Piezoelectric devices and methods and circuits for driving same

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.

1 . A pump comprising:
 a pump body for at least partially defining a pumping chamber and an inlet and an outlet which communicate with the pumping chamber;   a piezoelectric actuator situated in the pump body and responsive to a drive signal for pumping fluid between the inlet and outlet; and   a drive circuit which applies the drive signal to the piezoelectric actuator as a series of digital pulses.   
     
     
         2 . The pump of  claim 1 , wherein the drive circuit further comprises:
 a pulse generator which generates digital pulses;   a converter circuit which uses the digital pulses generated by the pulse generator to produce the series of high voltage charge packets.   
     
     
         3 . The pump of  claim 2 , wherein the drive circuit further comprises the piezoelectric actuator, 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. 
     
     
         4 . The pump of  claim 2 , wherein the pulse generator comprises a pulsed width modulator (PWM) circuit. 
     
     
         5 . The pump of  claim 4 , wherein the pulsed width modulator (PWM) circuit comprises a microcontroller. 
     
     
         6 . The pump of  claim 4 , wherein the pulses generated by the pulsed width modulator (PWM) circuit have a pulse width chosen to produced a desired amplitude for the drive signal. 
     
     
         7 . A method of operating a piezoelectric pump having a piezoelectric actuator situated in a pump body and responsive to a drive signal for pumping fluid between an inlet and an outlet of the pump body, the method comprising:
 applying a series of digital pulses as the drive signal to the piezoelectric actuator;   operating the piezoelectric actuator in response to the drive signal.   
     
     
         8 . The method of  claim 7 , further comprising:
 (1) generating digital pulses;   (2) using the digital pulses of step (1) to produce the series of high voltage charge packets.   
     
     
         9 . The pump of  claim 8 , further comprising using the piezoelectric actuator to integrate the charge packets and thereby shape a waveform of the drive signal. 
     
     
         10 . The pump of  claim 7 , further comprising modulating a pulse width of the digital pulses of step (1) in accordance with a desired waveform for the drive signal. 
     
     
         11 . 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. 
     
     
         12 . The drive circuit of  claim 11 , wherein the drive circuit comprises:
 a pulse generator which generates digital pulses;   a converter circuit which uses 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 12 , 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 12 , 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 12 , further comprising a filter for filtering components of the charge packets produced by the converter circuit. 
     
     
         19 . The drive circuit of  claim 12 , 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 12 , 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 12 , wherein neither a bridge switching circuit nor a charge storage circuit are connected between the converter circuit and the piezoelectric actuator. 
     
     
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