| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply which has a resonance circuit as a load, detects a capacitive operation securely when a resonance current is capacitive in an abnormal load state, and avoids malfunctionings caused by transient hair-shaped currents produced by a switching operation in a normal load state. <P>SOLUTION: An abnormality detecting control unit 42 of a control circuit 4 comprises a switch current detection circuit 42a, which detects the state of a resonance current according to a voltage between both ends of an impedance device Z, an oscillation synchronization circuit 42c which outputs an oscillation synchronization signal synchronized with a driving timing of a switching device Q2, a detection timer 42b which sets a detection region where an abnormality is detected, and an abnormality detection circuit 42d which detects abnormality in the detection region. A period, starting from the time when a regenerative current generated immediately after the switching device Q2 is turned on in a normal state, till the time when the drive of the switching device Q2 is turned off, is used as the abnormality detection region and the abnormality is detected, by deciding the polarity of the current applied to the switching device Q2. <P>COPYRIGHT: (C)2003,JPO |
