1. ECD 442 Power Electronics1 Power MOSFETs Two Types –Depletion Type Channel region is already diffused between the Drain and Source Deplete, or “pinch-off” the Channel –Enhancement Type No channel region exists between the Drain and Source “Invert” the region between the Drain and Source to induce a channel

2. ECD 442 Power Electronics2 Depletion MOSFET

3. ECD 442 Power Electronics3 N-Channel Depletion MOSFET Normally Reverse-Bias the Gate-Source Junction

4. ECD 442 Power Electronics4 Enhancement MOSFET

5. ECD 442 Power Electronics5 N-Channel Enhancement MOSFET The Gate-Source Junction will be Forward-Biased The bias voltage must be greater than a “threshold” voltage A Channel region is induced between the Drain and Source

6. ECD 442 Power Electronics6 Drain Characteristics

7. ECD 442 Power Electronics7 Steady-State Characteristics

8. ECD 442 Power Electronics8 Switching Characteristics

9. ECD 442 Power Electronics9 Equivalent Circuit

10. ECD 442 Power Electronics10 Switching Model

11. ECD 442 Power Electronics11 Switching Waveforms and Times

12. ECD 442 Power Electronics12 Turn-on Delay, t d(on) = time to charge the input capacitance to V T Rise time, t r = Charging time to charge the input capacitance to the full gate voltage, V GSP in order to drive the transistor into the linear region of operation

13. ECD 442 Power Electronics13 Turn-off delay time, t d(off) = time for the input capacitance to discharge from “overdrive” voltage V 1 to pinch-off. V GS must decrease significantly for V DS to rise. Fall time, t f = time for the input capacitance to discharge from pinch-off to the threshold voltage.