The alternating current generated by the automobile generator is transformed 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. The vehicle's engine is shaken, and there are situations such as gear shifting frustration, slow speed increase, unstable idle speed, and low efficiency of vehicle air conditioning. As a result, the performance and service life of on-board electrical equipment are greatly reduced; coupled with the aging of the circuit system of elderly cars, the impact of higher circuit resistance, the impact on the vehicle has become increasingly obvious. The role of the electronic rectifier is to help the car eliminate clutter interference, stabilize the output voltage, improve the instantaneous discharge capability of the power system, increase torque output, speed up the throttle response, extend battery life, shorten the car engine startup time, improve ignition efficiency, etc., especially For small displacement cars, the effect is more obvious.
The current of the semiconductor PN junction is large when it is forward biased, and the current is small when it is reverse biased. The rectifier diode is a kind of PN junction diode that uses the unidirectional conductivity of the PN junction to change the alternating current into a direct current. Generally, devices with a current capacity of less than 1 ampere are called rectifier diodes, and those with a current capacity of more than 1 ampere are called rectifiers. Commonly used semiconductor rectifiers include silicon rectifiers and selenium rectifiers. There are many product specifications, with voltages ranging from tens of volts to thousands of volts, and currents from a few amperes to several thousand amperes. Rectifiers are widely used in various forms of rectified power supplies.
The high-power rectifier power supply requires the rectifier to have large current capacity, high breakdown voltage, and good heat dissipation performance. However, 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 band gap and good thermal conductivity, which is suitable for making high-power rectifier devices. A high-voltage silicon stack is often used in high-voltage rectifiers. It is composed of multiple rectifier device cores in series. Its reverse withstand voltage is determined by the withstand voltage of the core and the number of series-connected tubes. The maximum withstand voltage can reach hundreds of thousands. Volt. If the high-frequency rectifier circuit is used at a very high frequency, when the cycle of the AC voltage is equivalent to the recovery time from the on-state to the off-state of the rectifier, the rectifier no longer rectifies the high-frequency voltage. In order to meet the needs of high-frequency operation, the method of doping gold is usually used in the silicon rectifier to shorten the life of the injected minority carriers, thereby achieving the purpose of reducing the recovery time.