Patent ID: 7474035

Claim:
A driving device for a piezoelectric actuator comprising: an inductor connected to the piezoelectric actuator in series so that the inductor and the piezoelectric actuator forms a series circuit; a charging circuit for supplying electric power from a DC power source through a charging switch to the series circuit; a discharging circuit that is connected to the series circuit in parallel and discharging charges charged in the piezoelectric actuator through a discharging switch; and a charge/discharge control unit for repeating a turn-on/off operation of the charging switch under a state that the discharging switch is turned off when a driving instruction is input from an external device, thereby charging and expanding the piezoelectric actuator, wherein the charge/discharge control unit includes a target value setting section for setting a target value of charge energy of the piezoelectric actuator during an ON-period of the charging switch based on charge energy to be charged in the piezoelectric actuator during one charging period and a power supply voltage of the DC power source, a current detecting section for detecting charge current supplied from the DC power source to the series circuit when the charging switch is turned on, an estimating section for estimating charge energy of the piezoelectric actuator during the ON-period of the charging switch by integrating the charge current detected by the current detecting section, and a charging switch driving section for turning on the charging switch at a preset period when the driving instruction is input, and turning off the charging switch every time an estimation value estimated by the estimating section reaches the target value set by the target value setting section.