Built-in Self-Test for LED Fault Detection in Automotive Headlights
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Solution Overview
Problem
Testing light emitting diodes (LEDs) and driver circuitry in complex automotive headlight systems is challenging due to the difficulty in accessing nodes between LEDs and drivers, leading to prolonged and costly analog testing, especially in high-resolution matrix arrays with thousands of LEDs.
Innovation Solution
A built-in self-test (BIST) system that processes circuitry is configured to test LEDs and drivers by measuring forward voltage across LEDs and detecting faults, allowing for quick digital domain testing and fault detection, even after hybridization when LEDs are mounted, using a differential analog-to-digital converter and connection network to access voltage levels at accessible points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog testing methods are used to test LEDs and driver circuitry, then measurement precision can be achieved, but testing time is prolonged and cost increases
Solution Approach 1:
The patent replaces analog testing methods with a digital built-in self-test (BIST) system. The BIST circuitry uses digital logic to automatically test LEDs and driver circuitry by measuring forward voltage and comparing it against threshold values, eliminating the need for external analog test equipment and significantly reducing testing time while maintaining measurement precision.
Solution Approach 2:
The patent implements a built-in self-test capability where the headlight system tests itself without external intervention. The BIST circuitry is integrated within the driver circuitry, allowing the system to autonomously detect faults in LEDs and drivers by measuring electrical parameters and generating test results, thereby eliminating prolonged external testing procedures.
2Adaptability or versatility
If high-resolution matrix arrays with thousands of LEDs are used, then light function capability is improved, but device complexity increases making testing more difficult
Solution Approach 1:
The patent segments the testing process by implementing individual driver circuitry for controlling groups of LEDs (pixel groups). Each driver can be independently tested using the BIST circuitry, allowing faults to be localized to specific segments rather than requiring testing of the entire complex array, thereby simplifying the testing of high-resolution matrices.
Solution Approach 2:
The patent creates a universal BIST solution that can test multiple types of components (LEDs, driver circuitry, connection points) using a single integrated testing mechanism. The BIST circuitry can adaptively test different parts of the system by selecting which LEDs to activate and measuring their forward voltage, providing a multi-functional testing capability that handles the complexity of high-resolution arrays.
3Productivity
If hybridization process is used to mount LED chip on driver chip, then manufacturing efficiency is improved, but fault detection capability deteriorates due to reduced node accessibility
Solution Approach 1:
The patent performs preliminary testing actions by implementing BIST circuitry that can test LEDs and drivers both before and after the hybridization process. The system includes test modes that can be executed at different manufacturing stages, allowing faults to be detected early in the process while maintaining the benefits of hybridization for final assembly efficiency.
Solution Approach 2:
The patent uses the driver circuitry as an intermediary element that provides both the hybridization interface and the testing interface. The driver chip serves as a mediator between the LED chip and the external world, allowing electrical connections to be made during hybridization while simultaneously providing access points for the BIST circuitry to measure forward voltage and detect faults in the integrated system.
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 BIST system enables rapid fault detection and diagnosis, reducing testing time from milliseconds to microseconds, improving testability and field return analysis, and optimizing manufacturing and assembly processes by identifying faults quickly and accurately.
Implementation Method 1
The self-test may then be configured to measure the forward voltage across the first LED and the forward voltage across the second LED
Data Source
AI summary
In some examples, a device includes a built-in self-test for detecting a fault between a first light emitting diode (LED) and a second LED. The device includes a first pair of pads configured to connect to the first LED and a second pair of pads configured to connect to the second LED. The built-in self-test is configured to control a first driver and a second driver to turn on, one-by-one, respective pass switches connected to the first and second pairs of pads. The built-in self-test is configured to then determine the first and second forward voltages across the first and second LEDs. The built-in self-test can determine whether the fault exists between the first and second LEDs based on the forward voltages.