Patent ID: 7291992

Claim:
A load failure protection circuit in a discharge lamp driving apparatus which is constructed so as not only to drive a plurality of discharge lamps on the basis of a feedback signal according to a drive state of the discharge lamps, but also to stop drive of the discharge lamps when the feedback signal becomes a predetermined voltage corresponding to a load failure, the load failure protection circuit comprising: bypass resistors which are provided corresponding each of the plurality of discharge lamps, and which bypass a part of current which flows through the corresponding discharge lamps; a resistor for full current detection into which currents which flow through the bypass resistors are made to flow; and a signal voltage setting circuit which not only outputs voltages at a common junction of the bypass resistors and the resistor for full current detection as the feedback signal, but also makes the feedback signal forcibly be a predetermined voltage corresponding to the load failure when any voltage at end parts of the bypass resistors in the discharge lamp sides respectively becomes equal to or more than a predetermined value.