Piezo Actuator Drive Circuit with Grounded Single-Ended Bipolar Signal Generation
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Solution Overview
Problem
Piezo actuators in micropumps require asymmetrical drive signals with distinct positive and negative amplitudes, but existing solutions struggle with generating such signals, especially when the actuator is grounded, and there is a need for compact, cost-effective driving solutions suitable for medical and mobile applications.
Innovation Solution
An apparatus comprising an AC voltage source, a DC voltage source, a capacitor, and a control apparatus that generates a drive signal by reducing the AC voltage using a predeterminable DC voltage, allowing for asymmetrical or symmetrical signal generation with adjustable amplitudes, and operates without a differential connection, enabling efficient driving of piezo actuators even when grounded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an AC voltage source is used to generate drive signals for piezo actuators, then the actuator can be driven with bipolar signals, but the circuit complexity increases and integration becomes difficult
Solution Approach 1:
The patent combines the AC voltage source, DC voltage source, capacitor, and control apparatus into a single integrated driving circuit. The control apparatus integrates multiple functions including voltage regulation, switching control, and signal generation, thereby reducing overall circuit complexity while maintaining the ability to generate bipolar drive signals for piezo actuators.
Solution Approach 2:
The control apparatus serves multiple functions: it regulates the AC voltage from the voltage source, switches the capacitor charging/discharging cycles, generates the drive signal with adjustable amplitudes, and provides protection against overvoltage. This multi-functionality reduces the need for separate circuits and components.
2Adaptability or versatility
If a DC voltage source with predeterminable magnitude is introduced to reduce AC voltage, then asymmetrical drive signals with adjustable amplitudes can be generated, but the device complexity increases
Solution Approach 1:
The DC voltage source provides a predeterminable reference voltage level before the AC voltage is applied to the capacitor. This preliminary voltage establishment enables the control apparatus to generate asymmetrical drive signals with precisely adjustable amplitudes by controlling the switching timing, without requiring complex real-time regulation circuits.
Solution Approach 2:
The capacitor acts as an intermediary energy storage element between the AC/DC voltage sources and the piezo actuator. By controlling the charging and discharging of this intermediate capacitor, the system can generate asymmetrical bipolar signals with adjustable amplitudes while isolating the complexity of voltage regulation from the actuator driving circuit.
3Reliability
If the piezo actuator is connected to electrical ground potential, then safety and reliability improve, but differential drive becomes impossible
Solution Approach 1:
Instead of using a differential drive approach where both sides of the piezo actuator are independently driven, the patent inverts the approach by grounding one side of the actuator and using a single-ended drive circuit that generates bipolar signals through controlled capacitor charging and discharging. This inversion maintains electrical safety through grounding while achieving the required bipolar signal generation.
Solution Approach 2:
The piezo actuator's own capacitance and the externally connected capacitor work together to generate the bipolar drive signal. The controlled charging of the capacitor to a predetermined voltage and subsequent discharge through the grounded actuator creates the asymmetrical bipolar signal without requiring complex differential drive circuitry, thereby maintaining simplicity and reliability.
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
The solution effectively generates drive signals with adjustable amplitudes, ensuring efficient operation of piezo actuators in micropumps and other devices, such as ultrasonic transducers and haptic systems, by controlling the connection between the DC voltage source and the capacitor, thereby reducing the AC voltage and allowing for bipolar signal generation from unipolar sources.
Implementation Method 1
piezo actuators comprising at least one piezoelectric element are special actuators. They take advantage of the fact that some solid bodies comprise a relationship between a change in electrical polarization—and therefore the occurrence of an electrical voltage at the solid body—and elastic deformation
Implementation Method 2
The piezo actuators move—using the inverse piezo effect—diaphragms in order to convey the media in certain directions
Data Source
AI summary
The invention refers to an apparatus for driving a load with a drive signal. The apparatus includes an AC voltage source, a DC voltage source, a capacitor and a control apparatus. The AC voltage source outputs an AC voltage. The DC voltage source outputs a DC voltage. The capacitor includes a first terminal and a second terminal. The AC voltage source is connected to the first terminal, and a signal output is connected to the second output. The control apparatus controls, depending on a voltage present at the signal output, a connection between the DC voltage source and the second terminal. Furthermore, the invention refers to a corresponding method as well as to a device.