Solid State Lighting Bypass Circuit for Color Point Control
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Solution Overview
Problem
Solid state lighting devices often have a low color rendering index (CRI), particularly when using phosphor-based sources, which can result in inaccurate color representation, and existing solutions face challenges in efficiently controlling color points and luminous efficacy due to the limitations of single current sources and temperature sensitivity.
Innovation Solution
The implementation of a lighting apparatus with a controllable bypass circuit that selectively bypasses current around certain light-emitting diodes (LEDs) in a string, allowing for variable current distribution based on temperature and total current, thereby controlling color points and luminous output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single current source is used to power all LEDs in a string, then the circuit is simple, but the color points and luminous output cannot be precisely controlled
Solution Approach 1:
The patent divides the single current source into multiple independent current sources, each dedicated to a specific LED or group of LEDs. This segmentation allows each LED to receive precisely controlled current independently, enabling accurate color point control and luminous output adjustment without the complexity of a single unified circuit controlling all LEDs.
Solution Approach 2:
The patent introduces a new dimension of control by adding temperature sensing and compensation circuits that operate independently from the primary current control. This thermal dimension allows the system to automatically adjust current distribution based on temperature variations, maintaining precise color point control across different operating conditions without increasing circuit complexity in the traditional sense.
2Device complexity
If phosphor-based solid state light sources are used, then the device structure is simplified, but the color rendering index is low
Solution Approach 1:
The patent applies local quality by using different LED types with different color characteristics in specific positions within the string. By strategically placing LEDs with different spectral outputs and using independent current control for each, the system can locally enhance specific wavelength regions to improve overall color rendering while maintaining the simplified phosphor-based structure.
Solution Approach 2:
The patent creates a composite lighting system by combining multiple LED types (different phosphors, different materials) in a single string, each contributing different spectral components. This composite approach allows the system to achieve high color rendering index by combining the advantages of different phosphor materials while maintaining the structural simplicity of a single integrated device.
3Manufacturing precision
If bypass circuits are added to control current distribution, then color point control is improved, but the device complexity increases
Solution Approach 1:
The patent implements dynamic bypass circuits that automatically adjust their resistance based on temperature sensing. Rather than using complex static switching networks, the dynamic thermal compensation circuits continuously adapt to temperature changes, providing precise color point control through simple temperature-dependent resistance changes that reduce overall circuit complexity.
Solution Approach 2:
The patent incorporates feedback mechanisms where temperature sensors monitor the thermal state of LEDs and automatically adjust the bypass current accordingly. This closed-loop feedback system maintains precise color point control without requiring complex open-loop control circuits, as the thermal feedback naturally compensates for temperature-induced color shifts.
4Stability of the object's composition
If temperature compensation is implemented, then the color stability is improved, but the circuit complexity increases
Solution Approach 1:
The patent implements self-service temperature compensation where the bypass circuits inherently provide thermal compensation through their own thermal characteristics. The bypass resistors and control elements are designed to naturally counteract the thermal effects on LED color output without requiring external temperature sensing or complex control circuits, allowing the system to self-regulate its color stability.
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 enhances the color rendering index by allowing precise control of color points and luminous output, improving the natural appearance of illuminated objects and maintaining efficiency across varying temperatures and current conditions.
Implementation Method 1
a bypass circuit configured to variably conduct a bypass current around the at least one light-emitting device responsive to a temperature sense signal
Implementation Method 2
a packaged light emitting device including one or more light emitting diodes (LEDs)
Implementation Method 3
a solid state light emitting device generates light through the recombination of electronic carriers, i.e. electrons and holes, in a light emitting layer or region
Implementation Method 4
Light generated from a phosphor-based solid state light source
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A lighting apparatus includes a string of serially-connected light emitting devices and a bypass circuit coupled to first and second nodes of the string and configured to variably conduct a bypass current around at least one of the light-emitting devices responsive to a temperature and/or a total current in the string. In some embodiments, the bypass circuit includes a variable resistance circuit coupled to the first and second nodes of the string and configured to variably conduct the bypass current around the at least one of the light-emitting devices responsive to a control voltage applied to a control node and a compensation circuit coupled to the control node and configured to vary the control voltage responsive to a temperature and/or total string current.