Ground-Leakage Power Supply for Neutral-Free Multimode Switches
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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 are unable to provide sufficient power while maintaining safe ground leakage levels.
Innovation Solution
A multimode switch powered by an AC hot wire and earth ground, incorporating a ground leakage power supply that generates a regulated voltage to power a switch controller and wireless transceiver, without requiring an AC neutral line, while limiting ground leakage current to a prescribed value, using a combination of a rectifier circuit, energy storage component, and current limiter to ensure efficient energy storage and power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
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 wire and AC hot wire to generate power for the controller through a rectifier circuit and energy storage component, eliminating the need for external battery replacement. The ground wire serves dual purpose as both safety ground and power source.
Solution Approach 2:
A rectifier circuit and energy storage component are introduced as intermediaries to convert the ground leakage current into usable power for the controller, enabling the system to operate without batteries or neutral wires.
2Power
If existing power supply circuits are used to power the controller, then the controller can be powered, but the ground leakage current exceeds safety limits
Solution Approach 1:
The system changes the parameters of power extraction by using a current limiter component to precisely control the ground leakage current to stay within safety limits (typically less than 5mA), while still generating sufficient power through the rectifier circuit to operate the controller and wireless transceiver.
3Object-affected harmful factors
If ground leakage current is limited to safe levels, then safety requirements are met, but insufficient power is available to operate the controller and wireless transceiver
Solution Approach 1:
An energy storage component (capacitor) is used to accumulate energy from the ground leakage current over time, storing sufficient power to operate the controller and wireless transceiver while maintaining safe ground leakage current levels at any given moment.
Solution Approach 2:
The rectifier circuit converts AC ground leakage current into DC power that charges the energy storage component periodically, building up sufficient energy reserves to power the controller and transceiver operations.
4Power
If a neutral wire is installed to provide power, then sufficient power is available for the controller, but installation cost and complexity increase
Solution Approach 1:
The ground wire is given multiple functions: it serves as both the safety ground connection and the power source for the controller and wireless transceiver, eliminating the need for additional neutral wire installation in existing buildings.
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
The solution provides sufficient power to remote or local loads for a prescribed period while maintaining safe ground leakage levels, enabling efficient operation of smart controllers and wireless communication within building automation systems, reducing installation costs and labor by eliminating the need for neutral connections.
Implementation Method 1
a rectifier circuit, energy storage component, and current limiter
Implementation Method 2
a rectifier circuit, energy storage component, and current limiter
Implementation Method 3
a rectifier circuit, energy storage component, and current limiter
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 first identifying information and a functional group designation for the device, and that controls the device according to the first identifying information and 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.