Phase-Cut Dimmer Circuit Eliminates Zero Crossing Detector
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Solution Overview
Problem
Existing dimming circuits for reference-free user interfaces, such as rocker-type interfaces, are complex and expensive, and they often rely on zero crossing detectors that can be inaccurate due to noise and frequency drift in AC Mains voltage, leading to undesirable light variations.
Innovation Solution
A phase-cut dimmer circuit that uses a bidirectional triode thyristor triggered by a controller, which adjusts the resistance of a variable resistance element to control the light output, eliminating the need for a zero crossing detector and incorporating a rocker-type user interface for intuitive dimming control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a zero crossing detector is used to trigger the TRIAC in existing dimming circuits, then the triggering time can be detected, but the detection becomes inaccurate due to noise and frequency drift in AC Mains voltage, leading to undesirable light variations
Solution Approach 1:
The patent extracts and removes the zero crossing detector from the dimming circuit, replacing it with a fixed time delay circuit that triggers the TRIAC based on a predetermined time period after the AC Mains voltage becomes positive, rather than detecting the zero crossing point. This eliminates the component that is sensitive to noise and frequency drift.
Solution Approach 2:
The patent replaces the complex and expensive zero crossing detector with a simple fixed time delay circuit using basic components (resistors, capacitors, and logic gates), which is more reliable and less sensitive to electrical noise and frequency variations in the AC Mains supply.
2Ease of operation
If a rocker-type user interface is used for dimming control, then the user interface is reference-free and intuitive, but the existing dimming circuits become complex and expensive
Solution Approach 1:
The patent removes the complex microcontroller-based control circuitry that is typically required to interface with rocker-type user interfaces, replacing it with a simplified fixed time delay circuit that can be controlled by basic logic signals from the rocker switch, thereby reducing overall circuit complexity and cost.
Solution Approach 2:
The patent replaces the electronic/microcontroller-based control system with a simpler logic circuit implementation that uses basic digital logic gates and timing circuits, making the system more suitable for integration with simple mechanical rocker-type user interfaces while reducing complexity.
3Illumination intensity
If the voltage V(load) is cutoff for a larger portion of each half cycle to achieve deeper dimming, then more dimming is achieved, but less power is delivered to the load
Solution Approach 1:
The patent implements a fixed time delay circuit that dynamically adjusts the TRIAC triggering time based on a predetermined time period, creating a consistent phase angle control that delivers a stable and predictable amount of power to the load while achieving the desired dimming effect, rather than using extreme cutoff portions.
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 provides a cost-effective and stable dimming solution for reference-free user interfaces, allowing precise control of light output without the drawbacks of existing systems, including reduced complexity and improved resistance to noise and frequency variations.
Implementation Method 1
a bidirectional triode thyristor configured to supply an AC input voltage to one or more lighting units when the bidirectional triode thyristor is triggered
Implementation Method 2
The triggering circuit includes a capacitor and a variable resistance element. The resistance of the variable resistance element is configured to set a time constant during each half cycle of a period of the AC input voltage for charging the capacitor to a triggering voltage
Implementation Method 3
The resistance of the variable resistance element is configured to set a time constant during each half cycle of a period of the AC input voltage for charging the capacitor to a triggering voltage which triggers the bidirectional triode thyristor
Data Source
AI summary
A device (500) and method (600) control a dimming level of one or more lighting units (130) in response to a user interaction with a reference-free user interface (410), such as a rocker-type interface. A bidirectional triode thyristor (460) supplies an AC input voltage (110) to the lighting unit(s) when it is triggered. A triggering circuit (510) triggers the bidirectional triode thyristor. The triggering circuit includes a capacitor (554) and a variable resistance element (510) which sets a time constant during each half cycle of a period of the AC input voltage for charging the capacitor to a triggering voltage which triggers the bidirectional triode thyristor. The resistance of the variable resistance element is controlled in response to a dimming input signal from the reference-free user interface. The dimming input signal indicates only relative changes in the output level of the lighting unit(s) with respect to the present level.