| 摘要 |
PROBLEM TO BE SOLVED: To solve the following problem: if a power supply voltage drops by short circuit of a discharge lamp, the high side transistor in a H bridge circuit is possibly hindered from switching on and off. SOLUTION: In this discharge lamp lighting circuit 100, the H bridge circuit 30 includes two pairs of a high side transistor and a low side transistor placed in series between a ground potential and a dc power supply voltage Vo, and supplies a driving voltage VL to the discharge lamp 4. A control circuit 10 controls switching on and off of the transistors. Two high side transistors are switched on using the power supply voltage Vo. The control circuit 10 performs control to stop supplying the driving voltage VL, if the abnormal state of the discharge lamp 4 continues for a period longer than an abnormality detecting period, and switches off the two high side transistors included in the H bridge circuit 30 as the control to stop supplying the driving voltage VL, if a state in which the power supply voltage Vo is lower than a prescribed short circuit detection voltage, among various abnormal states, continues for a period longer than a short circuit detection period shorter than the abnormality detecting period. COPYRIGHT: (C)2010,JPO&INPIT |
