Image Sensor Bias Current Circuit for Lower Power Readout
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Solution Overview
Problem
The increasing number of pixel circuits in image sensors leads to higher power consumption due to the need for multiple external reference electric current sources, which is inefficient and consumes more power.
Innovation Solution
An image sensor design that includes a readout circuit, a storage circuit with an analog/digital converter, and a first electric current source that generates and supplies electric current without requiring continuous input from an external reference electric current source, allowing for the internal resetting and refreshing of bias voltage, thereby reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of pixel circuits is increased, then the imaging performance is improved, but the power consumption increases due to the need for more external reference electric current sources
Solution Approach 1:
The patent combines multiple electric current source circuits into a single circuit that serves all pixel circuits. Instead of having separate reference electric current sources for each pixel circuit, one shared reference electric current source and one shared electric current source circuit are used to supply current to all pixel circuits, thereby reducing power consumption while maintaining imaging performance.
Solution Approach 2:
The patent makes the electric current source circuit universal by designing it to serve multiple pixel circuits simultaneously. The single electric current source circuit can supply electric current to any or all pixel circuits as needed, making it a multi-functional component that replaces multiple dedicated current sources.
2Reliability
If external reference electric current sources are used for each pixel circuit, then the bias voltage is maintained, but the device complexity and power consumption increase
Solution Approach 1:
The patent merges multiple external reference electric current sources into a single shared reference electric current source. This single source provides the reference current that is used by the electric current source circuit to generate and supply bias voltages to all pixel circuits, thereby reducing device complexity while maintaining reliable bias voltage levels.
Solution Approach 2:
The electric current source circuit is designed to automatically maintain the bias voltage of the capacitor without requiring continuous external intervention. The circuit uses the reference electric current to self-regulate and maintain the bias voltage, reducing the need for complex external control mechanisms.
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
This design reduces power consumption by eliminating the need for continuous external reference electric current input, allowing for efficient operation and refreshing of the electric current source within the image sensor.
Implementation Method 1
a signal reading transistor that reads out the signal to a signal line, the signal being generated by an electric charge resulting from a photoelectric conversion
Data Source
Figure 1(A)~1(B)
Figure 2
Figure 3(A)
AI summary
An image sensor includes: a readout circuit that reads out a signal to a signal line, the signal being generated by an electric charge resulting from a photoelectric conversion; a storage circuit including an analog/digital converter that converts a first voltage signal based on an electric current from a first power supply circuit into a digital signal and a first storage unit that stores the first voltage signal converted into a digital signal by the analog/digital converter; and a first electric current source that supplies the signal line with an electric current generated by the first voltage signal stored in the first storage unit.