Built-in Self-Test for LED Driver Fault Detection

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Solution Overview

Problem

Testing faults in modern automotive LED headlights with matrix arrays of thousands of LEDs is challenging due to inaccessible nodes and the time-consuming nature of analog testing, which can lead to delayed fault detection and increased costs.

Innovation Solution

A built-in self-test (BIST) system that processes circuitry is used to test drivers and LEDs individually by turning on pass devices and measuring forward voltage across anode and cathode pads, allowing for quick digital domain testing and fault detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If analog testing methods are used to test faults in LED headlights, then comprehensive fault detection can be achieved, but testing time increases significantly and costs increase

Engineering Contradiction:

Improvefault detection capabilityVSAvoidtesting time

Core Design Contradiction:

ReliabilityVSLoss of time

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 LED pixels by activating them and measuring their forward voltage through multiplexed scan lines, eliminating the need for time-consuming analog testing while maintaining comprehensive fault detection capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements a self-test capability where the LED driver circuitry contains integrated BIST circuitry that automatically tests the LED pixels without requiring external testing equipment. The system activates pixels through pass devices and measures forward voltage using internal circuitry, enabling the system to self-diagnose faults rapidly

Inventive Principle:

Principle #25Self-service

2Difficulty of detecting and measuring

If manual testing of each LED pixel is performed, then individual fault location can be identified, but the testing process becomes extremely time-consuming for thousands of pixels

Engineering Contradiction:

Improvefault localization precisionVSAvoidtesting speed

Core Design Contradiction:

Difficulty of detecting and measuringVSProductivity

Solution Approach 1:

The patent divides the LED matrix into individually addressable pixels with associated pass devices that can be activated independently. The BIST circuitry uses multiplexed row and column scan lines to selectively activate specific pixels, enabling precise fault localization while maintaining high testing speed through parallel processing capabilities

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates a universal testing architecture where the same driver circuitry and scan lines used for normal LED operation are also used for testing. The multiplexed scan line system serves both display functions and test functions, eliminating the need for separate dedicated test hardware and enabling rapid sequential testing of all pixels

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Loss of time

If built-in self-test circuitry is implemented to speed up testing, then testing time is reduced to microseconds, but device complexity increases

Engineering Contradiction:

Improvetesting timeVSAvoidcircuit complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The patent merges the BIST circuitry with the existing LED driver circuitry. The test function is integrated into the driver chip, sharing common elements such as power supply connections, scan lines, and measurement circuitry with the normal display operation, thereby reducing overall system complexity while achieving rapid testing

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces pass devices as intermediary elements between the driver circuitry and LED pixels. These pass devices serve dual purposes: controlling pixel activation during normal operation and enabling isolated testing of individual pixels during BIST by acting as controllable switches that connect test circuitry to specific pixels

Inventive Principle:

Principle #24Intermediary (Mediator)

4Adaptability or versatility

If multiple companies are involved in manufacturing and hybridization, then specialized expertise can be utilized, but multiple points of potential failure are introduced

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidproduct failure risk

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements preliminary testing of LED pixels before the hybridization process through the integrated BIST circuitry. By testing pixels in advance on the driver chip before bonding to the LED matrix, potential failures can be detected early, allowing defective chips to be identified and replaced before final assembly, thereby reducing the risk of product failures even when multiple manufacturers are involved

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20210311117A1Built-in self-test for light emitting diodes

Publication Date: 2021.10.07 INFINEON TECHNOLOGIES AG

AI summary

In some examples, a device includes a built-in self-test for detecting a fault on a light emitting diode (LED) or on a driver for an LED. The device includes a pair of pads that are configured to connect to the LED. The built-in self-test is configured to control the driver to turn on a respective pass switch connected to a pad of the pair of pads. The built-in self-test is configured to then determine a voltage level at each pad of the pair of pads. The built-in self-test can determine whether the fault exists on the LED, across the first anode pad and the first cathode pad, or on the driver based on the voltage level at each pad.