| 摘要 |
PURPOSE:To reduce loss of a transducer, a driving transformer, and a piezoelectric transformer by correcting the disturbance of current flowing into a switching element caused by the capacitor component at the driving section for the piezoelectric transformer and controlling the duty ratio at the time of high input voltage thereby discharging the driving section for the piezoelectric transformer. CONSTITUTION:Primary winding of a driving transformer T and a transistor Q are connected in series between an input voltage VIN and GND. An AC voltage induced on the secondary of the driving transformer T is applied to the driving section 1a for a piezoelectric transformer 1 and a boosted high frequency voltage is outputted from a generating section 1b and applied to a load 2. Secondary inductance of the driving transformer T and the capacitance at the driving section 1a constitute a parallel resonance circuit. Consequently, the OFF interval of the transistor Q is lengthened as the input voltage VIN detected by a voltage detection circuit 4 increases to cause zero-crossing of the collector-emitter voltage and the collector thus reducing the loss. |
