CMOS Image Sensor Column Driving Circuit Well-Bias Voltage Optimization
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Solution Overview
Problem
CMOS image sensors face increased power consumption with higher frame rates, which is a challenge in achieving high-speed and high-resolution imaging without compromising energy efficiency.
Innovation Solution
A method of operating CMOS image sensors that involves a test operation to determine the optimal well-bias voltage level for column driving circuits, reducing power consumption by setting the well-bias voltage based on test results, and performing image capture operations using the optimized voltage level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the frame rate of CMOS image sensor is increased to achieve high speed and high resolution imaging, then imaging speed and resolution are improved, but power consumption increases
Solution Approach 1:
The patent applies parameter changes by adjusting the well-bias voltage level applied to transistors in column driving circuits based on test results. The timing controller performs test operations at different voltage levels and selects an optimized voltage level that maintains imaging performance while reducing power consumption, directly addressing the contradiction between frame rate and power consumption
2Reliability
If the well-bias voltage level is increased to maintain imaging quality at high frame rates, then imaging quality is preserved, but power consumption increases
Solution Approach 1:
The patent implements feedback through test operations where the timing controller applies test patterns to column driving circuits at different well-bias voltage levels, evaluates the results, and selects the optimal voltage level. This feedback mechanism ensures imaging quality is maintained while minimizing power consumption by avoiding unnecessarily high voltage levels
3Use of energy by moving object
If the well-bias voltage is optimized through test operations, then power consumption is reduced, but device complexity increases due to additional test and bias setting operations
Solution Approach 1:
The timing controller performs multiple functions: it controls row and column driving circuits for normal imaging operations, executes test operations by applying test patterns, evaluates test results, and sets optimal bias voltages. By consolidating these diverse functions in a single controller, the patent reduces overall device complexity while achieving power consumption optimization
Data Source
AI summary
In a method of operating an image sensor, the image sensor includes a pixel array and a plurality of column driving circuits that are connected to a plurality of columns of the pixel array. A test operation is performed by applying a test pattern to the plurality of column driving circuits while changing a level of a well-bias voltage applied to a transistor included in the plurality of column driving circuits. A bias setting operation for setting the level of the well-bias voltage is performed based on a result of the test operation. An image capture operation for detecting incident light and generating a frame image is performed based on the pixel array, the plurality of column driving circuits and the well-bias voltage set by the bias setting operation.