LED Control Unit Duty Cycle and Current Adjustment
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Solution Overview
Problem
Conventional LED lighting systems face inefficiencies in power consumption and dimming resolution, particularly at lower intensities, due to limitations in duty cycle modulation and current control, leading to noticeable changes in brightness and potential overheating.
Innovation Solution
A lighting system comprising an LED assembly with serially connected LED units, a switched mode power supply, and a control unit that adjusts duty cycles and current levels to achieve desired brightness while optimizing power efficiency, using a capacitor in parallel to mitigate current ripple and enhance dimming resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If duty cycle modulation is used to control LED intensity, then power consumption is reduced at lower intensities, but dimming resolution deteriorates and brightness changes become noticeable
Solution Approach 1:
The LED assembly is divided into multiple LED units that can be independently controlled. By segmenting the LED assembly and controlling each unit with adjusted duty cycles based on reduced current, the system achieves finer dimming resolution while maintaining energy efficiency at lower intensities.
Solution Approach 2:
The control unit dynamically adjusts both the current level and duty cycle for each LED unit based on the desired output characteristic. This dynamic parameter adjustment allows the system to optimize between power consumption and dimming resolution across different intensity levels.
2Use of energy by moving object
If duty cycle is reduced to lower LED intensity, then power consumption decreases, but the change in intensity becomes more noticeable and less smooth
Solution Approach 1:
The system changes multiple parameters simultaneously - both the current level and duty cycle are adjusted together rather than just the duty cycle. This dual parameter adjustment allows for smoother brightness transitions while maintaining power efficiency, as the reduced current compensates for the reduced duty cycle to prevent noticeable brightness steps.
3Reliability
If nominal current is maintained for LED operation, then LED lifespan is ensured, but power losses increase at reduced brightness levels
Solution Approach 1:
The control unit dynamically determines an optimized current level for the switched mode power supply based on the desired output characteristic and operating conditions. This dynamic current adjustment allows the system to operate LEDs at reduced current levels during dimmed states, reducing power losses while maintaining adequate current to ensure LED lifespan through proper thermal management and controlled operation.
Solution Approach 2:
The system optimizes multiple operating parameters including current level, duty cycle, and switching frequency of the switched mode power supply. By changing these parameters adaptively based on the desired brightness level, the system reduces power losses at reduced brightness while maintaining LED reliability through controlled stress conditions.
Data Source
AI summary
A lighting system comprising an LED assembly that comprises a first and second LED unit said LED units being serial connected is described. The system comprises; □ a switched mode power supply for powering the LED assembly; □ a control unit for controlling the LED assembly 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 the respective first and second 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 or the largest of the duty cycles, □ provide output data for the LED assembly and the switched mode power supply based on the adjusted first and second duty cycles and the reduced current. The LED assembly of the system further comprises a capacitor connectable in parallel to the first and second LED units by operating a switch connected in series with the capacitor and wherein the control unit is arranged to control the switch based on at least one of the reduced current and the input signal.