Views:1 Author:Site Editor Publish Time: 2018-04-03 Origin:Site
In the positive half cycle, the conduction angle of the rectifier diode is much less than 1800 or even only 300-700. Due to the requirement of load power, great conduction current will be produced during the very narrow conduction angle. It not only reduces the efficiency of power supply, but also makes the supply current in the power supply circuit appear to be pulse state, what is more serious is that it has insufficient capacity in the power supply line. Or when the circuit load is high, the waveform distortion of AC voltage will be serious (fig. 3) and generate multiple harmonics, thus interfering with the normal operation of other electrical appliances (this is electromagnetic interference-EMI and electromagnetic compatibility-EMC problem).
Since the use of electrical appliances has changed from a previous inductive load (early power sources for television, radio, etc.) to capacitive loads with rectifier and filter capacitors, .
This is a new technology developed at the end of the last century (its background is the rapid development and wide application of switching power supply). Its main purpose is to solve electromagnetic interference (EM1) and electromagnetic compatibility (EMC) problems caused by severe distortion of the current waveform due to capacitive loads. . Make the system purely resistive technology (line current waveform correction technology), which is PFC (Power Factor Correction).
So modern PFC technology completes the correction of current waveform and solves the problem of voltage and current in phase.