Multi-Color Luminaire Thermal Feedback Control
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Solution Overview
Problem
Solid state light sources of different colors exhibit disparate efficacy changes with temperature, leading to undesirable color point shifts when combined, particularly noticeable in arrays generating white light.
Innovation Solution
A lighting system with thermal feedback and a duty cycle generator adjusts current flow through strings of solid state light sources using a temperature sensor and PWM signal, compensating for efficacy disparities by varying the duty cycle of switches connected to each string.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate strings of solid state light sources generating different colors are driven with constant current, then each string operates at stable current, but color point shifts occur due to disparate efficacy changes with temperature
Solution Approach 1:
The patent employs temperature sensing feedback to detect temperature changes in the solid state light source array. Based on the detected temperature, the system dynamically adjusts the duty cycle of PWM signals applied to individual strings, compensating for disparate efficacy changes and maintaining stable color point despite temperature variations.
Solution Approach 2:
The system transitions from static constant current driving to dynamic PWM-based current control. The duty cycle of PWM signals is dynamically adjusted based on temperature conditions, allowing each string's current to vary in response to temperature changes, thereby compensating for different thermal characteristics of various colored light sources.
2Stability of the object's composition
If PWM control is used to adjust current through strings, then color stability can be maintained, but circuit complexity increases
Solution Approach 1:
The patent combines multiple control functions into a single integrated controller that generates synchronized PWM signals for multiple strings. The controller integrates temperature sensing, duty cycle calculation, and PWM signal generation, reducing the need for separate control circuits for each string and simplifying the overall system architecture.
Solution Approach 2:
The controller is designed as a universal multi-functional device that can drive multiple strings of different colored solid state light sources. It performs temperature compensation, PWM generation, and current regulation for all strings through a single device, eliminating the need for dedicated control circuits for each string.
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
Maintains color stability and luminous efficacy across a temperature range, ensuring consistent color rendering index and color point within defined limits.
Implementation Method 1
a temperature sensor circuit configured to generate a temperature sense signal
Implementation Method 2
generate a pulse width modulated (PWM) signal having a duty cycle that changes in response to changes in temperature
Implementation Method 3
an array of solid state light sources comprising a plurality of strings of solid state light sources, wherein at least one string of solid state light sources in the plurality of strings of solid state light sources is operatively coupled to a switch controlled by the PWM signal
Data Source
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AI summary
Embodiments are disclosed for driving a multi-color solid state light source luminaire so as to maintain a color point as temperature varies within a given range. An array of solid state light sources includes two or more strings and is driven by a single constant current source. The array is topologically arranged to allow for control of the division of current between the strings of solid state light sources. In one such current-sharing scenario, the duty cycle of a switching control signal corresponds directly to the proportion of current that flows in one of two distinct strings of solid state light sources. Thermal feedback is used to control the duty cycle. In this way, the amount of current that flows in both strings may be adjusted as temperature changes.