LED Warm On Dim Circuit Using White and Deep Red LEDs
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Solution Overview
Problem
Existing LED dimming systems fail to emulate the dimming performance of incandescent lighting, particularly in maintaining coordinated-color-temperature (CCT) as a function of dim level, and are sensitive to temperature variations and aging, requiring complex circuitry and microcontroller control.
Innovation Solution
A circuit using white LEDs and deep red LEDs, with current control mechanisms that mimic the CCT and brightness of incandescent lighting, is insensitive to temperature and aging, and does not require a microcontroller or spectral sensor, utilizing a controllable constant current sink or switch-mode power supply for current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple colored LEDs (RGB) are used to achieve coordinated CCT dimming, then the CCT emulation of incandescent lighting is improved, but the device complexity and cost increase due to required microcontroller control and multiple LED types
Solution Approach 1:
The patent extracts only the essential function needed for warm-on-dim effect by using a single red LED alongside white LEDs, removing the need for complex RGB mixing control while still achieving CCT emulation through selective red LED activation at lower dim levels
Solution Approach 2:
The patent copies the visual effect of incandescent warm-on-dim behavior by adding red LED emission to complement white LEDs at specific dim levels, reproducing the characteristic color temperature shift without copying the entire incandescent system complexity
2Illumination intensity
If red LEDs are used to achieve warm-on-dim effect, then the CCT coordination is improved, but the reliability decreases due to significant light output changes with temperature and aging
Solution Approach 1:
The patent incorporates feedback mechanisms through ambient light sensors and temperature sensing to dynamically adjust red LED drive current, compensating for temperature-induced light output changes and aging effects to maintain stable CCT coordination
Solution Approach 2:
The patent dynamically changes the drive current parameter to the red LED based on detected temperature and ambient light conditions, adjusting the current level to compensate for the red LED's significant light output variations while maintaining desired CCT effect
3Ease of operation
If microcontroller control is implemented to manage multiple LED currents, then the dimming performance is improved, but the ease of manufacture and cost worsen due to additional components and firmware complexity
Solution Approach 1:
The patent implements self-service control where the red LED circuit automatically adjusts its operation based on ambient light sensor input and temperature feedback, eliminating the need for complex microcontroller firmware while achieving adaptive warm-on-dim performance
Solution Approach 2:
The patent makes the red LED serve multiple functions: providing warm-on-dim effect, enabling ambient light sensing calibration, and offering temperature compensation, thereby reducing overall system complexity while maintaining dimming 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 solution effectively emulates the dimming performance of incandescent lighting, maintaining CCT and brightness across various dim levels without the need for complex control systems or additional sensors, resulting in a cost-effective and compact LED dimming solution.
Implementation Method 1
Light emitting diodes (LEDs) are semiconductor light sources that are efficient, monochromatic, and are capable of having their light output controlled by the current applied to them
Implementation Method 2
These work by applying a DC current through them. The amount of light they emit is approximately proportional to the magnitude of the current
Implementation Method 3
The amount of light they emit is approximately proportional to the magnitude of the current. It is thus common to dim LEDs by controlling their current as a function of the dim level
Data Source
AI summary
A method and circuit to use light-emitting diodes to emulate the dimming performance of incandescent lighting, and more particularly, to making a circuit that uses only white and deep red light-emitting diodes to achieve a coordinated-color-temperature as a function of dim level that is close to that of an incandescent light being similarly dimmed.