Two-Wire Dimmer Gate Control for Low-Power LED Loads
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Solution Overview
Problem
Existing two-wire dimmer switches struggle to effectively control the intensity of high-efficiency light sources like LED and CFL lamps, due to their high input impedances and varying impedance characteristics, which can lead to improper power regulation and perceptible illumination when the light source should be off.
Innovation Solution
A two-wire load control device featuring a thyristor with a gate coupling circuit and control circuit that provides a pure phase-cut waveform to the lamp, independent of its specific characteristics, allowing for improved noise immunity and reduced susceptibility to cross-talk, and includes a controllable switching circuit to manage the gate current and prevent premature conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If existing two-wire dimmer switches are used to control high-efficiency light sources, then the device can be installed with simple two-wire connection, but the light source exhibits perceptible illumination when it should be off due to high input impedance and varying impedance characteristics
Solution Approach 1:
The patent introduces an artificial load circuit as an intermediary component between the dimmer switch and the high-efficiency light source. This artificial load circuit simulates the impedance characteristics of traditional incandescent loads, providing a consistent impedance profile that prevents perceptible illumination when the light should be off, while maintaining the simple two-wire installation configuration.
2Productivity
If forward phase-control dimming technique is used with high-efficiency light sources, then the dimmer can control power delivery, but the high input impedance of LED/CFL lamps causes improper power regulation and perceptible illumination when off
Solution Approach 1:
The patent changes the impedance parameter of the load by introducing an artificial load circuit that maintains a consistent impedance profile regardless of the actual light source characteristics. This parameter change ensures that the forward phase-control dimming technique operates with the expected impedance conditions, achieving precise power regulation and eliminating perceptible illumination when the light should be off.
3Extent of automation
If the dimmer switch conducts small timing current through the load when off, then the control circuit can operate, but the light source may be illuminated to a perceptible level
Solution Approach 1:
The patent segments the current path by introducing a separate artificial load circuit that is always connected to the dimmer switch, regardless of whether the light source is on or off. This segmentation allows the control circuit to conduct its small timing current through the artificial load rather than through the high-efficiency light source, preventing perceptible illumination while maintaining control circuit operation.
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 precise control of power delivery to high-efficiency light sources, ensuring accurate intensity adjustment and improved performance with LED and CFL lamps, while reducing noise and cross-talk interference.
Implementation Method 1
a thyristor having first and second main load terminals adapted to be coupled in series electrical connection between an alternating-current (AC) power source and an electrical load for conducting a load current from the AC power source to the electrical load, and a gate that conducts a gate current to render the thyristor conductive
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A two-wire load control device (such as, a dimmer switch) for controlling the amount of power delivered from an AC power source to an electrical load (such as, a high-efficiency lighting load) includes a thyristor coupled between the source and the load, a gate coupling circuit coupled between a first main load terminal and the gate of the thyristor, and a control circuit coupled to a control input of the gate coupling circuit. The control circuit generates a drive voltage for causing the gate coupling circuit to conduct a gate current to thus render the thyristor conductive at a firing time during a half cycle of the AC power source, and to allow the gate coupling circuit to conduct the gate current at any time through approximately the remainder of the half cycle, where the gate coupling circuit conducts approximately no net average current to render and maintain the thyristor conductive.