Solid-State Smart Plug Circuit for Local Fault Interruption
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Solution Overview
Problem
Existing smart plug devices lack protection against overload, short circuit, ground, arc, and voltage surge faults, relying on upstream circuit breakers for protection, which can lead to dangerous fault currents and power outages, and do not address insulation and wire degradation issues that can cause fire or shock hazards.
Innovation Solution
A wireless-controlled smart plug using solid state switches, including bidirectional semiconductor switches and sensors, to detect and interrupt fault currents, providing protection against overload, short circuit, ground, arc, and voltage surge faults, while allowing normal inrush current operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If upstream circuit breaker is used for protection against fault currents, then protection against overload and short circuit is provided, but response time is slow (tens of milliseconds) and causes power outages in non-fault outlets
Solution Approach 1:
The invention segments the protection function by placing a solid state switch and control circuitry directly in the smart plug device, enabling localized fault detection and interruption. This eliminates the need to wait for upstream circuit breaker response and prevents power outages in non-fault outlets by isolating only the affected circuit.
Solution Approach 2:
The solid state switch acts as an intermediary between the power outlet and the load, providing fast-acting protection against fault currents. The control circuitry monitors electrical parameters and triggers the solid state switch to interrupt fault currents within microseconds, much faster than traditional electromechanical relays or upstream circuit breakers.
2Ease of operation
If electromechanical relay is used in smart plug, then simple switching function is achieved, but protection against abnormal circuit conditions (overload, short circuit, ground, arc faults) is not provided
Solution Approach 1:
The smart plug device integrates multiple functions into a single unit: wireless-controlled switching, overcurrent protection, ground fault protection, arc fault detection, and voltage surge protection. The solid state switch and control circuitry enable the device to perform both switching operations and comprehensive electrical safety functions that were previously requiring separate devices.
Solution Approach 2:
The invention replaces the electromechanical relay with a solid state switch controlled by electronic circuitry. This substitution enables much faster response times and allows for sophisticated fault detection algorithms that can distinguish between normal inrush currents and dangerous fault conditions, providing comprehensive protection that mechanical relays cannot achieve.
3Speed
If solid state switch is used for fast fault response, then protection speed is improved, but device complexity increases
Solution Approach 1:
The control circuitry extracts and monitors specific electrical parameters (current, voltage, ground leakage) from the complex power signal, processing only the relevant information needed for fault detection. This selective monitoring approach enables fast protection responses without requiring the entire system to handle the full complexity of power signal analysis.
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 offers all-in-one protection against shock and fire hazards, enables faster fault response, reduces overcurrent stress, and facilitates easier isolation and identification of local faults, preventing damage and ensuring safer operation.
Implementation Method 1
A bidirectional semiconductor switch controls a current flow from the electrical plug to the electrical socket
Implementation Method 2
A current sensor measures a load current and is configured to detect an overcurrent condition
Implementation Method 3
A ground current sensor is configured to detect a ground fault condition
Implementation Method 4
A current rate-of-change (di/dt) sensor is configured to detect an arcing condition
Implementation Method 5
A gate driver circuit controls the bidirectional semiconductor switch as a function of the overcurrent or the arcing condition
Data Source
AI summary
A wireless-controlled smart plug device and methods of use and operation, using a solid state switch to provide electrical power from an outlet to a load, and provide protection against overload, short circuit, ground, arc, or voltage surge faults. The switch includes a bidirectional semiconductor switch with two back-to-back connected transistors, such as silicon power MOSFETs, silicon insulated-gate bipolar transistors (IGBTs), silicon carbide (SiC) transistors, or gallium nitride (GaN) transistors, each configured to control the current flow from the electrical receptacle to the external electrical load.