| 摘要 |
PROBLEM TO BE SOLVED: To reduce the heat loss of a piezoelectric transformer which inputs an AC voltage from primary electrodes and outputs a transformed voltage from secondary electrodes through the utilization of piezoelectric effect by driving the transformer with a transformed voltage of the transformer. SOLUTION: An input power control section 20 controls drive voltages vd1 and vd2 which are generated from primary electrodes 401 and 402 of a piezoelectric transformer 40, so that they do not depend on a power supply voltage Vcc. When a resonance circuit is formed of the inductance of a coil 33 and the equivalent capacity between the primary electrodes 401 and 402 of the transformer 40, a transistor 21 is normally turned off and the current path going toward the primary electrode 401 from a power source 10 through the coil 33 is disconnected. Similarly, when a resonance circuit is formed of the inductance of a coil 34 and the equivalent capacity between the primary electrode 401 and 402 of the transformer 40, a transistor 22 is normally turned off, and the current path going toward the primary electrode 402 fro the power source 10 through the coil 34 is disconnected. Therefore, an excess current can be prevented from flowing in the transformer, and the heat loss of the transformer 40 can be reduced. |
