LED Lamp Power Module Impedance Detection for Electric Shock Safety
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Solution Overview
Problem
Existing LED tube lamps with dual-end power supply structures face challenges in safety certification due to high risk of electric shock and leakage current, particularly in Type-B LED tube lamps, which can lead to skin effect and harm when not properly installed, hindering their commercialization.
Innovation Solution
A novel LED tube lamp design incorporating a power supply module with a detection path circuit and driving circuit that detects foreign external impedance and adjusts the driving current based on external driving signals, ensuring safe operation and reducing leakage current, thereby enhancing safety certification compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If Type-B LED tube lamp is installed without a ballast to enable direct AC power connection, then ease of operation and installation is improved, but safety deteriorates due to high risk of electric shock and leakage current
Solution Approach 1:
The patent introduces an isolation transformer as an intermediary device between the AC power source and the LED tube lamp. This transformer provides galvanic isolation, blocking the direct transmission of harmful leakage current to the user while still allowing the lamp to operate directly from AC power without a ballast. The transformer acts as a safety mediator that enables easy installation while preventing electric shock hazards.
Solution Approach 2:
The patent replaces the traditional mechanical ballast-based installation system with an electronic isolation-based safety system. Instead of requiring a physical ballast component for safety, the system uses electronic isolation technology to achieve the same safety objective while maintaining direct AC compatibility, thus improving ease of installation without compromising safety.
2Adaptability or versatility
If dual-end power supply structure is used in LED tube lamp, then adaptability and versatility are improved, but safety deteriorates due to increased leakage current and electric shock hazard
Solution Approach 1:
The isolation transformer serves as a mediator that enables the dual-end power supply configuration to operate safely. By placing the transformer between the AC source and the lamp's dual-end power input, it allows both ends to receive power while blocking the propagation of leakage current, thus maintaining adaptability while reducing harmful effects.
Solution Approach 2:
The patent converts the potential harm of leakage current in dual-end power supply configuration into a benefit by using the isolation transformer to detect and block the leakage. The system monitors the electrical characteristics and actively prevents harmful current flow, turning a safety risk into a controlled operational feature that maintains versatility while ensuring safety.
3Object-affected harmful factors
If detection path circuit and driving circuit are added to detect external impedance and adjust driving current, then safety is improved, but device complexity increases
Solution Approach 1:
The patent merges the detection path circuit and driving circuit into an integrated control system that shares common components and signal pathways. The detection circuit and driving circuit are combined on a single control board with shared microcontrollers, power management ICs, and communication interfaces, reducing overall component count and circuit complexity while maintaining the safety functionality of impedance detection and adaptive current control.
Solution Approach 2:
The control circuit is designed with multi-functional capabilities that serve both safety detection and normal operation. The same microcontroller and sensing circuits used for impedance detection also manage dimming control, fault diagnosis, and power management, eliminating the need for separate dedicated safety circuits and reducing overall system complexity while improving safety.
Data Source
AI summary
An LED lamp and a power supply module thereof are provided. The power supply module includes a driving circuit, a OVP circuit, and an impedance detection circuit. The OVP circuit is configured to determine whether an OVP condition is detected by sampling the driving signal, and the impedance detection circuit is configured to determine whether a user touching state is detected. When either the OVP condition or the user touching state is detected, the power switch of the driving circuit will be controlled to limit the amount of a current flowing through the power switch. In addition, the impedance detection circuit could detect the user touching state by comparing signals with a defined level sampled during each pulse, thus enhancing the detection accuracy.