| 摘要 |
PROBLEM TO BE SOLVED: To make drive efficiency higher by causing a drive frequency of a piezoelectric vibrator to coincide with its temperature characteristic, without using an external temperature sensor and so forth. SOLUTION: A measuring circuit 12 measures the specified impedance value of a piezoelectric element 32 which changes with the temperature of this piezoelectric element 32. On receiving a measured result from the measuring circuit 12, a correcting circuit 14 corrects a driving frequency for a piezoelectric vibrator 30, on the basis of an impedance value of the measured result. Namely, the correcting circuit 14 corrects the driving frequency for the piezoelectric vibrator 30 in accordance with the temperature change, on the basis of the precise temperature of the piezoelectric element 32. And, a drive circuit 16 generates an AC signal of the drive frequency corrected according to the temperature and supplies it to the piezoelectric vibrator 30, and drives the piezoelectric vibrator 30. |
