SPAD Control Circuit for Photon Detection
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Solution Overview
Problem
Existing single photon avalanche diodes (SPADs) face challenges in efficiently controlling the reverse bias voltage to enable and disable avalanche diodes, leading to suboptimal performance in detecting photons and maintaining low-light sensitivity.
Innovation Solution
A control circuit comprising active and passive modules, where the active module sets the reverse bias voltage above or at the breakdown voltage to enable the avalanche diode and the passive module, including a clamp diode, sets it below to disable it, using MOS switches in a cascode arrangement to manage the voltage supply connection to the avalanche diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reverse bias voltage is set above breakdown voltage to enable avalanche diode operation, then photon detection capability is improved, but the risk of unwanted avalanches and difficulty in controlling the diode increases
Solution Approach 1:
The patent implements dynamic control of the reverse bias voltage by using a control circuit that can adjust the voltage level in real-time. The circuit transitions the avalanche diode between enabled and disabled states by dynamically changing the reverse bias voltage, allowing the system to operate at high voltage for detection when needed and switch to low voltage for stable control when not detecting photons.
Solution Approach 2:
The control circuit changes the electrical parameter (reverse bias voltage) of the avalanche diode between two distinct states: above breakdown voltage for enabling photon detection, and below breakdown voltage for disabling and stable control. This parameter switching resolves the contradiction by allowing the system to achieve both high detection capability and stable control at different operational phases.
2Measurement precision
If the reverse bias voltage is continuously maintained above breakdown voltage, then the avalanche diode remains enabled for detection, but power consumption increases and heat generation occurs
Solution Approach 1:
The control circuit implements periodic switching of the reverse bias voltage, maintaining it above breakdown voltage only during periods when photon detection is required, and switching below breakdown voltage during periods when detection is not needed. This periodic action reduces average power consumption while maintaining detection readiness when required.
Solution Approach 2:
The control circuit automatically manages the voltage state of the avalanche diode based on operational requirements, enabling the diode only when detection is needed and disabling it otherwise, thereby eliminating the need for continuous high voltage maintenance and reducing overall power consumption.
3Measurement precision
If complex control circuits are used to precisely manage reverse bias voltage, then control precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent introduces a control circuit as an intermediary component that simplifies the management of reverse bias voltage. Rather than requiring complex integrated control mechanisms within the avalanche diode itself, the separate control circuit provides precise voltage management through simple switching operations, achieving control precision without excessive overall system complexity.
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 allows for precise control of the avalanche diode, enhancing photon detection efficiency and improving low-light performance by enabling and disabling the avalanche diode effectively, thereby improving the overall sensitivity and reliability of the SPAD.
Implementation Method 1
The at least one passive module may include at least one clamp diode arranged to connect a supply voltage to an electrode of the avalanche terminal
Implementation Method 2
The at least one active module may include at least one first switch controlled by at least one first control signal to connect and disconnect an electrode of the avalanche diode to a voltage supply
Implementation Method 3
The PN junction is reverse biased at a voltage exceeding a breakdown voltage. In this way, a carrier generated by a single photon can be injected into a depletion region and can cause a self-sustaining avalanche
Data Source
AI summary
Various embodiments provide a control circuit that includes at least one active module designed to enable an avalanche diode. The control circuit also includes at least one passive module designed to disable the avalanche diode.