LED Lighting System Mimicking Incandescent Color Shift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
LED lighting fixtures do not mimic the color change of incandescent bulbs when dimmed, lacking the warm color shift that users prefer, and they do not provide a smooth, gradual dimming process without perceptible steps in light or color.
Innovation Solution
A lighting system that includes a white light source and a color light source, with a control circuit that pulses and adjusts the relative duty cycles of both sources to alter the color output as brightness is changed, mimicking the color change of an incandescent bulb by using a hybrid combination of Pulse Width Modulation (PWM) and Time Division Multiplexing (TDM) with analog modulation, and a comparator to control the switching between the light sources based on current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LED lighting fixtures use a single white light source for interior lighting, then the lighting efficiency and reliability are improved, but the color change capability when dimming is lost
Solution Approach 1:
The patent divides the lighting system into multiple independent light sources with different color temperatures (e.g., warm white LEDs at 2700K and cool white LEDs at 6504K). Each light source operates independently and can be controlled separately through PWM dimming, allowing the system to simulate incandescent color changes while maintaining LED reliability and efficiency.
2Ease of operation
If LED lighting fixtures use simple PWM dimming control, then the dimming functionality is achieved, but the color output remains unchanged during dimming
Solution Approach 1:
The patent implements dynamic color temperature adjustment by continuously varying the ratio of warm white to cool white LED output based on the dimming level. As the overall brightness decreases, the system dynamically shifts the color temperature curve to match incandescent behavior, transitioning from cool white at high brightness to warm white at low brightness through real-time PWM control adjustment.
Solution Approach 2:
The system changes multiple parameters simultaneously during dimming: the duty cycle of individual LED channels, the effective color temperature, and the relative contribution of different wavelength components. By coordinating these parameter changes, the patent achieves both smooth brightness transitions and realistic color temperature shifts that mimic incandescent bulbs.
3Adaptability or versatility
If LED lighting fixtures use multiple light sources to mimic incandescent color change, then the color shifting capability is improved, but the device complexity increases
Solution Approach 1:
The patent designs the control circuit to perform multiple functions simultaneously: it controls the overall brightness level, adjusts the color temperature based on the dimming curve, and manages the individual LED channels. This multi-functional approach consolidates what would otherwise require separate control systems, reducing overall complexity while achieving realistic incandescent simulation.
Solution Approach 2:
The patent introduces a microcontroller or control circuit as an intermediary that translates simple dimmer switch commands into complex coordinated control signals for multiple LED channels. This intermediary layer abstracts the complexity from the user interface while enabling precise control over brightness and color temperature relationships, effectively managing system complexity.
4Duration of action of moving object
If LED lighting fixtures dim gradually from full brightness, then the smooth dimming transition is achieved, but perceptible discrete steps or jumps in light level may occur
Solution Approach 1:
The patent ensures continuous light output by coordinating the dimming of multiple LED channels so that as one channel's output decreases, another channel compensates or transitions smoothly. The control system maintains continuous illumination without interruptions or perceptible steps by carefully managing the duty cycles and transition timing of individual LED strings throughout the dimming range.
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 system effectively mimics the color change of incandescent bulbs during dimming, providing a smooth, gradual, and imperceptible change in light and color, maintaining a 'white' appearance at full brightness and shifting to a warmer color as dimmed, compatible with standard LED dimmer switches.
Implementation Method 1
PWM is used in LED's as a brightness control by switching fully on and off a fixed constant current and varying the ratio of on to off time
Implementation Method 2
Light Emitting Diodes (LEDs) are desirable for use in lighting fixtures due to the efficiency and reliability of LEDs
Data Source
AI summary
A lighting system has a white light source and a color light source, a control circuit pulses the white and color light sources and changes relative duty cycles of the light sources to alter a color output of the lighting fixture, in response to a change in a control signal from a controller. A comparator compares a reference voltage relating to an aggregate current driving the light sources to a signal voltage relating to the periodic signal from a signal generator. The comparator controls a switch that controls one of the light sources. A duty cycle of the color light source varies inversely to a duty cycle of the white light source.