Thyristor Dimmer Control for LED Load Latching Stability
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Solution Overview
Problem
Existing dimmer switches struggle to effectively control the intensity of high-efficiency light sources like LEDs and CFLs, as they often require higher power ratings and can cause unintended illumination when the light should be off, due to issues with load regulation devices having varying impedances and charging currents.
Innovation Solution
A two-wire load control device using a thyristor coupled in series with a gate coupling circuit and a control circuit that manages the gate current to ensure proper conduction times, allowing for precise control of power delivery to high-efficiency light sources without requiring a neutral connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a thyristor is used to control power delivery to high-efficiency light sources, then power control capability is improved, but the device fails to operate reliably when load current falls below latching and holding currents
Solution Approach 1:
The patent introduces an artificial load circuit as an intermediary component that draws additional current through the thyristor. This artificial load ensures the total current exceeds the thyristor's latching and holding current requirements, allowing reliable operation with high-efficiency light sources that would otherwise draw insufficient current.
Solution Approach 2:
The invention modifies the electrical parameters of the circuit by adding a parallel artificial load with specific resistance characteristics. This changes the overall current draw through the thyristor, transforming it from being insufficient (with high-efficiency loads alone) to sufficient (with artificial load added), thereby enabling reliable thyristor operation.
2Ease of operation
If dimmer switches are used with high-efficiency light sources, then intensity control is achieved, but unintended illumination occurs due to charging currents
Solution Approach 1:
The patent separates the charging current path from the main power control path by introducing dedicated charging circuits for the thyristor gate. This extraction of the charging function allows precise control of when the thyristor turns on, preventing unintended illumination while maintaining intensity control capability.
3Power
If phase-control dimming is used, then power delivery control is improved, but compatibility issues arise with loads having varying impedances
Solution Approach 1:
The patent creates a universal load control system that can handle various load types (incandescent, CFL, LED) with different impedance characteristics. The artificial load circuit and modified phase-control mechanism work across different load types, making the dimmer switch compatible with multiple lighting technologies despite their varying electrical characteristics.
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 accurate control of high-efficiency light sources by ensuring the thyristor conducts enough current to exceed latching and holding currents, preventing unintended illumination and maintaining desired intensity levels.
Implementation Method 1
a thyristor adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the thyristor having a gate for conducting a gate current to render the thyristor conductive
Data Source
AI summary
A load control device for controlling the power delivered from an AC power source to an electrical load includes a thyristor, a gate coupling circuit for conducting a gate current through a gate of the thyristor, and a control circuit for controlling the gate coupling circuit to conduct the gate current through a first current path to render the thyristor conductive at a firing time during a half cycle. The gate coupling circuit is able to conduct the gate current through the first current path again after the firing time, but the gate current is not able to be conducted through the gate from a transition time before the end of the half-cycle until approximately the end of the half-cycle. The load current is able to be conducted through a second current path to the electrical load after the transition time until approximately the end of the half-cycle.