Frequency-Dependent Bias Circuit for Image Sensor Current Optimization
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Solution Overview
Problem
Conventional analog circuits for image sensors require a constant high current supply regardless of the horizontal drive frequency, leading to inefficiency and battery life reduction in portable devices, and redesigning for varying specifications increases design time.
Innovation Solution
A frequency-dependent bias circuit that adjusts current supply based on the horizontal drive frequency by using pulse signals to operate noise reduction, gain variable amplifier, and AD converter circuits, ensuring optimal current usage across different frequency specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a constant high current is supplied to the noise reduction circuit, gain variable amplifier, and AD converter, then the circuits can process signals at the highest horizontal drive frequency specification, but the current consumption becomes excessive for lower frequency applications and reduces battery life
Solution Approach 1:
The bias circuit is designed to dynamically adjust the current supplied to the noise reduction circuit, gain variable amplifier, and AD converter based on the horizontal drive frequency of the image sensor. The circuit automatically increases current when high frequency processing is required and reduces current when lower frequencies are used, eliminating the waste of excessive current consumption while maintaining the capability to handle maximum frequency specifications.
2Adaptability or versatility
If a separate bias circuit is designed for each CCD specification, then the current can be optimized for each application, but the design time increases significantly
Solution Approach 1:
A single bias circuit is designed with the multi-functionality to serve multiple CCD specifications with different horizontal drive frequency requirements. The circuit incorporates frequency detection and automatic current adjustment capabilities, allowing it to adapt to various image sensor specifications without requiring separate bias circuit designs for each application, thereby significantly reducing design time while maintaining optimized current consumption.
Data Source
AI summary
An analog circuit includes a pulse control circuit for outputting pulse signals for operating component circuits based on reference pulse signals for driving an image sensor, a noise reduction circuit that is operated in accordance with a pulse signal of a horizontal drive frequency output from the pulse control circuit to reduce noise present in image signals output from the image sensor, a gain variable amplifier for adjusting an amplitude of signals output by the noise reduction circuit, an AD converter for converting the output signals of the gain variable amplifier into digital signals and output these digital signals, a clamp circuit that is operated in accordance with a pulse signal at a horizontal drive frequency output from the pulse control circuit to perform feedback control of the digital signals output by the AD converter, and a frequency-dependent bias circuit that supplies a current amount corresponding to the frequency of at least one kind of pulse signal from among the reference pulse signals and the pulse signals that are output from the pulse control circuit. The analog circuit is operated at a sufficient current amount required for the processing of signals from various image sensors having different horizontal drive frequency specifications.