Reconfigurable Photodiode Pixel Array for High-Voltage Energy Harvesting
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Solution Overview
Problem
CMOS image sensor systems face challenges in energy harvesting due to high voltage generation inefficiency, inflexibility, and additional circuitry requirements, which increase cost, complexity, and size, while low voltage generation results in low operating speed and accuracy, and shading issues with projected images reducing power generation.
Innovation Solution
A reconfigurable photodiode pixel array with deep trench isolation and mode selection circuitry that allows groups of photodiodes to switch between imaging and energy harvesting modes, using switch circuitry to connect photodiodes in series or parallel configurations for efficient energy harvesting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If separate photovoltaic devices are incorporated with CMOS image sensors to harvest energy, then energy harvesting capability is improved, but device cost, complexity, and size increase
Solution Approach 1:
The patent merges the image sensor pixels and photovoltaic energy harvesting pixels into a single integrated pixel array. Both imaging and energy harvesting functions share the same substrate, pixel structure, and readout circuitry, eliminating the need for separate photovoltaic devices while maintaining dual functionality.
Solution Approach 2:
The pixel array is designed to perform multiple functions: imaging pixels capture light for image sensing, while photovoltaic pixels convert light into electrical energy. The same basic pixel structure serves dual purposes, and the system can dynamically allocate different regions for different functions based on operational needs.
2Productivity
If high voltage generation is implemented using known CMOS technology, then energy harvesting efficiency is improved, but additional circuitry such as boost converters and charge pumps increases device complexity and size
Solution Approach 1:
The patent extracts and eliminates the need for additional boost converters and charge pumps by directly configuring photodiodes in series to generate high voltage. The high voltage generation is achieved through the photodiode series connection itself rather than through separate voltage boosting circuitry.
Solution Approach 2:
The photodiodes themselves perform the voltage multiplication function through their series connection configuration, without requiring external assistance from boost converters or charge pumps. The system uses its own components (photodiodes) to achieve the desired high voltage output.
3Power
If photodiodes are connected in series configurations for high voltage generation, then voltage output is improved, but device area efficiency decreases
Solution Approach 1:
The patent implements dynamic reconfigurability where the pixel array can switch between different connection configurations. Photodiodes can be dynamically connected in series for high voltage generation or reconfigured based on operational requirements, allowing the system to adapt its electrical configuration rather than being fixed in one arrangement.
Solution Approach 2:
The pixel array is segmented into different functional regions including imaging pixels and photovoltaic pixels, which can be independently configured. This segmentation allows efficient use of the device area by dedicating specific regions to specific functions while maintaining overall system integration.
4Device complexity
If low voltage generation is used to mitigate parasitic structure drawbacks, then device complexity is reduced, but operating speed and accuracy decrease
Solution Approach 1:
The patent changes the voltage parameter by configuring photodiodes in series connections, which multiplies the output voltage without requiring additional complex circuitry. This parameter change (from low to high voltage through series connection) simultaneously improves operating speed and accuracy while maintaining relatively simple device structure.
5Measurement precision
If CMOS image sensor systems are placed behind a lens for imaging, then imaging capability is improved, but projected image causes shading over energy harvesting pixels, reducing power generation
Solution Approach 1:
The pixel array is segmented into distinct imaging regions and photovoltaic regions. This spatial segmentation allows the imaging pixels to receive full optical input for high-quality imaging while photovoltaic pixels are positioned to maximize light exposure for energy harvesting, with each region optimized for its specific function.
Solution Approach 2:
Different regions of the pixel array have different local qualities optimized for their specific functions: imaging pixels are optimized for light detection and signal processing, while photovoltaic pixels are optimized for energy conversion. This local optimization allows both functions to perform well without mutual interference.
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 efficient and flexible energy harvesting while maintaining imaging capabilities, reducing power consumption and avoiding shading issues, thereby extending battery life in portable devices.
Implementation Method 1
A reconfigurable photodiode pixel array with deep trench isolation and mode selection circuitry that allows groups of photodiodes to switch between imaging and energy harvesting modes
Implementation Method 2
A reconfigurable photodiode pixel array with deep trench isolation and mode selection circuitry that allows groups of photodiodes to switch between imaging and energy harvesting modes
Data Source
AI summary
An imaging sensor includes a pixel array containing photodiodes, the photodiodes being isolated from one another by full thickness deep trench isolations. Row control circuitry controls which rows of the pixel array operate in an imaging mode and which rows of the pixel array operate in an energy harvesting mode, on a row-by-row basis. Switch circuitry selectively connects different groups of photodiodes in rows operating in the energy harvesting mode into forward biased series configurations between a voltage output line and a ground line, or into forward biased parallel configurations between the voltage output line and the ground line. In the forward biased series configurations, the cathode of at least one photodiode of a given group of photodiodes is directly electrically connected to ground.