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CaCO3 and TiO2 are proposed in this study as particles for scattering enhancement (SEPs) of phosphor-converted white light-emitting diodes (pc-WLEDs). The use of these two SEPs for scattering improvement enables boosting of the color homogeneity of the WLED devices. Each SEP is mixed with YAG:Ce3+ and silicone composition to examine their optical influences and performances on the high-power WLED packages with 7,000 K color temperature (CT). Miescattering theory is applied to calculate and investigate the scattering elements – scattering coefficients, anisotropic scattering, the reduced scattering, and scattering amplitudes – at the wavelengths of 450 nm and 550 nm. The results exhibit that TiO2 and CaCO3 considerably promote higher color uniformity and color-deviated reduction, respectively. The obtained results could be primarily attributed to the significant improvement in the scattering properties of the structure. Additionally, the effects of the presented scattering enhancement on luminous efficiency are displayed. The reduction in lumen output is observed to have a close connection with the concentration and particle size of TiO2 and CaCO3, which means that control must be exercised over these factors when utilizing these SEPs for WLED fabrication. [ABSTRACT FROM AUTHOR]

To achieve further enhancement in the lighting quality of white light-emitting diodes (WLEDs), this study proposed a packaging structure with three different phosphor layers, called triple-layer remote phosphor structure. This structure can provide an overall control over the light color distribution of WLEDs. The yellow-green-emitting CaAl2O4:Mn2+ phosphor and red-emitting CaMoO4:Eu3+ phosphor are used along with the original yellow-emitting YAG:Ce3+ phosphor to fabricate the triple-layer structure. The concentration of yellow-emitting YAG:Ce3+ phosphor is required to be decreased as the concentrations of other phosphors increase to keep the predetermined correlated color temperatures. The color rendering index (CRI) and the color quality scale (CQS) are measured to reach a thorough color quality assessment for WLEDs. The color management can be achieved by adjusting the concentration of red-emitting CaMoO4:Eu3+ phosphor to enhance the red emission. In addition, adjustment of the concentration of yellow-green-emitting CaAl2O4:Mn2+ phosphor can result in higher luminous efficiency owing to its control over the green light components. Higher CRI is observed when CaMoO4:Eu3+ concentration increases, while an increase in CaAl2O4:Mn2+ phosphor leads to much lower CRI. The CQS – on the other hand – is remarkably high when the CaMoO4:Eu3+ concentration range is about 10wt%–14wt%, regardless of the proportion of the CaAl2O4:Mn2+ phosphor. Furthermore, 40% enhancement in luminous efficiency is also achieved since light scattering is minimized by the boosted green-light emission spectra. Manufacturers can take these findings as reference to fabricate high-quality WLED lights that fulfill all their requirements. [ABSTRACT FROM AUTHOR]

A lumen efficiency (LE) simulation model with the Monte Carlo method is introduced to the white-light-emitting diode devices that utilize the red LED (light-emitting diode) dyes instead of red-emitting phosphors (R-WLEDs). By simulating this model, the desirable spectrum-related indices and photometric efficiencies, which are adequate for superior chromatic consistency (or Rf > 97), can be accomplished for R-WLEDs under the correlated color temperature (CCT) range of 5000–8000 K. The structure of the R-LED has LEDs in red and blue colors (650 nm and 448 nm) combined with phosphors possessing yellow and green emissions (586 nm and 507 nm). In comparison with pc-WLEDs (WLEDs operating with conversion phosphors) and QD-WLEDs (WLED devices with quantum dots), pc/R-WLED devices could present its outperformance to the others and become a promising way to achieve remarkable chromatic generation, particularly under the condition of small color temperature limit, and act as a substitute for the pc-WLED devices. [ABSTRACT FROM AUTHOR]

As implied in the title, the triple-layer remote phosphor (TRP), constructed with the yellow YAG:Ce3+ layer at the bottom, the red CaMgSi2O6:Eu2+,Mn2+ phosphor layer on the top, and the green Ba2Li2Si2O7:Sn2+,Mn2+ phosphor layer between these two layers, is suggested in this paper to improve the color and luminescence of white LEDs (WLEDs). In order to control the red light for the purpose of increasing the color rendering index (CRI), it is suggested that the red CaMgSi2O6:Eu2+,Mn2+ phosphor should be applied in the TRP structure. Simultaneously, the structure uses the green Ba2Li2Si2O7:Sn2+,Mn2+ phosphor layer to control the green light, which increases the luminous efficacy (LE) of WLEDs. In addition, when the concentration of these two phosphors increases, the yellow YAG:Ce3+ concentration must be reduced to keep the average correlated color temperatures (ACCTs) stable at 6000 K to 8500 K. Besides, appropriate adjusting of CRI, LE, and color quality scale (CQS) is also analyzed by modifying the concentration of the green phosphor and red phosphor. The results show that the CRI can get better values if CaMgSi2O6:Eu2+,Mn2+ concentration is higher. In contrast, the CRI decreases dramatically when the concentration of Ba2Li2Si2O7:Sn2+,Mn2+ increases. Meanwhile, CQS can be significantly increased in the range of 10 % to 14 % CaMgSi2O6:Eu2+,Mn2+, regardless of the concentration of Ba2Li2Si2O7:Sn2+,Mn2+. In particular, along with the improvement of CRI and CQS, LE can also be increased by more than 40 % by reducing the scattered light and adding the green light. Obtained results are a valuable reference for manufacturers for improving WLEDs color and luminescence quality to produce a broader range of WLEDs with better quality fulfilling social needs. [ABSTRACT FROM AUTHOR]

Adaptive filter techniques and the filtered-x least mean square (FxLMS) algorithm have been used in Active Noise Control (ANC) systems. However, their effectiveness may degrade due to the nonlinearities and modeling errors in the system. In this paper, a new feedback ANC system with an adaptive neural controller and variable step-size learning parameters (VSSP) is proposed to improve the performance. A nonlinear adaptive controller with the FxLMS algorithm is first designed to replace the traditional adaptive FIR filter; then, a variable step-size learning method is developed for online updating the controller parameters. The proposed control is implemented without any offline learning phase, while faster convergence and better noise elimination can be achieved. The main contribution is that we show how to analyze the stability of the proposed closed-loop ANC systems, and prove the convergence of the presented adaptations. Moreover, the computational complexities of different methods are compared. Comparative simulation results demonstrate the validity of the proposed methods for attenuating different noise sources transferred via nonlinear paths, and show the improved performance over classical methods. [ABSTRACT FROM AUTHOR]