LED Driver Circuit Modulating Current to Fill Spectral Gaps
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) exhibit spectral gaps in their emission, leading to reduced color rendering index (CRI) due to limited spectral range, especially when combining different color LEDs or using white LEDs with spectral conversion layers, resulting in poor color rendering of objects with colors within these gaps.
Innovation Solution
A control circuit and method that dynamically adjusts the intensity of LEDs over time, using a switched converter to operate the LEDs at different current intensities, ensuring the spectrum is temporally smeared to improve the color rendering index by exploiting the dependency of the LED's color spectrum on operating current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LEDs or white LEDs with spectral conversion layers are used, then the device structure is simple, but spectral gaps appear leading to reduced color rendering index
Solution Approach 1:
The patent applies periodic action by modulating the LED current in a periodic manner with multiple frequency components. The current waveform includes a fundamental frequency and harmonic frequencies, causing the LED spectrum to vary periodically. This temporal modulation smears the spectral gaps, improving color rendering index while maintaining simple LED device structure.
Solution Approach 2:
The patent applies dynamics by transitioning from static LED operation to dynamic current modulation. The LED current is dynamically varied over time with specific waveform characteristics (periodic modulation with harmonics), causing the emitted spectrum to dynamically change. This dynamic operation fills spectral gaps through temporal averaging, improving CRI without changing the physical LED structure.
2Device complexity
If LEDs are operated at constant current, then the control circuit is simple, but spectral troughs reduce color rendering quality
Solution Approach 1:
The control circuit implements periodic action by generating a periodic current waveform with specific spectral characteristics. The waveform includes fundamental and harmonic frequency components that modulate the LED operation. This periodic modulation causes the LED spectrum to vary over time, smearing spectral troughs and improving color rendering quality while using a relatively simple control circuit architecture.
Solution Approach 2:
The patent applies parameter changes by modulating the LED current parameters (amplitude, frequency, waveform shape) rather than changing the physical LED characteristics. The control circuit varies current amplitude periodically and introduces harmonic frequency components, causing the emitted spectrum to change over time. This parameter modulation improves color rendering by filling spectral gaps through temporal averaging.
3Manufacturing precision
If multiple LEDs of different colors are combined to extend spectrum, then color rendering improves, but device complexity increases
Solution Approach 1:
The patent applies periodic action to a single LED to achieve spectral coverage that would otherwise require multiple LEDs. By modulating the current with periodic waveforms containing multiple frequency components, the single LED emits a dynamically varying spectrum that temporally averages to cover a broader range, including filling spectral gaps. This approach achieves improved spectral coverage while maintaining simple single-LED module complexity.
Solution Approach 2:
The patent creates a temporal copy of multiple spectral characteristics using a single LED. Through periodic current modulation with harmonic components, the single LED reproduces spectral features that would normally require multiple LEDs of different colors. The temporal variation in emission spectrum effectively copies the spectral coverage of a multi-LED system, improving color rendering while maintaining simple device structure.
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 reduces spectral troughs and enhances the color rendering index by averaging the spectrum over time, providing a broader spectral range that is perceived by the human eye, thus improving the quality of color rendering.
Implementation Method 1
Conventional light emitting diodes (LEDs) emit light within a limited spectral range
Implementation Method 2
The light from the LED chip in a first spectrum is partially converted into a second spectrum by the phosphorous layer or color conversion layer formed thereby
Data Source
AI summary
An improved control circuit arrangement and control method is described for supplying power to, and for controlling, light-emitting diodes used for illuminating. The control circuit arrangement includes a driver circuit capable of operating in multiple modes for providing an operating current for operating at least one light-emitting diode, wherein the operating current has different positive intensities. In particular, the present control circuit arrangement and control method now deliberately exploit the fact that the color spectrum of a light emitting diode is dependent on the intensity or current with which it is operated, and improves the color rendering index by deliberately operating the light emitting diodes with different intensities over time.