SPAD Range Finder Quench Control for Shorter Dead Time
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Solution Overview
Problem
Time-of-flight sensors with single-photon avalanche diodes (SPADs) face prolonged dead times due to avalanche breakdowns, which are not adequately addressed by existing methods, leading to inefficiencies in light detection and range finding applications.
Innovation Solution
A light detector and range finder configuration that includes a SPAD connected to a resistor and switch element, controlled by a circuit to manage node discharge and charge, turning on the switch until a specific period after a potential change and turning off without the potential returning, then reactivating after a third period, to minimize dead time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a low-resistance switch is used to discharge the node quickly, then the dead time is shortened, but if an avalanche breakdown occurs during discharge, a state of equilibrium is established between avalanche current and switch current, fixing the node voltage and extending the dead time
Solution Approach 1:
The patent implements feedback control by monitoring the voltage state of the first node and adjusting the switch element's operation accordingly. The control circuit detects when the node voltage stabilizes (indicating equilibrium between avalanche current and discharge current) and uses this information to determine when to terminate the discharge operation, thereby resolving the contradiction between quick discharge and reliable completion.
Solution Approach 2:
The system uses the inherent electrical characteristics of the avalanche breakdown itself as a signal for control. The equilibrium state created by the avalanche current naturally provides feedback about the discharge status, allowing the system to self-regulate the discharge timing without external intervention, thus solving the reliability issue while maintaining short dead time.
2Reliability
If the switch element remains on to ensure complete discharge, then reliability is improved, but the dead time is prolonged
Solution Approach 1:
The control circuit continuously monitors the first node's voltage potential and uses this feedback to dynamically adjust the switch element's state. When the node voltage indicates complete or sufficient discharge, the control circuit terminates the discharge operation early, avoiding unnecessary extension of dead time while ensuring reliability through real-time voltage monitoring.
Solution Approach 2:
The patent transitions from a static discharge approach (keeping the switch on for a fixed duration) to a dynamic approach where the discharge duration is adjusted based on real-time voltage conditions. The switch element's state changes dynamically in response to the node's electrical state, optimizing the balance between discharge reliability and dead time minimization.
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 configuration reduces dead time in SPADs, enhancing the performance of time-of-flight sensors by ensuring they are ready for the next light incidence quickly, even during avalanche breakdowns, thereby improving the accuracy and efficiency of distance measurements.
Implementation Method 1
Single-photon avalanche diodes (SPADs) have been recently used as elements that detect light
Implementation Method 2
a time measured until light emitted from a light-emitting unit reflects on the detection target and is then detected by a light-receiving unit
Data Source
AI summary
A light detector includes a SPAD; a resistor component; a switch element; and a control circuit configured to control the switch element to discharge or charge a first node. In response to a change in a potential of the first node from a first potential to a second potential, the control circuit turns on the switch element until a second period elapses after a lapse of a first period measured from the change to the second potential, or until the potential of the first node changes back to the first potential during the second period, and the control circuit turns off the switch element upon a lapse of the second period without the potential of the first node changing back to the first potential, and the control circuit turns on the switch element again after a lapse of a third period measured from the turning off of the switch element.