In modern electrical devices for various purposes, IGBT transistors are widely used as a key element. In the process of restoring the functionality of a failed technique, the task of checking the health of this component arises. This procedure can be performed directly at home using a conventional multimeter. It is assumed that the tested transistor has been removed from the board before.
The procedures for determining the health of bipolar and IGBT transistors are based on the similarity of the equivalent circuits of these elements, Figure 1. For their implementation, the resistance value between the electrodes is controlled. When working with an IGBT element, certain features are taken into account, which are associated with the structure of its crystal.
Preparatory operations and checking the serviceability of the gate circuits
Further, the most difficult case is considered, which is shown in Figure 2, - the presence of an additional shunt diode in the transistor. The need for its introduction is determined by considerations of increasing the resistance of the semiconductor structure to voltage surges of reverse polarity.
The beginning of checking the health of the transistor begins with determining its pinout and internal structure. To do this, refer to the technical data that can be found on the websites of manufacturers and suppliers of the element base.
The first group of measurements is aimed at checking the health of the emitter-gate and collector-gate transitions. For this, the multimeter is switched to the resistance measurement mode. Regardless of the polarity of the applied test voltage, the device shall indicate an open circuit (a direct consequence of the isolated gate design).
Checking the serviceability of the collector-emitter channel
Before checking the main channel of the working current, it is necessary to completely close the transistor. To do this, it is enough to short-circuit the gate with the emitter for a short time (1 s), as shown in the diagram in Figure 3. This procedure is performed both with a jumper and with ordinary tweezers.
Next, a multimeter measures the resistance between the emitter and the collector. Taking into account the presence of an internal shunt diode, for one of the probe connection options, the device should show the final value, while when the polarity changes to the opposite, the multimeter readings should indicate an open current path.
Final check
It is advisable to supplement the dialing with a multimeter with the assembly of the simplest single-stage circuit, shown in Figure 4. It is a transistor switch powered from any source suitable for this. When the switch is open, the gate is tied to the minus of the source through a resistor with a resistance of 1 to 10 kOhm and the transistor is completely closed. After the key CL is closed, the gate receives a potential from the +12 V source, which turns the transistor into the open state and the lamp L lights up.
The functions of the key can be performed by both a switch and a conventional jumper.