Semiconductor devices & Power Electronics.

Power Electronics is combination of Power, electronics and Control.

It is primarily based on switching of power semiconductor devices. Development in Power handling capacity and switching speed of power device improving rapidly.


Power electronics tooks very important place in modern technology and used in many applications and high power products.

Some popular Applications-

1-Electric Vehicle

2-Furnace

3-High Frequency Lightings

4-High voltage DC

5-Heat Control

6-Laser Power supply

7-Motor control

8-Voltage regulator 

Power Semiconductor devices-

Since 1970 various types of power semiconductor devices were developed, which are made up of silicon or silicon carbide. Silicon carbide Device are still under development, majority of devices are made from Silicon.

Classification of Power semiconductor devices-

1- Power Diodes

2- Thyristors

3- Transistors

1-Diodes

It has 2 terminal cathode and anode. Diode conduct when anode voltage is greater than cathode and forward voltage drop of diode is from 0.5V to 1.2V. It is classified in 3 types, 

a- General Purpose- General purpose diode are available up to 6000V, 4500 Amp.

b- High speed- It also call fast recovery it ranges up to 6000V, 1100 Amp. Reverse recovery time varies from  0.1 us to 0.5 us.  These diodes are used in high frequency switching application.

c- Schottky Diodes- this diode has low in state voltage and very small recovery time in nano seconds. Rating are limited to 100 V, 300 Amp.

2- Thyristor

Thyristor is 3 terminal device, Anode, cathode and gate. When current passes through gate terminal to cathode and if  anode is at higher potential than cathode then thyristor conduct.

When thyristor is in conduction mode then gate has no control on it, thyristor is turned off when anode voltage is less than or equal to cathode voltage.





Thyristor are classified in to 11 types -

1- Forced commutated thyristor required extra circuit to turn off , called commutation circuit.

2- Natural/ Line commutated thyristor are turned off due to sinusoidal nature of input voltage. 

3-Gate Turn off thyristor (GTO) are available in range 6000V,6000A

4-Static Induction thyristor(SITH) are available in range 1200V, 300 A, used in medium power converter.

Both GTO and SITH thyristor are turned on by giving short positive pulse to gate and to turn off short negative pulse to gate.

5-Reverse Conducting Thyristor (RCT) is used when high speed Switching is required. Available range of RCT is 4000 V/ 2000A and switching time is 40 us.

6-Gate assisted turn off thyristor (GATT) is also used in high speed Switching application, available up to 1200 V, 400A and switching time is 8 us.

7- Light activated silicon controlled Rectifier (LASCR) used in high voltage power system and HVDC application available up to 6000V, 1500 A and switching time is 200us to 400 us.

8-MOS turn off thyristor (MTO) is combination of MOSFET and GTO, MTO overcome the limitations of GTO, MTO can be used high power application ranging from 1 MVA - 20 MVA.

9- Emitter turn off thyristor (ETO) combine both advantage of MTO and GTO. It has two gates one normal gate to turn on thyristor and other MOSFET in series to turn off thyristor.

10- Integrated gate commutated thyristor (IGCT) has multi-layered gate driver PCB. It is a hard switch GTO and large gate current pulse, that draws out all current from cathode into gate in 1 us. IGCT turned on by applying the turn on current to gate and turned off by gate driver PCB which gives fast rising turn off pulse.

11- MOS controlled Thyristor (MCT) is same as GTO but it's turn off gain is very high. It can be turned on by applying small negative pulse on MOSFET gate and turned off by small positive pulse.

3-Power Transistor

1- BJTs - A bipolar junction transistor has 3 terminal, Base, emitter and Collector. It is generally operated as switch in common emitter configuration. High Power BJT are commonly used in power converter at frequency below 10 kHz. Forward voltage drop is about 0.5 to 1.5 Volts.

2- MOSFET- Power MOSFETs are used in high speed power converter. They are available in ratings up to 1000 Volts, 100 Amp at a frequency range of several tens and of kHz.

3- IGBT are used in high voltage and high current application and suitable for frequency up to 20 kHz. IGBT are available in ratings up to 1700 Volts , 2400 Amp.

Difference between IGBT and MOSFET



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