Patent ID: 6657401
Filing Date: 2003-12-02
Classification: H05B,Y10S

Abstract:
A ballast for a discharge lamp comprising:a discharge lamp; an AC/DC conversion portion for converting a phase-controlled input AC voltage to a DC voltage; a dimming control portion for calculating a dimming control signal from the phase-controlled input AC voltage; and a DC/AC conversion portion for converting an output voltage of the AC/DC conversion portion to a high frequency voltage to be applied to the discharge lamp and for lighting and dimming the discharge lamp in response to the dimming control signal, wherein the DC/AC conversion portion has a first operation mode that supplies the discharge lamp with a voltage for maintaining the lighting and a second operation mode that supplies the discharge lamp with a voltage lower than the voltage for maintaining the lighting so as to turn off the discharge lamp, and the DC/AC conversion portion switches between the first and second operation modes in response to the magnitude of the dimming control signal.