Bridge-Rectifier AC-DC Supply for Two-Wire Smart Switches
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Solution Overview
Problem
Two-wire wall switches lack sufficient power for smart control circuits due to the absence of a neutral connection, making it challenging to incorporate smart control technologies effectively, and existing solutions like phase-cutting and Earth ground leakage current-based methods have limitations such as restricted input voltage and compliance challenges with safety standards.
Innovation Solution
An AC-DC power supply with a high power factor full bridge rectifier, step-down switching DC-DC converter, and fault-protection circuit that utilizes ultra-low ground leakage current, ensuring compliance with safety standards and providing sufficient power for smart control circuits in two-wire devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If phase-cutting method is used to power smart control circuits in two-wire devices, then power can be obtained without neutral connection, but input voltage range is restricted and smart control functions are limited
Solution Approach 1:
The patent changes the operating parameters of the power supply system by using a full-bridge rectifier circuit that can process both half-wave and full-wave rectified voltages. This allows the system to accept a wide input voltage range (85-265V AC) and convert it to stable DC voltage (5V/12V) suitable for smart control circuits, eliminating the voltage range restrictions of phase-cutting methods.
2Adaptability or versatility
If Earth ground leakage current-based method is used, then power can be obtained in two-wire devices, but compliance with safety standards becomes challenging
Solution Approach 1:
The patent extracts the earth ground leakage current path from the main power supply circuit and uses it only for providing a reference potential and fault detection. The main power conversion is achieved through the full-bridge rectifier and DC-DC converter, which process line-to-line voltage directly. This separation allows the system to meet safety standards by limiting ground leakage current to minimal levels while still obtaining sufficient power for smart control functions.
3Reliability
If full bridge rectifier with redundant diodes is used, then fault protection capability is improved, but device complexity increases
Solution Approach 1:
The patent implements fault protection by incorporating redundant diodes in the full-bridge rectifier circuit and capacitors in the filtering stage before faults can cause damage. These redundant components are positioned to catch and isolate faults (such as diode short circuits or capacitor failures) before they can propagate to sensitive smart control circuits. The fault detection circuit monitors these components and can disconnect power when faults are detected, providing beforehand protection.
4Loss of energy
If step-down switching DC-DC converter is used, then power conversion efficiency is improved, but electromagnetic compatibility challenges increase
Solution Approach 1:
The patent uses multiple intermediary filtering components to mediate between the high-frequency switching DC-DC converter and the rest of the circuit. A pi-filter (comprising capacitors and inductors) is inserted between the rectifier output and the DC-DC converter input, and additional filtering is provided at the converter output. These intermediary filters attenuate electromagnetic interference and switching noise, allowing the efficient DC-DC converter to operate while meeting electromagnetic compatibility requirements.
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 enables efficient and compliant power supply for smart control circuits in two-wire devices, supporting complex smart control functions while meeting safety and electromagnetic compatibility standards, even under single fault conditions.
Implementation Method 1
a bridge rectifier having four diode legs, each diode leg of the four diode legs having a respective plurality of diodes electrically coupled in-series
Implementation Method 2
a step-down switching DC-DC converter
Data Source
AI summary
Fault-protection is provided in electrical devices by redundancy in diodes on diode legs of the bridge rectifier and a fault-protection circuit. The fault-protection circuit is configured: (i) for electrical coupling between a return of input DC power to a step-down switching DC-DC converter and a return rail of rectified DC voltage of the output DC power generated by the bridge rectifier, and is configured to perform opening the switch based on sensing a current fault or voltage fault, or (ii) to sense current from a step-down switching DC-DC converter, a first voltage from the step-down switching DC-DC converter, and/or a second voltage at an output of the step-down switching DC-DC converter, and open the circuit on a fault.