Diode Array Test Circuit for LiDAR Open and Short Detection
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Solution Overview
Problem
Conventional LiDAR sensors with mechanically moving parts are inefficient and prone to failures under high stress conditions, such as high current and voltage transients, making it difficult to detect and locate short and open circuit failures in pulsed laser diode arrays used in LiDAR applications.
Innovation Solution
A testing circuit arrangement using low voltage CMOS devices to monitor and detect current in pulsed laser diode arrays, incorporating a diode array test circuit with input resistors, buffered amplifiers, and switches to determine circuit failures by comparing current measurements to a reference threshold, allowing for simultaneous temperature sensing and efficient fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanically moving parts are used for scanning laser beams, then beam steering capability is achieved, but sensor reliability and lifetime deteriorate under high stress conditions
Solution Approach 1:
The patent replaces mechanically moving parts with a solid-state laser diode array for beam steering. The laser diode array can be electrically controlled to steer laser beams without any mechanical moving parts, thereby improving sensor reliability and lifetime while eliminating mechanical failures under high stress conditions.
Solution Approach 2:
The laser diode array serves multiple functions: it acts as both the light source and the beam steering mechanism. By controlling which diodes are activated, the system can steer beams in different directions without requiring separate mechanical scanning components.
2Measurement precision
If conventional testing methods are used for diode arrays, then fault detection is possible, but detection accuracy and efficiency worsen under high current and voltage transients
Solution Approach 1:
The patent performs fault detection during a test mode before the diode array is subjected to high current and voltage transients during normal operation. By detecting potential failures in advance under controlled test conditions, the system avoids the harmful effects of transients on measurement accuracy.
Solution Approach 2:
The patent introduces a test circuit with buffered amplifiers and switches as an intermediary between the diode array and the measurement system. This intermediary circuit isolates the measurement process from the harmful high current and voltage transients, enabling accurate fault detection without exposing the measurement system to damaging conditions.
3Measurement precision
If high voltage devices are used for monitoring laser diode current, then current sensing capability is achieved, but power consumption and die area increase
Solution Approach 1:
The patent changes the voltage level parameter by using low voltage CMOS devices instead of high voltage devices for current monitoring. The test circuit includes voltage switches and buffered amplifiers that enable accurate current sensing at low voltage levels, thereby reducing power consumption while maintaining measurement precision.
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 accurate and efficient detection of short and open circuit failures in LiDAR diode arrays, improving reliability and reducing the complexity of die area requirements, suitable for high-temperature and high-power applications like VCSEL technology, and allowing for the use of low-cost, low-voltage CMOS devices.
Implementation Method 1
a buffered amplifier circuit located at a second input of the laser driver circuit and the second output of the voltage switch. The buffered amplifier circuit is electrically coupled to a current detector
Implementation Method 2
an ADC electrically coupled to an output of the buffered amplifier circuit and operable to convert an analog output from the buffered amplifier circuit to a digital output signal
Implementation Method 3
a DSP unit electrically coupled to an output of the ADC and operable to detect, from the digital output signal, a circuit failure of the diode array
Data Source
AI summary
An apparatus and method for circuit failure detection for a diode array. The apparatus includes a diode array, a diode array test circuit electrically coupled to the diode array and operable to perform circuit failure detection during a test mode when a test input voltage is applied, the diode array test circuit includes an input resistor, an input voltage node, a buffered amplifier circuit, and a plurality of amplifier circuit switches. The apparatus further includes a current detector electrically coupled to the output of the buffered amplifier circuit and operable to determine, during the test mode, a current measurement of the pulse laser diode array.