Supply Design Guide
Design Ideas
500W Telecom/Server Double Switch Forward Switch Mode Power Supply
Boost Diode
PWM MOSFET
Synch. Rectifier
PFC
(Power
Factor
Correction)
PFC MOSFET
Synch. Rectifier
PWM MOSFET
Optocoupler
Suggested Products
Bridge Rectifier
2KBP10M
PFC IC
ML4821
PFC MOSFET
FQA24N50
Boost Diode
ISL9R860
PWM MOSFET
Synch. Rectifier
FQH18NH50V2
FDP060AN08A0
H11A817
MOC819
GBU4M
FAN4810
FCP11N60
IRL9R1560
FQA24N50
FDP047AN08A0
GBU6M
FAN4822
FDH44N50
RHRP860
FQH27N50
FDP3652
FQH44N50
FDP3632
KBL10
RHRP1560
FCP11N60
Optocoupler
FQP90N10V2
FCP20N60
www.fairchildsemi.com/acdc
24
AC/DC Switch Mode Power Supply Design Guide
Design Ideas
500W Telecom/Server ZVS Phase-Shift Full Bridge Switch Mode Power Supply
Boost Diode
PWM MOSFET
Synch. Rectifier
PFC
(Power
Factor
Correction)
PFC MOSFET
Synch. Rectifier
PWM MOSFET
Optocoupler
Suggested Products
Bridge Rectifier
2KBP10M
PFC IC
ML4821
PFC MOSFET
FQA24N50
Boost Diode
PWM MOSFET
ISL9R860
FQH18N50V2
Synch. Rectifier
H11A817
MOC819
GBU4M
FAN4810
FCP11N60
IRL9R1560
FQA24N50
FDP047AN08A0
GBU6M
FAN4822
FCP20N60
RHRP860
FDH27N50
FDP3652
FDH44N50
RHRP1560
FDH44N50
FDP3632
FCP11N60
FQP90N10V2
KBL10
FCP20N60
www.fairchildsemi.com/acdc
25
Optocoupler
FDP060AN08A0
AC/DC Switch Mode Power Supply Design Guide
Application Note Highlight
Design Guidelines for Off-Line Flyback Converters
using Fairchild Power Switch (FPS™)
(AN-4137)
Introduction
Designing a switched mode power supply (SMPS) is a
complex process with many variables and considerations.
While most power supply design engineers have developed
their own methods, here is an overview describing the
design of a flyback converter using Fairchild FPS devices.
For a more detailed explanation of this procedure, refer to
Application Note AN-4137, Design Guidelines for Off-line
Flyback Converters Using Fairchild Power Switch on
www.fairchildsemi.com/an/AN/AN-4137.pdf
System Specifications
Once the initial parameters of the power supply are known,
the design can begin. These parameters include the min and
max input voltage, input frequency, maximum output power,
and estimated efficiency. From this, the initial system
specifications can be calculated. The maximum input power
can be determined by PIN = PO/Eff.
The bulk capacitor can be estimated as 2-3µF per watt of
input power for universal input range (85-265VRMS) and
1µF per watt of input power from European input range
(195V-265VRMS).
using the cross sectional area of the core (Ae) and the
saturation flux density (Bsat) which can be extracted from the
B-H curves on the manufacturer’s datasheet. The turns ratio
and resultant number of secondary turns for the transformer
can then be found. Once the number of turn on the primary
side is determined, the gap length of the core is calculated
followed by the calculation of the wire diameter for each
winding to make the transformer design is complete.
Output
In its most basic form, the output structure of a flyback
converter typically consists of a series rectifier diode and
output capacitor placed in parallel with the output. There
may be additional LC networks following this configuration
for filtering purposes in the event that the ripple current
specifications of the output capacitor cannot be met.
To determine the output rectifier diode, the maximum
reverse recovery voltage (VRRM) and the RMS current of the
diode must be calculated. With that, a diode can be chosen
from Fairchild’s diode selection guide.
Next, the maximum duty cycle can be determined. The duty
cycle should be as large as possible providing there is enough
margin in the MOSFET voltage rating.
When choosing the output capacitor, ensure that the
calculated ripple current is smaller than the ripple current
given on the capacitor’s datasheet. If a post filter is necessary,
set the corner frequency from 1/10th to 1/5th of the FPS
switching frequency.
Transformer and FPS Device
Snubber
Worst case conditions should be used when calculating the
inductance for the primary side of the transformer (LM). For
both continuous and discontinuous modes of operation, the
worst case condition is at full load and minimum input
voltage. Once LM is calculated, the maximum peak current
(Idspeak) and RMS current (Idsrms) of the MOSFET in normal
operation can be established.
