LED Driver Ground Fault Detection Logic
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Solution Overview
Problem
In light emitting devices with series connected bodies of LEDs, controlling the number of turned-on LEDs by short-circuiting switches can lead to misdetected ground faults when all LEDs are turned off, causing protection issues due to abnormal short circuits.
Innovation Solution
A light emitting element driving device with a reset signal generator, set signal generator, output voltage supply unit, determination unit, and signal output unit that prevents generation stop of output voltage upon detecting a potential ground fault, allowing for accurate fault detection and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the number of turned-on light emitting diodes is set to zero by turning on all short-circuiting switches, then the light output can be controlled to zero, but the ground fault protection function may misdetect this as a ground fault due to abnormality and stop the output
Solution Approach 1:
The determination unit checks whether all light emitting diodes are turned off by controlling before the ground fault protection function activates. This preliminary check prevents the misdetection of intentional zero-output state as a ground fault, allowing the system to distinguish between normal control operation and actual abnormality.
Solution Approach 2:
The system uses feedback from the determination unit to the ground fault protection function, providing information about the operational state of light emitting diodes. This feedback mechanism enables the protection function to differentiate between intentional shutdown (all diodes off) and actual ground faults, improving detection accuracy.
2Reliability
If the ground fault protection function is activated to detect abnormality, then protection against ground faults is improved, but the function may incorrectly trigger protection when all light emitting diodes are intentionally turned off
Solution Approach 1:
Before the ground fault protection function triggers, the determination unit performs a preliminary check to verify whether all light emitting diodes are in the turned-off state. This preliminary action prevents false triggering of protection when the zero-output state is intentional, while maintaining accurate detection of actual ground faults.
Solution Approach 2:
Instead of directly detecting ground fault conditions, the system inverts the approach by first determining whether all light emitting diodes are turned off, and only then evaluating ground fault conditions. This inverted logic prevents misinterpretation of the turned-off state as a ground fault, improving detection precision.
Data Source
AI summary
A light emission driving device includes an output voltage supply unit arranged to generate an output voltage from an input voltage so as to supply the output voltage to a load, a determination unit arranged to determine whether or not a ground fault due to abnormality may have occurred on the basis of an anode voltage of the load, and a signal output unit arranged to externally output a signal indicating that a ground fault due to abnormality may have occurred when the determination unit determines that a ground fault due to abnormality may have occurred. The output voltage supply unit does not perform generation stop of the output voltage by a trigger of determination by the determination unit that a ground fault due to abnormality may have occurred.