| US 7,538,473 B2 | ||
| Drive circuits and methods for ultrasonic piezoelectric actuators | ||
| Thomas P. Blandino, Cottage Grove, Wis. (US); Tai P. Luc, Oak Creek, Wis. (US); and Peter Zhou, Tian Jin (China) | ||
| Assigned to S.C. Johnson & Son, Inc., Racine, Wis. (US) | ||
| Filed on Aug. 14, 2006, as Appl. No. 11/464,419. | ||
| Application 11/464419 is a continuation in part of application No. 11/264952, filed on Nov. 02, 2005. | ||
| Application 11/264952 is a continuation in part of application No. 11/140329, filed on May 27, 2005, granted, now 7,350,720. | ||
| Application 11/140329 is a continuation in part of application No. 11/050242, filed on Feb. 03, 2005, granted, now 7,503,668. | ||
| Application 11/140329 is a continuation in part of application No. 11/464419. | ||
| Application 11/464419 is a continuation in part of application No. 11/401572, filed on Apr. 11, 2006. | ||
| Application 11/401572 is a continuation in part of application No. 11/247793, filed on Oct. 11, 2005. | ||
| Application 11/247793 is a continuation in part of application No. 11/050169, filed on Feb. 03, 2005. | ||
| Claims priority of provisional application 60/541067, filed on Feb. 03, 2004. | ||
| Claims priority of provisional application 60/617950, filed on Oct. 12, 2004. | ||
| Prior Publication US 2007/0046143 A1, Mar. 01, 2007 | ||
| Int. Cl. H01L 41/09 (2006.01) | ||
| U.S. Cl. 310—317 [310/316.03] | 45 Claims |
| 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.
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