LED Lighting System with Delayed String Activation for Color Temperature Shifting
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Solution Overview
Problem
Solid-state lighting systems, particularly LEDs, lack the ability to shift correlated color temperature during dimming operations, resulting in an undesirable light effect, as they maintain constant color temperature, unlike incandescent lamps, which create a warm light effect at low intensities.
Innovation Solution
A lighting system with a power-supply circuit and two strings of solid-state light sources, where one string is activated with a delay relative to the rising edge of the voltage and deactivated with the falling edge, allowing for a shift in correlated color temperature by adjusting the current flow through each string based on a dimming signal, using a delay circuit to generate an enable signal for the first string's current regulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If solid-state light sources (LEDs) are used for lighting, then energy efficiency and longevity are improved, but the ability to shift correlated color temperature during dimming is lost, resulting in an undesirable constant color temperature effect
Solution Approach 1:
The lighting system is divided into multiple independent LED strings, each with distinct correlated color temperatures (e.g., first string with higher CCT, second string with lower CCT). Each string can be controlled independently through separate current regulators, allowing the system to segment the color temperature control function and achieve variable color temperature by adjusting the relative contribution of each string during dimming operations.
2Adaptability or versatility
If multiple LED strings with different correlated color temperatures are used to achieve color shifting, then color temperature adaptability is improved, but device complexity increases due to requiring multiple current regulators and control circuits
Solution Approach 1:
Multiple LED strings with different correlated color temperatures are connected in parallel between the same power supply terminals, sharing a common power supply and control infrastructure. This merging approach allows the system to achieve color temperature shifting functionality while reducing overall complexity compared to completely independent control systems, as the strings share common electrical connections and can be controlled through a unified dimming signal.
Solution Approach 2:
The current regulators are designed to perform multiple functions: they control both the brightness (current magnitude) and the color temperature (through selective activation or ratio control of different LED strings). This multi-functionality reduces the need for separate dedicated control circuits for each function, thereby simplifying the overall device complexity while maintaining color temperature shifting capability.
3Manufacturing precision
If complex control circuits are used to manage current flow through multiple LED strings, then color temperature control precision is improved, but ease of manufacture and cost increase
Solution Approach 1:
The system utilizes the inherent electrical characteristics and natural response of the LED strings and current regulators to achieve color temperature control. The current regulators automatically adjust current distribution based on simple control signals, and the LED strings naturally emit their characteristic colors when energized. This self-service approach eliminates the need for complex active control circuits, sensors, or feedback mechanisms, thereby simplifying manufacturing while maintaining adequate color temperature control precision.
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 solution allows for a simpler and cost-effective implementation of correlated color temperature shifting during dimming, achieving a warm color effect at low brightness levels without requiring complex control circuits, while maintaining the average color temperature at high brightness levels.
Implementation Method 1
a first string of solid-state light sources and a first current regulator are connected in series between the two output terminals of the power-supply circuit, wherein the first current regulator is configured for regulating the current flowing through the first string
Implementation Method 2
a second string of solid-state light sources and a second current regulator are connected in series between the two output terminals of the power-supply circuit, wherein the second current regulator is configured for regulating the current flowing through the second string
Data Source
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AI summary
Described herein is a lighting system comprising a power-supply circuit and at least two strings of solid-state light sources. The power-supply circuit comprises two output terminals, wherein the power-supply circuit supplies a regulated voltage (Vout), wherein the regulated voltage (Vout) is periodically activated for a first duration and de-activated for a second duration as a function of a dimming signal. A first string (22a) of light sources and a first current regulator (24a) are connected in series between the two output terminals, wherein the first current regulator (24a) is configured for regulating the current flowing through the first string (22a). A second string (22b) of solid-state light sources and a second current regulator (24b) are connected in series between the two output terminals, wherein the second current regulator (24a) is configured for regulating the current flowing through said second string (22b). In particular, the system comprises means (28) configured to activate the current flowing through the first string (22a) when a given time has elapsed since a rising edge of the regulated voltage (Vout) and to deactivate the current flowing through the first string (22a) simultaneously with a falling edge of the regulated voltage (Vout).