Patent ID: 6744222
Filing Date: 2004-06-01
Classification: H02M,H05B,Y02B

Abstract:
A discharge lamp lighting apparatus, for controlling electric power supplied to a discharge lamp by a step-up/step-down converter comprising a transformer, a first switching element serially connected to the transformer on a side of a commercial ac power source, and a first diode and a first capacitor connected to the transformer on a load side, the discharge lamp lighting apparatus comprising:zero-cross detection means for detecting zero-cross of voltage of said commercial ac power source; a supplemental power circuit comprising a second diode connected to a junction between said transformer and said first switching element, a second capacitor for charging energy stored in a coil of said transformer on a side of said commercial ac power source via said second diode, and a second switching element, a third diode and an inductance through which the energy charged in the second capacitor is supplied to said discharge lamp; and a control circuit that calculates a voltage cycle of said commercial ac power source based on an output from said zero-cross detection means and then operates said second switching element in said supplemental power circuit at a high frequency during a predetermined period of time around the zero-cross.