Main supply zero crossing detection for PFC converter

摘要

A fault mode of a PWM module embedded in a microcontroller is used to detect main supply zero crossings for regulating output voltage of a PFC converter operating in BCM, without using an external detecting element or a comparator, ADC or other specialized component internal to the microcontroller. In some implementations, the end of decrease current flow in the energy storage inductor of the converter is used to reinitialize a PWM timer or counter (counting-up or counting-down timer). The current goes to zero for a time period when the main supply voltage goes to zero, resulting in the PWM timer or counter not being reinitialized prior to the end of the current PWM cycle. The failure to reinitialize the timer or counter can be used to generate a signal indicative of a zero voltage crossing of the main supply voltage.

主权项

1. A power-factor-correction (PFC) converter circuit, comprising:
a rectifier circuit; an energy storage device coupled to the rectifier circuit and configured to receive an input voltage from the rectifier circuit; a switch coupled to the energy storage device, the switch configurable to provide a path for removing energy from the energy storage device; a microcontroller coupled to the energy storage device and the switch; and an analog-to-digital converter (ADC) coupled to an output of the power-factor-correction (PFC) converter circuit and to the microcontroller, where the microcontroller includes a pulse width modulation (PWM) module coupled to the energy storage device, the PWM module being configured to enable the ADC to sample an output voltage of the power-factor-correction (PFC) converter circuit by detecting a zero voltage crossing point of the input voltage received from the rectifier circuit based on an absence of a trigger event that occurs external to the microcontroller, the absence of the trigger event being based on an end of decrease current flow in the energy storage device.