Patent ID: 8901856

Claim:
A detection circuit comprising: a first comparator including: a first input terminal configured to input an AC or pulsed first detection voltage on the basis of an AC voltage; a second input terminal configured to input a first threshold voltage; and a first output terminal configured to output a first output signal having a first state indicating that the first detection voltage is lower than the first threshold voltage and a second state indicating that the first detection voltage is not lower than the first threshold voltage; a second comparator including: a third input terminal configured to input an AC or pulsed second detection voltage on the basis of the AC voltage; a fourth input terminal configured to input a second threshold voltage higher than the first threshold voltage; and a second output terminal configured to output a second output signal having a third state indicating that the second detection voltage is lower than the second threshold voltage and a fourth state indicating that the second detection voltage is not lower than the second threshold voltage; and a determining unit configured to determine the presence or absence of conduction angle control of the AC voltage and whether the conduction angle control is a phase control system or an opposite phase control system on the basis of a time difference between the first output signal and the second output signal.