IGBT, the CPU of power electronics! Small and low-power semiconductor devices play a huge role in many power electronics-related fields. In recent years, IGBT has developed rapidly. Infineon and Japanese manufacturers continue to introduce new IGBT products for various applications, and the competition is becoming more and more fierce.

How to use the IGBT puzzles many engineers. What is IGBT?

IGBT (Insulated Gate Bipolar Transistor) is a composite fully controlled-voltage-driven-power semiconductor device composed of BJT (Bipolar Junction Transistor) and MOS (Insulated Gate Field Effect Transistor), with self-shutdown Characteristics. Simply put, it is a non-on-and-off switch that is used in strong currents with a voltage of tens to hundreds of volts on the order of kilovolts and a current of tens to hundreds of amperes. (Relatively speaking, the voltages running on the circuit boards of mobile phones and computers are low, and they mainly transmit signals, which are all weak currents.)

IGBT does not have the function of amplifying voltage. It can be regarded as a wire when it is turned on, and it is regarded as an open circuit when it is disconnected. IGBT combines the advantages of BJT and MOSFET, such as low driving power and reduced saturation voltage. To make it simpler, you can think of an IGBT as a transistor, but its voltage and current are very large. The internal structure and circuit symbols of the IGBT are as follows:

IGBT structure diagram

Using IGBT in the circuit, we can control the three-pole voltage of the IGBT just like controlling the triode and MOS tube, so as to realize the control of the three states of the IGBT (on/off/blocking state).

When the gate-emitter of the IGBT is applied with 0 or negative voltage, the channel in the MOSFET disappears and the IGBT is turned off.

When the collector-emitter voltage UCE<0, the PN junction of J3 is in reverse bias, and the IGBT is in a reverse blocking state.

When the collector-emitter voltage UCE>0, there are two situations: Case 1: If the gate-emitter voltage UGE<Uth, the channel cannot be formed, and the IGBT is in a positive blocking state. Case 2: If the gate-emitter voltage UGE>Uth, the gate channel is formed, and the IGBT is turned on (normal operation). At this time, holes are injected from the P+ region into the N base region for conductance modulation, reducing the value of the resistance RN of the N base region, and reducing the on-state voltage drop of the IGBT. At this time, some people may have questions. MOS transistors are also transistors, and they also have three poles. They can also be used as switches. How to choose between these two? The following considers the system voltage, current, switching power and other factors, and summarizes the differences between the two:

Where are IGBTs used?

In occasions with larger output power, such as inverters, UPS power supplies, EPS power supplies in the industrial field, wind power and solar power generation in the field of new energy power generation, charging piles, electric controls, and car air conditioners in the field of new energy vehicles, everywhere You can see the IGBT.

In new energy vehicles, IGBTs account for about half of the cost of the motor drive system, while the motor drive system accounts for 15-20% of the cost of the entire vehicle. That is to say, IGBTs account for 7-10% of the cost of the entire vehicle, which is the cost in addition to the battery. The second highest component also determines the energy efficiency of the vehicle.

In these applications, IGBT usually exists in the form of a module, a modular semiconductor product that is packaged by IGBT and FWD (freewheeling diode chip) through a specific circuit bridge. The advantage of using the module is that the IGBT has been encapsulated, the installation is very convenient, and there is a heat dissipation device on the shell, which quickly dissipates heat when working at high power.

Precautions for using IGBT

When using IGBTs, you must first pay attention to the data and application manuals provided by the original manufacturer. In the data manual, the important parameters of the IGBT, such as static parameters, dynamic parameters, short circuit parameters, and thermal performance parameters, should be paid special attention to. These parameters will tell us the absolute value of the IGBT, which is absolutely not surpassed. After the design is completed, the IGBT parameters also need to be within a reasonable range of data during operation.