AC-Driven LED Lighting Apparatus Flickering Prevention
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Solution Overview
Problem
AC-driven LED lighting apparatuses face challenges in achieving stable and linear dimming control due to unstable drive voltage and flickering issues when using TRIAC dimmers, particularly during sequential driving of LED groups.
Innovation Solution
The AC-driven LED lighting apparatus employs a phase cut reference value to block drive current to all LED groups at dimming levels below a preset threshold, using a comparator and drive current controller to manage LED group activation and deactivation, preventing flickering and improving dimming compatibility with TRIAC dimmers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sequential driving method is used to control LED groups, then power consumption is reduced and dimming function is achieved, but drive voltage becomes unstable due to internal impedance of AC power supply line and dimmer
Solution Approach 1:
The patent applies preliminary action by detecting the phase cut reference point before LED groups are turned on or off. The controller identifies the zero-crossing point of the AC waveform and uses this timing information to coordinate the switching of LED groups, ensuring that transitions occur at optimal moments in the AC cycle when voltage fluctuations are minimized. This preliminary detection and timing coordination prevents the drive voltage instability that would otherwise occur during LED group transitions.
2Illumination intensity
If LED groups are turned on or off during sequential driving, then dimming control is achieved, but flickering occurs due to drive voltage instability
Solution Approach 1:
The patent implements feedback by continuously monitoring the AC input voltage waveform and detecting the phase cut reference point (zero-crossing point) in real-time. This feedback information is used by the controller to dynamically adjust the timing of LED group switching operations. By basing the switching decisions on actual detected voltage conditions rather than fixed timing, the system achieves smooth dimming transitions without flickering, as the LED groups are switched only when the voltage conditions are favorable.
3Device complexity
If AC-driven LED lighting apparatus uses rectified voltage only, then circuit design is simplified, but dimming function cannot be realized with linearity
Solution Approach 1:
The patent applies parameter changes by utilizing the temporal characteristics of the AC voltage waveform rather than changing the circuit topology. Instead of adding complex dimming circuits, the controller varies the duration of LED group operation within each AC half-cycle based on the detected phase cut angle. By changing the operational timing parameter (how long LEDs remain on during each voltage cycle) rather than the circuit structure, the system achieves linear dimming control while maintaining simple rectified voltage circuitry.
Data Source
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AI summary
Disclosed is a dimmable alternating current-driven light emitting element lighting apparatus. The disclosed alternating current-driven light emitting element lighting apparatus of the present invention comprises: a triac dimmer for generating a modulated alternating current voltage by modulating a phase of alternating current power according to a selected level of dimming; a rectifying unit for generating drive voltage by full-wave-rectifying the alternating current voltage having the phase modulated by the triac dimmer; a dimming level detection unit for detecting a dimming level according to the drive voltage; a phase cut reference setting unit for setting a phase cut reference value to be compared with the detected dimming level; and a light emitting element driving module for constant-current-controlling a plurality of light emitting element groups by comparing the detected dimming level with the phase cut reference value, wherein the light emitting element driving module comprises a light emitting element current blocking unit for blocking a drive current supplied to the plurality of lighting emitting element groups when the dimming level is lower than the phase cut reference value. Thus, the present invention can prevent flickering by blocking a drive current of the entirety of the plurality of light emitting element groups at a dimming level lower than a preconfigured phase cut reference value, and can improve the compatibility of a dimmer by improving dimming characteristics changing according to characteristics of the triac dimmer.