Piezoelectric devices and methods and circuits for driving same

• US 20080018200A1
• Filed: 09/24/2007
• Published: 01/24/2008
• Est. Priority Date: 04/02/2004
• Status: Active Grant

• Current Assignee: Par Technology Corporation
• Original Assignee: Adaptivenergy, LLC
• Inventors: Schemmann, Marosh, Jones, Sanford Garin, Vogeley, James
• Granted Patent: US 7,969,064 B2
• Time in Patent Office: Days
• US Class Current: 310/317
• CPC Class Codes: F04B 43/046 with piezoelectric drive
• CPC Class Codes: H10N 30/802 Circuitry or processes for operating piezoelectric or electrostrictive devices not otherwise provided for, e.g. drive circuits

Abstract

A drive circuit (18) produces a drive signal for a pump (10) having a piezoelectric actuator (14), with the piezoelectric actuator (14) forming a part of the drive circuit (18) and serving to shape a waveform of the drive signal. The drive circuit (18) comprises a pulse generator (100) which generates pulses; a converter circuit (102) which receives the pulses and produces charge packets at a rate which equals a desired drive frequency; and, the piezoelectric actuator (14). The piezoelectric actuator (14) receives the charge packets and, by its capacitive nature, integrates the charge packets to shape the waveform of the drive signal. Preferably, the piezoelectric actuator (14) integrates the charge packets to yield a drive field that approximates a sine wave. In one non-limiting example embodiment, the pulse generator (100) comprises a microcontroller-based pulsed width modulator (PWM) circuit (116) and the converter circuit (102) comprises a flyback circuit.

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69. A drive circuit which produces a drive signal for a piezoelectric actuator, the drive circuit comprising:

a source of digital pulses;

a transformer;

power switching element which receives the digital pulses and selectively applies current to the transformer;

means for using an electromotive force generated by parasitic capacitance of the transformer providing to high voltage bipolar output to the piezoelectric actuator.

70. The apparatus of claim 69, wherein the transformer is has only one secondary winding with no taps.

71. The apparatus of claim 69, wherein the source produces a single PWM pulse train.

72. The apparatus of claim 69, wherein the source produces a unipolar, low frequency, low potential control signal to the means for using an electromotive force.

73. The apparatus of claim 69, further comprising a second transformer connected in parallel to the transformer.

74. A drive circuit which produces a drive signal for a device having a piezoelectric actuator, the piezoelectric actuator forming a part of the drive circuit and serving to shape a waveform of the drive signal, the drive circuit comprising:

a pulse generator configured to generate digital pulses;

a converter circuit configured to use the digital pulses generated by the pulse generator to produce high voltage charge packets; and

wherein the piezoelectric actuator, by a capacitive nature of the piezoelectric actuator, integrates the charge packets to shape the waveform of the drive signal.

13. The drive circuit of claim 74, wherein the pulse generator comprises a pulsed width modulator (PWM) circuit.

14. The drive circuit of claim 13, wherein the pulsed width modulator (PWM) circuit comprises a microcontroller.

15. The drive circuit of claim 13, wherein the digital pulses generated by the pulsed width modulator (PWM) circuit have a pulse width chosen to produced a desired amplitude for the drive signal.

16. The drive circuit of claim 74, wherein the converter circuit comprises a flyback circuit.

17. The drive circuit of claim 16, wherein the flyback circuit produces potentials that are bipolar with respect to an electrical ground.

18. The drive circuit of claim 74, further comprising a filter for filtering components of the charge packets produced by the converter circuit.

19. The drive circuit of claim 74, wherein a frequency of the charge packets produced by the converter circuit is greater than an ability of the piezoelectric actuator to mechanically respond.

20. The drive circuit of claim 19, wherein the frequency of the charge packets produced by the converter circuit is chosen to be greater than an ability of the piezoelectric actuator to mechanically respond so that the charge packets produced by the converter circuit do not contribute to one of mechanical inefficiency and noise in the piezoelectric actuator.

21. The drive circuit of claim 74, wherein the charge packets comprise positive and negative pulses, and wherein the piezoelectric actuator integrates the positive pulses and the negative pulses to yield a drive field that approximates a sine wave.

22. The drive circuit of claim 74, wherein neither a bridge switching circuit nor a charge storage circuit are connected between the converter circuit and the piezoelectric actuator.

75. A piezoelectrically-operated apparatus comprising:

a piezoelectric actuator which is responsive to a drive signal; and

a drive circuit which applies the drive signal to the piezoelectric actuator as a series of digital pulses, wherein the drive circuit further comprises;

a pulse generator configured to generate digital pulses;

a converter circuit configured to use the digital pulses generated by the pulse generator to produce high voltage charge packets; and

wherein the piezoelectric actuator, by a capacitive nature of the piezoelectric actuator, integrates the charge packets to shape a waveform of the drive signal.

59. The apparatus of claim 75, wherein the pulse generator comprises a pulsed width modulator (PWM) circuit.

60. The apparatus of claim 75, wherein the pulsed width modulator (PWM) circuit comprises a microcontroller.

61. The apparatus of claim 75, wherein the digital pulses generated by the pulsed width modulator (PWM) circuit have a pulse width chosen to produced a desired amplitude for the drive signal.

62. The apparatus of claim 75, wherein the converter circuit comprises a flyback circuit.

63. The apparatus of claim 75, wherein the flyback circuit produces potentials that are bipolar with respect to an electrical ground.

64. The apparatus of claim 75, further comprising a filter for filtering components of the charge packets produced by the converter circuit.

65. The apparatus of claim 75, wherein a frequency of the pulses produced by the converter circuit is greater than an ability of the piezoelectric actuator to mechanically respond.

66. The apparatus of claim 65, wherein the frequency of the charge packets produced by the converter circuit is chosen to be greater than an ability of the piezoelectric actuator to mechanically respond so that the charge packets produced by the converter circuit do not contribute to one of mechanical inefficiency and noise in the piezoelectric actuator.

67. The apparatus of claim 75, wherein the charge packets comprise positive pulses and negative pulses, and wherein the piezoelectric actuator integrates the positive pulses and the negative pulses to yield a drive field that approximates a sine wave.

68. The apparatus of claim 75, wherein neither a bridge switching circuit nor a charge storage circuit are connected between the converter circuit and the piezoelectric actuator.