1. Copyright (C) Siam Bee Technologies 2015
LTspice Version
Design Kit
Flyback Converter using PWM IC
02JUL2015
Bee Technologies
Copyright (C) Siam Bee Technologies 2015

2. Copyright (C) Siam Bee Technologies 2015
Contents
1. 50W Off-Line Adapter Circuit (VIN=85Vac) 1.1) Input Waveform 1.2) Output Waveform 1.3) Output Power 1.4) Gate Drive Output and Oscillator Timing (IC) 2. 50W Off-Line Adapter Circuit (VIN=110Vac) 2.1) Input Waveform 2.2) Output Waveform 2.3) Output Power 2.4) Gate Drive Output and Oscillator Timing (IC) 3. 50W Off-Line Adapter Circuit (VIN=265Vac) 3.1) Input Waveform 3.2) Output Waveform 3.3) Output Power 3.4) Gate Drive Output and Oscillator Timing (IC) 4. Transformer Specification 5. Operation Waveform (VIN=110Vac, Example) 5.1) Transformer Turn Ratio 5.2) Transformer Primary Side Inductance (LP) 5.3) VCC Output Waveform 5.4) MOSFET Switching Device (UQ101) 5.5) Output Rectifier Diode (D201 - D202) 5.6) Current Sensing and Feedback Circuit Conclusion Simulation Details Appendix A - Initial Condition Settings Appendix B - Bill of Materials Simulation Index
Copyright (C) Siam Bee Technologies 2015

3. 1. 50W Off-Line Adapter Circuit (VIN=85Vac) - Simulation Circuit
V(Out) starts from 11V by the initial condition
VIN=85Vac
.tran 0 50m 0 10n
.Option Gmin=75E-9
.Option Abstol=1.0E-9
.Option Vntol=1.0u
.Option Trtol=1000
.Option Method=Gear
* Engine Solver: Alternate
V(Vcc) starts from 12V
Initial condition are set ,so the simulation starts near the steady state.
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4. 1.1) Input Waveform - Simulation Result
VDC,AVG = V
VDC, MIN = 85.8V
VAC = 85Vrms
Time [sec]
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5. 1.2) Output Waveform - Simulation Result
The output voltage is regulated at 12.12V
V(Out) starts from 11V by the initial condition
The output current is 4.04A (RL=3)
Time [sec]
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6. 1.3) Output Power - Simulation Result
The simulation result shows the output power is 48.90W
Time [sec]
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7. 1.4) Gate Drive Output and Oscillator Timing (IC) - Simulation Result
PW = 3.877us
Oscillator frequency = 105kHz
VOSC
Time [sec]
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8. 2. 50W Off-Line Adapter Circuit (VIN=110Vac) - Simulation Circuit
V(Out) starts from 11V by the initial condition
VIN=110Vac
.tran 0 50m 0 10n
.Option Gmin=75E-9
.Option Abstol=1.0E-9
.Option Vntol=1.0u
.Option Trtol=1000
.Option Method=Gear
* Engine Solver: Alternate
V(Vcc) starts from 12V
Initial condition are set ,so the simulation starts near the steady state.
Copyright (C) Siam Bee Technologies 2015

9. 2.1) Input Waveform - Simulation Result
VDC,AVG = V
VDC, MIN = V
VAC = 110Vrms
Time [sec]
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10. 2.2) Output Waveform - Simulation Result
The output voltage is regulated at V
V(Out) starts from 11V by the initial condition
The output current is 4.039A (RL=3)
Time [sec]
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11. 2.3) Output Power - Simulation Result
The simulation result shows the output power is 48.95W
Time [sec]
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12. 2.4) Gate Drive Output and Oscillator Timing (IC) - Simulation Result
PW = 3.282us
Oscillator frequency = 105kHz
VOSC
Time [sec]
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13. 3. 50W Off-Line Adapter Circuit (VIN=265Vac) - Simulation Circuit
V(Out) starts from 11V by the initial condition
VIN=265Vac
.tran 0 50m 0 10n
.Option Gmin=75E-9
.Option Abstol=1.0E-9
.Option Vntol=1.0u
.Option Trtol=1000
.Option Method=Gear
* Engine Solver: Alternate
V(Vcc) starts from 12V
Initial condition are set ,so the simulation starts near the steady state.
Copyright (C) Siam Bee Technologies 2015

