Patent ID: 9622312
Date: 2017-04-11
CPC Classifications: H05B,Y02B

Claim:
1. A drive circuit for causing a light-emitting element to emit light, using a dimming signal which is an alternating current signal which has been phase-controlled in response to a dimming level, the drive circuit comprising a control signal generating unit configured to integrate a voltage of a signal obtained by rectifying the dimming signal to generate a control signal for controlling luminance of the light-emitting element, the voltage being greater than or equal to a first voltage and less than or equal to a second voltage lower than a maximum voltage of the dimming signal; a second capacitor connected between output ends of a second rectifier circuit which rectifies the dimming signal; a fourth resistor connected in parallel to the second capacitor; and a bypass circuit connected in parallel to the fourth resistor, wherein the bypass circuit includes a fifth resistor and a switch which are serially connected, the switch turns on if a voltage between the output ends of the second rectifier circuit is less than or equal to a predetermined threshold voltage, and the second capacitor, the fourth resistor, and the fifth resistor respectively have capacitance, resistance, and resistance that satisfy the following relations, provided that where C represents the capacitance of the second capacitor, R