Drive Circuits and Methods for Ultrasonic Piezoelectric Actuators

• US 20070046143A1
• Filed: 08/14/2006
• Published: 03/01/2007
• Est. Priority Date: 02/03/2004
• Status: Active Grant

• Current Assignee: SC Johnson & Son Incorporated
• Original Assignee: Bit 7, Inc. (Bb7 LLC)
• Inventors: Blandino, Thomas, Luc, Tai, Zhou, Peter
• Granted Patent: US 7,538,473 B2
• Time in Patent Office: Days
• US Class Current: 310/317
• CPC Class Codes: B05B 17/0607 generated by electrical means, e.g. piezoelectric transducers
• CPC Class Codes: B06B 1/0238 of a single frequency, e.g. a sine-wave
• CPC Class Codes: H10N 30/802 Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for

Abstract

A drive circuit for and method of driving a piezoelectric actuator utilizes 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 is provided that drives the actuator at the resonant frequency and a second circuit is further provided 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.

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 resistance 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.

2. The drive circuit of claim 1, wherein the first mode comprises automatically periodically energizing the actuator upon start-up of the drive circuit.

3. The drive circuit of claim 2, wherein the second mode temporarily overrides the first mode when the second mode is selected.

4. The drive circuit of claim 1, wherein the second mode comprises a boost mode of operation.

5. The drive circuit of claim 1, wherein operation in the first mode causes the actuator to dispense a volatile at a first rate and operation in the second mode causes the actuator to dispense the volatile at a second rate greater than the first rate,

6. The drive circuit of claim 1, wherein the second circuit operates the first circuit in a third mode of operation in response to detection of motion.

7. The drive circuit of claim 1, wherein the first circuit is responsive to a switch setting to establish a dwell interval between successive energizations of the actuator.

8. The drive circuit of claim 1, wherein the first circuit has a full-bridge topology.

9. The drive circuit of claim 1, wherein the first circuit has a half-bridge topology.

10. The drive circuit of claim 1, wherein the current detector includes a current sensing resistor for detecting current flowing through the actuator.

11. The drive circuit of claim 1, wherein the current detector includes current sensing diodes for detecting current flowing through the actuator.

12. The drive circuit of claim 1, %wherein the first circuit includes at least one transistor coupled to the actuator and further including a circuit that detects an on resistance of the at least one transistor to detect current flowing through the actuator.

13. The drive circuit of claim 5, wherein the second rate is about fourteen percent duty cycle and has a duration of about seven seconds.

14. The drive circuit of claim 5, wherein the second rate is about fifty percent duty cycle and has a duration determined by the length of time that a boost switch is activated.

15. The drive circuit of claim 1, wherein the first circuit further comprises a phase-locked-loop.

16. The drive circuit of claim 1, wherein the second circuit further comprises an oscillator that develops an oscillator signal that is dithered.

17. The drive circuit of claim 1, further including at least one LED driven by an energization waveform.

18. A drive circuit for a piezoelectric actuator that dispenses a volatile, 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 tank circuit and a feedback capacitor coupled to the resistance 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 dispense volatile at a first rate and a second mode that causes the actuator to dispense volatile at a second rate greater than the first rate, wherein the first mode comprises automatically periodically energizing the actuator upon start-up of the drive circuit, and wherein the second mode temporarily overrides the first mode when the second mode is selected.

19. The drive circuit of claim 18, wherein the second circuit operates the first circuit in a third mode of operation in response to detection of motion.

20. The drive circuit of claim 18, wherein the first circuit is responsive to a switch setting to establish a dwell interval between successive energizations of the actuator.

21. The drive circuit of claim 18, wherein the first circuit has a full-bridge topology.

22. The drive circuit of claim 18, wherein the first circuit has a half-bridge topology.

23. The drive circuit of claim 18, wherein the current detector includes a current sensing resistor for detecting current flowing through the actuator.

24. The drive circuit of claim 18 wherein the current detector includes current sensing diodes for detecting current flowing through the actuator.

25. The drive circuit of claim 18, wherein the first circuit includes at least one transistor coupled to the actuator and circuits for detecting an on resistance of the at least one transistor to detect current flowing through the actuator.

26. The drive circuit of claim 18, wherein the second circuit further comprises a phase-locked-loop.

27. The drive circuit of claim 18, wherein the second circuit further comprises al oscillator that develops an oscillator signal that is dithered.

28. The drive circuit of claim 18, further including at least one LED driven by am energization waveform.

29. A method of driving a piezoelectric actuator, the method comprising the steps of:

coupling an impedance to the piezoelectric actuator, wherein the impedance and the piezoelectric actuator together form a tank circuit that has a resonant frequency;

providing 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 tank circuit and a feedback capacitor coupled to the resistance for phase shifting the current signal; and

providing 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.

30. The method of claim 29, wherein the first mode comprises automatically periodically energizing the actuator upon start-up of the drive circuit.

31. The method of claim 29, wherein the second mode temporarily overrides the first mode when the second mode is selected.

32. The method of claim 29, wherein the second mode comprises a boost mode of operation.

33. The method of claim 29, wherein operation in the first mode causes the actuator to dispense a volatile at a first rate and operation in the second mode causes the actuator to dispense the volatile at a second rate greater than the first rate.

34. The method of claim 33, wherein the second rate is about fourteen percent duty cycle and has a duration of about seven seconds.

35. The method of claim 33, wherein the second rate is about fifty percent duty cycle and has a duration determined by the length of time that a boost switch is activated.

36. The method of claim 29, wherein the second circuit operates the first circuit in a third mode of operation in response to detection of motion.

37. The method of claim 29, wherein the first circuit is responsive to a switch setting to establish a dwell interval between successive energizations of the actuator.

38. The method of claim 29, wherein the first circuit has a full-bridge topology.

39. The method of claim 29, wherein the first circuit has a half-bridge topology.

40. The method of claim 29, wherein the current detector includes a current sensing resistor for detecting current flowing through the actuator.

41. The method of claim 29, wherein the current detector includes current sensing diodes for detecting current flowing through the actuator.

42. The method of claim 29, wherein the first circuit includes at least one transistor coupled to the actuator and further including a circuit that detects an on resistance of the at least one transistor to detect current flowing through the actuator.

43. The method of claim 29, wherein the second circuit further comprises a phase-locked-loop.

44. The method of claim 29, wherein the second circuit further comprises an oscillator that develops an oscillator signal that is dithered.

45. The method of claim 29, further including at least one LED driven by an energization waveform.