Patent ID: 7397197
Filing Date: 2008-07-08
Classification: H05B

Abstract:
1. A discharge lamp lighting circuit comprising: a DC/AC converter to receive a DC input voltage to perform a DC/AC conversion; a starting circuit to supply a start signal to a discharge lamp; and a control unit to control an electric power output from the DC/AC converter, wherein the DC/AC converter includes a plurality of switching elements driven by the control unit, and a series resonance circuit having a capacitor and at least one of an inductance element and a transformer, wherein the control unit is operable to set a driving frequency of the switching elements to a value higher than a resonance frequency Fon thereby to drive and control the switching elements at a time of lighting the discharge lamp, and wherein the control unit is operable to shift the driving frequency to a frequency region which is higher than a resonance frequency Foff when it is detected that the driving frequency reduces and the discharge lamp is extinguished, and wherein Foff corresponds to a resonance frequency of the series resonance circuit at a time of extinguishing the discharge lamp and Fon corresponds to a resonance frequency of the series resonance circuit at a time of lighting the discharge lamp.