What is an IGBT? Unknowable content

Everyone knows that the discovery and application of electricity has greatly saved human physical and mental labor, and has enabled human power to grow its wings and extend the reach of human information. The impact of electricity on human life has two aspects: the acquisition and transmission of energy, and the foundation of electronic information technology. The network planning agency of Qi Baotang believes that the discovery of electricity can be said to be a revolution in human history.

However, in the field of power electronics, one of the most important components is today's protagonist: IGBT, if there is no IGBT, then we will not have a convenient life with high-speed rail.

Interpretation of IGBT from Baidu Encyclopedia:

IGBT (Insulated Gate Bipolar Transistor), insulated gate bipolar transistor, is a composite fully controlled voltage-driven power semiconductor device composed of BJT (bipolar triode) and mos (insulated gate field effect transistor), and has MOSFET The advantages of both the high input impedance and the low turn-on voltage drop of the GTR. The GTR saturation voltage is reduced, the current carrying density is large, but the driving current is large; the MOSFET driving power is small, the switching speed is fast, but the conduction voltage drop is large, and the current carrying density is small. The IGBT combines the advantages of the above two devices, with low driving power and reduced saturation voltage. It is very suitable for converter systems with DC voltages of 600V and above, such as AC motors, inverters, switching power supplies, lighting circuits, traction drives, etc.

Let's take a look at the understanding of IGBTs from knowing users, as follows:

When I saw this question, I remembered me four years ago, and I also applied for the motor department for this problem. . . I will try to answer from the perspective of science. . .

Functionally, an IGBT is a circuit switch that is used on a high voltage of the order of tens to hundreds of volts and tens to hundreds of amps. (relatively speaking, mobile phones, computer circuit boards run low voltage, mainly based on transmission signals, are weak.) It can be considered as a transistor, voltage and current is too large.

The light switch at home is controlled by a button. The IGBT does not use a mechanical button, it is controlled by a computer. Specifically, the simplified model of the IGBT has three interfaces, two (collectors, emitters) are connected to the high-voltage circuit, and one receives the control electrical signal, which is called the gate. Give the gate a high level signal, the switch (between the collector and the emitter) will pass; and then give the low level signal, the switch will be broken. The signal to the gate is a digital signal (that is, only the high and low states), the voltage is very low, and it is a weak current, and can be connected to the computer through a relatively simple driving circuit. The actual "computer" is usually a microprocessor called DSP, which is good at processing digital signals and is relatively small.

There are many types of high-power switches that can be controlled with digital signals. As one of them, the IGBT is characterized in that it supports the highest switching speed at this current and voltage level, and can be switched tens of thousands of times in one second. GTO was also used in rail transit trains before, but GTO has low switching speed and high loss. Now it is only used when the maximum voltage and current exceeds the IGBT receiving range; IGCT is also GTO in essence, but the structure is optimized, switching speed and maximum voltage and current. Both are between GTO and IGBT; high-power mosFETs are fast, but they cannot support such large voltages and currents, otherwise they will burn out.

What is the use of such a fast switch? The common strong power is only 50Hz AC, the transformer can change its voltage, but it can't change its frequency, it can't turn it into DC. With the IGBT switch, a type of circuit can be designed to control the IGBT by computer, turn the alternating current on the power supply side into a direct current of a given voltage, or turn the various electric power into an alternating current of the desired frequency to the load. use. Such circuits are collectively referred to as converters. The circuit that converts AC power into DC power is called a rectifier; the inverter that converts DC power into AC power is called an inverter; the DC-DC converter is called a switching power supply; and the three-phase AC-to-AC is called a matrix converter.

How to achieve it? Need to talk about the concept of PWM, I may not be very clear here. The subject has never seen a flashing light when the lighting of the home is not good. Does the flashing light look like no normal light? This is because the flashing light is on for 0.1 second and is off for 0.1 second. In a total of 0.2 seconds, it only emits light energy of 0.1 second for the normal light, so it appears dark. Power is essentially the transmission of electrical energy, so this principle can also be used. If the current in the appliance is almost constant, the voltage of 300V is connected in 0.2 seconds before the appliance is used, and the voltage of 0V is connected in 0.1 second, which is equivalent to the appliance in 0.3 seconds. The terminal is always followed by a voltage of 200V. We call this 300V voltage, which lasts only 0.2 seconds, as a pulse. By changing the time occupied by the pulse in 0.3 seconds, we can achieve any value within the range of 0 to 300V at this time. Pulse Width Modulation (PWM). The shorter the total time of voltage change from high to low, the closer the voltage is to the equivalent voltage.

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