Photoelectric Conversion Pixel Current Balancing for Stable Signal Readout
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Solution Overview
Problem
The accuracy of output signals from solid-state image capturing apparatuses deteriorates due to variations in power supply voltage, as seen in Japanese Patent Application Laid-Open No. 2008-187565, where the variation of power supply voltage affects the current values in comparator pixels, leading to noise and decreased signal-to-noise ratio.
Innovation Solution
A photoelectric conversion apparatus with a control unit that manages current flow between multiple sources and lines, allowing for the adjustment of current through the second source to counteract changes in the first source, thereby stabilizing the total current and reducing voltage variations, which improves signal accuracy by maintaining a consistent power supply voltage and ground voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the current value of the comparator is switched depending on the AD conversion gain, then the adaptability to different conversion gains is improved, but the accuracy of the output signal deteriorates due to power supply voltage variation
Solution Approach 1:
The patent changes the current parameter of the current sources dynamically based on the AD conversion gain setting. When the AD conversion gain is switched between first and second values, the control unit switches the current sources between first and second current sources with different current values, allowing the system to adapt to different conversion gains while maintaining signal accuracy through coordinated current adjustment.
Solution Approach 2:
The patent implements feedback control where the control unit monitors the AD conversion gain setting and automatically adjusts the current source configuration accordingly. The control unit receives information about the conversion gain state and switches between different current sources to maintain optimal operating conditions, creating a closed-loop system that compensates for voltage variations.
2Adaptability or versatility
If multiple current sources are used for different pixel groups, then the adaptability to different reading modes is improved, but the stability of power supply voltage deteriorates
Solution Approach 1:
The patent dynamically changes the current parameter of the current sources based on the reading mode. When switching between first reading mode (all pixels) and second reading mode (thinned-out pixels), the control unit switches between current sources with different current values to match the pixel group being read, enabling mode adaptability while managing power supply stability.
Solution Approach 2:
The patent makes the current source configuration dynamic by switching between different current sources based on the reading mode. The system transitions from a static current supply to a dynamic one that adapts to the selected reading mode, allowing the first current source to serve all pixels in first mode and the second current source to serve thinned-out pixels in second mode.
3Use of energy by moving object
If the current flowing through one source is decreased to reduce power consumption, then the energy efficiency is improved, but the total current variation increases causing voltage fluctuation
Solution Approach 1:
The patent changes the current parameters of multiple current sources in a coordinated manner. When the second current source current is decreased to save power during thinned-out pixel reading, the first current source current is simultaneously increased to compensate, maintaining the total current at a relatively constant level and preventing voltage fluctuations.
Solution Approach 2:
The patent applies counterbalancing current adjustment where the increase in one current source compensates for the decrease in another. The first current source acts as a counterweight to the second current source, ensuring that when one is reduced for power savings, the other increases to maintain overall current stability and prevent power supply voltage variation.
Data Source
AI summary
An apparatus includes a plurality of pixels arranged in an array, a first group of pixels that are arranged in a first direction among the plurality of pixels, a first line to which the first group is connected, a second group of pixels that are arranged in the first direction among the plurality of pixels, and a second line to which the second group is connected. The first line is connected to a first source. The second line is connected to a second source. The apparatus further includes a control unit configured to: (1) perform control to increase a current flowing through the second source while performing control to decrease a current flowing through the first source, or (2) suppress a variation of total amount of flowing current by changing the current flowing through the second source in response to a change in the current flowing through the first source.