1. POWER ELECTRONICS Instructor: Eng.Moayed N. EL Mobaied The Islamic University of Gaza Faculty of Engineering Electrical Engineering Department بسم الله الرحمن الرحيم EELE 5450 — Fall 2009-2010 Lecture 3

2. Chapter Two Power Semiconductor Diodes Power diodes have large power-, voltage-, current- handling capabilities than that of ordinary signal diodes.

3. Chapter Two Power Diodes symbol and type of packaging

4. Chapter Two Diode Characteristics

5. Chapter Two V-I characteristics Forward-biased region Reverse biased region Breakdown region

6. Chapter Two N=1,2( Germanium, Silicon) practically 1.1—1.8 Shockley’s equation V T = Thermal voltage I S = Saturation current

7. Chapter Two Shockley diode equation

8. Chapter Two Forward-bias V D >0

9. Chapter Two Reverse-bias V D <0

10. Chapter Two Reverse Recovery Characteristics Tb/Ta is the softness factor (SF)

11. Chapter Two Power Diode Types Ideally, a diode should have no reverse recovery time, However, the manufacturing cost of such diode will increase. The power diodes can be classified into three categories: Standard or general-purpose diodes Fast-recovery diodes Schottky diodes

12. Chapter Two Standard or general-purpose diodes Reverse recovery time= 25 us (relatively high). Used in Low-speed applications. Current rating : From less than 1 Ampere to several thousands of Amperes. Voltage rating 50 v to 5 kV.

13. Chapter Two Fast-Recovery Diodes Reverse recovery time< 5 us ( Low). Used in DC-DC and DC-AC converter circuit (high speed applications). Current rating : From less than 1 Ampere to several hundreds of Amperes. Voltage rating 50 v to 3 kV. Platinum or gold.

14. Chapter Two Schottky Diodes No minority carriers. Recovered charge is much less than P-n junction diodes. Used in high current and low voltage dc power supplies. Current rating : From 1 Ampere to 300 Amperes. Voltage rating <100 V.

15. Chapter Two End of Lecture **** Eng.moayed The reverse recovery time of a diode is trr=3us and the rate of fall of the diode current is di/dt=30 A/us Determine (a) the storage charge Q rr (b) Peak reverse current I rr