In terms of function, IGBT module is a circuit switch realized by transistors. When turned on, it can withstand a current of tens to hundreds of amperes; When turned off, it can withstand hundreds to thousands of volts.

As a transistor, IGBT module does not have a mechanical button, but by other circuits to control. The simplified model of IGBT has three interfaces, namely collector, emitter and gate. Among them, the collector and emitter are connected to the strong electric circuit, and the gate is used to receive the control electrical signal. When the gate receives the high level signal, the switch (between collector and emitter) is turned on; If a low level signal is received, the switch is off. The circuit that issues control instructions to the gate is called the control circuit, which can be understood as "computer", but the actual "computer" is usually a single-chip microcomputer or digital signal processor (DSP), which is good at processing digital signals and relatively small. For some basic applications, reliable simple chips and circuits can be controlled without programming. But it should be noted that the voltage of the so-called digital signal at the gate also needs 10 to 20 volts, so a small "drive circuit" is needed between the control circuit and the IGBT module to convert the signal.

There are many kinds of strong electric switches that can be controlled by digital signals. As one of them, IGBT module is characterized by the highest switching speed supported by IGBT module in its current and voltage level, which can be switched nearly ten thousand times per second. In other words, switching frequency of IGBT can reach 10kHz level. GTO (Gate Turn Off Thyristor) was also used in rail transit trains, but its switching speed is low, so it is now used only when the maximum voltage and current exceeds the IGBT module's tolerance range. IGCT (Integrated Gate-commutated Thyristor) is also GTO in nature, but its structure has been optimized so that the switching speed and maximum voltage and current are between GTO and IGBT. High-power MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) is faster than IGBT, but its maximum voltage and current it supports are all smaller than IGBT.

So why the need for such a fast switch? The common strong current is only 50Hz AC, the transformer can change its voltage but can not change its frequency or even turn it into DC; On the other hand, the direct current generated by photovoltaic plants cannot be converted into AC. Using IGBT, a kind of circuit can be designed, through controlling IGBT, the alternating current of the power supply side becomes the direct current of given voltage, or all kinds of current becomes the alternating current of the desired frequency. This kind of circuit is called power electronic circuit, and the equipment made of power electronic circuit is called converter. The circuit that changes alternating current into direct current is called a rectifier, the circuit that changes direct current into alternating current is called an inverter, and the circuit that changes direct current into direct current is generally called a converter.

To implement the above operations, what the need to do? This requires Pulse Width Modulation (PWM). The essence of the power circuit is to transmit electric energy. If the electric appliance is connected with 300V voltage in 0.2 seconds before opening, and 0V voltage is connected in 0.1 seconds after, it is equivalent to the voltage of 200V at both ends of the electric appliance. The 300V voltage lasting only 0.2 seconds is called the pulse. By changing the time occupied by the pulse in 0.3 seconds (i.e. the pulse width), the equivalent voltage can be achieved in this moment to any value in the range of 0~300V. This is pulse width modulation. The shorter the total time of voltage change is, the closer the voltage is to the equivalent voltage from a macroscopic point of view. Pulse width modulation requires at least two switches, one between the electric appliance and 300V, one between the electric appliance and 0V. Pulse width modulation can be realized only when two switches are switched on alternately.

Now having strong current with controlled voltage and frequency, and this strong current can be used to drive the motors of G-series high-speed trains. G-series high-speed trains use AC motors, which have a simple structure and save electricity, but the speed is difficult to adjust. The speed and the input AC power frequency has a close relationship, so the converter of IGBT can be used to flexibly control the speed of the motor. Reflected in the G-series high-speed rail, is the speed of G-series high-speed rail, namely, Variable Voltage and Variable Frequency control (VVVF). In addition to G-series high-speed rail, electric vehicle, variable frequency air conditioning, wind driven generator and many other occasions where AC motors are used, IGBT and supporting circuits can be used to control the motor. In the fields of power generation and energy storage, IGBT is mainly used for conversion between AC and DC.

The NTC chip for IGBT produced by EXSENSE Electronics Technology Co., Ltd. can be used for temperature controlling and temperature monitoring in IGBT module.