Chapter 2 Overview of Power Semiconductor Devices

1. Chapter 2 Overview of Power Semiconductor Devices • Introduction • Diodes • Thyristors • Ideal switches • Bipolar transistors • MOSFETs • MOS-Controlled Thyristors • Comparison of controllable switches

5. Thyristors • Semi-controlled device • Latches ON by a gate-current pulse if forward biased • Turns-off if current tries to reverse

7. Thyristor in a Simple Circuit • For successful turn-off, reverse voltage required for an interval greater than the turn-off interval

8. Generic Switch Symbol • Idealized switch symbol • When on, current can flow only in the direction of the arrow • Instantaneous switching from one state to the other • Zero voltage drop in on-state • Infinite voltage and current handling capabilities

9. Switching Characteristics (linearized) • Switching Power Loss is proportional to: • switching frequency • turn-on and turn-off times

10. Switch: ideal characteristics • Small leakage current in off state • Small on state voltage • Short turn-on and turn-off • Large forward and reverse voltage • High on state current rating • Positive temperature coefficient • Small control power required to switch • Capability to survive rated voltage and rated current simultaneously

11. Bipolar Junction Transistors (BJT) #1 • Used commonly in the past • Now used in specific applications • Replaced by MOSFETs and IGBTs

12. Bipolar Junction Transistors (BJT) #2

13. Bipolar Junction Transistors (BJT) #3

14. Various Configurations of BJTs

15. Conclusions BJTs

16. MOSFETs #1 • Easy to control by the gate • Optimal for low-voltage operation at high switching frequencies • On-state resistance a concern at higher voltage ratings

17. MOSFETs #2

20. IGBT

22. Conclusions IGBT

23. Gate-Turn-Off Thyristors (GTO) • Slow switching speeds • Used at very high power levels • Require elaborate gate control circuitry

24. MOS CONTROLLED THYRISTORS (MCT)

26. Comparison of Controllable Switches

27. Summary of Device Capabilities