Phase-Angle Dimming Control for Capacitive Loads
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Solution Overview
Problem
Existing phase control methods for dimming lamps with capacitive behavior, such as LEDs and compact fluorescent lamps, face challenges in maintaining stable dimming and sufficient voltage supply, often resulting in flickering due to phase shifts and unstable states, especially in two-wire systems.
Innovation Solution
The method involves shifting the start time of the charging process for the ignition capacitor by a specific period within the half-wave, comparing the actual charging time with a reference time, and adjusting it to maintain a constant charging time, ensuring stable power supply and reducing flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phase-angle control method is used to dim light sources, then brightness adjustment is achieved, but flickering occurs due to phase shifts between detected and actual zero crossings
Solution Approach 1:
The patent measures the actual charging time of the ignition capacitor and compares it with a target charging time. Based on this feedback, the release time of the charging process is dynamically adjusted to compensate for phase shifts between detected and actual zero crossings, eliminating flickering and ensuring stable dimming operation.
Solution Approach 2:
The patent replaces the conventional potentiometer-based manual adjustment mechanism with an automated electronic control system. The release time is adjusted electronically based on measured charging time, eliminating the need for manual mechanical adjustment and providing more precise and stable control.
2Productivity
If charging time is reduced for higher brightness levels, then response speed improves, but voltage supply to dimmer becomes insufficient
Solution Approach 1:
The patent shifts the release time of the charging process to start earlier in the half-wave, before the detected zero crossing. This preliminary action ensures that the ignition capacitor has sufficient charging time even at higher brightness levels, maintaining adequate voltage supply to the dimmer while still achieving fast response.
3Adaptability or versatility
If phase-angle control is applied to capacitive loads, then dimming function is enabled, but inrush currents occur during switch-on
Solution Approach 1:
The patent shifts the release time to start the charging process before the detected zero crossing. This preliminary action allows the ignition capacitor to be partially charged in advance, reducing the inrush current that occurs when the load is switched on while still enabling dimming functionality for capacitive loads.
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
This approach ensures reliable dimming and power supply to capacitive loads, reducing flickering and maintaining consistent brightness across different dimmer settings, while also protecting the dimmer from inrush currents by controlling the load differently during switch-on.
Implementation Method 1
an R/C element is preset accordingly to generate the phase angle that determines the brightness of the light source
Data Source
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Figure 3
AI summary
A method for dimming at least one light source in two-wire operation according to the phase-angle control method is implemented in such a way that, depending on the level of the voltage to be supplied, the voltage to the light source is only switched on from a certain phase angle within a half-wave and is switched off again at the next zero crossing for the coming half-wave, and an R/C element is preset accordingly to generate the phase angle that determines the brightness of the light source.This method provides that: - the charging process of the capacitor of the R/C circuit is started by a release that is shifted in time from the actual zero crossing of the half-wave, - the time required to charge the ignition capacitor of the R/C circuit is recorded, - the recorded time is compared as the actual charging time with a reference charging time as the target charging time, and - if a deviation is detected between the actual charging time and the target charging time, the charging start time is changed in such a way that a better agreement with the reference time is achieved.