SPAD Control Circuit Reducing Afterpulsing via State Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing SPAD control circuits face challenges in efficiently detecting low-intensity photons due to parasitic effects such as afterpulsing and memory effects, and are prone to saturation from intense laser beams, which limits their ability to sense low-intensity light.
Innovation Solution
A SPAD control circuit comprising a single photon avalanche diode, a switch, a combinational circuit, and a sequential circuit, where the sequential circuit includes flip-flop elements to manage the SPAD's active and standby states, minimizing the setting period and using a switch to control the SPAD's voltage, thereby reducing parasitic effects and allowing efficient photon detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a typical SPAD control circuit uses several transistors and logic circuits to control the SPAD, then the SPAD can be biased and quenched, but the circuit complexity increases and parasitic effects such as afterpulsing and memory effects occur
Solution Approach 1:
The patent extracts and removes unnecessary transistors and logic circuits from the conventional SPAD control circuit. By taking out redundant components, the circuit complexity is reduced while maintaining the essential functions of biasing and quenching the SPAD, thereby reducing parasitic effects without sacrificing detection accuracy
Solution Approach 2:
The patent implements a self-service mechanism where the SPAD's own state changes (voltage transitions during avalanche breakdown) are directly utilized to control the switching elements. The circuit uses the SPAD's inherent electrical characteristics to drive the quenching process, eliminating the need for external complex control logic and reducing parasitic interactions
2Power
If the SPAD is irradiated with an intense laser beam for sample excitation, then fluorescence can be generated, but the photosensor saturates and cannot sense low-intensity light
Solution Approach 1:
The patent applies periodic action by synchronizing the SPAD's active detection periods with the laser pulse timing. The SPAD is activated only during specific time windows when low-intensity fluorescence is expected, while remaining in a protected or inactive state during intense laser illumination, thus preventing saturation while maintaining detection capability
Solution Approach 2:
The patent implements preliminary action by pre-biasing the SPAD and configuring the control circuitry in advance to automatically respond to laser pulse timing. The circuit is prepared beforehand to switch the SPAD into a protected state before intense laser illumination occurs, preventing saturation before it can occur
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 proposed solution enables efficient detection of low-intensity photons by minimizing parasitic effects and preventing saturation from intense laser beams, thereby improving the SPAD's ability to detect low-intensity light without deteriorating its operational performance.
Implementation Method 1
a reverse bias is applied on the diode above its breakdown voltage to increase the input light-output current gain, thus enabling detection of light at the single-photon level. At this time, detection of a single photon triggers an avalanche breakdown in the SPAD.
Data Source
AI summary
A SPAD control circuit for detecting a photon is provided. The SPAD control circuit includes a single photon avalanche diode (SPAD), a switch, a combinational circuit, and a sequential circuit. The SPAD has two terminals. The switch applies a voltage to one of the two terminals of the SPAD. The combinational circuit detects whether the SPAD is in an active state or a standby state. The sequential circuit includes a terminal that receives input of a pulse signal used to set the SPAD to the active state, a terminal that receives input of a reset-related signal, and an output terminal. The switch is controlled by an output signal output from the output terminal of the sequential circuit. An output signal of the combinational circuit is input to the terminal of the sequential circuit that receives input of the reset-related signal.