| 摘要 |
PURPOSE:To prevent failures of high-voltage rectifying diodes and the like, by detecting the increase in the secondary voltage of a feedback transformer which is connected to a piezoelectric transformer at the time of the short-circuit of a load, and stopping the oscillation of a driving transistor. CONSTITUTION:An oscillator, which contains a feedback transformer 6, a driving transistor 9, and a capacitor C, drives a piezoelectric transformer 1. The stepped-up output therefrom is supplied to a load RL through a voltage doubler rectifier comprising high-voltage rectifier diodes 15 and 16. While, the voltage of the secondary winding of the feedback transformer 6 is supplied to a load-shorting protection circuit containing a control rectifier 7 and a switching transistor 8. Therefore, abnormal current flows through the piezoelectric transformer 1 at the time of the short circuit of the load. Said current is converted to a voltage by the feedback transformer 6, the control rectifier 7 is conducted, and the oscillation of the driving transistor 9 can be stopped, thereby secure protecting action can be accomplished. |
