Patent ID: 7208884

Claim:
A discharge lamp lighting circuit comprising a control circuit, a buck converter, a resonant converter, one or more discharge lamps, and a feedback circuit, which are connected in series, wherein the discharge lamp lighting circuit further comprises: an open protection circuit, which is connected to the discharge lamps and the control circuit, to detect whether any of the discharge lamps are unlit, and to send a voltage control signal to the control circuit if one of the discharge lamps is not lit, whereby the control circuit sends a pulse signal to the buck converter according to the voltage control signal, and the buck converter generates and outputs a direct current (DC) voltage according to the pulse signal; and an over-voltage detecting circuit, one end of which is respectively connected with the buck converter and the resonant converter, and the other end of which is connected to the control circuit; wherein the over-voltage detecting circuit conducts current and sends a voltage control signal to the control circuit if the DC voltage from the buck converter reaches a predetermined voltage, and the control circuit ceases operating according to the voltage control signal.