Wireless Light Switch Power Supply Without Neutral Wiring
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Solution Overview
Problem
Existing smart light switches that require fast response to external commands often cannot be low power, making energy harvesting or battery power unsuitable, particularly for Wi-Fi-based systems, which necessitate mains power and face challenges in powering wireless electronics without a neutral connection in standard light switch fittings.
Innovation Solution
A lighting control system that uses a controllable switching element and a switch mode power supply to generate a DC voltage from leakage current between the mains live and earth terminals, allowing a wireless controller to be powered without a mains neutral connection, with a current monitor ensuring the leakage current remains below a predetermined threshold for safety and regulatory compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wireless transceiver (e.g., Wi-Fi) is used in a smart light switch, then wireless communication capability is improved, but power consumption increases making low-power operation impossible
Solution Approach 1:
The system uses itself (the live-earth voltage differential) to generate its own power through the switch-mode power supply, eliminating the need for external power sources or neutral connections. The smart light switch extracts power from the existing mains voltage between live and earth terminals, allowing the wireless transceiver to operate without requiring additional power infrastructure.
2Use of energy by moving object
If energy harvesting or battery power is used to achieve low-power operation, then power consumption is reduced, but fast response to external commands becomes impossible
Solution Approach 1:
The system continuously draws power from the mains supply through the live-earth path, maintaining constant power availability without batteries or energy harvesting mechanisms. This ensures the wireless transceiver and processing units always have immediate power, enabling fast response to external commands while maintaining low overall power consumption by only using necessary power from mains.
3Reliability
If a standalone power source is used to power the wireless controller, then power supply reliability is improved, but device complexity increases
Solution Approach 1:
The power supply function is merged with the existing switching element that controls the lighting load. The same switch that controls the light also controls power delivery to the wireless controller, eliminating the need for separate power supply circuits, batteries, or neutral connections. The live-earth path serves dual purposes: controlling the load and powering the controller.
Solution Approach 2:
The switching element performs multiple functions: it controls the lighting load and simultaneously regulates power supply to the wireless controller. The live-earth voltage path serves both as a control signal path and a power delivery path, reducing the number of required components and simplifying the overall device structure.
4Power
If leakage current is increased to provide sufficient power for the wireless controller, then power availability is improved, but safety and regulatory compliance deteriorate
Solution Approach 1:
The system dynamically adjusts the leakage current based on the power requirements of the wireless controller. The switch-mode power supply regulates the current flow through feedback control, increasing current only when needed for wireless operation and reducing it during standby periods. This dynamic adjustment ensures sufficient power availability while maintaining leakage current within safety limits set by regulations.
Solution Approach 2:
The switch-mode power supply incorporates feedback control that monitors the power requirements of the wireless controller and adjusts the leakage current accordingly. The system continuously regulates the current through the live-earth path, ensuring that power is supplied at the exact level needed without exceeding safety thresholds. Feedback signals from the power supply circuitry modulate the switching duty cycle to maintain optimal current levels.
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
Enables the use of a wireless transceiver, such as Wi-Fi, in smart light switches without a mains neutral connection, reducing the need for a standalone power source and improving energy efficiency by avoiding linear regulators, while meeting safety and regulatory requirements.
Implementation Method 1
a switch mode power supply connected between the mains live input terminal and a mains earth terminal, said switch mode power supply being arranged to selectively pass a leakage current between the mains live input terminal and the mains earth terminal to generate a DC output voltage
Implementation Method 2
a controllable switching element arranged between a mains live input terminal and a mains live output terminal, said controllable switching element arranged to operate in an on state in which a connection path between the mains live input terminal and a mains live output terminal is enabled, and an off state in which the connection path is disabled
Data Source
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AI summary
A lighting control (4) for selectively supplying an AC input voltage to an external lighting load. A controllable switching element (34, 36) is between mains live input (16) and mains live output terminals (22, 24). An earth leakage power supply (26) includes a switch mode power supply, connected between the mains live input terminal (16) and a mains earth terminal (18), that selectively passes a leakage current between the mains live input terminal (16) and the mains earth terminal (18) to generate a DC output voltage (42). The earth leakage power supply (26) also includes a current monitor that measures the leakage current and generates a feedback signal having a first value when the leakage current is below a threshold value and a second value otherwise. The switch mode power supply enables the leakage current when the feedback signal has its first value, and disables it otherwise. A wireless controller (32) operates the controllable switching element (34, 36) in response to a received control signal, wherein the DC output voltage (42) generated by the switch mode power supply is supplied to the controller (32).