LED Control Unit Optimizing Dimming Resolution
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Solution Overview
Problem
Conventional LED lighting systems face inefficiencies in power consumption and dimming resolution, especially at lower intensities, due to the limitations of existing control methods that rely solely on duty cycle modulation, leading to noticeable changes in brightness and potential power inefficiencies.
Innovation Solution
A control unit that adjusts the duty cycles and current of LED units in a serial connection to optimize power efficiency and dimming resolution by reducing the output current and increasing the duty cycles, allowing for higher brightness resolution and smoother dimming across a range of intensities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If duty cycle modulation is used to control LED intensity, then lighting intensity control is achieved, but dimming resolution deteriorates at lower intensities
Solution Approach 1:
The patent changes the operating parameters of the LED units by adjusting both duty cycle and forward current simultaneously. Instead of relying solely on duty cycle modulation, the system varies the forward current parameter to compensate for the loss of dimming resolution at low duty cycles, thereby maintaining precise intensity control across the full brightness range.
Solution Approach 2:
The control unit dynamically adjusts both duty cycle and forward current based on the desired output characteristic. The system transitions from static duty cycle control to dynamic dual-parameter control, where the forward current is adapted in real-time according to the operating point to optimize dimming resolution.
2Illumination intensity
If duty cycle is reduced to lower LED intensity, then brightness is reduced, but power efficiency deteriorates
Solution Approach 1:
The system changes from single-parameter (duty cycle) control to dual-parameter control by simultaneously adjusting forward current and duty cycle. This allows the system to maintain higher power efficiency by operating LEDs at optimized current levels rather than relying solely on reduced duty cycles, which cause inefficiencies in the power supply operation.
Solution Approach 2:
The control unit pre-calculates the optimal combination of duty cycle and forward current to achieve the desired brightness while maximizing power efficiency. By determining the largest duty cycle among LED units and calculating the appropriate reduced current beforehand, the system avoids inefficient operating conditions.
3Illumination intensity
If duty cycle is reduced to achieve lower intensity, then brightness is controlled, but dimming smoothness deteriorates
Solution Approach 1:
The patent introduces forward current as an additional control parameter to complement duty cycle modulation. By varying both parameters, the system achieves finer granularity in brightness adjustment, especially at low intensity levels where duty cycle alone provides insufficient resolution. This results in smoother dimming transitions that are more perceptually uniform.
Data Source
AI summary
A control unit for a LED assembly includes a first and second LED unit, the LED units being serial connected. The LED assembly, in use, is powered by a switched mode power supply. The control unit being arranged to receive an input signal representing a desired output characteristic of the LED assembly, determine a first and second duty cycle for respective LED units associated with a nominal current of the switched mode power supply, for providing the desired output characteristic, determine the largest of the first and second duty cycles for respective LED units, determine a reduced current based on at least the largest of the duty cycles, adjust the first and second duty cycle for respective LED units based on the reduced current, and provide an output signal for the LED assembly and the switched mode power supply based on the adjusted first and second duty cycles and the reduced current for obtaining the desired characteristic.