Classification of Power Semiconductor Devices

Classification of Power Semiconductor Devices     


Semiconductor devices having high voltage and current ratings are known as Power Semiconductor Devices. The Power Devices are classified into various categories based on their Turn ON and Turn OFF capability, Type of gate signal required, Current Conduction Capability and Voltage withstanding ability. The Power semiconductor devices classification is discussed in this post.

                 When the power semiconductor devices are forward biased, except diode they wont start to conduct the current immediately. We have to apply gate/base voltage to make them conduct the current. Based on this scenario, the power devices are classified as uncontrolled devices, partially controlled devices and fully controllable devices.

                  When applying gate voltage to the devices, some of the power devices require this voltage continuously to maintain their ON status. Whereas in some devices, just short duration of gate voltage is sufficient to enable the current conduction. Once the device starts to conduct the current, we can remove the applying gate voltage. Based on this scenario, the power semiconductor devices are classified as pulse gate required devices and continuous gate voltage required devices.

                   After the device turned on, some power devices have the nature of conducting current in one direction only. For example, consider a power device has two terminals namely Terminal-1 (T1) and Terminal-2 (T2). If this device has the capability to conduct the current  from T1 to T2 only, then it is known as Unidirectional current device.  Suppose this device has the capability of conducting the current from T1 to T2 and T2 to T1, then this device is known as bidirectional current device.

                    In some of power semiconductor devices, we should not reverse the polarities while applying the supply voltage.It means, if we apply positive voltage to the negative terminal and negative voltage to the positive terminal, the device will get damaged. ie, there is no reverse voltage protection. On the other hand, some of power semiconductor devices have the capability of withstanding bipolar voltage.

                For better understanding the abbreviations of power semiconductor devices are given below:
SCR – Silicon Controlled Rectifier
RCT – Reverse Conducting Thyristor
GTO –  Gate TurnOff Thyristor
BJT – Bipolar Junction Transistor
SIT – Static Induction Transistor
MOSFET – Metal Oxide Semiconductor Field Effect Transistor
IGBT – Insulated Gate Bipolar Transistor
TRIAC – TRIode for Alternating Current
MCT – MOS Controlled Thyristor

Based on Turn ON and Turn OFF Capability:

  1. Uncontrollable power semiconductor devices
    Diode: The ON and OFF state are not depend on the control signal. They depend  on the power source.
  2. Partially controllable power semiconductor devices
    SCR, TRIAC, DIAC — They are turned ON by applying gate signal. But these devices can not be turned OFF with the help of gate signals. They are turned off by load or by commutation.
  3. Fully controllable power semiconductor devices
    Power BJT, MOSFET, IGBT, GTO  — These devices can be both turned ON and turned OFF by applying gate signals

Based on Gate signal:

  1. Pulse gate requirement
    Example: SCR, GTO, SITH, MCT
    To Turn ON these devices, pulse voltage is applied as a control signal. Once the device is turned on, the gate pulse is not required and thus removed.
  2. Continuous gate requirement
    Example: BJT, MOSFET, IGBT
    For these devices, continuous gate signal is required to maintain them in ON state.

Based on Current Conduction Capability: 

  1. Unidirectional Current Devices
  2. Bidirectional Current Devices
    Ex:- TRIAC, RCT(Reverse Conducting Thyristor)

Based on Voltage withstanding ability:

  1. Unipoloar voltage withstanding devices
  2. Bipolar voltage withstanding devices
    Ex:- SCR, GTO

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