SPAD Quench Resistor Switch for Waveform Circuit Protection
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Solution Overview
Problem
Existing photo-detection devices face reliability issues due to the risk of high voltage being applied to waveform shaping circuits, leading to potential destruction and reduced reliability, especially when power source failures or disconnections occur.
Innovation Solution
Incorporating a switch on the path between the second node and the input terminal of the waveform shaping circuit, controlled by a switch control circuit, to prevent high voltage from being applied when the second power source is not supplied, thereby protecting the waveform shaping circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high voltage power source is connected to the SPAD and quench resistor to enable avalanche amplification, then single photon detection capability is improved, but the risk of high voltage damage to the waveform shaping circuit increases when power source failure or disconnection occurs
Solution Approach 1:
A protection circuit is introduced as an intermediary component between the high voltage power source and the waveform shaping circuit. This protection circuit includes a first switching element connected in parallel with the quench resistor and a second switching element connected in parallel with the SPAD. When the second power source fails or disconnects, these switching elements automatically activate to prevent high voltage from reaching the waveform shaping circuit, thus protecting it while maintaining the high voltage supply capability for normal operation.
Solution Approach 2:
The protection circuit performs preliminary protective action by monitoring the power source status and preemptively activating the switching elements before high voltage damage can occur. The control circuit detects when the second power source is not supplied and activates the protection mechanism in advance, preventing the harmful high voltage from being applied to the waveform shaping circuit during power source failure or disconnection events.
2Reliability
If the second power source is disconnected to prevent high voltage damage, then waveform shaping circuit protection is improved, but the ability to perform avalanche amplification is lost
Solution Approach 1:
The power supply system is segmented into independent control paths for the first and second power sources. The first power source (high voltage) and second power source (low voltage) can be independently controlled through separate switching elements. This segmentation allows the system to maintain avalanche amplification capability by keeping the first power source connected while using the protection circuit to isolate the waveform shaping circuit from high voltage during second power source failure, thus resolving the contradiction between protection and functionality.
Solution Approach 2:
The protection circuit introduces dynamic switching capability that adapts the circuit configuration based on operational conditions. The switching elements can dynamically change their state (on/off) depending on whether the second power source is properly supplied. During normal operation, the switching elements remain off allowing full functionality. During power source failure, the switching elements dynamically activate to provide protection, thus maintaining both avalanche amplification capability and waveform shaping circuit protection under different conditions.
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 ensures the reliability of the photo-detection device by preventing high voltage from reaching the waveform shaping circuit, thus preventing damage and ensuring continuous operation even during power source failures or disconnections.
Implementation Method 1
An APD can use an avalanche amplification phenomenon (avalanche breakdown phenomenon) generated by an intense electric field induced on a p-n junction of a semiconductor to amplify the amount of signal charges excited by photons several times to one million times
Implementation Method 2
a photo-detection element for implementing the photon counting may be an avalanche photodiode (APD)... a brightness resolution at a single photon level can be realized
Data Source
AI summary
A photo-detection device includes a quench resistor having one terminal connected to a first node, an avalanche photodiode having one terminal connected to a second node, a waveform shaping circuit having an input terminal connected to the other terminal of the quench resistor and the other terminal of the avalanche photodiode, and a switch arranged on a path between the second node and the input terminal of the waveform shaping circuit.