1. Power Electronics Lecture (3)
Prof. Mohammed Zeki Khedher
Department of Electrical Engineering
University of Jordan 1

2. Diode Symbol and Shape

3. Power Diode 3

4. Diode Characteristics4

5. Comparison between different types of Diodes
General Purpose Diodes
Fast Recovery Diodes
Schottky Diodes
Up to 6000V & 3500A
Up to 6000V and 1100A
Up to 100V and 300A
Reverse recovery time – High
Reverse recovery time – Low
Reverse recovery time – Extremely low. 5

6. General Purpose Diodes Fast Recovery Diodes Schottky Diodes
Turn off time – High
Turn off time – Low
Turn off time – Extremely low
Switching frequency – Low
(Max 1KHz)
Switching frequency – High
(Max 20KHz)
Switching frequency – Very high.
(Max 30KHz) 6

7. Typical Diode Characteristics

9. Practical representation

10. Diode Forward Characteristics

11. Example

12. Reverse Biased Region

13. Example

14. Diode reverse recovery process with various softness factors
Diode reverse recovery process with various softness factors. (a) Soft recovery; and (b) abrupt recovery

15. Reverse recovery …. Soft recovery is common
ta is due to charge storage
Softness factor (SF) = tb/ ta
Total recovery time trr = ta+tb
IRR = ta di/dt
Reverse recovery charge QRR

16. Approximation