An actively switchable power electronic switch integrates a combination of power semiconductor and driver (driver stage).
On the one hand, the parameters of a switch result from the behaviour of the power semiconductors. On the other hand, the driver unit is responsible for all main parameters of the switch and takes charge of the most important protection and diagnostic functions.
A hard switch (HS) is a single switch (e.g. IGBT) with hard turn-on and turn-off switching behaviour (see Four Types of Switching Processes). Except for the theoretical case of pure ohmic load, it can only be used together with a neutral switch (diode) in a commutation circuit with minimum passive energy store. When a neutral switch is used, the current and voltage drop to zero at the point of switching. The hard switch may be equipped with two control options, namely individually adjustable turn-on and turn-off.
With a hard switch, high switching power losses make maximum control options possible. This allows for the whole system to be operated using the pulse width modulation (PWM) control method.
For more information, please read:
Four Types of Switching Processes
Power Electronic Switches: Neutral Switches
Power Electronic Switches: Zero Voltage Switching and Zero Voltage Resonant Switches