| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply fault detecting circuit capable of detecting a fault in open mode surely in addition to short circuit fault of a switching element while performing fault detection through a simple arrangement. SOLUTION: Power converting circuits 5 and 7 comprising a switching element operating with a DC voltage are provided with step-up circuits 13 and 14, output voltage from the step-up circuit is varied on the basis of a preset duty ratio and a load 2 is driven by operating the power converting circuits 5 and 7 alternately on the basis of the relation of magnitude of the voltage. The power supply fault detecting circuit comprises means 21 and 22 for detecting the currents flowing through two power converting circuits 5 and 7, an operational amplifier 23 for amplifying the difference of currents from two current detecting means 21 and 22, a circuit 24 for integrating an alternate operation signal from the operational amplifier 23, and normal operation judging means 25 and 26 for judging whether a voltage level from the integrating circuit 24 exists within a preset voltage level or not. COPYRIGHT: (C)2005,JPO&NCIPI
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