Patent ID: 7646225

Claim:
A mains phase detection apparatus comprises a zero-crossing detector, wherein said mains phase detection apparatus further comprises: an all-digital phase-locked loop, wherein said all-digital phase-locked loop comprises an edge detector, a digital phase detector, a digital loop filter, and a phase accumulator, wherein said edge detector couples said zero-crossing detector, and is triggered by either a rising edge or a falling edge of an output signal of said zero-crossing detector to generate a detecting pulse; and wherein said digital phase detector couples said zero-crossing detector and said phase accumulator to generate a phase difference signal between output signals of said zero-crossing detector and said phase accumulator; and wherein said digital loop filter couples said edge detector and said digital phase detector to perform low-pass filtering between each two detecting pulses of said edge detector; and wherein said phase accumulator is coupled to said digital loop filter, wherein a most significant bit of said phase accumulator is an output signal output to said digital phase detector.