Inspection method of rectifier diode

Inspection method of rectifier diode

Rectifier diode is a semiconductor device used to convert alternating current into direct current. The most important characteristic of a diode is its unidirectional conductivity. In the circuit, current can only flow in from the anode of the diode and flow out from the cathode. Usually it contains a PN junction with two terminals, a positive electrode and a negative electrode. The carriers in the P area are holes, and the carriers in the N area are electrons, forming a certain barrier between the P area and the N interval. When the applied voltage makes the P region a positive voltage relative to the N region, the potential barrier is lowered, and stored carriers are generated near both sides of the potential barrier, which can pass large currents and have a low voltage drop, which is called the forward conduction state. If the opposite voltage is applied, the potential barrier is increased, which can withstand a high reverse voltage and flow a small reverse current, which is called the reverse blocking state. The rectifier diode has obvious unidirectional conductivity. The rectifier diode can be made of materials such as semiconductor germanium or silicon. The silicon rectifier diode has high breakdown voltage, low reverse leakage current and good high temperature performance. Generally, high-voltage and high-power rectifier diodes are made of high-purity monocrystalline silicon. This kind of device has a large junction area and can pass a large current, but the operating frequency is not high, generally below tens of kilohertz. Rectifier diodes are mainly used in various low-frequency half-wave rectifier circuits. If full-wave rectification is required, they must be connected as a rectifier bridge.

First remove all the rectifier diodes in the rectifier, use the 100×R or 1000×R ohm gear of a multimeter to measure the two lead wires of the rectifier diode. If the resistance value measured twice is very different, for example, the resistance value is as large as several hundreds of KΩ to infinity, and the resistance value is only a few hundred Ω or less, indicating that the diode is good. If the resistance value measured twice is almost the same and the resistance value is very small, it means that the diode has been broken down and cannot be used. If the resistance value measured twice is infinite, it means that the diode has been internally disconnected and cannot be used.