| 摘要 |
PURPOSE: To obtain a power supply employing a piezoelectric transformer in which high efficiency operation can be ensured constantly regardless of fluctuation in the input power supply or the load. CONSTITUTION: A comparator 9 detects the output from a piezoelectric transformer 1 reaching a predetermined level. Subsequently, a frequency sweep circuit 13 sweeps the oscillation frequency of a driving frequency control circuit 10 around the resonance frequency thereof. An efficiency operating circuit 4 operates the efficiency of the piezoelectric transformer 1 at the time of frequency sweeping and means 7 detects the frequency corresponding to the maximum efficiency. That frequency is sustained in the subsequent operation thus operating the power supply at a frequency corresponding to the maximum efficiency. |
