IGBTs have the input characteristics of BJT and the output characteristics of MOSFETs. It combines the characteristics of BJT and MOSFET, and has three pins: gate, collector, and emitter.
Structure of IGBT
IGBT is divided into N-channel and P-channel, which are the IGBT circuit diagram and equivalent circuit diagram of N-channel.
IGBTs, like MOSFETs, can control the port through voltage, such as this N-channel, where collector-emitter currents flow through the collector when a positive voltage is applied to the gate.
How IGBTs work
When the positive input voltage passes through the gate, the emitter keeps the drive circuit on, and when the gate voltage is 0 or negative, the circuit is turned off.
This is a semiconductor structure diagram (cross-section) of an IGBT
The blue arrow indicates the flow of the collector current IC. When a positive Vge is applied to the gate, as in the case of MOSFETs, electrons gather in the P+ layer just below the gate electrode, forming a channel. The current starts flowing from the collector to the emitter.
We know that BJT has a relatively low on-resistance under high voltage conditions, but has the disadvantages of low input impedance and slow switching speed, while MOSFET has high input impedance and fast switching speed, but has a high on-resistance at high voltage.
IGBTs make up for the shortcomings of both, achieving low on-resistance even at high input impedance and high switching speeds.
Therefore, IGBTs are superior in high-voltage applications, and MOSFETs can be used in low-voltage environments.
Application scheme of IGBT
In addition to the single component used, power components are also used in modules that combine components and other basic components.
From the perspective of output capacity and working frequency, IGBT is mainly used in the field of trams and HEV/EV that handle some high-voltage and high-current applications.
IGBT discrete products cover the frequency range of 1kHz~50 and 60kHz, and the output capacity is higher than 1kVA. IGBT modules, depending on the combination of other components, generally have the same upper limit of operating frequency, but the output capacity range can be as high as 100MVA or more.
From the perspective of output capacity and operating frequency, IGBT is mainly used in the field of electric vehicles and HEV/EV that handle some high-voltage and high-current applications.
This is IGBT. Okay, that's all for today.