Power ElectronicsLecture (3)

Prof. Mohammed Zeki Khedher

Department of Electrical Engineering

University of Jordan

1

Diode Symbol and Shape

Power Diode

3

Diode Characteristics

4

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.

25rrt s 0.1 s to 5 srrt a few nano secrrt

5

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)

0.7 to 1.2VFV 0.8 to 1.5VFV 0.4 to 0.6VFV

6

Typical Diode Characteristics

Practical representation

Diode Forward Characteristics

Example

Reverse Biased Region

Example

Diode reverse recovery process with various softness factors.

(a) Soft recovery; and (b) abrupt recovery

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

Approximation