Switch mode power supply

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 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 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 . 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 Cost Energy Storage Voltage Relation Features Buck 0-1000 1.0 Single inductor 0 ≤ Out ≤ In V2=D.V1 Continuous current at output Boost 0-150 1.0 Single inductor Out ≥ In V2=V1.[(1)/(1-D)] Continuous current at input Buck-boost 0-150 1.0 Single inductor Out ≤ 0 V2= -V1[(D)/(1-D)] No continuous current

10. Use of various transformer isolated topologies:

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

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

13. Mode 2 Operation -- Q 1 turned OFF Polarity of the windings reverses Diode D 1 conducts, charging C and providing current to the load R L 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: Q 1 ON, V s across the lower primary winding Q 2 ON, V s across the upper primary winding

17. 3.Half-Bridge Converter:

18. Mode 1 Operation Q 1 ON, D 1 is conducting Energy transferred to the load

19. Mode 2 Operation Both transistors are OFF D 1 continues to conduct due to current in L 1

20. Mode 3 Operation: Q 2 ON, D 2 conducting Energy transferred to the load

21. Mode 4 Operation Both transistors OFF D 2 continues to conduct due to current in L 1

22. Waveform Summary – k<0.5

23. Full-Bridge Converter:

24. Mode 1 Operation Q 1 ,Q 4 ON, Q 2 ,Q 3 OFF D 1 conducting, energy transferred to the load

25. Mode 2 Operation All transistors are OFF D 1 continues to conduct due to current in L 1

26. Mode 3 Operation Q 2 ,Q 3 are ON, Q 1 ,Q 4 OFF D 2 conducting, energy transferred to the load

27. Mode 4 Operation All transistors are OFF D 2 continues to conduct due to current in L 1

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 Rs. 4700 Antec 750W Rs. 6600 Cooler master 550W Rs. 3800 Corsair 750W Rs. 10700 Seasonic 500W Rs. 3600 UMAX 450W Rs. 570

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!! Questions?