The compound full-control voltage-driven power electronic device composed of bipolar transistors and MOSFET tubes is a widely used IGBT tube.

A wide range of applications of IGBT tubes can be found in many products, such as induction cookers, frequency converters, switching power supplies, motor control, electric welding machines, etc. In the process of product maintenance, it is necessary to check whether the IGBT tubes are damaged to determine Whether it needs to be replaced. In the repair process, there will be different situations, such as a diode without damping, or a multi-element module composed of more than one single IGBT tube, etc., which will judge the detection and judgment of the IGBT tube during product repair. Increase a certain degree of difficulty.

In fact, it is not difficult to detect whether the performance of the IGBT tube is damaged. When we are familiar enough with the undamped diode, that is, a single IGBT tube, on this basis, we can draw conclusions by analyzing the internal circuit of the tested model tube.

Regarding the structure of the PN junction inside the IGBT tube, when testing the IGBT tube without damping diode, select the pointer multimeter Rx10k block, connect the red pen to the c pole and the black pen to the E pole, the resistance value is about 400kΩ, and the red pen and The black pen is reversed and the resistance is measured again and it is infinite. Connect the black pen to the G level, and the red pen to the other two levels for detection, and then adjust the red pen and the black pen to test. The needles of the two detections are slightly swayed and stay at ∞, that is, the resistance is very large.

If it is to detect the IGBT tube with damping diode, take the IGBT tube FGA25N120ANTD as an example: a diode is connected in parallel between the collector C and the emitter E, use the MF-47 multimeter Rx1k block, connect the black pen to the E pole, red The pen is connected to the C pole, and the forward resistance of the tube can be measured to be about 6kΩ. After adjusting the red pen and black pen, the measured resistance is infinite. Then select the Rx10kΩ block, connect the red pen to the C pole or the E pole, and the black pen to the G pole. After the measurement, the black pen and the red pen are also measured, and the measured resistance values are both infinite.

 Similar to a capacitor with a small measuring capacity, only after one measurement, the tube electrode is short-circuited and discharged, and this phenomenon occurs when the measurement is performed again, which is a charging phenomenon.

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