Patent ID: 7538473
Filing Date: 2009-05-26
Classification: B05B,B06B,H01L

Abstract:
1. A drive circuit for a piezoelectric actuator, comprising: an impedance coupled to the piezoelectric actuator, wherein the impedance and the piezoelectric actuator together form a tank circuit that has a resonant frequency; a first circuit that drives the actuator at the resonant frequency, the first circuit including a current detector coupled to the tank circuit and that develops a current signal representing current flow in the circuit and a feedback capacitor coupled to the current detector for phase shifting the current signal; and a second circuit responsive to the phase shifted current signal and a gating signal that selectively operates the first circuit in one of at least two modes of operation including a first mode that causes the actuator to be energized at a first duty cycle and a second mode that causes the actuator to be energized at a second duty cycle greater than the first duty cycle, wherein the second circuit includes at least one NAND gate and the at least one NAND gate receives the gating signal as a first input and the phase shifted current signal as a second input and develops an output signal to operate the first circuit.