Power semiconductor devices
Overview
Application of power devices
Power devices
characteristiocs of power devices
Since power devices are used in large power applications it should have the following characteristics:
It should have high voltage rating.
It should have high current rating.
It should have high power rating.
It should offer less forward resistance.
It should have less forward voltage drop.
It should have zero leakage current.
It should have capability to handle high temperature.
Some of the Power Devices are
Power Diode
Power BJT
Silicon controlled rectifier
Triac [TRI AC - 3 Terminals Tri state for AC]
Power MOSFET
IGBT [Insulated gate bipolar junction transistor]
Power devices are used in many applications. The applicatins of power devices can be broasdly classfied into 4 different areas
1. AC to DC converters- Rectifiers
2.AC to AC converters - Voltage controllers
3. DC to DC converters - DC Choppers
4. DC to AC converters - Power Inverters
in this article am going to discuss concepts on Fully contrrolled rectifiers only
Rectifiers:
Circuits that are used to convert AC to DC are called as Rectifiers. As we know the application of DC is enormous, we need to convert AC signal into DC signal. Rectifiers can be designed by using components like diode,SCR etc which are unidirectional in nature.
Rectification can be of two types
Uncontrolled rectification
the angle at which the device start conducting cannot be decided
usually designed using components like diodes
Controlled rectification
The angle at which the device can start conducting can be decided.
Usually designed using components like Thyristor (SCR)
Single phase fully controlled HALF WAVE Rectifier
A fully controlled HWR using SCR is as shown above.
It consists of a transformer, SCR & a load ®During –ve Half cycle, SCR will be in reverse biased. Hence it will be in reverse blocking mode. \ During –ve half, no o/p voltage is obtained.
During +ve half cycle, anode will be connected to +ve& cathode will be connected to –ve making SCR forward bias. But SCR will be in forward blocking mode, \ o/p is zero.
In order to move SCR from forward blocking mode to forward conduction mode, a gate triggering voltage must be applied as shown in the waveform.