1. Switching-Mode Regulators
Convert an unregulated DC voltage into a regulated DC voltage
ECE 442 Power Electronics

2. Output Voltage is Less Than the Input Voltage
Buck Regulator
Output Voltage is Less Than the Input Voltage
BJT Chopper L-C Filter Load
Control Voltage Freewheeling Diode
ECE 442 Power Electronics

3. Mode 1 Operation – Q1 switched ON
Input current flows through L, C, and the Load – rises linearly
ECE 442 Power Electronics

4. Mode 2 Operation – Q1 switched OFF
Inductor current continues to flow through L, C, the Load, and Dm, falling linearly until Q1 is turned ON again.
ECE 442 Power Electronics

5. Waveforms for the Buck Regulator
ECE 442 Power Electronics

6. Summary for the Buck Regulator
The peak-to-peak ripple current is
The peak-to-peak ripple voltage is
ECE 442 Power Electronics

7. Summary for continuous current case
The critical value of the inductor is
The critical value of the capacitor is
ECE 442 Power Electronics

8. Output Voltage is Greater Than the Input Voltage
Boost Regulator
Output Voltage is Greater Than the Input Voltage
ECE 442 Power Electronics

9. Mode 1 Operation – M1 switched ON
Input current flows through L and M1 (linearly)
ECE 442 Power Electronics

10. Mode 2 Operation – M1 switched OFF
Current that flowed through the transistor now flows through L, C, the Load, and diode Dm until transistor M1 is turned ON again.
ECE 442 Power Electronics

11. Waveforms for the Boost Regulator
ECE 442 Power Electronics

12. Summary for the Boost Regulator
The peak-to-peak ripple current is
The peak-to-peak ripple voltage is
ECE 442 Power Electronics

13. Summary for continuous current case
The critical value of the inductor is
The critical value of the capacitor is
ECE 442 Power Electronics

14. Buck-Boost Regulator
The output voltage could be less than or greater than the input voltage
The polarity of the output voltage is opposite to the polarity of the input voltage Vs – Inverting Regulator
ECE 442 Power Electronics

15. Mode 1 Operation – Q1 turned ON
Input current flows through inductor L and Q1 linearly.
ECE 442 Power Electronics

16. Mode 2 Operation – Q1 switched OFF
Current flowing through L now flows through L, C, Dm and the Load.
ECE 442 Power Electronics

17. Waveforms for the Buck-Boost Regulator
ECE 442 Power Electronics

18. Summary for the Buck-Boost Regulator
The peak-to-peak ripple current is
The peak-to-peak ripple voltage is
ECE 442 Power Electronics

19. Summary for continuous current case
The critical value of the inductor is
The critical value of the capacitor is
ECE 442 Power Electronics

20. Converter with a highly inductive Load
Input Current is “pulse” shaped
ECE 442 Power Electronics

21. Connect an input filter
Filter out the converter-generated harmonics from the supply line.
ECE 442 Power Electronics

22. Equivalent circuit for the converter-generated harmonic currents
ECE 442 Power Electronics

23. Example 5.10
ECE 442 Power Electronics

24. Buck Chopper for PSpice Simulation
ECE 442 Power Electronics

25. Results from PSpice
ECE 442 Power Electronics

26. Fourier Coefficients of the input current
ECE 442 Power Electronics

27. Example 5.10 in MultiSim7
ECE 442 Power Electronics

28. ECE 442 Power Electronics

29. Fourier Coefficients of the Input Current
ECE 442 Power Electronics

30. ECE 442 Power Electronics

31. ECE 442 Power Electronics

32. ECE 442 Power Electronics