| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply circuit for performing an appropriate protection operation and power supply to a load accordingly by accurately discriminating the abnormal operation of a boosting circuit or the like and the stable standby state of the load. SOLUTION: A load 302 is driven by a piezoelectric transformer 301 that is driven by a boosting circuit 304 being controlled by a frequency control circuit 303 and a drive voltage control circuit 311. An output voltage Vp2 of the piezoelectric transformer 301 and a load current Io of the load 302 are detected, and it is judged whether a value that is obtained by converting the load current Io to a voltage is equal to or less than a reference voltage Vs by a comparator 405. A delay circuit 402 sets long delay time when the load current Io is equal to or less than a reference and short delay time when an output voltage Vp2 that is equal to or more than a specific value is outputted. With the delay time (delay signal) as operation start time, a break circuit 403 controls the operation stop of an output system. |
