Switch Mode Regulator Dimming Control for LED Light Output
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Solution Overview
Problem
Current dimming methods for Solid State Light (SSL) sources, such as LEDs and OLEDs, face challenges in achieving high precision dimming over wide current ranges, often resulting in sharp intensity or color steps, especially at low light levels, due to inefficient control of current flow and modulation techniques.
Innovation Solution
The proposed solution involves a control system that varies the output power signal by adjusting the ratio of on and off states in a switch mode regulator, using a combination of open and closed control loops, and a digital power supply with high-resolution PWM outputs and feedback sensors to maintain continuous conduction mode, enabling precise current and voltage regulation and extended dimming range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional dimming methods (CCR or PWM) are used to reduce current through SSL devices, then light output can be reduced, but sharp intensity steps and poor dimming resolution occur at low light levels
Solution Approach 1:
The patent applies periodic pulsed current action instead of continuous current reduction. By delivering current in precisely timed pulses rather than continuously, the system achieves smooth dimming at low light levels while maintaining high dimming resolution. The pulsed nature allows precise control of average current without the sharp steps that occur with conventional methods.
Solution Approach 2:
The system dynamically adjusts the switching regulator operation between continuous conduction mode and discontinuous conduction mode based on the desired dimming level. This dynamic adaptation allows optimal performance across the full dimming range, maintaining high resolution at low intensities while preserving efficiency at higher intensities.
2Use of energy by moving object
If constant current reduction is used to dim SSL devices, then power consumption is reduced, but efficiency deteriorates due to excessive current flow at intermediate dimming levels
Solution Approach 1:
The switching regulator delivers current in periodic pulses rather than continuously. This allows the system to reduce average power consumption by minimizing the duration current flows through the SSL devices, while maintaining high efficiency by ensuring that when current does flow, it does so in an optimized manner through the switching regulator.
Solution Approach 2:
The system maintains continuous conduction mode operation of the switching regulator even during dimmed states, ensuring that the regulator operates in its most efficient range continuously. This prevents the efficiency losses that occur when the regulator operates in discontinuous modes or when excessive current is dissipated as heat during intermediate dimming levels.
3Ease of operation
If PWM dimming is used to control light output, then dimming capability is achieved, but flicker and instability occur at low dimming levels
Solution Approach 1:
The system incorporates feedback control that monitors the actual current through the SSL devices and adjusts the pulsed current delivery accordingly. This feedback mechanism eliminates flicker and instability by ensuring precise control of the average current level, compensating for variations in device characteristics and maintaining stable light output even at very low dimming levels.
Solution Approach 2:
The patent replaces conventional PWM mechanical switching with a more sophisticated electronic control system that uses precise pulse timing and feedback. This substitution eliminates the flicker inherent in simple PWM by using higher frequency switching and intelligent pulse distribution, achieving stable dimming control that conventional mechanical or simple electronic PWM cannot provide.
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 allows for smooth, high-resolution dimming across a wide dynamic range, minimizing flicker and achieving stable light output even at low intensities, while also enabling data transmission through the lighting system by modulating the power signal.
Implementation Method 1
LED, OLED and SSDL based illumination systems have been devised which, through the use of multiple light emitting devices having discrete wavelengths/colours, can produce a variety of colours and intensities
Implementation Method 2
varying the actual or time-averaged forward current through the light emitting device load over an acceptable range in order to provide dimming capabilities
Data Source
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AI summary
A control system arranged to provide dimming control of light output of one or more light emitting device (124), the control system comprising: a switch mode regulator (91) arranged to provide an output power signal to the one or more light emitting device (124), and to vary the output power signal; one or more feedback sensors (304) arranged to measure characteristic parameters of the output power signal, the characteristic parameters comprising at least one of: current, voltage and power; and a controller arranged to: when a characteristic parameter of the output power signal is above a threshold (210), vary the output power signal in a closed control loop, based on feedback from the one or more feedback sensors (304); and when the characteristic parameter of the output power signal is below the threshold (210), vary the output power signal in an open control loop.