Ground Leakage Power Supply Using Energy Storage Without Neutral
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Solution Overview
Problem
Existing building automation systems face challenges in powering smart controllers and wireless transceivers 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 reliability.
Innovation Solution
A ground leakage current power supply circuit that utilizes an AC hot wire and earth ground, incorporating a current limiter and energy storage component to regulate charging and provide a sufficient output voltage for a multimode switch and wireless transceiver, allowing operation without an AC neutral connection while limiting ground leakage current within prescribed limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground leakage current is limited to prescribed values (less than 5 milliamperes), then safety and regulatory compliance are improved, but power supply capability for smart controllers and wireless transceivers deteriorates
Solution Approach 1:
The energy storage component (capacitor) is charged in advance during periods when power demand is low or ground leakage current limits are not exceeded, storing energy that can be discharged later when power-intensive operations are needed. This preliminary charging action allows the system to accumulate sufficient power while maintaining compliance with ground leakage current limits at any given moment.
Solution Approach 2:
The system operates in periodic cycles, alternating between charging the energy storage component during low-power periods and discharging during high-power periods. This periodic operation allows the microprocessor to enter low-power modes periodically, reducing average ground leakage current while still providing adequate power during active operation of wireless transceivers and other high-consumption components.
2Power
If energy storage component is added to accumulate sufficient power, then power supply capability is improved, but device complexity increases
Solution Approach 1:
The energy storage component serves multiple functions: it acts as a capacitor for power accumulation, provides voltage regulation during power transitions, and enables the system to bridge power gaps during microprocessor wake-up and wireless transmission. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity while achieving improved power supply capability.
3Productivity
If microprocessor operates in active mode continuously, then processing capability is improved, but energy consumption increases
Solution Approach 1:
The microprocessor dynamically transitions between low-power sleep modes and active processing modes based on operational requirements. During low-power modes, the system maintains essential functions with minimal energy consumption. When processing capability is needed, the microprocessor wakes to active mode, utilizing the pre-charged energy storage component to provide the necessary power bursts without requiring continuous high-power operation.
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 reliable power supply to remote or local loads and wireless transceivers for extended periods, ensuring compliance with ground leakage current regulations and supporting various power-intensive applications like LED lighting and wireless communication.
Implementation Method 1
a rectifier, coupled to the hot node, the earth ground node, and a return node
Implementation Method 2
an energy storage component, coupled between the current limiter and the return node
Implementation Method 3
a current limiter that enables the energy storage component to charge to a voltage at a rate that limits ground leakage current to a prescribed value
Implementation Method 4
a low voltage power supply that includes a linear voltage regulator, coupled to the energy storage component and to a return node, where the low voltage power supply receives the voltage and generates an output voltage
Data Source
AI summary
A power supply, includes: a hot node coupled to a hot wire of an AC source, and a ground node coupled to an earth ground, where a neutral wire of the source is not present; a storage component, coupled to a return node and in series with a current limiter, where the current limiter enables the storage component to charge to a voltage while limiting leakage current to a prescribed value; a low voltage power supply including a linear voltage regulator, coupled to the storage component and to a return node that provides a reference voltage, where the low voltage power supply receives the voltage and generates an output voltage on an output node that is referenced to the reference voltage; and a microprocessor that employs the output voltage to wake from a low power mode to an active mode.