Ground-Leakage Powered Switch Without Neutral Wiring
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Solution Overview
Problem
Existing building automation systems face challenges in powering smart controllers within wall- or surface-mounted switches without an AC neutral line, as conventional ground leakage current limits are insufficient for practical operation, leading to issues with energy storage and power supply efficiency.
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 wireless transceiver and switch controller, while limiting ground leakage current to a prescribed value, eliminating the need for an AC neutral connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground leakage current is limited to less than 5 milliamperes to meet regulatory requirements, then safety and compliance are improved, but power supply capability for smart controllers deteriorates
Solution Approach 1:
The patent segments the power supply function into two independent parts: a ground leakage power supply that provides baseline power within safety limits, and an energy storage component that provides additional power during high-demand periods. This segmentation allows the system to meet both safety requirements and power demands without requiring neutral wire connection.
Solution Approach 2:
The energy storage component is charged in advance during periods when power demand is low and ground leakage current is within safe limits. This preliminary charging action ensures that sufficient energy is available when the smart controller needs to operate at higher power levels, such as during wireless communication transmissions.
2Power
If battery is used as power source within the switch, then power supply capability is improved, but reliability deteriorates due to battery failure and replacement requirements
Solution Approach 1:
The system uses the ever-present ground leakage current from the AC power source to continuously recharge the energy storage component, creating a self-sustaining power system. As long as the switch remains connected to the AC power source, the energy storage component will be replenished, eliminating the need for battery replacement and ensuring continuous operation.
3Power
If transformers and triacs are used to harvest power from AC hot lead, then power supply capability is improved, but ground leakage current limits are exceeded
Solution Approach 1:
The energy storage component acts as an intermediary between the ground leakage power supply and the smart controller. It decouples the direct connection between the AC hot lead and the controller, allowing power to be transferred through the ground reference without creating excessive ground leakage current. The energy storage component buffers and regulates the power transfer.
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 adhering to ground leakage current limits, enabling efficient operation of smart controllers and wireless communication within the switch without requiring an AC neutral line.
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 wireless transceiver and 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
Data Source
AI summary
A multimode switch includes a wireless transceiver, that transmits/receives messages over a wireless network; a line voltage switch, coupled to a line voltage and associated devices; a switch controller, responsive to first messages received over the wireless network, that directs the line voltage switch to provide line voltage to, and subsequently remove line voltage from, the associated devices, and that receives identifying information and functional group designation for the associated devices in second messages over the wireless network, and that controls the associated devices according to the identifying information and functional group designation via transmission of third messages over the wireless network; 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 wireless transceiver and 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.