Image Sensor Control Circuit for Ground-to-Positive Substrate Switching
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Solution Overview
Problem
Existing image sensors, particularly global shutter and indirect time of flight types, face high power consumption due to the need for generating high power by the power supply circuit to switch between positive and negative voltages for transfer gates, leading to significant leakage currents.
Innovation Solution
An image sensor design that applies a ground potential during integration and a positive potential with respect to ground during readout phases, using a control circuit to manage transfer gates, reducing the need for negative power supply generation and minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transfer gates are driven with voltages switching between positive and negative levels to avoid leakage currents, then charge transfer capability is improved, but power consumption increases significantly
Solution Approach 1:
The patent changes the voltage parameter from bidirectional switching (positive and negative levels) to unidirectional switching (positive and ground levels). By applying a positive voltage to activate transfer gates and grounding them to deactivate, the system maintains effective charge transfer while dramatically reducing power consumption requirements.
Solution Approach 2:
The patent extracts and eliminates the need for negative voltage generation from the power supply circuit. Instead of requiring the power supply to generate both positive and negative voltages, the design uses only positive voltages relative to ground, simplifying the power supply requirements and reducing power consumption.
2Speed
If high power is generated by the power supply circuit to switch transfer gates at significant frequencies, then switching speed is improved, but power consumption increases significantly
Solution Approach 1:
The patent changes the voltage switching parameters from high-power bidirectional switching to low-power unidirectional switching. By using only positive voltages relative to ground instead of alternating positive and negative voltages, the system achieves the required switching speeds while dramatically reducing the power supply requirements.
3Reliability
If negative power supply voltages are used to control transfer gates, then leakage current is reduced, but device complexity increases
Solution Approach 1:
The patent extracts and removes the negative power supply voltage generation capability from the system. Instead of requiring a complex power supply circuit that can generate both positive and negative voltages, the design uses only positive voltages relative to ground, thereby simplifying the power supply circuit while maintaining effective transfer gate control.
Solution Approach 2:
The patent inverts the conventional approach by using positive voltages relative to ground instead of negative voltages to control transfer gates. This inversion eliminates the need for negative power supply generation and simplifies the overall device architecture while maintaining the ability to control leakage currents effectively.
Data Source
AI summary
An image sensor includes an array of pixels inside and on top of a substrate. A control circuit is configured to apply voltage potentials to the substrate. During a first phase, the control circuit applies a ground potential to the substrate. During a second phase, the control circuit applies a potential positive with respect to the ground potential to the substrate.