LED Module Isolation Fault Detection via Switching Frequency Harmonics
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Solution Overview
Problem
Existing LED drivers lack protection against isolation fault conditions, which can lead to fault current flow, potentially causing damage or fire hazards due to the absence of ground-fault circuit protection.
Innovation Solution
A method for detecting isolation fault conditions in LED modules supplied by non-isolated switched LED converters involves analyzing the operation frequency signal of the converter's switch to identify harmonic contributions within the mains voltage frequency range. If the harmonic contribution exceeds a set threshold, the electrical power to the LED module is stopped or reduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a non-isolated LED driver is used to simplify the converter structure, then device complexity is reduced, but isolation fault detection capability is lost leading to potential fire hazards
Solution Approach 1:
The patent uses feedback from the LED module's operation frequency signal to detect isolation faults. The control circuit monitors the switching frequency signal and analyzes harmonics that indicate fault conditions, enabling automatic detection and response without requiring complex isolation mechanisms.
Solution Approach 2:
The patent replaces mechanical/isolation-based protection systems with an electrical signal analysis approach. Instead of relying on physical isolation barriers, the system uses electrical signal processing (harmonic analysis of the switching frequency signal) to detect faults and trigger shutdown, simplifying the overall system while maintaining safety.
2Reliability
If isolation fault detection is implemented by analyzing switching frequency harmonics, then reliability is improved, but device complexity increases due to additional signal processing
Solution Approach 1:
The control circuit performs multiple functions: it generates the switching frequency signal for LED operation, monitors the signal for harmonic content indicating faults, and controls the shutdown response. This multi-functionality reduces the need for separate dedicated fault detection hardware.
Solution Approach 2:
The system uses its own operating signal (the switching frequency signal) as the detection probe. By analyzing harmonics in the signal it already generates and processes, the system performs self-diagnosis without requiring external monitoring equipment or additional sensors.
3Object-affected harmful factors
If rapid shutdown is implemented to prevent fire hazards, then safety is improved, but loss of time increases due to fault detection and response time
Solution Approach 1:
The control circuit continuously monitors the switching frequency signal for harmonic content in real-time, preparing the shutdown mechanism in advance. When fault conditions are detected, the system can immediately execute shutdown without delay, as the monitoring and decision-making infrastructure is already in place and operational.
Data Source
AI summary
The invention relates to a method for detecting an isolation fault condition of a LED module supplied with electrical power by a non-isolated switched LED converter, the switched LED converter having a control circuit for issuing a control signal for at least one switch and being supplied with at least one feedback signal from the LED in order to implement a feedback-controlled operation of the LED module. The method comprises the step of: obtaining and analysing a signal indicating the operation frequency of the switch of the switched converter in order to evaluate the contribution of a harmonic in the frequency range of a mains voltage supplying the converter in said signal, and stopping or reducing the electrical power supplied to the LED module in case the contribution of said harmonic exceeds a given threshold value during at least a preset time period or preset number of cycles.