Load Control Circuit Timing for Reduced Earth-Ground Leakage
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Solution Overview
Problem
Existing load control devices face challenges in minimizing current conducted through the earth ground connection, particularly when equipped with occupancy detection circuits that require substantial current for operation, often exceeding the 500 μA limit set by standards.
Innovation Solution
The load control device incorporates a controllably conductive device and a control circuit that generates a detect signal indicating the magnitude of the switched-hot voltage, allowing the device to monitor and reduce the total current conducted through the earth ground connection by disconnecting the detect circuit when an edge on the detect signal is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If occupancy detection circuits are included in the load control device, then the device can automatically control lighting loads, but the current conducted through the earth ground connection increases beyond the 500 μA limit
Solution Approach 1:
The patent applies periodic action by controlling the detect circuit to operate only during specific intervals within each AC power cycle. The control circuit enables the detect circuit to generate detect signals during predetermined time periods and disables it during other periods, creating a periodic operation pattern that reduces average leakage current while maintaining occupancy detection functionality.
Solution Approach 2:
The patent implements dynamics by making the conductive state of the detect circuit variable rather than static. The control circuit dynamically adjusts the conductivity of the detect circuit based on timing signals, transitioning between conductive and non-conductive states to optimize the balance between detection accuracy and leakage current reduction.
2Measurement precision
If the detect circuit is continuously conductive to monitor switched-hot voltage, then detection accuracy is maintained, but leakage current through earth ground increases
Solution Approach 1:
The patent applies periodic action by controlling the detect circuit to operate only during specific intervals within each AC power cycle. The control circuit enables the detect circuit to generate detect signals during predetermined time periods and disables it during other periods, creating a periodic operation pattern that reduces average leakage current while maintaining occupancy detection functionality.
Solution Approach 2:
The patent applies partial action by providing detection coverage for only a portion of each AC power cycle rather than continuous monitoring. The detect circuit operates during sufficient time intervals to capture occupancy events while accepting that not every moment is monitored, thus reducing overall current consumption while maintaining adequate detection precision.
Data Source
AI summary
A load control device for controlling power delivered from an AC power source to an electrical device may be configured to conduct current through earth ground and may disconnect a switching circuit to reduce an amount of current conducted through the earth ground. The load control device may comprise a controllably conductive device configured to control the power delivered from the AC power source to the electrical device so as to generate a switched-hot voltage, a switching circuit electrically coupled with a detect circuit, and a control circuit configured to render the switching circuit conductive and nonconductive. The detect circuit may generate a detect signal indicating a magnitude of the switched-hot voltage. The control circuit may be configured to monitor the detect signal and to render the switching circuit non-conductive after detecting an edge on the detect signal to reduce the total current through the earth ground.