SPAD Voltage Control Using Current Feedback to Limit Dark Current
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Solution Overview
Problem
Existing methods for controlling the voltage applied to single photon avalanche diodes (SPADs) face challenges in accurately determining the optimal voltage range to prevent false outputs (dark current) and ensure photon detection, particularly in applications like LIDAR, where reference light paths are cumbersome and increase costs, and calibration times are significant.
Innovation Solution
The method involves a circuitry system with measurement and voltage setting components that dynamically control the voltage across SPADs by comparing current outputs to thresholds, using transistors and op-amps to maintain the voltage within optimal ranges, eliminating the need for reference light paths and enabling continuous automatic control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the voltage applied across the SPAD is increased to ensure photon detection, then the detection sensitivity is improved, but the false output current (dark current) increases
Solution Approach 1:
The patent implements dynamic voltage control by continuously monitoring the current output from the SPAD and adjusting the voltage in real-time. The voltage is increased when photon detection is prioritized and decreased when dark current suppression is needed, making the system adaptive rather than static. This resolves the contradiction by allowing the voltage to fluctuate within an optimal range based on actual operating conditions.
Solution Approach 2:
The patent employs a feedback mechanism where the current output from the SPAD is continuously measured and fed back to the voltage control circuitry. This feedback loop enables the system to automatically adjust the voltage to maintain optimal detection sensitivity while suppressing dark current, resolving the contradiction through closed-loop control.
2Measurement precision
If reference light paths are added to determine optimal voltage range, then the voltage control accuracy is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the complex reference light path structure from the system. Instead of using external reference paths, the invention uses the SPAD's own current output as the measurement signal, simplifying the device architecture while maintaining voltage control accuracy through direct electrical measurement rather than optical path comparison.
Solution Approach 2:
The patent replaces the mechanical/optical reference light path system with an electrical measurement and control system. By substituting optical components with electrical circuitry for voltage monitoring and adjustment, the device complexity is reduced while achieving the same goal of accurate voltage control through direct current measurement.
3Device complexity
If manual calibration methods are used to determine optimal voltage, then the equipment simplicity is maintained, but the calibration time and productivity decrease
Solution Approach 1:
The patent implements a self-service calibration system where the SPAD automatically determines its own optimal voltage range through continuous monitoring of its current output. The system performs self-calibration without external intervention, eliminating manual calibration steps and significantly reducing calibration time while maintaining simplicity through automated feedback control.
Solution Approach 2:
The patent performs preliminary voltage calibration automatically during system initialization or manufacturing testing. By pre-determining the optimal voltage range through automated measurement and storing this information for ongoing operation, the system eliminates the need for repeated manual calibration, thus improving productivity without adding complex real-time control mechanisms.
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 effectively reduces false outputs, enhances detection accuracy, and simplifies the manufacturing process by eliminating the need for reference light paths, while allowing for continuous and automatic voltage adjustment, thereby improving the reliability and efficiency of SPAD operations in applications like LIDAR.
Implementation Method 1
A photon impinging on a detection region of a SPAD generates an electron and hole pair via the photoelectric effect
Implementation Method 2
If the kinetic energy of the accelerated carriers is sufficient, additional carriers will be generated from the semiconductor lattice, which are in turn accelerated by the field, and may liberate further carriers in an exponentially increasing fashion
Data Source
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AI summary
There is provided a method for controlling a voltage across a single photon avalanche diode, the method comprising: providing an output dependent on a current flowing through the single photon avalanche diode; and controlling the voltage applied across the single photon avalanche diode in dependence on the provided output.