Patent ID: 7429829

Claim:
A discharge lamp lighting circuit comprising a plurality of discharge lamps, a driving circuit, a control circuit for controlling the driving circuit to power the discharge lamps, an open protection circuit, which are connected in series, wherein: the open protection circuit comprises an open detecting unit, an open control circuit, and a delay circuit; wherein the open detecting unit comprises a plurality of open detecting circuits connected in series, each open detecting circuit is connected to a corresponding one of the discharge lamps, a first predetermined one of the open detecting circuits is connected to the open control circuit, and a second predetermined one of the open detecting circuits is connected to one terminal of the delay circuit and ground; one terminal of the open control circuit is connected to the control circuit, and the other terminal of the open control circuit is connected to the other terminal of the delay circuit and the second predetermined open detecting circuit; and each of the open detecting circuits detects whether the corresponding discharge lamp is unlit; if the corresponding discharge lamp is not lit, the open control circuit sends a voltage control signal to the control circuit, which in turn ceases operating.