SMPS with multiple isolated outputs design SEPIC, FLYBACK and FORWARD Converter.

1. DESIGN OF DC-DC CONVERTER FOR
SMPS WITH MULTIPLE ISOLATED
OUTPUTS
PRAJWAL RAJ M B

2. Content
1. SMPS
2. DC-DC Converter Topologies
3. SEPIC Converter, Operation and simulation
results
4. Flyback Converter, Operation and Simulation
results
5. Forward Converter , Operation and Simulation
results
6. Closed Loop circuit for the SEPIC Converter, PI
controller and Simulation results.
7. Conclusion.

3. SMPS
What is SMPS?
• An electrical power supply that incorporates a
switching regulator to convert electrical power
efficiently.
• Voltage regulation is achieved by varying the ratio
of on-to-off time
• The SMPS has dc-to-dc switching converter for
conversion from unregulated dc input to
regulated dc output voltage.
• Typical frequency range of SMPS is from 50 kHz
to several MHz.

4. Switched-mode power supply
• The input supply drawn from ac mains is first
rectified to get a unregulated dc voltage.
• The unregulated dc voltage then fed to a high
frequency dc- to dc converter.
• Most of the dc-dc converters used in SMPS
circuits have high frequency transformer for
voltage scaling & isolation.
• Output voltage is again filtered at the
secondary side.

5. Advantages of SMPS
• Lower weight
• Smaller size
• Higher efficiency
• Reduced costs
• Lower power dissipation
• Provide isolation between multiple outputs.
Disadvantages of SMPS
• Greater circuit complexity.

6. Applications of SMPS
• Personal computers
• Space stations
• Electric vehicles
• Mobile battery chargers
• Security Systems (Closed circuit cameras) etc

7. DC-DC CONVERTER TOPOLOGIES
• SEPIC Converter
• Flyback Converter
• Forward Converter

8. Objective :
• To design multiple isolated outputs.
• The output voltages is designed for 12V, 5V
and 3.3V for an input voltage of the order of
200-400V input supply.
• The simulation of the circuits is done in
Matlab.

9. 1. SEPIC CONVERTER

10. Operation of SEPIC Converter
Two modes of operation
• Mode1: when ‘Sw’ is ON
• Mode2 :when Sw is off

11. Parameters
Input voltage 357.8V
Output voltage V1=12V, V2=3.3V, V3=5V
Inductor L1=12mH
Capacitors C1=40nf, C01=150mf, C02=40mf,
C03=100mf
Duty cycle 50%
Switching frequency 61923.381Hz

12. Simulation Results
• Input Voltage :357.8V
• 12V output
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-400
-300
-200
-100
0
100
200
300
400
Time(s)
V(in)
0 1 2 3 4 5 6 7 8 9 10
0
2
4
6
8
10
12
14
Time(s)
V1(V)

13. • 5V output
• 3.3V output
0 1 2 3 4 5 6 7 8 9 10
0
1
2
3
4
5
6
Time(s)
Voltage(v3)V
0 1 2 3 4 5 6 7 8 9 10
0
1
2
3
4
Time(s)
V(2)V

14. Flyback Converter

15. Operation of Flyback Converter
Two modes of operation
• Mode1: when ‘Sw’ is ON
• Mode2: when ‘Sw’ is off

16. Parameters for Flyback Converter
Input voltage 357.8V
Output voltages V1=12V, V2=5V and V3=3.3V
Inductor Lm=15mH
Capacitor C01=150mf, C02=100mf, C03=50mf
Duty cycle 50%
Switching frequency 50kHz

17. Simulation Results
• Input Voltage :357.8V
• 12V output
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
x 10
5
0
2
4
6
8
10
12
14
Time(s)
V1(V)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-400
-300
-200
-100
0
100
200
300
400
Time(s)
V(in)

18. • 5V output
• 3.3V output
0 1 2 3 4 5 6 7 8 9 10
0
1
2
3
4
5
6
Time(s)
V(2)
0 1 2 3 4 5 6 7 8 9 10
0
1
2
3
4
5
Time(s)
V(3)V

19. Forward Converter

20. Operation of the Forward Convereter
Two modes of operation:
• When switch ‘sw’ is on
• When switch ’sw’ is off

21. Parameters for the forward Converter
Input Voltage 200V
Output Voltage V1=12V, V2=3.3V
Inductance L1=8.5µH, L2=19.2mH
Capacitance C1=385mf, C2=120mf
Switching Frequency 100kHz
Duty ratio 50%

22. Simulation Results
• Input voltage:200V
• Output Voltage: 3.3V
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-200
-150
-100
-50
0
50
100
150
200
Time(s)
Vin(V)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
0.5
1
1.5
2
2.5
3
3.5
Time(s)
V1(V)

23. • 12V output:
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
2
4
6
8
10
12
14
Time(s)
V2(V)

24. Closed Loop Circuit for SEPIC
Converter Using PI Controller

25. • The Kp and Ki values selected for PI Controller
Kp Ki
PI Controller 0.4 2
PI Controller 1 0.2 5
PI Controller 2 0.1 8

26. Simulation Results
• Input voltage:357.8
• 12V output
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
2
4
6
8
10
12
14
Time(S)
V1(V)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-400
-300
-200
-100
0
100
200
300
400
Time(s)
V(in)

27. • 5V output
• 3.3V output
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
1
2
3
4
5
Time(s)
V2(V)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
1
2
3
4
5
6
Time(s)
V3(V)

28. Conclusion
• The closed loop circuit is more efficient in
terms of settling time when compared to open
loop condition which is verified in the SEPIC
Converter.
• Constant voltage can be maintained even
though there is variation in the load if closed
loop control circuit is employed.

29. THANK YOU