Piezoelectric Driver Circuit with Variable Capacitance Hysteresis Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Piezoelectric transducers exhibit hysteresis and creep when driven by voltage, leading to distortion in audio applications due to multiple possible displacements for a given driving voltage.
Innovation Solution
The implementation of amplifier circuitry with a variable capacitor and control circuitry that compensates for hysteresis by adjusting the capacitance and gain based on parameters of the drive signal, such as volume or instantaneous value, to maintain a predefined signal level and mitigate distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric transducer is driven by voltage, then it can provide audio output, but it exhibits hysteresis and distortion due to multiple possible displacements for a given driving voltage
Solution Approach 1:
The patent transforms the control parameter from voltage to charge. By using a current source to directly control the charge on the piezoelectric transducer, the system eliminates hysteresis and distortion. The charge control is achieved through an integrator circuit that integrates the input voltage signal to generate the appropriate drive voltage, ensuring a one-to-one correspondence between input signal and transducer response.
2Manufacturing precision
If a series capacitor is added to compensate for hysteresis, then distortion is reduced, but signal attenuation occurs due to the capacitor's impedance
Solution Approach 1:
The patent employs feedback through an integrator circuit that monitors the voltage across the piezoelectric transducer and adjusts the drive signal accordingly. The integrator continuously integrates the difference between the desired and actual transducer response, generating a corrected drive voltage that compensates for signal attenuation while maintaining accurate charge control and eliminating hysteresis effects.
3Power
If the drive signal level is increased to compensate for capacitor attenuation, then signal strength is maintained, but distortion increases due to the piezoelectric transducer's non-linear response
Solution Approach 1:
The patent replaces the conventional voltage-driven electrical control system with a charge-controlled system. By using a current source to directly control the charge on the piezoelectric transducer rather than applying voltage, the system eliminates the non-linear voltage-displacement relationship that causes distortion. The integrator circuit ensures that the charge is precisely controlled in proportion to the input signal, maintaining accuracy without requiring signal level increases.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces distortion in piezoelectric transducers by compensating for hysteresis and signal attenuation, ensuring accurate and undistorted audio outputs.
Implementation Method 1
Piezoelectric transducers can be voltage-driven. However, when driven by voltage piezoelectric transducers exhibit both hysteresis and creep
Implementation Method 2
a variable capacitor configured to be coupled in series with the piezoelectric transducer; and control circuitry, wherein the control circuitry is configured to control a capacitance of the variable capacitor to compensate for hysteresis
Data Source
AI summary
The present disclosure relates to circuitry for driving a piezoelectric transducer. The circuitry comprises amplifier circuitry configured to receive a drive signal and to output an output signal, based on the drive signal, to the piezoelectric transducer, a variable capacitor configured to be coupled in series with the piezoelectric transducer, and control circuitry. The control circuitry is configured to control a capacitance of the variable capacitor to compensate for hysteresis in the piezoelectric transducer and to control a gain of the amplifier circuitry to compensate for signal attenuation caused by the variable capacitor.