14. 3.1) Input Waveform - Simulation Result
VDC,AVG = V
VDC, MIN = V
VAC = 265Vrms
Time [sec]
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15. 3.2) Output Waveform - Simulation Result
The output voltage is regulated at V
V(Out) starts from 11V by the initial condition
The output current is 4.025A (RL=3)
Time [sec]
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16. 3.3) Output Power - Simulation Result
The simulation result shows the output power is 48.70W
Time [sec]
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17. 3.4) Gate Drive Output and Oscillator Timing (IC) - Simulation Result
PW = 1.706us
Oscillator frequency = 105kHz
VOSC
Time [sec]
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18. 4. Transformer Specification
Winding Specification
Pin (S--F)
Turns NP
1 → 3 54 NS
9 → 12 10
NSUB
5 → 6 NP NS
Electrical Specification
Pin
Value
Inductance
1 - 3
600uH
Leakage
15uH
NSUB
To model the transformer (or coupled inductors), we can use the SPICE primitive k,
which describes the coupling ratio between a primary and a secondary.
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19. 5. Operation Waveform (VIN=110Vac, Example) - Simulation Circuit
V(Out) starts from 11V IF
VKA ID +
VDS -
The system parameter are as follows:
Maximum output power : 50W
Input voltage : 110Vrms
AC line frequency : 50Hz
Switching frequency : 100kHz +
VCC -
V(Vcc) starts from 12V
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20. 5.1) Transformer Turn Ratio - Simulation ResultVP VS
VCC
Time [sec]
This figure shows the waveforms of the voltages at each side of the transformer.
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21. 5.2) Transformer Primary Side Inductance (LP) - Simulation Result
VPWM
IF(D201, D202)
ID(UQ101)
Time [sec]
This figure shows the waveforms of ID(UQ101) and IF(D201, D202) in the CCM mode.
The primary-side inductance (LP) of the transformer determines the converter operation mode.
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22. 5.3) VCC Output Waveform - Simulation Result
VCC = V
Time [sec]
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23. 5.4) MOSFET Switching Device (UQ101) - Simulation Result
Switching loss (turn-off)
Switching loss (turn-on)
Conduction loss (VDS x ID)
VDS(t)
ID(t)
Time [sec]
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24. 5.5) Output Rectifier Diode (D201 - D202) - Simulation Result
Conduction loss (VF,AK x IF)
PLOSS_(D201, 202) (t)
Peak magnitude current
VKA(t)
IF(t)
Time [sec]
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25. 5.6) Current Sensing and Feedback Circuit - Simulation Result
1V Comparator
VCS
Time [sec]
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26. Copyright (C) Siam Bee Technologies 2015
Conclusion
Simulation Results
Input voltage
Output power
Oscillator frequency PW
85Vac
48.95 W
105 kHz
3.877 us
110Vac
3.278 us
265Vac
48.70 W
1.706 us
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27. Copyright (C) Siam Bee Technologies 2015
Simulation Details
Analysis directives:
.Tran 0 50m 0 10n
.Option Gmin=75E-9
.Option Abstol=1.0E-9
.Option Vntol=1.0u
.Option Trtol=1000
.Option Method=Gear
* Engine Solver: Alternate
Libraries:
.LIB 2sk4101ls.lib
.LIB an1431t.lib
.LIB pc817c.lib
.LIB d2sba60.lib
.LIB mbrf20100ct.lib
.LIB era91-02.lib
.LIB 1n5408.lib
.LIB fan7601.lib
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28. Appendix A - Initial Condition Settings
.IC V(Vdc_in)= {Vac*√2}
.IC V(Out) = 11V
Initial phase= 90
.IC V(Cs)= 0V
.IC V(Vcc)= 12V
.IC V(Ls)= 2V
.IC V(Rt_Ct)= 0V
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29. Appendix B - Bill of Materials
Designator
Manufacturer
Part Number
Comment R1 -
10Ω
C109
0.47uF
R103
56kΩ
C112
0.1uF
R105
100Ω
C201
1000uF
R107
0.5Ω
C202
R108
1kΩ
C203
1nF
R109
8kΩ
C222
2.2nF
R110
3.9kΩ D1
Fairchild
1N5408
Spice model
R201
3.3kΩ
D101
R202
1.2kΩ
D102
R204
27kΩ
D103
Fuji Electric
ERA91-02
R205
7kΩ
D201
ON Semi.
MBRF20100CT
R206
D202 C1 U1
Shindengen
D2SBA60
C103
150uF
U101
FAN7601
C105
10pF
UQ101
Sanyo
2SK4101LS
C106
2.7nF
U201
Panasonic
AN1431T
C107
47uF
U301
Sharp
PC817C
C108
0.01uF
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30. Copyright (C) Siam Bee Technologies 2015
Simulation Index
Simulations
Folder name
1. 50W Off-Line Adapter Circuit (VIN=85Vac)
2. 50W Off-Line Adapter Circuit (VIN=110Vac)
3. 50W Off-Line Adapter Circuit (VIN=85Vac)
4. Operation Waveform (VIN=110Vac, Example)
../Simulation data/VIN_85VAC
../Simulation data/VIN_110VAC
../Simulation data/VIN_265VAC
../Simulation data/Operation Waveform
Copyright (C) Siam Bee Technologies 2015