Voice Coil Motor Position Control via Voltage Frequency Conversion
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Solution Overview
Problem
Conventional camera module position control methods, such as those using hall sensors, face challenges like increased material costs, current consumption, and mechanical design limitations, necessitating a more accurate position detection technique without external sensing units.
Innovation Solution
The apparatus employs a voltage/frequency conversion technique using a driving circuit, filter circuit, and digital control circuit to detect positional information based on AC voltage extracted from a voice coil motor, eliminating the need for separate sensing units like hall sensors by utilizing a coil with specific frequency components to measure impedance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a hall sensor is used for position detection, then position detection capability is provided, but additional current consumption occurs due to bias current and amplifier requirements
Solution Approach 1:
The patent combines the position detection function with the existing voice coil motor coil by superimposing a detection current on the driving current. This merging eliminates the need for separate hall sensors and their associated bias currents, thereby reducing overall current consumption while maintaining position detection capability.
Solution Approach 2:
The voice coil motor's own coil is made to serve dual purposes: driving the motor and detecting position. By using the coil's impedance changes to detect position, the system eliminates external sensing components and their power requirements, achieving self-service position detection.
2Measurement precision
If a hall sensor and position sensing magnet are used, then position control is achieved, but mechanical design flexibility is reduced and material costs increase
Solution Approach 1:
The patent merges the position sensing magnet with the lens carrier structure, eliminating the need for separate hall sensors. This integration reduces the number of components, simplifies mechanical design, and lowers material costs while maintaining accurate position control through impedance-based detection.
Solution Approach 2:
The voice coil motor coil is designed to perform multiple functions: driving the motor and detecting position simultaneously. This multi-functionality eliminates the need for dedicated sensing components, reducing device complexity and material requirements.
3Measurement precision
If a hall sensor is used, then position detection is provided, but reference value drift occurs due to temperature and external conditions
Solution Approach 1:
The patent implements feedback by continuously monitoring the impedance of the voice coil motor coil, which changes with position. This feedback mechanism allows for real-time position detection without relying on temperature-sensitive reference values, improving reliability under varying environmental conditions.
Solution Approach 2:
The system detects position by measuring changes in the coil's impedance parameters rather than relying on voltage-based hall sensor readings. Impedance changes provide a more stable measurement that is less susceptible to temperature drift and external condition variations.
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 approach reduces power consumption, manufacturing costs, and miniaturizes the camera module while providing precise position control and correction, enhancing noise exclusion characteristics and temperature compensation without requiring an analog-to-digital converter.
Implementation Method 1
The voltage/frequency conversion circuit may include a voltage controlled oscillator that is configured to generate the frequency signal, and the frequency signal may have a frequency based on a magnitude of the AC voltage extracted by the filter circuit.
Implementation Method 2
a filter circuit configured to extract an alternating current (AC) voltage from a voltage across the coil
Implementation Method 3
a driving circuit configured to apply a superimposed current, including a driving current and a position detecting current, to the coil
Data Source
AI summary
An apparatus for controlling a position of a voice coil motor (VCM) includes a coil disposed to face a magnetic member provided on one surface of a lens carrier; a driving circuit applying a superimposed current, including a driving current and a position detecting current, to the coil; a filter circuit extracting an alternating current (AC) voltage from a voltage across the coil; a voltage/frequency conversion circuit converting the AC voltage extracted by the filter circuit into a frequency signal; and a digital control circuit detecting positional information of the VCM based on a frequency component of the frequency signal.