Avalanche Photodiode Charging Circuit for Shorter TOF Dead Time
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light detection devices using the time of flight method face challenges in reducing distance measurement errors while shortening dead time, as increasing charging current can lead to increased voltage at the connection node, potentially causing output issues before charging is complete, and reducing charging current lengthens dead time.
Innovation Solution
A light detection device incorporating an avalanche photodiode, a logic gate, a voltage limiting transistor, a rapid charging transistor with a thinner gate oxide film, and a pulse generation unit to manage charging current and voltage, along with optional components like forced quenching transistors, constant current sources, and clamp voltage generation circuits to optimize signal processing and reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the charging current is increased to shorten the dead time, then the dead time is shortened, but the distance measurement error increases
Solution Approach 1:
The patent changes the physical parameter of the gate oxide film thickness in the transistor structure. By using a transistor with a thinner gate oxide film, the transistor achieves lower on-resistance, which allows rapid charging of the photodiode with reduced voltage drop, thereby shortening dead time without increasing distance measurement error
Solution Approach 2:
The patent applies different gate oxide film thicknesses to different transistors within the circuit. Specifically, the rapid charging transistor has a thinner gate oxide film compared to other transistors, optimizing its performance for rapid charging while other transistors maintain thicker films for stability and voltage limiting functions
2Measurement precision
If the charging current is reduced to reduce the distance measurement error, then the distance measurement error is reduced, but the dead time is lengthened
Solution Approach 1:
The patent modifies the transistor's gate oxide film thickness parameter to achieve lower on-resistance. This allows the system to use reduced charging current while still achieving rapid charging speed, thereby reducing distance measurement error without lengthening dead time
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 solution effectively shortens dead time and reduces distance measurement errors by managing charging currents and voltages, ensuring accurate and efficient light detection.
Implementation Method 1
a light receiving element that performs avalanche multiplication
Implementation Method 2
a rapid charging transistor in which a film thickness of a gate oxide film is less than that of the voltage limiting transistor and that supplies a charging current to the avalanche photodiode
Data Source
AI summary
In a light detection device and a distance measuring system that obtain a distance from a round-trip time of light, a distance measurement error is reduced while a dead time is shortened. A logic gate outputs an output signal on the basis of a result of comparison between an input voltage depending on a voltage of one terminal of the cathode or the anode of an avalanche photodiode and a predetermined threshold voltage. A voltage limiting transistor limits the input voltage. A rapid charging transistor, in which a film thickness of a gate oxide film is less than that of the voltage limiting transistor, supplies a charging current to the avalanche photodiode in accordance with a predetermined pulse signal. A pulse generation unit generates the pulse signal on the basis of the output signal and supplies the pulse signal to the rapid charging transistor.