Patent ID: 7332870

Claim:
A driving voltage controller for a light-emitting source, which controls a light-emitting source driving voltage that is applied to the light-emitting source, the driving voltage controller comprising: determining means for determining if a power supply voltage drops below an initial driving voltage after the initial driving voltage fixing a desired luminance of the light-emitting source is established and the light-emitting source is driven by applying the light-emitting source driving voltage thereto at the initial driving voltage; voltage-adjusting means for causing the light-emitting source driving voltage to be applied thereto at the power supply voltage when the power supply voltage drops below the initial driving voltage, and for holding undervoltage information of the power supply when the power supply voltage drops therebelow; and voltage-returning means for gradually returning the light-emitting source driving voltage to the initial driving voltage when the determining means determines that the power supply voltage has returned to a level higher than or equal to the initial driving voltage after the voltage-returning means holds the undervoltage information of the power supply.