Ejector devices, methods, drivers, and circuits therefor

Abstract

In a piezoelectric ejector assembly, a piezoelectric actuator is attached to an ejector mechanism, while a drive signal generator and a controller are coupled to the actuator. The drive signal generator is configured to generate a drive signal for driving the actuator to oscillate the ejector assembly. The controller is configured to control the drive signal generator to drive the actuator at a resonant frequency of the ejector assembly, and an auto-tuning circuit is provided to define the optimum drive signal frequency.

1 . A device comprising:
 a droplet generator plate having a plurality of openings therethrough, and one or more channels for fluid communication with a reservoir of fluid, the droplet generator plate defining a fluid-filled droplet generator plate when the openings are filled with fluid;   an actuator coupled to the droplet generator plate;   a driver circuit in signal communication with the actuator, the driver configured to drive the actuator into oscillation based on a drive waveform that includes at least two separate drive signals; and   a feedback circuit in signal communication with the actuator and the driver circuit, wherein the feedback circuit is configured to determine a relaxation time for inclusion in the drive waveform between drive signals in order to reduce the oscillation of the actuator between drive signals by a predetermined amount.   
     
     
         2 . The device of  claim 1 , further comprising a back EMF sensor coupled to the actuator, wherein the back EMF sensor is configured to generate a feedback signal for use by the feedback circuit based on a back EMF generated by the actuator. 
     
     
         3 . The device of  claim 2 , wherein the actuator comprises a piezoelectric component and the back EMF is generated by oscillation thereof. 
     
     
         4 . The device of  claim 3 , wherein the back EMF sensor comprises a conducting material mechanically coupled to and electrically isolated from the piezoelectric component. 
     
     
         5 . The device of  claim 1 , wherein the duration of the drive signals is selected to generate at least one droplet from at least some of the plurality of openings, during each drive signal. 
     
     
         6 . The device of  claim 1 , wherein the driver circuit is configured to generate an active damping signal following a drive signal, the active damping signal being configured to reduce the relaxation time based on the feedback signal. 
     
     
         7 . The device of  claim 6 , wherein the active damping signal has a phase and polarity configured to time match the feedback signal and oppose oscillation of the actuator. 
     
     
         8 . The device of  claim 7 , wherein the active damping signal has a magnitude and duration configured to energy match the feedback signal and remove energy stored in the oscillation of the actuator. 
     
     
         9 . The device of  claim 8 , wherein the active damping signal is configured as a single pulse. 
     
     
         10 . The device of  claim 1 , wherein the driver circuit comprises a full bridge circuit for generating the driver waveform based on one or more oscillator outputs. 
     
     
         11 . The device of  claim 10 , further comprising an inductance circuit coupled to the driver circuit between the full bridge circuit and the actuator, wherein the inductance circuit is configured to amplify the drive waveform. 
     
     
         12 . The device of  claim 1 , wherein the feedback circuit includes a resonance detector configured to identify a drive signal that drives the actuator and fluid-filled droplet generator plate into resonance. 
     
     
         13 . A method of generating droplets, the method comprising:
 actuating a droplet generator mechanism in fluid communication with a reservoir of fluid into oscillation by means of discrete drive signals of defined duration, the droplet generator mechanism including a droplet generator plate including at least one opening configured to generate drops of the fluid when actuated;   measuring the oscillation of the droplet generator mechanism loaded with the fluid;   determining a relaxation time of the droplet generator mechanism loaded with the fluid, following a drive signal based on a defined reduction in oscillation, and   generating the next drive signal after a delay based on the relaxation time.   
     
     
         14 . The method of  claim 13 , wherein the droplet generator assembly includes a piezoelectric actuator mechanically coupled to the droplet generator plate, and measuring the oscillation comprises sensing a back EMF generated by the piezoelectric actuator. 
     
     
         15 . The method of  claim 14 , further comprising generating an active damping signal after a drive signal, configured to reduce the amplitude of the oscillation. 
     
     
         16 . The method of  claim 15 , wherein the active damping signal comprises a signal having a phase and polarity configured to time match and oppose the oscillation. 
     
     
         17 . The method of  claim 15 , wherein the active damping signal has a phase, duration, and magnitude configured to energy match the oscillation. 
     
     
         18 . A drive waveform for oscillating a piezoelectric mechanism, comprising a first drive signal and a second drive signal, wherein the second drive signal is separated from the first drive signal by a relaxation period, for allowing the piezoelectric mechanism oscillation to be reduced to a defined amplitude. 
     
     
         19 . The drive waveform of  claim 18 , wherein the drive waveform further comprises an active damping signal following the first drive signal, the active damping signal being configured to reduce the duration of oscillation of the piezoelectric mechanism. 
     
     
         20 . A system comprising:
 a droplet ejector assembly including a piezoelectric actuator coupled to a droplet generator plate having a plurality of openings therethrough, the droplet generator plate defining a fluid-filled droplet generator plate when the openings are filled with fluid;   a drive signal generator electrically coupled to the piezoelectric actuator, the drive signal generator being configured to generate a drive signal for driving the piezoelectric actuator, and a controller electrically coupled to the actuator and the drive signal generator, wherein the controller is configured to control the drive signal to drive the piezoelectric actuator at a resonance frequency of the droplet generator assembly.   
     
     
         21 .- 67 . (canceled)