Patent ID: 8896288

Claim:
A line voltage detection circuit comprising: a first digital filter module configured to output a first high signal when an input signal reaches a first threshold voltage on a leading edge of the input signal and configured to output a first low signal when the input signal reaches the first threshold voltage on a trailing edge of the input signal; a second digital filter module configured to output a second high signal when the input signal reaches a second threshold voltage on the leading edge of the input signal and configured to output a second low signal when the input signal reaches the second threshold voltage on the trailing edge of the input signal; and a third digital filter module configured to output a third high signal when the input signal reaches a third threshold voltage on the leading edge of the input signal and configured to output a third low signal when the input signal reaches the third threshold voltage on the trailing edge of the input signal, wherein the line voltage detection circuit is configured to determine whether the input signal includes a leading edge chopped signal or a trailing edge chopped signal based on times at which the first threshold, the second threshold, and the third threshold are reached on the leading edge or the trailing edge.