Two-Wire Load Control Circuit for Neutral-Free Power Estimation
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Solution Overview
Problem
Two-wire load control devices lack the capability to accurately compute and report real-time power consumption due to the absence of a direct connection to the neutral side of the AC power source, preventing them from determining the actual voltage drop across the load.
Innovation Solution
A two-wire lighting control device is configured with a controllably conductive device and a control circuit that measures voltage across the device during a half-cycle, generates a complementary voltage waveform to approximate the voltage across the load, and computes power consumption based on this estimation and measured current, enabling accurate power consumption estimation without a neutral connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a two-wire load control device is used, then device complexity is reduced, but measurement precision of power consumption deteriorates
Solution Approach 1:
The patent applies preliminary action by measuring the voltage across the two-wire load control device during the first portion of the half-cycle (when the controllably conductive device is non-conductive) before the actual power delivery occurs. This preliminary voltage measurement is then used to generate a complementary voltage waveform that represents the voltage across the load during the second portion (when power is delivered), enabling power consumption calculation without direct neutral connection.
2Measurement precision
If a three-wire load control device is used, then measurement precision of power consumption is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential function of power measurement from the traditional three-wire configuration by removing the requirement for a neutral wire connection. It achieves this by measuring voltage across the two-wire device itself and using complementary waveform generation to infer the load voltage, thereby extracting accurate power measurement capability from a simplified two-wire topology.
3Measurement precision
If voltage measurement is performed during the first portion of half-cycle, then power consumption estimation accuracy is improved, but loss of time for actual power delivery occurs
Solution Approach 1:
The patent applies periodic action by dividing each half-cycle into two distinct portions: the first portion for voltage measurement (when the controllably conductive device is non-conductive) and the second portion for power delivery (when the device is conductive). This periodic alternation between measurement and power delivery modes enables accurate power consumption estimation while maintaining efficient power transfer during the appropriate time intervals.
Data Source
AI summary
A two-wire load control device may be configured to compute an accurate estimate of real-time power consumption by a load that is electrically connected to, and controlled by, the two-wire load control device. The load control device may be adapted to measure a voltage drop across the device during a first portion of a half-cycle of an AC waveform provided to the device. The device may be further configured to estimate a voltage drop across the load during the second portion of the half-cycle. The estimated voltage drop may be based on the measured voltage drop. The device may be further configured to measure a current supplied to the load during a second portion of the half-cycle. The device may be configured to estimate power consumed by the load based on the measured current and the estimated voltage drop.