Hall Element Control Circuit for Camera Autofocus
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Solution Overview
Problem
Existing camera modules in mobile devices face challenges in achieving a smaller size and simplified structure for autofocus functionality due to complex wiring and component arrangements in hall element control circuits, which affect the reliability and efficiency of lens position detection and adjustment.
Innovation Solution
A hall element control circuit is designed with a P-channel type transistor connected between the power supply potential and the high-potential-side input terminal of the hall element, along with an operational amplifier to control the gate voltage, reducing the number of terminals and wirings needed, and employing a differential amplifier to maintain a constant current drive for the hall element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional hall element control circuit is used, then the hall element can be driven with constant current, but the number of terminals and wirings increases, making the camera module larger and more complex
Solution Approach 1:
The patent combines the constant current drive function and the position detection function into a single integrated circuit. The hall element control circuit integrates the constant current source, differential amplifier, and position detection functionality, reducing the number of separate terminals and wiring connections needed while maintaining reliable position detection.
Solution Approach 2:
The control circuit performs multiple functions simultaneously: it provides constant current drive to the hall element, amplifies the differential output signal, and enables position detection. This multi-functional integration reduces the overall system complexity and terminal count while maintaining detection reliability.
2Device complexity
If the number of terminals and wirings is reduced, then the camera module size and structure are simplified, but the constant current drive stability may be affected
Solution Approach 1:
The patent merges the constant current generation circuitry with the signal amplification circuitry into a single integrated unit. This integration maintains constant current stability through internal feedback mechanisms while reducing the overall terminal count and simplifying the camera module structure.
Solution Approach 2:
The operational amplifier in the integrated circuit provides feedback control to maintain stable constant current drive to the hall element. The differential amplifier configuration ensures stable operation by comparing the actual output with the desired output, maintaining current stability despite the reduced terminal count.
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 configuration simplifies the camera module and its wiring by reducing the number of terminals and wirings, ensuring reliable and efficient lens position detection and adjustment while maintaining a constant current drive for the hall element, thus enhancing autofocus performance in mobile devices.
Implementation Method 1
an operational amplifier for controlling a gate voltage of the transistor by differentially amplifying a voltage between a predetermined set voltage and a voltage at the first terminal
Implementation Method 2
Hall elements are elements used to detect the position of an object
Data Source
AI summary
A first terminal supplies the bias voltage to a high-potential-side input terminal of a hall element. A second terminal supplies the ground potential to a low-potential-side input terminal of the hall element. A P-channel type transistor is configured such that the source terminal is connected to the power supply potential and the drain terminal is connected to the first terminal. An operational amplifier differentially amplifies the voltage between a predetermined set voltage and the voltage at the first terminal so as to control the gate voltage of the P-channel type transistor.