SPAD Circuit with Reset Unit for Power and Linearity Control
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Solution Overview
Problem
Existing photoelectric conversion apparatuses using single photon avalanche diodes (SPADs) face challenges with high power consumption and nonlinearity in photoelectric conversion characteristics due to pileup effects at high illuminance levels, leading to inaccurate photon counting and increased wasteful power consumption.
Innovation Solution
A photoelectric conversion apparatus is designed with an avalanche diode, a detection unit, a switch, and a reset unit. The reset unit resets a node between the switch and the detection unit during the switch's off state, allowing for controlled operation and reducing power consumption by preventing continuous current flow during pileup states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single photon avalanche diode (SPAD) is used for each pixel to achieve high sensitivity photon detection, then photoelectric conversion capability is improved, but power consumption increases due to high voltage requirements for avalanche multiplication
Solution Approach 1:
The patent implements periodic action by switching the avalanche diode between Geiger mode (high sensitivity) and non-Geiger mode (low power consumption) based on accumulated photon count. The counter accumulates count values from the detection unit, and when it reaches a threshold, the control unit switches the operating mode, creating a periodic cycle of high-sensitivity detection followed by power-saving state.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the operating mode of the avalanche diode based on the photon incident rate. The control unit changes the operational parameters (Geiger mode vs. non-Geiger mode) according to the count value from the counter, allowing the system to adapt between high sensitivity and low power consumption states.
2Measurement precision
If the avalanche diode operates in Geiger mode to maintain high detection sensitivity, then photon counting accuracy is improved, but pileup effects occur at high illuminance levels causing nonlinearity and inaccurate counting
Solution Approach 1:
The patent implements feedback by using the counter to continuously monitor the photon incident rate and feed this information back to the control unit. The control unit then adjusts the operating mode based on this feedback, switching from Geiger mode to non-Geiger mode when the count value reaches the threshold, thereby preventing pileup effects and maintaining counting accuracy.
Solution Approach 2:
The patent applies preliminary action by accumulating the count value before the actual mode switching occurs. The counter continuously accumulates photon count data, and only when the accumulated value reaches the threshold does the control unit switch to non-Geiger mode, allowing the system to anticipate and prevent pileup effects before they significantly degrade performance.
3Use of energy by moving object
If the count value reaches a threshold to switch to non-Geiger mode to reduce power consumption, then power efficiency is improved, but detection sensitivity decreases
Solution Approach 1:
The patent applies dynamics by making the operating mode flexible and adaptable rather than fixed. The system dynamically switches between Geiger mode (high sensitivity) and non-Geiger mode (low power consumption) based on real-time photon incident rate conditions, allowing optimal performance across varying illumination levels.
Solution Approach 2:
The patent implements periodic action by creating a cyclical operation pattern where the system alternates between high-sensitivity Geiger mode and power-saving non-Geiger mode. The periodic switching is triggered when the counter reaches the threshold, allowing the system to periodically reset and maintain both sensitivity and power efficiency.
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 configuration effectively reduces power consumption and maintains linear photoelectric conversion characteristics even at high illuminance levels, ensuring accurate photon counting and minimizing wasteful energy use.
Implementation Method 1
avalanche multiplication is caused by a single signal carrier generated by a single incident photon
Implementation Method 2
image sensors in which a single photon avalanche diode (SPAD) is used for each pixel
Data Source
AI summary
According to an aspect of the present disclosure, an avalanche diode, a detection unit configured to detect an avalanche current generated by avalanche multiplication in the avalanche diode, a switch disposed between the avalanche diode and the detection unit, and a reset unit configured to reset a node between the switch and the detection unit. The reset unit resets the node during a period in which the switch is in an off state.