Thyristor Gate Timing for Two-Wire LED Dimmer Latching
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Solution Overview
Problem
Existing two-wire dimmer switches struggle to effectively control the intensity of high-efficiency lighting loads like LED and CFLs, as they either fail to conduct sufficient current to latch thyristors or cause unintended illumination due to charging currents, especially when coupled with load regulation devices having varying impedances.
Innovation Solution
A load control device using a thyristor with a gate coupling circuit and control circuit to manage conduction times, ensuring sufficient current is conducted to latch the thyristor and prevent unintended illumination, while accommodating capacitive impedances of load regulation devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a two-wire dimmer switch uses a thyristor to control power delivery, then the device can regulate lighting intensity, but it fails to conduct sufficient current to latch the thyristor when controlling high-efficiency loads
Solution Approach 1:
The patent introduces an artificial load circuit as an intermediary element that provides additional current path to ensure sufficient current flows through the thyristor for reliable latching. This artificial load acts as a mediator between the dimmer control circuit and the high-efficiency lighting load, solving the current insufficiency problem without requiring modifications to the main lighting circuit.
Solution Approach 2:
The patent modifies the electrical parameters of the circuit by adding a parallel artificial load with specific resistance value. This parameter change ensures that the total current drawn from the AC source is sufficient to latch the thyristor, while the dimmer control can still regulate the current to the actual lighting load for intensity control.
2Ease of operation
If the dimmer switch conducts current through the load regulation device, then intensity control is achieved, but unintended illumination occurs due to charging currents
Solution Approach 1:
The patent implements preliminary action by ensuring the thyristor is fully latched before the dimmer control begins regulating current to the load. The artificial load circuit provides immediate current path upon thyristor triggering, ensuring reliable conduction establishment before the dimmer's phase-angle control reduces the current to the lighting load, thereby preventing unintended illumination during the transition phase.
3Adaptability or versatility
If the load control device accommodates varying impedances of load regulation devices, then compatibility with different lighting loads is improved, but the device complexity increases
Solution Approach 1:
The patent achieves universality by designing the artificial load circuit to work with any high-efficiency lighting load regardless of its specific impedance characteristics. The parallel artificial load provides a consistent current path that complements various load regulation devices (LED drivers, CFL ballasts, etc.), making the dimmer switch universally compatible without requiring impedance-matching circuits or load-specific configurations.
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 allows precise control of high-efficiency lighting loads without requiring a neutral connection, ensuring consistent intensity regulation and preventing unwanted illumination, even with varying load impedances.
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.