Patent ID: 6333607
Filing Date: 2001-12-25
Classification: H02H,H05B,Y02B,Y10S

Abstract:
A discharge lamp device for turning on a discharge lamp by alternating current by converting power from a direct current power source into alternating current by an inverter circuit, the discharge lamp device comprising:a transformer in which a primary side connected to a side of the direct current power source and a secondary side connected to a side of the discharge lamp are electrically conducted;a bridge circuit having a plurality of switching elements connected to the secondary side of the transformer, constituting the inverter circuit, inverting alternately a direction of discharge current of the discharge lamp and arranged in an H-bridge shape; anda fail-safe circuit for interrupting conduction of all of the plurality of semiconductor switching elements for bridge when a predetermined abnormal state is detected;wherein the fail-safe circuit prevents a state where overcurrent larger than a predetermined value flows in the bridge circuit as the predetermined abnormal state;the fail-safe circuit detects grounding of an electric wiring portion between the bridge circuit and the discharge lamp as the predetermined abnormal state; andthe fail-safe circuit detects lowering of a voltage signal between the transformer and the discharge lamp as compared with a predetermined voltage value and lowering of a current signal between the transformer and the discharge lamp as compared with a predetermined current value as the predetermined abnormal state.