Avalanche Photodiode Pixel Circuit Excess Voltage Regulation
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Solution Overview
Problem
In photoelectric conversion apparatuses with multiple pixels, maintaining uniform characteristics across pixels is challenging due to variations in breakdown voltage and excess voltage among avalanche photodiodes, leading to increased circuit complexity.
Innovation Solution
The apparatus includes a capacitive element and switch elements to manage the excess voltage, detecting avalanche breakdown and resetting the pixel nodes to maintain uniformity, thereby reducing the variation in excess voltage and simplifying the circuit scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a signal processing unit and bias regulation unit are added to regulate excess voltage variations among pixels, then uniformity of characteristics among pixels is improved, but circuit scale increases
Solution Approach 1:
The patent extracts the excess voltage regulation function from a complex signal processing unit and bias regulation unit, and implements it through a simple capacitive element connected to the cathode of the APD. This capacitive element directly compensates for excess voltage variations without requiring additional complex circuits, thereby maintaining pixel characteristic uniformity while minimizing circuit scale increase
Solution Approach 2:
The capacitive element acts as an intermediary component between the power supply and the APD cathode. It mediates the excess voltage variations by storing and releasing charge to compensate for voltage fluctuations, thereby regulating the actual voltage applied to the APD without requiring complex active regulation circuits
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 approach ensures uniform pixel characteristics while minimizing circuit complexity, resulting in improved reliability, reduced power consumption, and decreased crosstalk, with the excess voltage variation reduced from ±0.5V to ±0.2V, enhancing the overall performance of the photoelectric conversion apparatus.
Implementation Method 1
an avalanche photodiode arranged between a first potential supply line and a second potential supply line
Implementation Method 2
a photoelectric conversion apparatus is known in which each pixel is provided with a single photon avalanche photodiode (SPAD) element capable of detecting weak light at the single photon level
Implementation Method 3
a capacitive element including a first terminal and a second terminal connected to a first node that connects the first switch element and the second switch element
Data Source
AI summary
A photoelectric conversion apparatus in which a plurality of pixels are arranged is provided. Each of the plurality of pixels includes an avalanche photodiode arranged between a first potential supply line and a second potential supply line, a first switch element arranged between the first potential supply line and the avalanche photodiode, a second switch element arranged between the first switch element and the avalanche photodiode, a capacitive element including a first terminal and a second terminal connected to a first node that connects the first switch element and the second switch element, and a detection circuit configured to detect occurrence of avalanche breakdown of the avalanche photodiode in accordance with a change of a potential of a second node that connects the second switch element and the avalanche photodiode.