Neutral-Free Multimode Switch Powering via Ground Leakage
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Solution Overview
Problem
Conventional building automation systems face challenges in powering smart controllers within wall- or surface-mounted switches without a neutral wire, as existing solutions either rely on batteries that fail or exceed ground leakage current limits, and existing power supply circuits either limit energy storage or require constant neutral connection.
Innovation Solution
A ground leakage power supply circuit that uses only an AC hot wire and earth ground, coupled with a switch controller and line voltage switch, generates a regulated voltage to power the controller while limiting ground leakage current to a prescribed value, eliminating the need for a neutral connection and providing sufficient power for a multimode switch and wireless transceiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a battery is used to power the smart controller in the switch, then the controller can operate without a neutral wire, but the battery fails over time and requires replacement
Solution Approach 1:
The system uses the existing ground leakage current in the building's electrical system to power the controller, eliminating the need for external batteries. The ground leakage power supply circuit automatically harvests power from the ground wire, making the system self-powered without requiring periodic battery replacement or maintenance.
2Power
If a transformer and triac are used to harvest power from the AC hot lead, then sufficient power can be provided to the controller, but the ground leakage current limit is exceeded
Solution Approach 1:
The invention extracts power from the ground wire instead of the hot wire. By using a ground leakage power supply circuit that harvests power from the ground connection, the system avoids the ground leakage current limits that would be exceeded by traditional hot wire harvesting methods using transformers and triacs.
Solution Approach 2:
The patent introduces a ground leakage power supply circuit as an intermediary device that converts the small ground leakage current into sufficient power for the controller. This intermediary circuit includes a rectifier, capacitor, and voltage regulator that efficiently convert the limited ground current into usable power without exceeding safety limits.
3Quantity of substance
If an energy storage capacitor is used in the power supply circuit, then power can be stored for controller operation, but the ground leakage current is limited which restricts the capacitor size and stored energy
Solution Approach 1:
The system changes the operating parameters by using a higher voltage capacitor (e.g., 400V or 600V rating) to store more energy within the same ground leakage current constraints. By increasing the voltage parameter rather than the current, the energy storage capacity is significantly increased while remaining within safe ground leakage limits.
4Power
If a conventional power supply circuit requiring neutral connection is used, then sufficient power can be provided, but the installation complexity increases and neutral wire is required
Solution Approach 1:
The ground leakage power supply circuit serves multiple functions: it powers the controller, provides commissioning capability, and enables wireless communication without requiring additional wires or a neutral connection. This multi-functional approach eliminates the need for complex wiring while providing all necessary power and communication functions.
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 a multimode switch to be powered exclusively by ground leakage current, supporting both line voltage switching and wireless communication without exceeding ground leakage limits, thus reducing installation costs and enhancing reliability by eliminating the need for batteries and constant neutral connections.
Implementation Method 1
a ground leakage power supply, coupled to an AC hot line and to an earth ground, configured to generate a regulated voltage to power the switch controller
Implementation Method 2
limiting ground leakage current to the earth ground to a prescribed leakage value
Data Source
AI summary
A multimode switch includes a line voltage switch, coupled to a line voltage and a device; a switch controller that directs the line voltage switch to provide line voltage to, and subsequently remove line voltage from, the device, and that receives a functional group designation for the device, and that controls the device according to the functional group designation; and a ground leakage power supply, coupled to an AC hot line and to an earth ground, that generates a regulated voltage to power the switch controller without requiring connection to an AC neutral line, while limiting ground leakage current to the earth ground to a prescribed leakage value.