Drive Wave Generation Circuit for Piezo Lens Positioning
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Solution Overview
Problem
Piezo actuators used in devices like camera lenses face challenges in determining the absolute position of movable objects without position detectors, and existing drive wave generation circuits are inefficient in generating drive waves for varying movement speeds, which is crucial for downsizing and cost reduction in portable devices.
Innovation Solution
A drive wave generation circuit that uses a combination of standard waveforms and counters to generate drive waves based on direction control signals and drive pulses, allowing for the generation of drive waves with a low frequency and enabling the reset of excessive drive pulses, thereby determining the initial position of the lens without a position detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a piezo actuator is used to drive a lens without a position detector, then the device size and cost are reduced, but the absolute position of the lens cannot be determined
Solution Approach 1:
The patent implements feedback by using a microcomputer to count drive pulses and calculate lens position based on the relationship between drive wave cycles and lens displacement. The microcomputer tracks the number of drive waves generated and uses this information to determine lens position without requiring a physical position detector, thus resolving the contradiction between reducing device complexity and maintaining position information.
2Speed
If standard waveforms and counters are used to generate drive waves, then drive waves with low frequency can be generated, but the circuit complexity increases
Solution Approach 1:
The patent employs a microcomputer that performs multiple functions: generating drive waves, counting drive pulses, calculating lens position, and controlling drive waveform generation. This multi-functional approach allows the system to generate low-frequency drive waves while avoiding the need for separate dedicated circuits for each function, thereby reducing overall circuit complexity despite the sophisticated control requirements.
Solution Approach 2:
The patent introduces a counter as an intermediary component between the drive pulse input and the drive wave generation. The counter mediates the relationship between external drive pulses and the internal waveform generation, allowing flexible control of drive wave frequency and enabling the system to generate low-frequency drive waves in a controlled manner.
3Device complexity
If voltage is applied to the piezo element to cause elongation and contraction, then linear movement is achieved without coils, but the moving speed in one direction must differ from the opposite direction to move objects in frictional contact
Solution Approach 1:
The patent implements dynamic control of the piezo actuator by varying the voltage waveform characteristics. The microcomputer generates drive waves with asymmetric characteristics - slow elongation and quick contraction - by controlling the voltage application pattern to the piezo element. This dynamic waveform control enables the actuator to move objects in frictional contact effectively while maintaining the simplified coil-free structure.
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 circuit effectively generates drive waves to control the movement of lens positions in piezo actuators, enabling precise positioning without sensors and reducing processing load on microcomputers, thus facilitating downsizing and cost reduction in portable devices.
Implementation Method 1
a voltage is applied to a piezo element (piezoelectric element) so as to cause elongation and contraction of the element, thereby generating a reciprocating movement of a drive shaft
Data Source
AI summary
Two standard waves from a standard waveform generation circuit are output via an output gate while being interchanged by a direction selector. The switching operation of the direction selector is controlled by a direction control signal M/I. 200 cycles of the standard waveforms are counted by a 200-cycle counter. A drive counter is downcounted every 200 cycles, while the drive counter is upcounted in accordance with the number of drive pulses DRIVE. When the count value of the drive counter becomes zero, output from the output gate is thereby stopped.