When choosing the FPS device for the design, it is important
to make sure that the pulse-by-pulse current limit level (Iover)
is greater than the maximum peak current of the MOSFET.
Once the proper FPS device is chosen, the transformer can be
designed. The first step is to choose the proper core depending
on the input voltage range, number of outputs and switching
frequency of the FPS device. The initial core selection will
be somewhat rough due to the many variables involved, but
the manufacturer’s core selection guide should be referred to
when making this initial choice. With the selected core,
calculate the minimum number of primary turns (NPmin) by
An RCD snubber network is needed when there is a high
voltage spike on the drain of the FPS MOSFET when it is in
the OFF state. This spike can lead to failure of the FPS
device. The snubber network will clamp the voltage and
protect the circuit. The first step is to determine the snubber
capacitor voltage at the minimum input voltage and
maximum load (Vsn). The power dissipated in the snubber
network can then be calculated.
The snubber resistor should be chosen with the proper
wattage rating according to the power loss of the circuit.
The capacitor voltage for the snubber is then calculated
under maximum input and full load conditions.
After choosing the snubber resistor and capacitor, the
snubber diode can then be chosen. The maximum voltage
stress on the MOSFET drain (Vdsmax) should be calculated
and should be below 90% of the rated voltage of the
MOSFET (BVdss). The voltage rating of the snubber diode
should be higher than the MOSFET BVdss.
REV. 0.0.1 2/28/05
www.fairchildsemi.com/acdc
26
AC/DC Switch Mode Power Supply Design Guide
Application Note Highlight
Design Guidelines for Off-Line Flyback Converters
using Fairchild Power Switch (FPS™) (Continued)
(AN-4137)
Feedback loop
Most FPS devices employ current mode control, therefore the
feedback loop can be typically implemented with a one pole
and one zero compensation circuit. Calculating the controlto-output transfer function origin is different depending on
whether the circuit is operating in continuous or discontinuous mode. When a continuous mode converter design has
multiple outputs, the low frequency control-to-output transfer
function is proportional to the parallel combination of all of
the load resistances, adjusted by the square of the turns ratio.
Design of the feedback loop consists of the following steps.
a) Determine the crossover frequency (fc). For CCM mode
flyback, set fc below 1/3 of right half plane (RHP) zero
to minimize the effect of the RHP zero. For DCM mode
fc can be placed at a higher frequency, since there is no
RHP zero.
b) When an additional LC filter is employed, the crossover
frequency should be placed below 1/3 of the corner
frequency of the LC filter, since it introduces a -180
degrees phase drop. Never place the crossover frequency
beyond the corner frequency of the LC filter. If the
crossover frequency is too close to the corner frequency,
the controller should be designed to have a phase margin
greater than 90 degrees when ignoring the effect of the
post filter.
c) Determine the DC gain of the compensator (wi/wzc) to
cancel the control-to-output gain at fc.
d) Place a compensator zero (fzc) around fc/3.
e) Place a compensator pole (fpc) above 3fc.
For the complete Application Note, please visit us at
www.fairchildsemi.com/an/AN/AN-4137.pdf
www.fairchildsemi.com/acdc
27
REV. 0.0.5/05
AC/DC Switch Mode Power Supply Design Guide
Application Note Highlight
Power Factor Correction (PFC) Basics
(AN-42047)
What is Power Factor?
Power Factor (PF) is defined as the ratio of the real power (P)
to apparent power (S), or the cosine (for pure sine wave for
both current and voltage) that represents the phase angle
between the current and voltage waveforms (see Figure 1).
The power factor can vary between 0 and 1, and can be either
inductive (lagging, pointing up) or capacitive (leading, pointing down). In order to reduce an inductive lag, capacitors are
added until PF equals 1. When the current and voltage waveforms are in phase, the power factor is 1 (cos (0°) = 1). The
whole purpose of making the power factor equal to one is to
make the circuit look purely resistive (apparent power equal
to real power).
Real power (watts) produces real work; this is the energy
transfer component (example electricity-to-motor rpm).
Reactive power is the power required to produce the magnetic fields (lost power) to enable the real work to be done,
where apparent power is considered the total power that the
power company supplies, as shown in Figure 1. This total
power is the power supplied through the power mains to produce the required amount of real power.
When the power factor is not equal to 1, the current waveform does not follow the voltage waveform. This results not
only in power losses, but may also cause harmonics that
travel down the neutral line and disrupt other devices connected to the line. The closer the power factor is to 1, the
closer the current harmonics will be to zero since all the
power is contained in the fundamental frequency.
