LED Lighting Circuit Color Point Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Combined-color LED lighting arrangements face challenges in maintaining a constant color output due to temperature-dependent light output variations among different colored LEDs, leading to noticeable color shifts that affect the perceived quality of lighting, especially in applications like refrigerated display lighting and horticulture, where sensors and additional LEDs are used to compensate but increase costs.
Innovation Solution
A lighting circuit with primary and secondary sets of LEDs, where the flux ratio fixing arrangement maintains a constant ratio between the light outputs of the primary and secondary sets by using a first current source for the primary set, a second current source for the secondary set, and a DC constant voltage supply, along with a compensation resistor to adjust currents based on temperature-dependent reductions, ensuring the color point remains constant without the need for additional sensors or measurement circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If sensors and additional LEDs are used to compensate for color shifts, then color point stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies self-service by utilizing the inherent temperature-dependent forward voltage characteristics of the LED junctions themselves as the sensing mechanism. The circuit uses the LED's own electrical properties (forward voltage drop varying with temperature) to automatically regulate and compensate for color shifts, eliminating the need for external temperature sensors or complex control systems. This self-regulating approach maintains color point stability while minimizing device complexity.
2Stability of the object's composition
If sensors and additional LEDs are used to compensate for color shifts, then color point stability is improved, but manufacturing cost increases
Solution Approach 1:
The invention eliminates expensive external temperature sensors and complex control electronics by using the LED junction's inherent electrical characteristics for temperature compensation. The circuit requires only basic electronic components (resistors, capacitors, and the LED array itself), significantly reducing manufacturing costs while maintaining color point stability through automatic temperature-dependent current regulation.
3Illumination intensity
If LED current is increased to compensate for temperature-dependent light output reduction, then light output stability is improved, but energy consumption increases
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting the forward current through each LED based on its temperature-dependent forward voltage characteristics. As temperature increases and forward voltage decreases, the circuit automatically increases the current to maintain constant light output. This active parameter regulation ensures stable illumination intensity while optimizing energy consumption by providing exactly the current needed at each temperature condition, rather than using excessive fixed current.
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 maintains a consistent color point across varying temperatures, avoiding noticeable color shifts and reducing overall lighting costs by eliminating the need for expensive sensors and additional LEDs, while allowing for automatic and immediate light output correction.
Implementation Method 1
In any diode, the P/N junction activation energy levels exhibit temperature dependency, which can be quantified as a relationship between junction temperature and the drop in diode forward voltage.
Implementation Method 2
the drop in diode forward voltage. This relationship will depend to a large extent on the material used for the diode.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention describes a lighting circuit (1) comprising a primary set (11, 13) of light-emitting diodes (110, 130) of a first color and a secondary set (12) of light-emitting diodes (120) of a further color; wherein a temperature-dependent reduction in light output of the primary set (11, 13) of light-emitting diodes (110, 130) is greater than a temperature- dependent reduction in light output of the secondary set (12) of light-emitting diodes (120); and a flux ratio fixing arrangement realized to maintain an essentially constant ratio between the light output of the primary set (11, 13) and the light output of the secondary set (12) during a temperature-dependent overall reduction in light output of the light-emitting diodes (110, 120, 130) of the lighting circuit (1). The invention also describes a lighting arrangement (4, 4') for illuminating objects (40, 41) with light of a predefined color point, which lighting arrangement (4, 4') comprises at least one such lighting circuit (1), wherein the light-emitting diode sets(11, 12, 13) of a lighting circuit (1) are chosen to emit, in combination, light of the predefined color point at an initial temperature, and wherein the flux ratio fixing arrangement of the lighting circuit (1) is realized to maintain that color point at a temperature higher that the initial temperature.