Dimmable Lighting Control Module for Flicker-Free Phase Cut Dimming
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Solution Overview
Problem
Solid state lighting systems face challenges in dimming control, particularly with phase cut dimming, due to rapid response times of LEDs and variations in input signals, leading to flicker and unreliable detection of dimming presence, and resulting in excessive dimming or failure to reach full output.
Innovation Solution
A dimming control module that detects toggling of the power signal and adjusts the brightness of the light source, using a microcontroller and AC detector to generate dimming control signals, including DALI and 0-10V signals, to control the current supply to the LEDs, allowing for smooth dimming without external dimming systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase cut dimming is used with solid state lighting, then dimming control is achieved, but flicker occurs and detection of dimming presence becomes unreliable
Solution Approach 1:
The system dynamically adapts its detection threshold based on the minimum expected pulse width rather than using a fixed threshold. The microcontroller measures the actual minimum pulse width from the rectified AC signal and sets the detection threshold to 50% of this measured value, allowing the system to dynamically adjust to variations in line frequency and dimming conditions.
Solution Approach 2:
The invention changes the detection parameter from a fixed threshold to a variable threshold that is 50% of the measured minimum pulse width. This parameter change allows the system to accommodate variations in pulse width caused by different line frequencies (50Hz vs 60Hz) and dimming positions, resolving the unreliability in dimming detection.
2Illumination intensity
If pulse width of AC signal is reduced for dimming, then light output decreases, but LEDs may never reach full output and excessive dimming occurs
Solution Approach 1:
The system performs preliminary measurement of the minimum pulse width from the rectified AC signal before setting the dimming detection threshold. By measuring the actual minimum pulse width first and then setting the threshold to 50% of this value, the system ensures that normal variations in pulse width will not be misinterpreted as dimming commands, allowing LEDs to reliably reach full output when required.
Solution Approach 2:
The microcontroller continuously monitors the AC signal pulse width and uses this feedback to dynamically adjust the detection threshold. The feedback mechanism ensures that the threshold remains at 50% of the measured minimum pulse width, preventing false dimming detection and ensuring that LEDs can achieve full output when the switch is in the on position.
3Ease of operation
If direct control of LEDs by AC pulse width is used, then dimming is achieved, but ability to dim below certain level is limited and power supply cannot be energized
Solution Approach 1:
The invention introduces an intermediary detection mechanism that measures the minimum pulse width and uses it to set an appropriate threshold (50% of minimum). This intermediary step allows the system to distinguish between normal pulse width variations and actual dimming commands, enabling reliable detection of dimming presence even at low dimming levels where the power supply might otherwise fail to energize.
Data Source
AI summary
A lighting apparatus includes a light source, a power input coupled to the light source, and a dimming control module coupled to the power input and the light source. The dimming control module is configured to change a brightness level of the light source in response to toggling of a power signal supplied at the power input. Related methods of operating a lighting apparatus are also disclosed.