Abstract text

A drive device for a piezoelectric element includes a transformer, a driver circuit, and a control circuit. The transformer has a primary side and a secondary side. The drive circuit causes the secondary side to generate a drive signal whose frequency varies in accordance with a control signal input to the primary side and to supply the generated drive signal to the piezoelectric element. The control circuit changes a frequency of the control signal in a predetermined frequency range multiple times, detects an impedance change in the piezoelectric element each time the control-signal frequency is changed, determines a resonant frequency of the piezoelectric element on the basis of a transition of the impedance change, and controls the control-signal frequency so that the determined resonant frequency is obtained.