LED Control Circuit for TRIAC Dimmer Flicker Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
TRIAC dimmers cause flicker in LED light sources due to unstable duty cycles and current variability, which existing solutions like dummy loads and delayed activation fail to fully mitigate, leading to flicker and ripple issues.
Innovation Solution
A control circuit with switching circuits and comparators that manage a dummy current and LED current, stabilizing the duty cycle of the TRIAC dimmer by turning it off at a predetermined AC voltage, thereby reducing electricity consumption and flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dummy load is used to prevent TRIAC dimmer turn-off, then the TRIAC dimmer remains on, but the holding current varies from dimmer to dimmer causing unstable duty cycle and flicker
Solution Approach 1:
The patent uses a feedback mechanism where the controller monitors the actual current through the dummy load and adjusts the dummy load resistance dynamically to maintain a constant duty cycle. This closed-loop control ensures that variations in TRIAC holding current are compensated, stabilizing the duty cycle and eliminating flicker.
Solution Approach 2:
The patent implements dynamic adjustment of the dummy load resistance based on real-time current measurements. Rather than using a fixed resistance value, the system continuously adapts the dummy load characteristics to maintain stable operation across different TRIAC dimmer units and operating conditions.
2Reliability
If the dummy load turns on before the switching current falls below holding current, then the TRIAC dimmer is inhibited from turning off, but this causes variability in switching current during the AC cycle leading to flicker
Solution Approach 1:
The controller continuously monitors the current through the dummy load and uses this feedback to adjust the dummy load resistance, ensuring that the duty cycle remains constant and the LED current is stable, thereby preventing flicker while maintaining TRIAC on-state.
Solution Approach 2:
The patent changes the resistance parameter of the dummy load dynamically based on operating conditions. By adjusting the dummy load resistance, the system optimizes the current distribution to maintain stable LED operation and eliminate flicker caused by variable switching currents.
3Illumination intensity
If delayed activation of dummy load is used to mitigate flicker, then flicker is reduced, but ripple is created in the LED current
Solution Approach 1:
The system uses real-time current sensing and feedback control to adjust the dummy load activation and resistance values, ensuring that LED current remains stable without ripple while minimizing flicker. The feedback loop compensates for any current variations introduced by dummy load activation.
Solution Approach 2:
The patent implements dynamic control of the dummy load timing and resistance values based on real-time operating conditions. This dynamic adjustment ensures smooth current transitions without ripple while maintaining flicker reduction, adapting to different dimming levels and load conditions.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
In accordance with an embodiment, a control circuit for controlling a light emitting diode includes a first switching circuit having first and second inputs and an output and a second switching circuit having at least first and second inputs and an output, the first input coupled to the second input of the first switching circuit. Another embodiment includes a method for reducing flicker by generating an adjusted rectified voltage in response to a TRIAC dimmer signal from a TRIAC dimmer and a switching current in response to the adjusted rectified voltage being greater than a first reference voltage. The switching current is decreased in response to the adjusted rectified voltage becoming less than the first reference voltage. The TRIAC dimmer is turned off in response to decreasing the switching current.