| 摘要 |
PURPOSE:To maintain a light emission power from other normal light-emitting elements even in the case where some of a plurality of the light-emitting elements failed due to disconnection. CONSTITUTION:The drive circuit gas series connection paths for connecting a plurality of light-emitting elements with a constant current source and a plurality of light emission power control circuits 1 for controlling the light emission power of the opposed light-emitting elements. Each of the circuits 1 has bypass current control elements 2 connected in parallel to the opposed light-emitting elements, a photodetecting element 3 which is connected to these elements 2 and detects the light emission power of the light-emitting elements, a current control circuit 4 for controlling a current, which is made to flow through the elements 2, according to the photodetection level of the element 3 and a voltage detecting circuit 5 of a constitution, wherein the circuit 5 detects the voltage value between terminals of the opposed light-emitting elements and when the voltage value reaches a prescribed voltage value or higher, the circuit 5 controls the circuit 4 in such a way that the current, which is made to flow through the elements 2, is increased. |
