Piezoelectric Load Control Circuit Using Periodic Charge Pumping
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Solution Overview
Problem
Controlling piezoelectric loads for actuating deformable lenses is challenging due to the need for precise elongation or contraction control and monitoring of piezoelectric characteristics, especially for maintaining image quality and accounting for aging effects.
Innovation Solution
An electronic circuit that includes a charge pump, measurement circuit, and comparator to control the charging current of piezoelectric loads by adjusting the reference voltage and switching off components to minimize noise and power consumption, allowing for predictable deformation of deformable lenses and characterization of piezoelectric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the charge pump continuously supplies charging current to maintain precise control of piezoelectric load, then the control precision of piezoelectric load is improved, but the power consumption increases
Solution Approach 1:
The charge pump operates periodically rather than continuously. The control circuit switches the charge pump on and off based on the comparison between load voltage and reference voltage, providing charging current only when needed to maintain voltage within the acceptable range, thus reducing overall power consumption while maintaining control precision.
Solution Approach 2:
The control circuit continuously monitors the load voltage and compares it with a reference voltage to determine when charging is needed. This feedback mechanism ensures the piezoelectric load is charged only when the voltage drops below the reference level, maintaining precise control while minimizing unnecessary power consumption.
2Stability of the object's composition
If the charge pump operates continuously to maintain load voltage, then the control stability is improved, but the noise emission increases
Solution Approach 1:
The charge pump operates periodically with on/off cycles controlled by the comparison between load voltage and reference voltage. This periodic operation maintains voltage stability within acceptable ranges while minimizing the duration of charge pump operation, thereby reducing noise emission during imaging periods.
3Measurement precision
If the measurement circuit operates continuously to monitor load voltage, then the measurement precision is improved, but the power consumption increases
Solution Approach 1:
The measurement circuit operates periodically rather than continuously. It monitors load voltage at specific intervals or triggers measurements based on voltage thresholds, ensuring accurate voltage detection while minimizing power consumption during battery-powered operation.
4Use of energy by moving object
If the charge pump is switched off to reduce power consumption, then the power savings are improved, but the control precision deteriorates
Solution Approach 1:
The control circuit uses feedback from voltage comparison to intelligently switch the charge pump on and off. The charge pump is activated only when the load voltage drops below the reference voltage, ensuring precise voltage control is maintained exactly when needed, while allowing power savings when the voltage is already within the acceptable range.
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 enables precise control of piezoelectric loads for maintaining desired optical power within limits, reduces power consumption, and allows for the characterization of piezoelectric characteristics, thereby improving image quality and extending battery life.
Implementation Method 1
The magnitude of the charging current is dependent on the size of the pump capacitors and other physical parameters which remain constant during the lifetime of the circuit
Implementation Method 2
Piezoelectric loads, e.g. piezoelectric elements, are normally powered by a charge pump or current amplifier
Data Source
AI summary
The invention relates to an electronic circuit (100) for controlling charging of a piezoelectric load (190). The electronic circuit comprises a charge pump (111) configured to supply a charging current to the piezoelectric load dependent on a charge control signal (131), a measurement circuit (113) configured to obtain a load voltage corresponding to a terminal voltage at a load terminal of the piezoelectric load, a comparator circuit (114) configured to compare an adjustable reference voltage with the load voltage. The electronic circuit is configured to determine the charge control signal dependent on the comparison so that the control signal controls delivery of the charging current dependent on the comparison. The electronic circuit is further configured to set the adjustable reference voltage to a target voltage (VT) and to set the adjustable reference voltage to a low limit voltage (Vlow), being lower than the target voltage, when the load voltage reaches the target voltage.