Solid State Lighting Control via Combined Electrical Biasing
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Solution Overview
Problem
Existing methods for controlling the intensity of light emissions from solid-state devices like LEDs often result in unacceptable wavelength shifting and color distortions, particularly at low current levels, leading to instability and inaccurate color control, which complicates lighting applications.
Innovation Solution
A system and method that utilize a combination of electrical biasing techniques, such as pulse width modulation and constant current regulation, to generate a combined electrical biasing that cancels out wavelength shifts, maintaining a stable perceived color emission across various intensity levels and temperatures without requiring extensive feedback systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional current control methods (PWM or analog) are used to regulate LED intensity, then light intensity can be adjusted, but wavelength shifting and color distortions occur particularly at low current levels
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting both the amplitude and frequency of the drive current simultaneously. Instead of using fixed PWM duty cycles or simple analog dimming, the system varies multiple current parameters (peak current, pulse width, frequency) in combination to achieve intensity control while compensating for wavelength shifts. This multi-parameter approach allows the LED to operate at optimal current levels that maintain color accuracy even at low intensities.
Solution Approach 2:
The patent implements dynamics by using time-varying current waveforms with changing characteristics. The drive current is not a simple DC or fixed PWM signal but a dynamic waveform whose amplitude, frequency, and duration are continuously adjusted based on the desired output intensity and color stability requirements. This dynamic current control allows the system to adapt to the LED's nonlinear characteristics and maintain color accuracy across the full intensity range.
2Device complexity
If simple current regulation is used, then device complexity is reduced, but color stability and wavelength control deteriorate
Solution Approach 1:
The patent merges multiple control functions into a single integrated control mechanism. Instead of using separate circuits for PWM dimming and color compensation, the system combines intensity regulation and wavelength stabilization into one unified current control approach. The controller simultaneously manages amplitude modulation, frequency modulation, and pulse width control in a single integrated circuit, reducing overall system complexity while achieving both intensity and color stability.
Solution Approach 2:
The patent applies self-service by implementing an open-loop control system that uses pre-calculated current waveforms stored in memory. The controller selects appropriate current profiles from lookup tables based on the desired intensity level, eliminating the need for complex real-time feedback sensors and wavelength measurement circuits. The system serves itself by using predetermined current characteristics that inherently compensate for known LED behaviors, achieving color stability without extensive feedback systems.
3Manufacturing precision
If extensive feedback systems are implemented to maintain color stability, then color control accuracy improves, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal current waveforms in memory before operation. Instead of using feedback to determine the correct current characteristics, the system has already determined the optimal amplitude, frequency, and pulse width combinations during the design and characterization phase. These pre-computed current profiles are stored and simply retrieved during operation, eliminating the need for real-time wavelength measurement and feedback adjustment while maintaining high color control accuracy.
Solution Approach 2:
The patent uses a simplified controller architecture that replaces expensive, complex feedback hardware with a low-cost microcontroller and lookup tables. Instead of investing in precision wavelength sensors, feedback amplifiers, and complex control hardware, the system uses an inexpensive digital controller that retrieves pre-stored current profiles from memory. This approach achieves high color control accuracy using much cheaper, simpler components.
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 allows for precise control of light intensity while maintaining color stability, reducing power losses and component count, and extending battery life in portable devices, with fewer components and lower costs.
Implementation Method 1
a light emitting diode is a semiconductor device that emits incoherent, narrow-spectrum light when electrically biased in the forward direction of its (p-n) junction
Data Source
AI summary
Exemplary embodiments of the invention provide a system, apparatus, and method of controlling an intensity and spectrum of light emitted from a solid state lighting system. The solid state lighting has a first emitted spectrum at full intensity and at a selected temperature, with a first electrical biasing for the solid state lighting producing a first wavelength shift, and a second electrical biasing for the solid state lighting producing a second, opposing wavelength shift. Exemplary embodiments provide for receiving information designating a selected intensity level or a selected temperature; and providing a combined first electrical biasing and second electrical biasing to the solid state lighting to generate emitted light having the selected intensity level and having a second emitted spectrum within a predetermined variance of the first emitted spectrum over a predetermined range of temperatures.