Image Sensor Voltage Generation Circuit for Miniaturization
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Solution Overview
Problem
Existing imaging devices face miniaturization limitations due to the need for additional input terminals to generate driving voltage between power source and reference voltages, and existing voltage generation methods are inefficient in generating stable driving voltages for CMOS image sensors.
Innovation Solution
The imaging device incorporates a voltage generation circuit that uses a capacitor and voltage-current conversion circuit to generate a driving voltage lower than the power source voltage, which gradually decreases, allowing for miniaturization by reducing the number of necessary transistors and ensuring stable operation within a predetermined voltage range synchronized with a clock signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a driving voltage is generated outside the image sensor and input to the image sensor, then the driving voltage can be provided to the pixels, but the number of input terminals of the image sensor increases, inhibiting miniaturization
Solution Approach 1:
The voltage generation circuit is integrated inside the image sensor, merging the voltage generation function with the pixel array. This eliminates the need for separate external voltage input terminals, as the driving voltage is generated internally by the voltage generation circuit using a capacitor and transistor network that operates with the existing power source and reference voltage terminals.
Solution Approach 2:
The voltage generation circuit uses existing power source and reference voltage terminals for dual purposes: both powering the image sensor and generating the driving voltage through capacitive division. This multi-functional use of existing terminals avoids increasing the terminal count while still providing the necessary driving voltage to the pixels.
2Device complexity
If a power source voltage is divided by using a resistor to generate driving voltage, then the driving voltage can be generated inside the image sensor, but the voltage stability and controllability are insufficient for reliable pixel operation
Solution Approach 1:
The invention changes the voltage generation mechanism from resistive division to capacitive division. By using a capacitor charged to the power source voltage and then discharging it through a transistor, the system achieves better voltage stability and controllability. The capacitive approach allows for more precise voltage regulation and maintains stability even when power source voltage fluctuates.
Solution Approach 2:
The voltage generation circuit incorporates feedback mechanisms where the generated driving voltage is monitored and used to control the transistor operation, ensuring the voltage remains within the required range. The circuit adjusts the charging and discharging cycles based on the actual voltage levels, providing stable and reliable operation.
3Device complexity
If the number of input terminals is reduced for miniaturization, then the image sensor size decreases, but the ability to generate driving voltage inside the sensor is limited
Solution Approach 1:
The image sensor performs self-service by generating its own driving voltage internally using the voltage generation circuit. The circuit uses the power source voltage and reference voltage already present in the sensor to create the necessary driving voltage through capacitive division, eliminating the need for external voltage generation equipment or additional input terminals.
Solution Approach 2:
The voltage generation circuit dynamically adjusts the driving voltage by controlling the charging and discharging cycles of the capacitor through transistor switching. This dynamic operation allows the circuit to generate stable driving voltage levels adaptively, maintaining reliable pixel operation while keeping the terminal count low for miniaturization.
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 solution enables miniaturization of the image sensor while maintaining reliable operation by generating a stable driving voltage that is adjustable within a specific range, ensuring efficient photoelectric conversion and charge transfer, even when the power source voltage changes.
Implementation Method 1
a capacitor and a voltage-current conversion circuit. The capacitor is configured to hold a voltage. The voltage-current conversion circuit is configured to convert the voltage held in the capacitor into a current. The voltage held in the capacitor may gradually decrease and may be output as the driving voltage
Implementation Method 2
Each of the two or more pixels includes a photoelectric conversion element and a transistor. The photoelectric conversion element is configured to perform photoelectric conversion and generate an electric charge in accordance with an amount of received light
Data Source
AI summary
An imaging device includes two or more pixels and a voltage generation circuit. Each of the two or more pixels includes a photoelectric conversion element and a transistor. The photoelectric conversion element is configured to perform photoelectric conversion and generate an electric charge in accordance with an amount of received light. The transistor is driven by using a driving voltage. The voltage generation circuit is configured to generate the driving voltage that is lower than the power source voltage and gradually decreases.