| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply circuit using a piezoelectric transformer which is easy of design and quality management. Ž<P>SOLUTION: The power supply circuit A includes a piezoelectric transformer 30, a piezoelectric transformer driving circuit 10, which has a switching element Q1 for drive consisting of a MOSFET, and a turn off circuit part 60, which turns off the switching element Q1 for drive. The piezoelectric transformer 30 includes a detecting electrode 34, which outputs a detected voltage where the voltage changes with frequency conforming to the natural resonance frequency of the piezoelectric transformer 30. The switching element Q1 for drive is turned on with the natural resonance frequency of the piezoelectric transformer 30 by the detected voltage that the detecting electrode 34 outputs. A turn off circuit part 60 includes a capacitor C5 for turn off, which turns off the switching element Q1 for drive, being charged with a current that flows to the switching element Q1 for drive. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
|
