Pixel Amplification Apparatus for CMOS Image Sensor Noise Reduction
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Solution Overview
Problem
CMOS image sensors face challenges with high pixel density leading to increased loading capacitance, resulting in insufficient pixel conversion time and potential noise during image data transmission, as the existing technologies struggle to balance high-speed data reading with power consumption.
Innovation Solution
A pixel amplification apparatus dynamically controls the pixel bias current by sampling a first pixel bias voltage and adding a second pixel bias current based on a period control signal, specifically during the initial period of pixel signal transmission, to reduce conversion time while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel density is increased to achieve high-speed data reading, then productivity is improved, but loading capacitance increases causing pixel conversion time to become insufficient
Solution Approach 1:
The patent applies dynamics by making the bias current adjustable and time-variable. A bias current adjustment unit dynamically changes the bias current supplied to the pixel output node during the pixel conversion period, allowing the system to adapt to varying loading conditions and optimize conversion speed without permanently increasing power consumption.
Solution Approach 2:
The patent changes the bias current parameter dynamically during operation. By adjusting the bias current level based on the pixel conversion time requirement, the system optimizes the charging speed of the output node capacitance, thereby reducing pixel conversion time while maintaining energy efficiency.
2Loss of time
If bias current is increased to reduce pixel conversion time, then pixel conversion time is improved, but power consumption increases
Solution Approach 1:
The patent applies periodic action by applying increased bias current only during the specific pixel conversion period when it is needed, rather than continuously. The bias current adjustment unit activates temporarily to accelerate voltage transfer, then returns to normal levels, thus reducing overall power consumption while achieving faster conversion when required.
Solution Approach 2:
The system dynamically adjusts bias current based on operational requirements, increasing it only during the critical pixel conversion phase and maintaining lower levels during other periods. This dynamic control optimizes the trade-off between conversion speed and power consumption.
3Productivity
If pixel density is increased, then productivity is improved, but noise occurs due to insufficient pixel conversion time
Solution Approach 1:
The patent changes the bias current parameter during the pixel conversion period to ensure complete voltage transfer even with high pixel density. By temporarily increasing the bias current, the system guarantees sufficient conversion time for all pixels, preventing the incomplete transfers that cause noise while maintaining high pixel density.
4Device complexity
If conventional pixel structure is used, then device complexity is low, but pixel conversion time is insufficient for high frame rates
Solution Approach 1:
The patent introduces a bias current adjustment unit as an intermediary component between the pixel array and the readout circuitry. This unit mediates the voltage transfer process by dynamically controlling the bias current, enabling faster pixel conversion without fundamentally redesigning the complex pixel structure itself.
Data Source
AI summary
Disclosed are a pixel amplification apparatus and a CMOS image sensor thereof. The pixel amplification apparatus includes a pixel bias sampling unit that samples a first pixel bias voltage, a pixel bias current supply unit that supplies an output node of a pixel signal with a first pixel bias current based on a sampled bias voltage outputted from the pixel bias sampling unit, and a pixel bias current adding unit that additionally supplies the output node with a second pixel bias current in response to a second pixel bias voltage and a period control signal.