Patent ID: 8723449
Filing Date: 2014-05-13
Classification: H05B,Y02B

Abstract:
1. A light emitting element drive circuit for driving a light emitting element circuit in which a plurality of light emitting elements are connected with each other in parallel, the light emitting element drive circuit comprising: a constant current driver including a plurality of transistors whose collector terminals are connected with the respective plurality of light emitting elements and whose emitter terminals are grounded; a control circuit for setting a voltage, to be commonly applied to the plurality of light emitting elements, in accordance with a maximum base current out of base currents of the respective plurality of transistors; and a current mirror circuit for flowing identical currents through (i) the light emitting element included in the light emitting element circuit and (ii) an additional light emitting element connected in parallel with the light emitting element, the control circuit being not connected with any of the collector terminals of the respective plurality of transistors and collector terminals of a pair of transistors included in the current mirror circuit, the control circuit being connected with the emitter terminals of the respective plurality of transistors and emitter terminals of the pair of transistors included in the current mirror circuit, and the control circuit setting a voltage, to be commonly applied to the plurality of light emitting elements, in accordance with a maximum base current out of (a) the base currents of the respective plurality of transistors and (b) a base current flowing through base terminals, which are connected with each other, of the pair of transistors included in the current mirror circuit.