Understanding Recent Regulations
In 2001, the European Union put EN61000-3-2, into effect to
establish limits on the harmonics of the ac input current up to
the 40th harmonic. Before EN61000-3-2 came into effect,
there was an amendment to it passed in October 2000 that
stated the only devices required to pass the rigorous Class D
(Figure 2) emission limits are personal computers, personal
computer monitors, and television receivers. Other devices
were only required to pass the relaxed Class A (Figure 3)
emission limits.
“Total Power”
Apparent Power
(S) = Volt Amperes = I2Z
Reactive Power
(Q) = vars = (XL – XC) | 2
θ
Real Power
(P) = Watts = (I2R)
Figure 2. Both Current and Voltage Waveforms are in
Phase with a PF =1 (Class D)
Figure 1. Power Factor Triangle (Lagging)
The previously-stated definition of power factor related to
phase angle is valid when considering ideal sinusoidal waveforms for both current and voltage; however, most power
supplies draw a non-sinusoidal current. When the current is
not sinusoidal and the voltage is sinusoidal, the power factor
consists of two factors: 1) the displacement factor related to
phase angle and 2) the distortion factor related to wave
shape. Equation 1 represents the relationship of the displacement and distortion factor as it pertains to power factor.
PF =
Irms(1)
cos θ = Kd ⋅ Kθ
Irms
Irms(1) is the current’s fundamental component and Irms is
the current’s RMS value. Therefore, the purpose of the power
factor correction circuit is to minimize the input current
distortion and make the current in phase with the voltage.
Figure 3: This is What is Called Quasi-PFC Input,
Achieving a PF Around 0.9 (Class A)
Refer to the complete application note, AN-42047, for
additional information on:
• Inefficiency causes
• Boost converters
• Modes of operation
For the complete Application Note, please visit us at
www.fairchildsemi.com/an/AN/AN-42047.pdf
5/05
www.fairchildsemi.com/acdc
28
AC/DC Switch Mode Power Supply Design Guide
Application Note Highlight
Choosing Power Switching Devices
for SMPS Designs
(AN-7010)
This application note identifies the key parametric considerations for comparing IGBT and MOSFET performance in
specific switch mode power supply (SMPS) applications.
Parameters such as switching losses are investigated in both
hard-switched and soft-switched zero voltage switching
(ZVS) topologies. The three main power switch losses:
turn-on, conduction and turn-off are described relative to both
circuit and device characteristics. The differences in gate
drive requirements are explained for the two voltage
controlled products. Finally, the impact of the specific cooling
system on device selection is explored.
pulses to measure EON. The first pulse raises the inductor to
the desired test current and the second pulse then measures
the EON loss recovering this current from the diode.
FGH20N6S2D
DIODE TA49469
L = 500µH
RG = 25Ω
Turn-On Losses
FGH20N6S2D
-
The turn-on characteristics of IGBTs and power MOSFETs are
quite similar except that IGBTs have a longer voltage fall time.
Referencing the basic IGBT equivalent circuit, Figure 1, the
time required to fully modulate the minority carrier PNP BJT
collector base region results in a turn-on voltage tail.
Collector
PNP
Collector
Modulation
NPN
Gate
+
IGBT
Gate
Rshorting
Body Region
Emitter
Emitter
Figure 1 - IGBT Equivalent Circuit
This delay results in a Quasi-Saturation effect wherein the
collector-emitter voltage does not immediately fall to its
VCE(SAT) value1. This turn-on effect also results in a VCE
voltage bump under ZVS conditions at the point where the
load current transitions from the co-packed inverse parallel
diode to the IGBT collector. The EON energy losses specified
in datasheets is the time integral of Icollector times VCE in joules
per switching cycle and includes the additional losses
associated with quasi-saturation.
Two EON energy parameters EON1 and EON2 are provided in
IGBT datasheets. EON1 is the energy loss without the losses
associated with hard-switched diode recovery. EON2 includes
the hard-switched turn-on energy loss do to diode recovery.
EON2 is measured recovering a diode identical to the co-packed
diode associated with the device. A typical EON2 test circuit is
illustrated in Figure 2. The test is performed with the diode at
the same Tj as the DUT. The IGBT is switched through two
VDD = 390V
Figure 2 - Typical EON and EOFF Test Circuit
Under hard-switched turn-on the gate drive voltage and
impedance and the recovery characteristics of the commutated
diode determine the EON switching loss. For circuits such as
the conventional CCM boost PFC circuit the boost diode
recovery characteristics are extremely important in controlling
EON (turn-on) energy losses. In addition to selecting a boost
diode with minimal Trr and QRR it is also important to ensure
that the diode has soft recovery characteristics. Softness, the
ratio of tb/ta, has a considerable impact on the electrical noise
and voltage spikes generated across the switching device.
