Download 3 – Power Diode

3 – Power Diode
Symbol:
Review of Operation:
Reverse Bias: Anode (-) is less positive with respect to cathode (+). The diode is OFF.
Forward Bias: Anode (+) is more positive with respect to cathode (-). The diode is ON.
Structure:
3 – Power Diode
Power Electronics Track 1 Lecture Notes
A. R. Sombilla
Page 1
I-V Characteristics:
Categories / Types of Power Diodes:
1. General Purpose Diodes
-used to handle power at 50 – 60 Hz or frequencies below 1 Khz
-reverse recovery time of 25 microseconds
-Ratings vary from 1A/50V – 5 KA / 10 KV
-used in rectifiers and other types of converters
2. Fast-Recovery Diodes
-have reverse recovery time of the order of 25 – 100 ns (less than 5 microseconds)
-have ratings from 1 A / 50 V to 1 KA / 3 KV
-used in inverters, choppers, SMPS, UPS, etc.
3 – Power Diode
Power Electronics Track 1 Lecture Notes
A. R. Sombilla
Page 2
3. Schottky Diodes
-may be made of metals such as molybdenum, platinum, chrome, tungsten
-no p-n junction, hence have fast switching action
-have low threshold voltage (0.2 V)
-low reverse breakdown voltage (about 50 volts compared to 150 V of p-n
junction diodes)
-used in SMPS, AC to DC converters, feedback and freewheeling operations of
power converters.
-I-V characteristics of Schottky diodes
3 – Power Diode
Power Electronics Track 1 Lecture Notes
A. R. Sombilla
Page 3
General Areas of Application of power diodes:
1. Uncontrolled Rectifiers
2. Feedback and Freewheeling operations in choppers, inverters, and controlled rectifiers
3. Commutation Circuits for SCRs
4. Half-controlled Converters and Half-bridge Inverters
Common Ratings:
Type
Gen. purpose
High Speed
Schottky
V-I Ratings
10 KV/5KA
3KV/1KA
50 V/50 A
Max. Frequency
2 Khz
12 Khz
20 Khz
On-state drop
1-2 V
1-1.5 V
0.5 -1 V
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3 – Power Diode
Power Electronics Track 1 Lecture Notes
A. R. Sombilla
Page 4