This document describes LTspice simulations of a 50W flyback converter circuit using different input voltages. It includes the circuit schematic, input and output waveforms, power output, and gate drive timing for input voltages of 85Vac, 110Vac and 265Vac. It also provides more detailed waveforms and analysis for an example simulation with 110Vac input, examining the transformer operation, MOSFET switching, and feedback circuit. Specifications and simulation settings are provided in appendices.

1. Bee Technologies
http://www.bee-tech.info/
Design Kit
Flyback Converter using PWM IC
LTspice Version
1Copyright (C) Siam Bee Technologies 2015
02JUL2015

2. 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
2Copyright (C) Siam Bee Technologies 2015

3. 1. 50W Off-Line Adapter Circuit (VIN=85Vac)
- Simulation Circuit
3Copyright (C) Siam Bee Technologies 2015
.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
 Initial condition are set ,so the simulation starts near the steady state.
VIN=85Vac
V(Out) starts from 11V
by the initial condition
V(Vcc) starts from 12V

4. 1.1) Input Waveform
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 4
Time [sec]
VDC,AVG = 104.33V
VAC = 85Vrms
VDC, MIN = 85.8V

5. 1.2) Output Waveform
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 5
The output voltage is regulated at 12.12V
Time [sec]
The output current is 4.04A (RL=3)
V(Out) starts from 11V
by the initial condition

6. 1.3) Output Power
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 6
Time [sec]
The simulation result shows the output power is 48.90W

7. 1.4) Gate Drive Output and Oscillator Timing (IC)
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 7
Time [sec]
VOSC
Oscillator frequency = 105kHz
PW = 3.877us

8. 2. 50W Off-Line Adapter Circuit (VIN=110Vac)
- Simulation Circuit
8Copyright (C) Siam Bee Technologies 2015
.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
 Initial condition are set ,so the simulation starts near the steady state.
VIN=110Vac
V(Vcc) starts from 12V
V(Out) starts from 11V
by the initial condition

9. 2.1) Input Waveform
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 9
Time [sec]
VDC,AVG = 142.41V
VAC = 110Vrms
VDC, MIN = 128.621V

10. 2.2) Output Waveform
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 10
The output voltage is regulated at 12.118V
Time [sec]
The output current is 4.039A (RL=3)
V(Out) starts from 11V
by the initial condition

11. 2.3) Output Power
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 11
Time [sec]
The simulation result shows the output power is 48.95W

12. 2.4) Gate Drive Output and Oscillator Timing (IC)
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 12
Time [sec]
PW = 3.282us
VOSC
Oscillator frequency = 105kHz

13. 3. 50W Off-Line Adapter Circuit (VIN=265Vac)
- Simulation Circuit
13Copyright (C) Siam Bee Technologies 2015
.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
 Initial condition are set ,so the simulation starts near the steady state.
VIN=265Vac
V(Vcc) starts from 12V
V(Out) starts from 11V
by the initial condition

14. 3.1) Input Waveform
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 14
Time [sec]
VDC,AVG = 367.58V
VAC = 265Vrms
VDC, MIN = 361.264V

15. 3.2) Output Waveform
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 15
The output voltage is regulated at 12.075V
Time [sec]
The output current is 4.025A (RL=3)
V(Out) starts from 11V
by the initial condition

16. 3.3) Output Power
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 16
Time [sec]
The simulation result shows the output power is 48.70W

17. 3.4) Gate Drive Output and Oscillator Timing (IC)
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 17
Time [sec]
PW = 1.706us
VOSC
Oscillator frequency = 105kHz

18. 4. Transformer Specification
Copyright (C) Siam Bee Technologies 2015 18
NP NS
NSUB
Pin (S--F) Turns
NP 1 → 3 54
NS 9 → 12 10
NSUB 5 → 6 10
Winding Specification
Pin Value
Inductance 1 - 3 600uH
Leakage 1 - 3 15uH
Electrical Specification
 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.

19. 5. Operation Waveform (VIN=110Vac, Example)
- Simulation Circuit
19Copyright (C) Siam Bee Technologies 2015
+
VDS
-
ID
- +
VKA
IF
The system parameter are as follows:
- Maximum output power : 50W
- Input voltage : 110Vrms
- AC line frequency : 50Hz
- Switching frequency : 100kHz
VIN=110Vac
+
VCC
-
V(Out) starts from 11V
V(Vcc) starts from 12V

20. 5.1) Transformer Turn Ratio
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 20
Time [sec]
VP
VS
VCC
 This figure shows the waveforms of the voltages at each side of the transformer.

21.  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.
5.2) Transformer Primary Side Inductance (LP)
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 21
Time [sec]
ΟNΤ
Τ
IF(D201, D202)
VPWM
ID(UQ101)

22. 5.3) VCC Output Waveform
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 22
Time [sec]
VCC = 12.367V

23. 5.4) MOSFET Switching Device (UQ101)
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 23
Time [sec]
VDS(t)
ID(t)
Switching
loss (turn-off)
Switching loss
(turn-on)
Conduction loss
(VDS x ID)

24. 5.5) Output Rectifier Diode (D201 - D202)
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 24
Time [sec]
VKA(t) IF(t)
Peak magnitude
current
Conduction loss
(VF,AK x IF)
PLOSS_(D201, 202) (t)

25. 5.6) Current Sensing and Feedback Circuit
- Simulation Result
Copyright (C) Siam Bee Technologies 2015 25
Time [sec]
1V Comparator
VCS

26. Conclusion
Copyright (C) Siam Bee Technologies 2015 26
Input voltage Output power Oscillator frequency PW
85Vac 48.95 W 105 kHz 3.877 us
110Vac 48.95 W 105 kHz 3.278 us
265Vac 48.70 W 105 kHz 1.706 us
Simulation Results

27. 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
27Copyright (C) Siam Bee Technologies 2015

28. Appendix A
- Initial Condition Settings
Copyright (C) Siam Bee Technologies 2015 28
Initial phase= 90
.IC V(Vdc_in)= {Vac*√2}
.IC V(Vcc)= 12V
.IC V(Out) = 11V
.IC V(Cs)= 0V
.IC V(Rt_Ct)= 0V
.IC V(Ls)= 2V

29. Appendix B
- Bill of Materials
Copyright (C) Siam Bee Technologies 2015 29
Designator Manufacturer Part Number Comment Designator Manufacturer Part Number Comment
R1 - 10Ω - C109 - 0.47uF -
R103 - 56kΩ - C112 - 0.1uF -
R105 - 100Ω - C201 - 1000uF -
R107 - 0.5Ω - C202 - 1000uF -
R108 - 1kΩ - C203 - 1nF -
R109 - 8kΩ - C222 - 2.2nF -
R110 - 3.9kΩ - D1 Fairchild 1N5408 Spice model
R201 - 3.3kΩ - D101 Fairchild 1N5408 Spice model
R202 - 1.2kΩ - D102 Fairchild 1N5408 Spice model
R204 - 27kΩ - D103 Fuji Electric ERA91-02 Spice model
R205 - 7kΩ - D201 ON Semi. MBRF20100CT Spice model
R206 - 10Ω - D202 ON Semi. MBRF20100CT Spice model
C1 - 1nF - U1 Shindengen D2SBA60 Spice model
C103 - 150uF - U101 Fairchild FAN7601 Spice model
C105 - 10pF - UQ101 Sanyo 2SK4101LS Spice model
C106 - 2.7nF - U201 Panasonic AN1431T Spice model
C107 - 47uF - U301 Sharp PC817C Spice model
C108 - 0.01uF -

30. Simulation Index
30
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