Driving circuit for piezoelectric element

PURPOSE: To obtain a drive circuit for piezoelectric element to be employed in the injection valve driving mechanism for an internal-combustion engine fuel injector in which desired expanding/contracting amount can be ensured regardless of variation of capacitance due to temperature variation of the piezoelectric element. CONSTITUTION: The driving circuit for piezoelectric element comprises first control means 10, 11 for detecting the amount of charge of a piezoelectric element and controlling the positive voltage at the time of charging so that the amount of charge thus detected will match with a target value, and second control means 12, 13 for detecting the capacitance of the piezoelectric element and controlling the negative voltage at the time of discharge such that the higher the capacitance the higher the negative voltage. COPYRIGHT: (C)1993,JPO&Japio