Light source control device

摘要

A semiconductor light source control device includes a driver circuit, which generates a drive current Iout flowing through a plurality of LEDs connected in series and which performs control such that the amount of the drive current is brought close to a target value, and bypass switches, which are on-off controlled by a control signal, the bypass switches being connected in parallel with the corresponding LEDs. The semiconductor light source control device is configured such that when the control signal indicates the off-state of the bypass switches, a voltage across the corresponding LEDs is clamped at an upper limit by using the bypass switches.

主权项

1. A light source control device comprising:
a driver circuit that generates a drive current flowing through a plurality of semiconductor light sources connected in series and that performs control such that an amount of the drive current is brought close to a target value; and a bypass/limiter circuit connected in parallel with at least part of the plurality of semiconductor light sources, wherein the bypass/limiter circuit includes:
a bypass switch including an N-channel MOSFET having a gate, a source and a drain, wherein ON/OFF state of the bypass switch is controlled according to a drive signal applied across the gate and the source of the N-channel MOSFET; anda clamp circuit provided between the gate and the drain of the N-channel MOSFET, wherein the clamp circuit clamps the gate-drain voltage of the N-channel MOSFET below a predetermined voltage level VCL, and wherein in a condition where a low voltage VL is applied across the gate and the source of the N-channel MOSFET such that the bypass switch is in off-state, a voltage across the at least part of the plurality of semiconductor light sources is clamped below an upper limit given by VL+VCL.