SPAD Voltage Compensation Circuit for Temperature-Stable LiDAR Detection
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Solution Overview
Problem
Existing voltage supplies for lidar systems are inadequate, particularly in managing temperature-related variations that affect the sensitivity and accuracy of Single-Photon Avalanche Diodes (SPADs), leading to reduced light sensing capability and detection accuracy.
Innovation Solution
A voltage compensation mechanism is introduced, utilizing a reference voltage generation module with an adjustable temperature coefficient, which includes a band gap reference unit, temperature coefficient adjustment unit, voltage adjustment unit, and voltage superimposing unit, coupled with a charge pump to generate a compensation voltage that adjusts the output voltage based on temperature changes, ensuring the SPADs operate within an avalanche critical state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional voltage supply is used for SPADs, then the circuit structure is simple, but the detection accuracy and light sensing capability deteriorate due to temperature-related variations
Solution Approach 1:
The patent implements a feedback mechanism where the voltage supply continuously monitors and adjusts the reverse bias voltage applied to the SPAD based on temperature changes. The voltage compensation module detects temperature variations and automatically adjusts the voltage to maintain the SPAD in the avalanche critical state, ensuring stable detection accuracy across different operating conditions.
Solution Approach 2:
The patent changes the voltage parameter dynamically in response to temperature variations. By adjusting the reverse bias voltage according to temperature, the system maintains optimal SPAD performance. The voltage supply transitions from a fixed conventional design to a variable parameter system that adapts to environmental conditions, resolving the contradiction between simplicity and precision.
2Reliability
If the reverse high voltage is applied to make SPAD in breakdown critical state, then the light sensing capability is improved, but the stability across temperature changes deteriorates
Solution Approach 1:
The patent converts the harmful effect of temperature sensitivity into a beneficial feature by using temperature as a control parameter. The voltage compensation module exploits temperature variations to automatically adjust the bias voltage, transforming what was previously a source of instability into a trigger for self-correction. This allows the SPAD to maintain stable operation by leveraging the temperature effect rather than fighting against it.
Solution Approach 2:
The system takes preliminary action by pre-compensating for temperature effects through the voltage adjustment mechanism. Before temperature variations can cause instability, the compensation module detects the temperature change and applies the appropriate voltage correction in advance, preventing the breakdown critical state from being disrupted. This proactive approach maintains reliability despite environmental fluctuations.
3Measurement precision
If voltage compensation mechanism is added to stabilize output voltage, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The voltage compensation mechanism is designed to be self-regulating, automatically adjusting the bias voltage without requiring external intervention or complex control systems. The module monitors temperature and voltage conditions and self-corrects to maintain the SPAD in the optimal operating state, reducing the need for additional complex control circuitry while achieving improved detection accuracy.
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 stabilizes the output voltage of the SPADs across temperature changes, enhancing light sensing capability and detection accuracy by ensuring the SPADs remain in a breakdown critical state, thereby improving the overall performance of the lidar system.
Implementation Method 1
a band gap reference unit, configured to output a bias current with a positive temperature coefficient and a first voltage with a negative temperature coefficient
Implementation Method 2
The reference voltage is coupled to a charge pump that generates a compensation voltage for the diodes
Implementation Method 3
Once the light receiving unit is hit by the returned photons, an avalanche effect is generated. In addition, an electrical signal is generated
Data Source
AI summary
The present invention is directed to electrical circuits and methods. According to a specific embodiment, the present invention provides a voltage compensation mechanism for one or more single-phone avalanche diodes (SPADs). A reference voltage is generated based at least on an operating voltage of the SPADs. The reference voltage is coupled to a charge pump that generates a compensation voltage for the diodes. There are other embodiments as well.