AC LED Dimmer Using Pulse Width Modulation Control
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Solution Overview
Problem
Conventional dimmers for AC LEDs have limited dimming ranges due to Triac drive voltage and R/C phase controller characteristics, leading to flickering and excessive harmonic generation.
Innovation Solution
A dimmer system that includes a switch, current detector, and controller for AC LEDs, using pulse width modulation to adjust the AC voltage and current, eliminating the need for fixed phase angles and reducing harmonic generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a Triac switch and R/C phase controller are used to dim AC LEDs, then the dimming function is achieved, but the dimming range is limited and flickering occurs
Solution Approach 1:
The patent changes the control parameter from fixed phase angle to variable pulse width modulation duty cycle. The controller adjusts the duty cycle of switching control signals to achieve continuous dimming without the fixed phase angle limitations of Triac, thereby expanding the dimming range and eliminating flickering caused by abrupt switching.
Solution Approach 2:
The patent replaces the mechanical Triac switch with an electronic switching device controlled by pulse width modulation. This substitution allows for more precise and continuous control of power delivery to the AC LED, eliminating the abrupt switching characteristics of Triac that cause flickering.
2Ease of operation
If a Triac switch is abruptly switched by gate turn-on signal, then switching control is achieved, but excessive harmonics are generated
Solution Approach 1:
The patent employs periodic pulse width modulation switching control instead of abrupt Triac switching. The switching device is controlled by periodic pulses with variable duty cycles, which smoothly adjust power delivery and reduce harmonic generation while maintaining effective switching control.
Solution Approach 2:
The patent incorporates feedback mechanisms where the controller receives information about the actual power delivery and adjusts the pulse width modulation duty cycle accordingly. This feedback control enables smoother switching transitions and reduces harmonic distortion compared to open-loop Triac control.
3Device complexity
If fixed phase angle control is used in Triac dimmer, then dimming control is simplified, but output voltage varies with AC voltage changes causing flickering
Solution Approach 1:
The patent uses feedback control where the controller monitors the actual power delivery to the AC LED and adjusts the pulse width modulation duty cycle to maintain stable output. This feedback mechanism compensates for AC voltage variations and maintains consistent lighting output, eliminating the flickering problem caused by fixed phase angle control.
Solution Approach 2:
The patent transitions from static fixed phase angle control to dynamic pulse width modulation control. The duty cycle is dynamically adjusted based on actual operating conditions and AC voltage variations, enabling the system to adapt to changing conditions and maintain stable output voltage and lighting performance.
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 system provides a wider dimming range with reduced flickering and harmonic generation, offering more stable and efficient control of AC LED brightness.
Implementation Method 1
switching an alternating current (AC) input voltage at a high speed under pulse width modulation control to adjust the root-mean-square (RMS) value of the AC input voltage
Data Source
AI summary
Exemplary embodiments of the present invention relate to a dimmer for a light emitting device using an alternating (AC) voltage source. The dimmer includes a switch to be switched in response to a switching control signal and to deliver an AC voltage of an AC voltage source to the light emitting device, a current detector to detect an electric current to be provided to the light emitting device and to output a current detection signal, and a controller to output the switching control signal in response to a dimming control signal and the current detection signal.