Row Driver Buffer Voltage Monitoring to Prevent White Pixels
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Solution Overview
Problem
Existing solid-state imaging devices face challenges with high pixel-to-pixel variations and limited dynamic range, leading to issues such as 'white pixels' due to improper setting of low buffer supply voltages, which affect image quality and reliability.
Innovation Solution
A row driver assembly with an error detection circuit that monitors the low buffer supply voltage to ensure it remains within a target voltage window, using a voltage converter circuit and comparator to generate an active error signal when deviations occur, thereby preventing pixel defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a charge pump circuit is used to generate low buffer supply voltage, then voltage conversion is achieved, but voltage fluctuations occur causing pixel defects
Solution Approach 1:
The patent implements a feedback mechanism where a comparator continuously monitors the low buffer supply voltage and compares it against threshold values. When voltage deviations are detected, the comparator generates error signals that feed back to control the charge pump circuit, thereby stabilizing the voltage and preventing pixel defects while maintaining voltage conversion capability
Solution Approach 2:
The patent employs prior cushioning by establishing voltage threshold limits before defects occur. The comparator is configured with upper and lower threshold values that define a safe operating window, and the error detection circuit activates preventive measures before voltage fluctuations can cause pixel defects, thus cushioning against potential failures
2Reliability
If voltage monitoring is implemented to detect fluctuations, then reliability is improved, but device complexity increases
Solution Approach 1:
The monitoring circuit is designed to be self-service by using the existing low buffer supply voltage line to power the comparator and error detection circuitry. The system monitors itself without requiring external control or additional power sources, thereby improving reliability while minimizing the increase in device complexity
Solution Approach 2:
The error detection circuit is designed with multi-functionality, serving both as a voltage monitor and as a defect prevention mechanism. The same circuit that detects voltage fluctuations also generates the error signals needed to correct them, reducing the need for separate monitoring and correction systems
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
The solution enhances image sensor reliability by detecting and addressing voltage fluctuations, reducing the occurrence of 'white pixels' and ensuring high-quality image capture with reduced pixel-to-pixel variations.
Implementation Method 1
A voltage converter circuit includes a charge pump circuit converting the first voltage to a second voltage in accordance with a pump clock signal
Implementation Method 2
A comparator circuit has a non-inverting input electrically connected to the reference voltage and an inverting input electrically connected to an output of the error detection circuit
Data Source
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AI summary
A row driver assembly (13) includes a row driver unit (140). The row driver unit (140) includes a buffer circuit (141) that drives a control signal to a pixel circuit (100). The buffer circuit (141) is electrically connected to a high buffer supply voltage (VDDH) and to a low buffer supply voltage (VRL). A voltage converter circuit (150) supplies5 the low buffer supply voltage (VRL) to the buffer circuit (141). An error detection circuit (160) outputs an active error signal (XERROR) when the low buffer supply voltage (VRL) is outside a target voltage window.