PURPOSE: To prevent burnout of a wiring and generation of fire by providing a circuit to break the primary side current on the basis of change in the primary side current due to abnormality in a high pressure discharge lamp, and equipping it with a malfunction preventive mechanism.

CONSTITUTION: A primary side power supply system 1 is equipped with a current sensing part 5 and a judged object output part 6, and the primary side current is sensed at all time, and the value obtained directly from this current or by converting into voltage is compared with the reference value, and when the measured current is deviated from this reference value, a breaking switch 15 installed on the primary side current supplying system 1 is actuated to stop supply of the primary side current. Thus the device is prevented from malfunction by a means for ex. of summarizing the output from a delay circuit 14, which is set by reference to the voltage change time when a lamp 4 is lighted up, and the signal from an abnormality sensing part. This should preclude burnout of the wiring system and occurrence of fire due to wire severance, etc., in the lamp 4.