| 摘要 |
<p>When an input voltage rises, (the amplitude of) a sine-wave voltage for driving a piezoelectric transformer (1) increases, so that a detection voltage (Vti) rectified by a rectifying circuit (9) also increases. An output voltage from an error amplifier (10) for comparing the detection voltage (Vti) with a reference voltage (Vref2) rises. If the output voltage from the error amplifier (10) rises, a voltage-controlled oscillation circuit (11) decreases the duty ratio of an oscillation signal to be output. In a driving circuit (7), as the duty ratio of the oscillation signal decreases, the amplitude of a fundamental wave contained in a rectangular wave to be output decreases to be a small driving voltage to the piezoelectric transformer (1).</p> |
