Photodetection Feedback Circuit for SPAD Overvoltage Control
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Solution Overview
Problem
Conventional photodetection devices using active pixel circuits are prone to overvoltage, which can lead to circuit element deterioration, despite offering higher adjustment freedom compared to passive systems.
Innovation Solution
A photodetection device incorporating a light-receiving element, a load circuit, a switch circuit, and a feedback circuit with a delay circuit that adjusts delay based on element characteristics and power supply fluctuations to prevent overvoltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an active pixel circuit system is used to control avalanche current timing, then the degree of freedom of adjustment is improved, but the risk of overvoltage causing circuit element deterioration increases
Solution Approach 1:
The patent implements a feedback circuit that monitors the cathode voltage of the SPAD element and controls the switch circuit accordingly. When the cathode voltage exceeds a predetermined threshold, the feedback circuit automatically adjusts the timing control signal to prevent overvoltage conditions, thus maintaining reliability while preserving the adaptability of the active system
Solution Approach 2:
The patent dynamically adjusts the timing control signal based on real-time cathode voltage conditions. The system transitions from static timing control to dynamic control where the timing parameters are continuously adapted to prevent overvoltage, allowing the system to maintain both flexibility and safety under varying operating conditions
2Reliability
If timing control is performed accurately in active system, then malfunction risk is reduced, but circuit complexity increases
Solution Approach 1:
The patent introduces a feedback circuit as an intermediary between the timing control unit and the switch circuit. This intermediary monitors cathode voltage and mediates the control signals to ensure accurate timing while preventing malfunctions, distributing the complexity across multiple functional blocks rather than concentrating it in one complex controller
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
The solution effectively reduces the risk of overvoltage, maintaining the advantages of active systems while minimizing circuit element deterioration, thereby enhancing device reliability.
Implementation Method 1
a light-receiving element; a pixel circuit including a light-receiving element and a circuit portion
Implementation Method 2
the feedback circuit has a delay circuit
Data Source
AI summary
A photodetection device according to the present disclosure includes: a light-receiving element; a load circuit connected to the light-receiving element; a switch circuit connected to the light-receiving element; and a feedback circuit configured to operate the switch circuit in accordance with an output from the light-receiving element. The feedback circuit has a delay circuit. A distance measurement device according to the present disclosure includes: a light source configured to radiate light toward a measurement object; and a photodetection device configured to detect light reflected by the measurement object, wherein the photodetection device configured as described above is used as the photodetection device.