Efficient inrush current control in power factor corrected AC-to-DC converter

摘要

An AC-to-DC converter involves a rectifier, an inductor, a storage capacitor, a switch, and a microcontroller. In a capacitor pre-charge operation, the periodicity and voltage amplitude of an AC supply voltage are determined. Based on this, the microcontroller identifies one of a plurality of stored sequences. Each sequence is a list of values. The microcontroller turns off the switch on AC supply voltage zero crossings and turns on the switch in accordance with the values. As a result, a sequence of identical pulses of charging current flows into the storage capacitor. Each pulse passes in a current path from the rectifier, through the inductor, through the capacitor, through the switch, and back to the rectifier. During the pre-charge operation, the microcontroller does not measure the capacitor voltage and use that to calculate when to the turn the switch on next, but rather the sequence of precalculated stored values is used.