Chapter 1
Chapter1
Chapter 1 Power Electronic Devices
Outline
An introductory overview of power electronic devices
1. Uncontrolled device—power diode
2. Half- controlled device—thyristor
3. Typical fully- controlled devices-------BJT
An introductory overview of power electronic devices
The concept and features
Power electronic devices: are the electronic devices that can be directly
used in the power processing circuits to convert or control electric
power.
Vacuum devices: Mercury arc
rectifier
In broad sense
Power electronic devices
thyratron, etc. . seldom
in use today
Semiconductor devices:
major power electronic devices
Very often: Power electronic devices= Power semiconductor devices
Major material used in power semiconductor devices——Silicon
Features of power electronic devices
a) The electric power that power electronic device deals with is usually
much larger than that the information electronic device does.
b) Usually working in switching states to reduce power losses
On-state
Voltage across the device is 0
p=vi=0
V=0
Off-state
Current through the device is 0
p=vi=0
i=0
c)Need to be controlled by information electronic circuits.
d)Very often, drive circuits are necessary to interface between
information circuits and power circuits.
e)Dissipated power loss usually larger than information electronic
devices —special packaging and heat sink are necessary.
Power loss in PD
Objectives



Identify the difference between the forward characteristic of a power
diode and a signal level diode and explain it.
Draw the “Turn On” and “Turn Off” characteristics of a power diode.
Define “Forward recovery voltage”, “Reverse recovery current”
“Reverse Recovery charge” as applicable to a power diode.
Power diodes
Similar to normal PN diode except the ability to carry large
currents. These power devices, however, are required to carry
up to several KA of current under forward bias condition and
block up to several KV under reverse biased condition.
 Three types of power diodes exists
1. General purpose diodes
2. Fast recovery diodes
3. Schottky diodes
4. Silicon carbide diode(ultra low power loss, Ultra fast
switching behavior, highly reliable but they are expesive)

Constructional difference
Power diode
Diode characteristics