| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem in a conventional multiswitching-type charging method which compensates temperature characteristics, where, as a large peak current is generated in an initial state of charging, large noise is produced and large dimensions of an energy storing coil 44 are required. SOLUTION: A charge/discharge controller controlling a charging switch 41 has a constant current means for supplying a constant current to a piezoelectric device 1 and a temperature compensating means for storing a constant energy in the piezoelectric device 1. The constant current means controls the ONs/OFFs of the charging switch so as to make a current value supplied to the piezoelectric device 1 repeat increase/decrease within a range between upper and lower limit values. The temperature compensating means converts a voltage value applied to the piezoelectric device 1 into a current value, integrates the current value by using a reference capacitor 55, and, when the integrated value (charged voltage) reaches a deciding value, stops charging the piezoelectric device 1. With such a constitution, as the piezoelectric device 1 is charged by a constant current, a problem that a large current is supplied to the piezoelectric device can be avoided. |
