| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and device for driving piezoelectric transformer, which can widen the variable range of the output voltage of a high-voltage power unit using a piezoelectric transformer. SOLUTION: A method for driving piezoelectric transformer incorporates a first control method for controlling the boosting rate of a piezoelectric transformer 13 and a second control method for controlling the driving waveform of the transformer 13. A hysteresis characteristic is given to the threshold for switching the control methods to each other, so as to avoid the drive of the transformer 13 at its natural frequency by eliminating the occurrence of an irregular drive frequency. When the power supply voltage is fixed, the drive frequency is raised and the boosting rate is reduced from that at the time of the maximum output voltage, by changing the resistance value of a resistor 16 for detected, until the drive frequency reaches the natural frequency at which a trouble occurs. When the frequency reaches the natural frequency, the amplitude of the driving waveform is reduced by reducing the power supply to a drive circuit 12 so as to lower the driving frequency, without changing the output voltage. The minimum output voltage is obtained by raising the drive frequency to the natural frequency, by again changing the resistance value of the resistor 16 while the amplitude is small. |
