Patent ID: 8305047

Claim:
A safety capacitor discharging apparatus for AC-to-DC converters, wherein the AC-to-DC converters have a safety capacitor connected between two line voltages, the apparatus comprising: a line detector, used for detecting at least one line voltage to generate a line-off signal, wherein the line-off signal is at a first state when a peak voltage of the at least one line voltage is above a reference voltage, and the line-off signal is at a second state when the peak voltage of the at least one line voltage is below the reference voltage; and a discharging circuit, used for discharging the safety capacitor by generating a conduction path between two plates of the safety capacitor when the line-off signal is at the second state, the line detector comprising: a peak voltage detector, coupled to at least one of the two line voltages to generate the peak voltage; and a comparator, having a first negative input coupled to the peak voltage, a first positive input coupled to the reference voltage, and a first output for generating the line-off signal, wherein the line-off signal is at the second state when the peak voltage is below the reference voltage.