The document discusses switched mode power supplies (SMPS). It defines SMPS and explains their advantages over linear power supplies, including higher efficiency and smaller size. The document outlines the typical stages in an SMPS, including rectification, inversion and regulation. It examines factors to consider when selecting an SMPS topology for an application and describes the operating principles of common isolated topologies like flyback, push-pull, half bridge and full bridge converters. Finally, it provides examples of SMPS applications and discusses SMPS usage in Indian consumer markets.

1. Switched Mode Power Supply

2. Contents:-
• General description of Power Supply
• Advantages/Disadvantages of SMPS
• Block diagram of SMPS
• Basic topologies and practical
• requirements
• Working of various SMPS topologies:
1. Flyback Converter
2. Push-pull Converter
3. Half bridge Converter
4. Full bridge Converter
• Applications of SMPS
• Conclusion

3. Power Supply:-
Any device that supplies electric
power to an electric load.
The different types of power
supplies include:
-Battery
-DC power supply
-AC power supply
-Linear regulated power supply
-Switched mode power supply
-Programmable power supply
-Uninterruptible power supply

4. Switched Mode Power Supply:
 An electrical power supply that incorporates a switching
regulator to convert electrical power efficiently.
 It transfers power from a source, to a load, while
converting voltage and current characteristics.
 Voltage regulation is achieved by varying the ratio of on-
to-off time.

5. Advantages of SMPS over Linear Power Supplies:
• 1. Lower weight
• 2. Smaller size
• 3. Higher efficiency
• 4. Lower power dissipation
• 5. Wide ac input voltage range
• 6. Reduced costs
Disadvantages of SMPS:
1. Complexity of the circuit

6. Block diagram of a SMPS
1. Input rectifier stage:
It is used to convert an ac input to dc. A SMPS with dc
input does not require this stage. The rectifier
produces unregulated dc which is then passed through
the filter circuit.

7. • 2. Inverter stage:
– The inverter stage converts DC, whether directly from the input
or from the rectifier stage described above, to AC by running it
through a power oscillator, whose output transformer is very
small with few windings at a frequency of tens or hundreds
of kilohertz.
3. Output transformer:
- If the output required is to be isolated from input, the inverted
AC is used to draw the primary windings of a high frequency
transformer. This converts the voltage up or down to the
required output level on it’s secondary winding.
4. Output rectifier:
- If the dc output is required, the ac output from the transformer
is rectified.
5. Regulation:
- Feedback circuit monitors the output voltage and compares it
with the reference voltage.

8. Factors to be considered while selecting a
topology for a particular application:-
• 1. Is input-to-output dielectric isolation required for the application?
• 2. Are multiple outputs required?
• 3. Does the prospective topology place a reasonable voltage stress
across the voltage semiconductors?
• 4. Does the prospective topology place a reasonable current stress
across the voltage semiconductors?
• 5. How much of the input voltage is placed across the primary
transformer winding or inductor?
• Typical maximum output power available from each topology:
Converter Topology Maximum output power
Flyback 200W
Forward 300W
Push-pull 500W
Half bridge 1000W
Full bridge >1000W

9. Use of non-isolated topologies:
• Non isolated topologies are the simplest, with the three basic types using a
single inductor for energy storage.
Type Power(W) Relative Energy Voltage Relation Features
Cost Storage
Buck 0-1000 1.0 Single 0 ≤ Out ≤ In Continuous
inductor V2=D.V1 current at
output
Boost 0-150 1.0 Single Out ≥ In Continuous
inductor V2=V1.[(1)/(1-D)] current at
input
Buck- 0-150 1.0 Single Out ≤ 0 No
boost inductor V2= -V1[(D)/(1-D)] continuous
current

10. Use of various transformer isolated topologies:

11. Working of various SMPS Topologies:
1. Flyback converter:

12. Mode 1 Operation -- Q1 ON
• Current builds up in the primary winding
• Secondary winding has the opposite polarity D1 OFF
• C maintains the output voltage, supplies load current

13. Mode 2 Operation -- Q1 turned OFF
• Polarity of the windings reverses
• Diode D1 conducts, charging C and providing current to the load RL
• Secondary current falls to 0 before the next cycle begins

14. Waveform Summary:

15. 2. Push-Pull Converter:

16. Operation of the Push-Pull Converter:
• Q1 ON, Vs across the lower primary winding
• Q2 ON, Vs across the upper primary winding

17. 3.Half-Bridge Converter:

18. Mode 1 Operation
• Q1 ON, D1 is conducting
• Energy transferred to the load

19. Mode 2 Operation
• Both transistors are OFF
• D1 continues to conduct due to current in L1

20. Mode 3 Operation:
• Q2 ON, D2 conducting
• Energy transferred to the load

21. Mode 4 Operation
• Both transistors OFF
• D2 continues to conduct due to current in L1

22. Waveform Summary – k<0.5

23. Full-Bridge Converter:

24. Mode 1 Operation
• Q1,Q4 ON, Q2,Q3 OFF
• D1 conducting, energy transferred to the load

25. Mode 2 Operation
• All transistors are OFF
• D1 continues to conduct due to current in L1

26. Mode 3 Operation
• Q2,Q3 are ON, Q1,Q4 OFF
• D2 conducting, energy transferred to the load

27. Mode 4 Operation
• All transistors are OFF
• D2 continues to conduct due to current in L1

28. Waveform Summary – k<0.5

29. Applications of SMPS:-
• 1. Machine tool industries
• 2. Security Systems
• (Closed circuit cameras)
• 3. Support supplies with PLC’s
• 4. Personal Computers
• 5. Mobile Phone chargers

30. SMPS in Indian markets:
iball 600W Antec 750W Cooler master 550W
Rs. 4700 Rs. 6600 Rs. 3800
Seasonic 500W UMAX 450W
Corsair 750W
Rs. 3600 Rs. 570
Rs. 10700

31. Conclusion:
• The most common SMPS topologies: flyback, push-pull,
half bridge and full bridge converters have been outlined.
• Each has it’s own particular operating characteristics and
advantages, which makes it suitable to particular
applications.
• Some of the most common applications of SMPS have
been discussed.
References:
www.wikipedia.org
www.howstuffworks.com
Philips semiconductors manual
Lambda semiconductors manual
Motorola semiconductors manual
Microchip manual

32. Thank you!!