APD Bias Circuit Temperature Coefficient Matching for Gain Stability
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Solution Overview
Problem
In radiation detection using the photon counting method, maintaining a constant photoelectric conversion gain of avalanche photodiodes (APDs) is challenging due to temperature variations, requiring complex feedback control systems with temperature sensors and voltage adjustments, which increase processing time and complexity.
Innovation Solution
A photon detecting element with a circuit that matches the temperature coefficient of the setting potential to the breakdown voltage of the APDs, ensuring a constant excessive voltage is applied, thereby canceling out voltage variations caused by temperature changes without the need for external temperature sensors or complex control circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control with temperature sensor and voltage adjustment is used to maintain constant photoelectric conversion gain, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent uses a self-service principle where the circuit automatically compensates for temperature-induced breakdown voltage changes in APDs. The circuit is designed with components (resistors, capacitors, diodes) that inherently track temperature variations and adjust the bias voltage accordingly, eliminating the need for external temperature sensors and complex control algorithms. The system serves itself by using the temperature dependence of semiconductor components to automatically counteract the temperature drift of the APD breakdown voltage.
Solution Approach 2:
The patent introduces an intermediary circuit between the power supply and the APD array that acts as a mediator to compensate for temperature effects. This circuit includes temperature-compensation components (such as diodes and resistors with specific temperature coefficients) that generate a compensating voltage signal proportional to the temperature-induced breakdown voltage change. This intermediary circuit translates temperature variations into appropriate bias voltage adjustments without requiring direct temperature measurement or complex processing.
2Measurement precision
If feedback control with temperature sensor and voltage adjustment is used to maintain constant photoelectric conversion gain, then measurement accuracy is improved, but processing time increases
Solution Approach 1:
The patent replaces the mechanical/electronic feedback control system (temperature sensing, A/D conversion, CPU processing, D/A conversion) with an analog electronic compensation circuit. The temperature-compensation circuit directly generates the corrected bias voltage through analog component interactions (resistors, capacitors, diodes) that respond instantaneously to temperature changes. This substitution of analog circuitry for digital processing eliminates the time delays associated with sampling, conversion, and computational processing while maintaining measurement accuracy.
3Stability of the object's composition
If complex feedback control circuitry is installed to compensate for temperature variations, then photoelectric conversion gain stability is improved, but ease of operation deteriorates
Solution Approach 1:
The patent merges the temperature compensation function directly into the bias voltage supply circuit for the APD array. The compensation components (resistors, capacitors, diodes) are integrated with the existing power supply circuitry, combining multiple functions (voltage generation, temperature sensing, and compensation) into a single unified circuit block. This merging eliminates the need for separate temperature sensors, control circuits, and adjustment mechanisms, thereby simplifying the overall system configuration and improving ease of operation while maintaining gain stability.
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 enhances the accuracy of maintaining a constant photoelectric conversion gain across temperature variations, simplifying the system and reducing processing time, while maintaining high accuracy in radiation photon energy measurement.
Implementation Method 1
the photoelectric conversion gain of an avalanche photodiode (APD) for photon detection, which detects radiation photons
Implementation Method 2
An APD has a voltage higher than the breakdown voltage applied in between the anode and the cathode, and operates in a Geiger mode
Implementation Method 3
a first temperature coefficient representing variation of a setting potential with respect to temperature variation when constant-current driving is performed so that electrical potential of the cathodes becomes equal to the setting potential is substantially the same as a second temperature coefficient representing variation of breakdown voltage of the one or more avalanche photodiodes with respect to temperature variation
Data Source
AI summary
According to an embodiment, a photon detecting element includes one or more avalanche photodiodes and a circuit. The circuit is connected between cathodes of the one or more avalanche photodiodes and an external power source. The circuit is configured in which a first temperature coefficient representing variation of a setting potential with respect to temperature variation when constant-current driving is performed so that electrical potential of the cathodes becomes equal to the setting potential is substantially the same as a second temperature coefficient representing variation of breakdown voltage of the one or more avalanche photodiodes with respect to temperature variation.