How does a rectifier work

A rectifier is a rectifying device, which in simple terms is a device that converts alternating current (AC) into direct current (DC). It has two main functions: first, to convert alternating current (AC) into direct current (DC), which is filtered and supplied to the load, or to the inverter; second, to provide charging voltage to the battery. Therefore, it also acts as a charger at the same time.

The alternating current generated by the automobile generator is converted into direct current after being rectified by the rectifier, but its waveform still has irregular fluctuations, which directly affects the accuracy of vehicle ignition; the output voltage cannot be kept relatively constant, resulting in the energy difference of each spark plug ignition, which is easy to The engine of the vehicle is shaken, the gear shift is stuttered, the acceleration is slow and weak, the idle speed is unstable, and the efficiency of the vehicle air conditioner is low. As a result, the performance and service life of the on-board electrical equipment are greatly reduced; coupled with the aging of the circuit system of the elderly car, the impact of the circuit resistance pit becoming higher, the impact on the vehicle has become increasingly obvious. The function of the electronic rectifier is to help the car to eliminate clutter interference, stabilize the output voltage, improve the instantaneous discharge capacity of the power system, increase the torque output, speed up the throttle response, prolong the battery life, shorten the starting time of the car engine, improve the ignition efficiency, etc., especially For small displacement cars, the effect is more obvious.

The semiconductor PN junction has a large current when it is forward biased, and a small current when it is reverse biased. A rectifier diode is a PN junction diode that uses the unidirectional conduction characteristics of the PN junction to convert alternating current into direct current. Usually, a device with a current capacity of less than 1 amp is called a rectifier diode, and a device with a current capacity of more than 1 amp is called a rectifier. Commonly used semiconductor rectifiers include silicon rectifiers and selenium rectifiers, with many product specifications, voltages ranging from tens of volts to several thousand volts, and currents from several amperes to several thousand amperes. Rectifiers are widely used in various forms of rectified power supplies. High-power rectifier power supply requires large current capacity, high breakdown voltage and good heat dissipation performance of the rectifier, but this device has a large junction area and large junction capacitance, so the operating frequency is very low, generally below tens of kilohertz. The silicon material has a large forbidden band width and good thermal conductivity, and is suitable for making high-power rectifier devices. High-voltage silicon stacks are often used in high-voltage rectifier devices, which are composed of multiple rectifier device cores connected in series. Volt. If the high-frequency rectifier circuit is used at a very high frequency, when the period of the AC voltage is equivalent to the recovery time from the on-state to the off-state of the rectifier, the rectifier will no longer rectify the high-frequency voltage. In order to meet the needs of high-frequency operation, gold doping is usually used in silicon rectifiers to shorten the lifespan of injected minority carriers, thereby reducing the recovery time.

In order to reduce the possibility of damage to the device due to overvoltage breakdown and improve the reliability of the rectifier, a silicon avalanche rectifier can be used. In this device, when the reverse voltage exceeds the allowable peak value, a uniform avalanche breakdown occurs on the entire PN junction, and the device can work under high voltage and high current, so it can withstand considerable reverse surge power. The fabrication of this device requires less material defects, uniform resistivity, and smooth junction surface. The exposed junction area should also be properly protected to avoid surface breakdown. The selenium rectifier has a large anti-overload capacity and a strong ability to withstand reverse surge power.