SPAD Light Detection Recharge Control for Dead Time and Latching
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Solution Overview
Problem
Conventional light detection apparatuses using SPAD elements face issues with latching current problems and extended dead time due to temperature dependence of avalanche current, particularly when operating in wide temperature ranges.
Innovation Solution
A light detection apparatus with a control portion that adjusts the recharge current through a load circuit based on the element characteristics of the SPAD element, such as temperature, avalanche current, or breakdown voltage, to maintain optimal operation across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a large recharge current is used to recover cathode voltage quickly, then the dead time is shortened, but a latching current problem occurs where the cathode voltage does not drop sufficiently and through-current continues to flow
Solution Approach 1:
The recharge current is made dynamically adjustable based on temperature conditions. The control portion changes the recharge current magnitude according to the detected temperature, allowing optimal current selection for each operating condition. This resolves the contradiction by enabling fast recovery (short dead time) when safe, while preventing latching current problems when temperature requires more conservative current levels.
Solution Approach 2:
The recharge current parameter is changed based on temperature. By detecting temperature and adjusting the recharge current magnitude accordingly, the system adapts the electrical parameter to environmental conditions. This allows the system to avoid latching current problems at temperatures where avalanche current is lower while maintaining short dead time at temperatures where higher current is safe.
2Reliability
If the recharge current is set to prevent latching current problems under worst-case temperature conditions, then reliability is improved, but the dead time becomes unnecessarily extended at lower temperatures
Solution Approach 1:
Instead of using a fixed recharge current set for worst-case conditions, the system dynamically adjusts the current based on actual temperature. This allows the system to achieve reliable latching current prevention when needed while recovering performance (shorter dead time) when environmental conditions permit higher current operation.
Solution Approach 2:
The control portion uses temperature feedback to adjust the recharge current. By continuously monitoring temperature and adjusting current accordingly, the system ensures reliable operation across all temperature conditions while optimizing dead time performance. The feedback mechanism prevents both latching current problems and unnecessary dead time extension.
3Device complexity
If a fixed recharge current is used without temperature consideration, then device complexity is reduced, but the light detection apparatus cannot operate reliably across a wide temperature range
Solution Approach 1:
The system uses the temperature information already present in the operating environment to self-adjust its behavior. By detecting temperature and automatically adjusting recharge current, the system adapts to temperature variations without requiring complex external control mechanisms. This maintains relatively simple device architecture while achieving wide temperature range reliability.
Solution Approach 2:
The recharge current parameter is changed based on temperature detection. This simple parameter adjustment mechanism enables the system to adapt to different temperature conditions without requiring fundamentally different circuit architectures. The parameter change approach maintains device simplicity while achieving reliable operation across wide temperature ranges.
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
Enables reliable light detection without latching current issues and optimal dead time management across a wide temperature range, enhancing accuracy and efficiency.
Implementation Method 1
a SPAD (Single Photon Avalanche Diode) element is used, a recharge operation of passing a recharge current through the light-receiving element must be performed in order to recover a cathode voltage having been lowered by an avalanche current
Implementation Method 2
an element that generates a signal in response to receiving a photon
Data Source
AI summary
A light detection apparatus according to the present disclosure includes a light-receiving element, a load circuit connected to the light-receiving element, and a control portion configured to control a recharge current that flows through the load circuit in accordance with an element characteristic of the light-receiving element. In addition, a ranging apparatus according to the present disclosure includes: a light source configured to radiate light toward a measurement object; and a light detection apparatus configured to detect light reflected by the measurement object, when the light detection apparatus configured as described above is used as the light detection apparatus.