Ejector devices, methods, drivers, and circuits therefor
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 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;
wherein the controller is configured to determine the resonance frequency based on a decay signal from the piezoelectric actuator; and
wherein the controller includes a capacitor and an ADC to determine a time-energy product (TEP) of the decay signal.
2. The system of claim 1 , wherein the controller comprises a resonant measurement and control circuit configured to determine the resonance frequency of the droplet ejector assembly by controlling the drive signal generator to produce a set of frequency signals across a range of frequencies and monitoring the effect on the decay signal.
3. The system of claim 2 , wherein the each frequency signal is repeated multiple times and a resultant time-energy product (TEP) signal is monitored each time to ensure consistency.
4. The system of claim 1 , wherein the drive signal comprises at least two different frequency signals, the resonance frequency being defined by interference between the at least two different frequency signals.
5. The system of claim 4 , wherein each of the different frequency signals is non-resonant with respect to the droplet ejector assembly.
6. A method of operating a droplet ejector assembly, the method comprising:
applying a drive signal to a droplet ejector assembly including a piezoelectric actuator coupled to a fluid-loaded droplet generator plate;
determining a resonance frequency of the ejector assembly based on accumulated magnitude or peak value of a feedback signal from the piezoelectric actuator, and
controlling the drive signal to drive the piezoelectric actuator at a resonance frequency of the ejector assembly;
wherein the feedback signal is defined by a decay signal following a drive or test signal to the actuator, wherein the controlling is performed by a controller coupled to the piezoelectric actuator, the controller comprising a capacitor and an ADC to determine a time-energy product (TEP) of the decay signal.
7. The method of claim 6 , wherein the drive signal is adjusted to account for changes in the resonance frequency of the ejector assembly due to changes in one or more of an amount of fluid loading of the droplet generator plate, temperature, humidity, and pressure.
8. The method of claim 6 , wherein applying the drive signal to the actuator comprises generating at least a first and a second different drive frequency signals that separately are non-resonant with respect to the fluid-loaded droplet generator plate, but together are resonant with respect to the fluid-loaded droplet generator plate.