Photoelectric Conversion Pixel Bias Circuit With Split Reference Lines
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Solution Overview
Problem
Existing photoelectric conversion devices experience image quality deterioration due to fluctuations in bias voltage caused by incident light, particularly in strong lighting conditions, as the voltage of vertical signal lines fluctuates, affecting the reference voltage and bias voltage supplied to current sources.
Innovation Solution
A photoelectric conversion device is designed with a pixel array, signal lines, current sources, a first voltage supply line for aperture pixels, a second voltage supply line electrically separated from the first, and a bias circuit that uses a second reference voltage to stabilize the bias voltage, reducing the impact of light-induced fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single voltage supply line is used to supply reference voltage to both aperture pixels and bias circuitry, then device complexity is reduced, but bias voltage stability deteriorates under strong light conditions
Solution Approach 1:
The voltage supply system is segmented into two separate voltage supply lines: a first voltage supply line that supplies reference voltage to aperture pixels, and a second voltage supply line that supplies reference voltage to the bias circuitry. This segmentation prevents light-induced voltage fluctuations in the aperture pixel region from affecting the bias voltage, thereby resolving the technical contradiction between device complexity and bias voltage stability.
2Reliability
If voltage supply lines are electrically separated to reduce light-induced fluctuations, then bias voltage stability is improved, but device complexity increases
Solution Approach 1:
The bias circuitry's voltage supply is extracted from the aperture pixel region and connected to a separate second pad that is electrically isolated from the first pad supplying voltage to aperture pixels. This extraction removes the harmful coupling between light-induced voltage fluctuations and the bias voltage, achieving improved reliability while maintaining manageable device complexity through clear spatial and electrical separation.
Data Source
AI summary
A photoelectric conversion device includes a pixel array having aperture pixels arranged so as to form rows and columns, signal lines arranged in the pixel array so as to allow readout of signals from the aperture pixels, current sources connected to the signal lines, a first voltage supply line configured to supply a first reference voltage to the aperture pixels, a first pad connected to the first voltage supply line, a bias circuit configured to supply a bias voltage to the current sources, a second voltage supply line electrically separated from the first voltage supply line, and configured to supply a second reference voltage to the bias circuit, and a second pad connected to the second voltage supply line.