LED Dimming Control via Variable Frequency Modulation
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Solution Overview
Problem
Existing methods for dimming and color mixing LEDs, such as Pulse Width Modulation, Variable Frequency Modulation, Bit Angle Modulation, and Pulse Amplitude Modulation, face challenges like noticeable intensity steps, wide dynamic frequency ranges, and electromagnetic compatibility issues, leading to inefficient control and potential color shifting.
Innovation Solution
A method and apparatus that control LEDs by varying both on and off times and periods, using a controller to translate dimming and color mixing information into load control signals, which are then transmitted to current sources, allowing for non-constant operation and maintaining a narrow dynamic range of dimming frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Pulse Width Modulation is used for LED dimming, then lighting intensity can be controlled, but noticeable intensity steps occur at low intensity levels
Solution Approach 1:
The patent applies dynamics by making the PWM frequency variable rather than fixed. The controller dynamically adjusts the PWM frequency based on the desired dimming level, using higher frequencies for higher intensity levels and lower frequencies for lower intensity levels. This dynamic frequency adjustment allows for smoother intensity transitions and reduces noticeable steps at low intensity levels while maintaining effective dimming control.
2Illumination intensity
If Variable Frequency Modulation is used for LED dimming, then dimming current can be adjusted, but wide dynamic frequency range is required causing EMC issues
Solution Approach 1:
The patent applies parameter changes by modifying the PWM frequency based on the dimming level. Instead of using a wide dynamic frequency range, the system adjusts the frequency parameter adaptively - using higher frequencies at higher intensity levels and lower frequencies at lower intensity levels. This controlled parameter adjustment achieves effective dimming while keeping frequency variations within EMC-compatible limits.
3Illumination intensity
If LED current is varied to control intensity, then dimming is achieved, but color shifting occurs
Solution Approach 1:
The patent applies periodic action by using PWM to control LED intensity. Instead of continuously varying the current (which causes color shifting), the system uses periodic switching at high frequencies. The LED is turned on and off in rapid succession, creating a duty cycle that controls perceived intensity while maintaining constant current during conduction periods. This periodic action preserves color stability while achieving effective dimming.
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 enables smooth and efficient dimming and color mixing of LEDs, reducing noticeable intensity steps and maintaining a stable output frequency, while minimizing electromagnetic compatibility issues and preventing color shifting.
Implementation Method 1
The creation of light emitting diodes (LEDs) has also helped enhance the field lighting technology
Data Source
AI summary
There is provided apparatus for controlling a set of light emitting diodes (LEDs) comprising at least one current source for powering the set of LEDs; a main controller for receiving dimming and/or color mixing information and for translating the information into LED control information and transmitting the LED control information to control the set of LEDs; wherein the LED control information is based on and off times.