Image Sensor Driving Circuit Power Gating for Leakage Reduction
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Solution Overview
Problem
The increasing leakage current in image sensor driving circuits due to reduced manufacturing scales, high-resolution image acquisition, and smaller electronic device sizes leads to higher power consumption and temperature, degrading image quality.
Innovation Solution
An image sensor driving circuit with a power switch that connects and isolates the power supply voltage based on operation signals, reducing leakage current by powering off digital logic circuits during idle times and using power gating signals to manage power supply to row logic circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reduced scale manufacturing technology is applied to the driving circuit, then high-resolution image acquisition is enabled, but leakage current increases
Solution Approach 1:
The driving circuit is divided into multiple independent logic circuits (first logic circuit and second logic circuit) that can be independently controlled. Each logic circuit has its own power supply voltage control, allowing selective power gating to reduce leakage current in non-active segments while maintaining high-resolution imaging capability.
Solution Approach 2:
Power supply voltage is periodically supplied to different logic circuits based on their operational needs. The power supply voltage is connected to the first logic circuit during a first period and to the second logic circuit during a second period, creating a periodic power gating pattern that reduces overall leakage current while maintaining functional performance.
2Measurement precision
If the number of internal elements of the driving circuit is increased for high-resolution image acquisition, then image quality improves, but leakage current increases
Solution Approach 1:
The driving circuit with multiple internal elements is segmented into separate logic circuits that can be independently powered. This segmentation allows the circuit to maintain high resolution capability when needed while reducing the active number of elements during idle periods, thereby reducing leakage current proportional to the number of active elements.
Solution Approach 2:
Power supply voltage is discarded (disconnected) from logic circuits during periods when they are not needed for high-resolution operation, and recovered (reconnected) when high-resolution imaging is required. This dynamic power management allows the system to maintain peak performance when needed while minimizing energy loss during normal operation.
3Volume of moving object
If the size of electronic device is decreased, then portability improves, but operating temperature increases due to increased leakage current
Solution Approach 1:
By periodically connecting and disconnecting power supply voltage to different logic circuits based on operational requirements, the system reduces average power consumption and heat generation. This periodic power gating allows smaller device sizes while maintaining acceptable operating temperatures through reduced thermal load during non-critical periods.
4Reliability
If power supply voltage is continuously supplied to the driving circuit, then operational reliability is maintained, but power consumption increases
Solution Approach 1:
Power supply voltage is supplied periodically rather than continuously, with specific timing coordinated with image acquisition operations. The power is connected during periods when imaging operations are active and disconnected during idle periods, maintaining operational reliability when needed while significantly reducing average power consumption.
Data Source
AI summary
A driver circuit of an image sensor is provided. The driver circuit includes a row decoder to decode an address of a target row of a pixel array and generate an operation directing signal corresponding to the target row; a digital logic circuit including: a target row logic circuit to generate a pixel control signal based on the operation directing signal; a power switch configured to connect a power supply voltage to the target row logic circuit during a first time and isolate the power supply voltage from the target row logic circuit during a second time, based on the operation directing signal; and an output circuit configured to output a default signal during the second time; and a row driver configured to drive the target row based on the pixel control signal during the first time and drive the target row based on the default signal during the second time.