Solid State Lighting Duty Cycle Control for Appliance Thermal Management
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Solution Overview
Problem
Solid state lighting devices in appliances like refrigerators consume high power and generate excessive heat, complicating thermal management and increasing energy costs, while maintaining high light levels.
Innovation Solution
Implementing a power controller that supplies a pulse modulated power signal with a duty cycle to the solid state lighting devices, cycling them on and off, which reduces power consumption and heat dissipation while maintaining or increasing perceived brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If solid state lighting devices operate at high light levels continuously, then illumination intensity is improved, but power consumption increases and heat generation worsens
Solution Approach 1:
The patent applies pulse width modulation (PWM) to cycle the solid state lighting devices on and off at high frequency, providing illumination only during the 'on' portion of each cycle. This periodic operation reduces average power consumption while maintaining perceived brightness through persistence of vision, directly resolving the contradiction between continuous high light levels and power consumption.
Solution Approach 2:
The system dynamically adjusts the duty cycle of the PWM signal to optimize the balance between illumination intensity and power consumption. By varying the on-time proportion within each cycle, the system can adapt to different lighting requirements while controlling energy usage, transforming a static high-power operation into a dynamic, efficiency-optimized operation.
2Illumination intensity
If solid state lighting devices operate at high light levels continuously, then illumination intensity is improved, but heat generation increases
Solution Approach 1:
By cycling the lighting devices on and off using PWM, the system reduces the total time the devices are active, thereby reducing cumulative heat generation. The periodic operation allows thermal dissipation during the 'off' periods while maintaining adequate perceived illumination during the 'on' periods, resolving the contradiction between high light levels and heat generation.
3Use of energy by moving object
If solid state lighting devices are cycled on and off with duty cycle, then power consumption decreases, but perceived brightness may be reduced
Solution Approach 1:
The PWM technique exploits the persistence of vision phenomenon, where the human eye integrates light stimuli over time. By operating at frequencies above the flicker fusion threshold (typically >100Hz), the cycled lighting appears continuously illuminated to human observers. This allows significant power reduction through duty cycling while maintaining perceived brightness, resolving the contradiction between power consumption and perceived brightness.
Solution Approach 2:
The system changes the temporal parameter (duty cycle) of the lighting operation to optimize the balance between power consumption and perceived brightness. By adjusting the duty cycle percentage and frequency, the system can achieve different perceived brightness levels at corresponding power consumption levels, transforming the trade-off into a controllable parameter relationship.
Data Source
AI summary
An appliance includes a cabinet, a solid state lighting device assembly integrated in the cabinet, and a power controller coupled to the solid state lighting device assembly for supplying electrical power to the solid state lighting device lighting assembly. The power controller is configured to provide a pulse modulated power signal to the solid state lighting device assembly that has a duty cycle. Each solid state lighting device in the solid state lighting device assembly cycles on and off in accordance with duty cycle.