Snappy diodes with a high tb period di/dt fall from IRM(REC)
create large voltage spikes in the circuit parasitic inductances.
These voltage spikes create EMI and can result in excessive
reverse voltage across the diode.
In hard-switched circuits such as the full-bridge and half
bridge topologies where the IGBT co-packed or MOSFET
body diodes are conducting when the alternate switching
device is turned on, the diode recovery characteristics
determine the EON loss. For this reason it is important to
select MOSFETs with Fast body diode recovery characteristics
such as the Fairchild FQA28N50F FRFET™. Unfortunately,
MOSFET parasitic or body diodes are relatively slow
compared to state-of-the-industry discrete diodes. For
hard-switched MOSFET applications the body diode is often
the limiting factor determining the SMPS operating
frequency.
Typically IGBT co-packed diodes are selected for compatibility with their intended applications. Slower Ultrafast diodes
with lower forward conduction losses are co-packed with
slower lower VCE(SAT) motor drive IGBTs. Conversely soft
5/05
www.fairchildsemi.com/acdc
29
AC/DC Switch Mode Power Supply Design Guide
Application Note Highlight
Choosing Power Switching Devices
for SMPS Designs (Continued)
(AN-7010)
recovery Hyperfast diodes such as the Fairchild Stealth™
series are co-packed with the high frequency SMPS2 switched
mode IGBTs.
Beyond selecting the right diode the designer can control Eon
losses by adjusting the gate drive turn-on source resistance.
Decreasing the drive source resistance will increase the IGBT
or MOSFET turn-on di/dt and decrease the Eon loss. The
tradeoff is between Eon losses and EMI since the higher di/dt
will result in increased voltage spikes and radiated and
conducted EMI. Selecting the correct gate drive resistance to
meet a desired turn-on di/dt may require in-circuit testing and
verification. A ballpark value may be determined from the
MOSFET transfer curve, Figure 3. Assuming the FET current
will rise to 10A at turn-on and looking at the 25°C curve of
Figure 3, the gate voltage must transition from 5.2V to 6.7V to
reach the 10A and the average GFS is (10A/6.7V - 5.2V) = 6.7Ω.
Similar Gate drive turn-on resistance may be calculated for
the IGBT. Again VGE(avg) and GFS may be determined from
the IGBT transfer characteristic curve and the CIES value at
VGE(avg) should be substituted for Ciss. The comparable
calculated IGBT turn-on gate drive resistance is 100Ω.
This higher ohm requirement is indicative of the higher IGBT
GFS and lower CIES. A key point here is that gate drive circuit
adjustments must be made for a transition from MOSFET to
IGBT.
Refer to the complete application note, AN-7010, that
continues with the comparisons between MOSFETs and
IGBTs on the following subjects:
• Conduction losses
• Turn off losses
• Gate drive requirements
• Thermal management
ID, Drain Current (A)
1
101
150°C
25°C
100
Pittet, Serge and Rufer, Alfred "Analytical analysis of Quasi-Saturation
Effect in PT and NPT IGBTs" PCIM Europe 2002
http://leiwww.epfl.ch/publications/pittet_rufer_pcim_02.pdf
-55°C
NOTE
1. VDS = 40V
2. 250µs Pulse Test
10-1
2
4
6
8
VGS, Gate-Source Voltage (V)
10
Figure 3 - FCP11N60 Transfer Characteristics
Rgate = [Vdrive - VGS(avg)] •
GFS
(di/dt) • Ciss
Eq. 1 - Gate drive resistance for desired turn-on di/dt
Applying this average GFS value to Equation 1 with a gate
drive of Vdrive = 10V, a desired di/dt = 600 A/µs and typical
FCP11N60 values VGS(avg) = 6V, Ciss = 1200pF; a 37Ω turn-on
gate drive resistance is calculated. Since the instantaneous
GFS value is the slope in Figure 3 curves, GFS will vary during
the Eon period, which implies a varying di/dt. The exponentially decaying gate drive current and decreasing Ciss as a
function of VFS also enter into this equation with an overall
effect of surprisingly linear current rise.
For the complete Application Note, please visit us at
www.fairchildsemi.com/an/AN/AN-7010.pdf
REV. 0.0.1 3/05
www.fairchildsemi.com/acdc
30
AC/DC Switch Mode Power Supply Design Guide
Global Power Resource™
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customer design labs, and advanced web-based design tools, tutorials and other application-specific on-line information.
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31
AC/DC Switch Mode Power Supply Design Guide
Notes
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