Neutral-Free Multimode Switch Power Supply Under Leakage Limits

Solution Overview

Problem

Conventional building automation systems face challenges in powering smart controllers within wall- or surface-mounted switches without an AC neutral line, as existing solutions either fail to provide sufficient power or exceed ground leakage current limits, limiting the functionality of devices like LED lighting and wireless transceivers.

Innovation Solution

A ground leakage power supply circuit that utilizes an AC hot wire and earth ground to generate a regulated voltage for a multimode switch controller and wireless transceiver, while limiting ground leakage current to a prescribed value, eliminating the need for an AC neutral connection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a smart controller is powered using ground leakage current from AC hot line and earth ground, then the controller can operate without AC neutral connection, but the ground leakage current must be limited to less than 5 milliamperes

Engineering Contradiction:

ImproveAbility to operate without AC neutral connectionVSAvoidGround leakage current limit

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

A current limiting circuit is introduced as an intermediary component between the AC hot line and the controller power supply. This circuit actively monitors and limits the ground leakage current to remain below 5 milliamperes, enabling the controller to operate from ground leakage current without violating safety regulations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system changes the electrical parameters by deriving power from the AC hot line through a controlled impedance path to earth ground, transforming the conventional power supply approach (requiring neutral connection) into a ground-referenced power supply that operates within leakage current limits.

Inventive Principle:

Principle #35Parameter changes

2Power

If ground leakage current is increased to provide sufficient power to the controller, then the controller can function properly, but the ground leakage current exceeds regulatory limits

Engineering Contradiction:

ImprovePower supplied to controllerVSAvoidGround leakage current

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

A current limiting circuit is introduced as an intermediary component between the AC hot line and the controller power supply. This circuit actively monitors and limits the ground leakage current to remain below 5 milliamperes, enabling the controller to operate from ground leakage current without violating safety regulations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system utilizes the periodic nature of AC power cycles to efficiently transfer energy to the controller while maintaining continuous current limitation, allowing sufficient power delivery within regulatory constraints.

Inventive Principle:

Principle #19Periodic action

3Reliability

If a battery is used to power the controller in the switch, then the controller can operate independently, but the battery fails and requires replacement

Engineering Contradiction:

ImproveIndependent operationVSAvoidBattery lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The controller is designed to harvest and utilize ground leakage current from the AC power system to power itself, eliminating the need for external batteries. The controller performs its own power provisioning by drawing minimal current through the ground path, achieving continuous operation without consumable power sources.

Inventive Principle:

Principle #25Self-service

4Power

If transformers and triacs are used to harvest power from AC hot lead, then sufficient power can be provided to the controller, but the ground leakage current limit is exceeded

Engineering Contradiction:

ImprovePower harvested from AC hot leadVSAvoidGround leakage current

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

A current limiting circuit is introduced as an intermediary component between the AC hot line and the controller power supply. This circuit actively monitors and limits the ground leakage current to remain below 5 milliamperes, enabling the controller to operate from ground leakage current without violating safety regulations.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 sufficient power supply to remote or local loads for a prescribed period while adhering to ground leakage current limits, supporting the operation of smart controllers and wireless communication within switches, reducing installation costs and enhancing energy efficiency.

Implementation Method 1

a ground leakage power supply circuit that utilizes an AC hot wire and earth ground to generate a regulated voltage for a multimode switch controller and wireless transceiver, while limiting ground leakage current to a prescribed value

Methodology Applied

Scientific EffectGround leakage current: Conduction (electrical)

Data Source

PatentUS11659644B2Apparatus and method for commissioning and controlling a device over a network

Publication Date: 2023.05.23 FABRIQ

AI summary

A multimode switch includes a line voltage switch, coupled to a line voltage and a device; a switch controller, responsive to first messages received over a network, 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 in second messages over the network, and that controls the device according to the first identifying information and the functional group designation via transmission of third messages over the 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 switch controller without requiring connection to an AC neutral line, while limiting ground leakage current to the earth ground to a prescribed leakage value.