Patent ID: 9106144
Filing Date: 2015-08-11
Classification: H02M

Abstract:
1. A sub-harmonic detector of a pulse width modulation (PWM) signal for a voltage converting apparatus, comprising: a pulse eliminating circuit for receiving a reference PWM signal having a same period with the PWM signal and receiving the PWM signal from the voltage converting apparatus, the PWM signal having a plurality of pulses, and the reference PWM signal having a plurality of reference pulses, wherein the pulse eliminating circuit subtracts each of the corresponding reference pulses from each of the pulses and generates a processed signal; a counter for receiving and counting the processed signal and the PWM signal respectively within a time period to obtain a first counting value and a second counting value; and a comparator being coupled to the counter and the comparator comparing the first counting value and the second counting value to detect whether a sub-harmonic condition happens or not in the PWM signal.