Working Principle of Insulated Gate Bipolar Transistor (IGBT)

Insulated Gate Bipolar Transistor (IGBT) is a composite fully-controlled voltage-driven power semiconductor device that combines the high input impedance of MOSFETs with the low conduction voltage drop of GTRs.

 

Core Structure and Driving Mechanism
Three-terminal composite structure: The IGBT consists of a gate, collector, and emitter, internally equivalent to a MOSFET driving a bipolar transistor (PNP).

Voltage-controlled characteristics: As a voltage-controlled device, the recommended gate driving voltage is 15V ± 1.5V, with high input impedance and low driving power.

 

Turn-on and Turn-off Mechanism
Turn-on process: When a forward voltage exceeding the threshold is applied between the gate and emitter, a channel is formed within the MOSFET, providing base current to the PNP transistor and turning on the IGBT. At this time, the conductivity modulation effect is utilized; holes are injected into the N region to reduce resistivity, achieving a low on-state voltage drop.

Turn-off process: When a reverse voltage is applied to the gate or the signal is removed, the MOSFET channel disappears, the base current is cut off, and the IGBT turns off. During turn-off, there is a tail current phenomenon which requires optimized design to reduce losses.

 

Main Characteristics and Applications
Electrical characteristics: Suitable for regions with voltage withstand over 600V, current over 10A, and frequency above 1kHz, combining high-speed performance with low resistance.

Application fields: Mainly used in photovoltaic inverters, new energy vehicle electronic control systems, industrial frequency conversion equipment, and induction heating.