LED Lighting Device Human Body Detection Circuit
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Solution Overview
Problem
LED-based lighting devices, particularly double-ended TLEDs, pose a shock hazard during installation due to conductive paths and leakage currents, existing solutions increasing complexity and cost, and there is a need for a safe and cost-effective method to detect human presence in the power loop.
Innovation Solution
An LED-based lighting device with a zero-crossing detection module, detection pulse module, and human body detection module that measures current drawn from the AC mains supply to determine human body presence, using a detection pulse after zero-crossing and a current limiter to maintain constant current, allowing safe installation by ensuring no human body is present before powering on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolation is used to ensure safety, then safety is improved, but device complexity increases
Solution Approach 1:
The patent introduces a detection pulse module as an intermediary that generates test pulses during zero-crossing periods to detect human body presence. This mediator enables safety detection without requiring galvanic isolation, thus improving safety while avoiding the complexity of isolation circuitry.
Solution Approach 2:
The patent replaces the mechanical/electrical approach of galvanic isolation with an electronic detection system that uses zero-crossing detection and pulse generation. This substitution achieves safety through intelligent detection rather than physical isolation, reducing device complexity.
2Reliability
If additional safety switches are installed, then safety is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing driver circuitry multi-functional by enabling it to perform both normal LED operation and safety detection functions. The driver can operate in normal mode or switch to detection mode during zero-crossing periods, eliminating the need for separate safety switches and reducing device complexity.
Solution Approach 2:
The patent enables the existing circuitry to perform safety detection on its own without requiring additional safety switches. The driver circuitry self-monitors for human body presence by generating detection pulses and measuring current draw, providing self-service safety functionality.
3Measurement precision
If detection pulse is provided during AC voltage, then human body detection accuracy is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic detection by generating detection pulses only during zero-crossing periods of the AC voltage waveform. This periodic approach allows accurate human body detection while minimizing energy consumption by limiting detection activity to brief intervals rather than continuous operation.
Solution Approach 2:
The patent maintains continuous monitoring capability by utilizing every zero-crossing event to generate detection pulses. This ensures continuous safety monitoring throughout operation while keeping energy consumption low by leveraging the naturally occurring zero-crossing points in the AC waveform.
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
This solution enables accurate and safe human body detection in the power loop, reducing the risk of electrical shock during installation and allowing multiple LED devices to share a circuit breaker, while maintaining cost-effectiveness by eliminating the need for additional safety switches or circuitry.
Implementation Method 1
a zero-crossing detection module arranged for detecting a zero-crossing in an AC voltage supplied by said AC mains supply
Implementation Method 2
a human body detection module arranged for determining a current drawn from said AC mains supply during said provided detection pulse, and for determining presence of a human body based on said determined current
Data Source
AI summary
A Light Emitting Diode, LED, based lighting device arranged for connection to an Alternating Current, AC, mains supply, comprising a zero-crossing detection module arranged for detecting a zero-crossing in an AC voltage supplied by said AC mains supply, a detection pulse module arranged for providing a detection pulse based on said detected zero-crossing, a human body detection module arranged for determining a current drawn from said AC mains supply during said provided detection pulse, and for determining presence of a human body based on said determined current, wherein said detection pulse module is arranged for providing said detection pulse during a rising, positive, edge of said AC voltage.