Camera Actuator Driver Circuit for Stable Position Control
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Solution Overview
Problem
Existing linear current driving technologies for camera module actuators in mobile devices face challenges in accurately and stably controlling the position of actuators due to sensitivity to temperature changes and process deviations, particularly with small resistance values and NMOS transistors.
Innovation Solution
The implementation of a differential current digital-to-analog converter and a linear driver that uses a PID controller to output digital signals for precise control of forward and reverse currents, along with an H-bridge circuit to manage current magnitudes and direction, allowing for resistance values of several hundred ohms to several kilo ohms and transistor gate width ratios, reducing sensitivity to temperature and process deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a small resistance value (0.5 to 1 ohm) is used to obtain a driving current of 100 mA, then the driving current can be achieved, but the system becomes sensitive to temperature change and process deviation, making it difficult to obtain stable performance
Solution Approach 1:
The patent changes the resistance parameter from a small value (0.5-1 ohm) to a larger value (several hundred ohms to several kilo ohms). This parameter change reduces sensitivity to temperature and process deviations while maintaining driving capability through the differential current DAC architecture that provides current amplification.
Solution Approach 2:
The patent introduces a differential current digital-to-analog converter as an intermediary component between the control signal and the actuator. This mediator enables precise current control with higher resistance values by converting digital signals to differential analog currents, which are then amplified to drive the VCM.
2Quantity of substance
If a small resistance value is used to achieve the required driving current, then the current magnitude can be sufficient, but the system reacts sensitively to temperature change and process deviation
Solution Approach 1:
The patent changes the resistance parameter from small (0.5-1 ohm) to large (several hundred ohms to several kilo ohms) values. This parameter change reduces temperature sensitivity and process deviation effects while the differential current DAC architecture ensures sufficient current magnitude is achieved through controlled current amplification.
Solution Approach 2:
The patent employs feedback mechanisms within the differential current DAC and linear driver to maintain precise current control. The system monitors and adjusts the differential currents to compensate for variations, reducing the impact of temperature and process deviations on the actual current delivered to the actuator.
3Device complexity
If a simple current driving circuit is used, then the device complexity is low, but the control precision and linearity of actuator position are insufficient
Solution Approach 1:
The patent segments the current driving function into multiple specialized components: a differential current DAC for precise digital-to-analog conversion, a linear driver for accurate current amplification, and an H-bridge circuit for bidirectional current control. This segmentation enables high precision actuator positioning while managing complexity through functional decomposition.
Solution Approach 2:
The patent implements dynamic control capabilities through the differential current DAC and H-bridge circuit, enabling rapid and precise adjustment of current magnitude and direction. This dynamic control allows for accurate actuator positioning and quick response to position corrections, enhancing measurement and control precision.
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 enables more accurate and rapid control of actuator positions by linearly controlling currents, providing stable performance and reducing the impact of temperature and process variations on output currents.
Implementation Method 1
The VCM used to move a lens module in the AF and the OIS moves the lens module to a desired position by controlling the direction and amount of current flowing in a coil which is mounted outside a camera lens module
Data Source
AI summary
Embodiments of the invention provide an apparatus for driving an actuator of a camera module in a mobile device. The apparatus includes a proportional-integral-derivative (PID) controller configured to compare an output of a gyro sensor with an output of a hall sensor configured to sense a position of an actuator to output a digital signal of plural bits, and a differential current digital-to-analog converter configured to convert the digital signal output from the PID controller into an analog current signal. The apparatus further includes a linear driver configured to receive the signal output from the differential current digital-to-analog converter to output a linear driving signal, an H-bridge circuit configured to control magnitudes of a forward driving current and a reverse driving current flowing in the actuator based on the output of the linear driver, and a driving direction controller configured to output a signal controlling a direction of current flowing in the actuator to the H-bridge circuit based on the digital signal output from the PID controller.