Patent ID: 8427078

Claim:
A light-emitting element driving device comprising: a plurality of light emitters each including at least one light-emitting element for emitting light at a luminance level depending on a current flowing therethrough; a power supply for adjusting an output voltage depending on a signal supplied to a control terminal of a switch device and supplying the output voltage to ends of said light emitters; a plurality of current control transistors connected between respective other ends of said light emitters and a reference potential, said current control transistors being rendered conductive by respective energization signals; a plurality of constant-current circuits connected respectively in series to said current control transistors between the other ends of said light emitters and reference potential; a voltage selecting circuit for selecting a minimum voltage and a maximum voltage from junction terminal voltages between said current control transistors and said constant-current circuits; a control circuit for outputting a signal having a pulse duration depending on the minimum voltage selected by said voltage selecting circuit, to the control terminal of said switch device; and a voltage controller for generating a control voltage so as to make the maximum voltage selected by said voltage selecting circuit equal to or smaller than a preset maximum reference voltage and setting the level of said energization signals to the level of said control voltage.