Output Luminous Flux Research Articles

Laser light illuminant based on YAG: Ce phosphor ceramic with ultra-high luminance, stable output, and excellent heat dissipation

A hundred-watt level blue collimated laser is used to excite YAG: Ce phosphor ceramics to prepare a high-power white laser-based illuminant. A composite ceramic cooling device is prepared to reduce the operating temperature of YAG: Ce phosphor ceramics by using nano-silver to weld ceramics onto a copper block with a water-cooling device. Phosphor ceramics encapsulated with the above device can withstand the excitation of a 123W blue laser, and its output luminous flux value reaches 14600lm. The stable output time of the laser-based illuminant is over 30 minutes, and the operating temperature of the phosphor ceramic surface is only 270°C. Compared with the non-cooling device package, the luminous flux of the laser-based illuminant composed of phosphor ceramics packaged with the above structure is increased by 252.8%. The experimental results show that the composite ceramic cooling device can effectively reduce the operating temperature of phosphor ceramics which is an effective way to realize white laser-based illuminants over 10000lm.

Passive anti-leakage of blue light for phosphor-converted white LEDs with crystal nanocellulose materials

A phenomenon known as "blue-light leakage" caused by overheating pcW-LEDs has recently been identified, and it poses a risk to users. This study focuses on investigating and optimizing a solution to address this issue. To tackle the problem of overheating and blue light leakage, we explored the application of a specific thermochromic material called crystal nano cellulose (CNC). We introduced CNC inside the epoxy lens of white LEDs. Importantly, under standard conditions, CNC has a negligible impact on the optical properties of the output white light. However, when overheating conditions arise, leading to blue light leakage, the temperature increase triggers a darkening effect in CNC. This thermochromic behavior of CNC allows it to strongly absorb the blue light, resulting in a significant suppression of the output luminous flux. As a result, the lamp dims, which not only prevents the user's eyes from being exposed to harmful bluish light but also serves as an indicator of aging in the pcW-LED. By implementing CNC as a responsive material in the design of white LEDs, this study offers a practical and effective solution to mitigate the negative effects of blue-light leakage caused by overheating. This improvement enhances the safety and comfort of users while also providing an early warning system for the aging of pcW-LEDs.

Application of smart grid and non-dominated sorting genetic algorithm in adaptive energy-saving control of building lighting

Introduction: In the wave of urbanization, the increase of public lighting equipment in buildings has brought about more prominent problems of energy saving and consumption reduction.Methods: In order to solve the above problems, this paper designs a set of intelligent lighting solutions for digital buildings by combining the smart grid and non-dominant sorting genetic algorithms. Firstly, an intelligent lighting monitoring solution is constructed through ZigBee ad hoc network and sensor technology to monitor the relevant environment and lighting control of the laboratory building. Secondly, this paper uses the DIALux software network to build a public lighting light distributiona public lighting light distribution model in the building, and deeply studies the dimming control strategy of the system under the principle of making full use of sunlight and natural light.Results: The purpose ofself-adaptive intelligent control of desktop illuminance, finally using this scheme to achieve the optimal balance of desktop lighting.Discussion: The simulation experiment counts the power data of the intelligent lighting system under different weather conditions. The experimental results verify that the intelligent lighting control scheme can effectively reduce the output luminous flux of the lamps, thereby reducing power consumption.

Research on combined solar fiber lighting and photovoltaic power generation system based on the spectral splitting technology

Modern buildings tend to be high-rise and dense, and indoor lightings are extensively depending on electricity even on sunny days currently. In addition, for those existing solar lighting technologies in development, only the visible light of solar radiation has been used, with the extra spectral energy dissipated by waste heat. A solar fiber optic lighting and photovoltaic power generation system based on spectral splitting technology (SSLP) is proposed and tested in this study. The sunlight is divided into different wave bands through a spectral beam splitter, where the visible light is used for optical fiber illumination, and the near-infrared radiation is used for photovoltaic power generation. The designed SSLP system is simulated with the Monte Carlo ray tracing method, and then experimentally tested. The effects of structural parameters and tracking accuracy on the optical performances of the system are examined. The experimental results show that the sunlight transmitted to the room using optical fiber is bright and comfortable, with an average lighting efficiency of 15.1 %; meanwhile, the average power generation efficiency of the system is about 6.1 %, reaching one-third of the value of conventional PV modules. When the output luminous flux is converted by the luminous efficiency of fluorescent lamps, the overall average efficiency of the system can reach to 29.5 %; when converted by LED lamps, the overall average efficiency can reach to 25.4 %, which are both more efficient than the conventional PV power generation. Taking the solar radiation conditions in Beijing as an example, when the sunlight collection area of the system is 1 m2, it can provide 8 h of sunlight illumination of 500 lx per day for a room of 19.7 m2, while the daily generated electricity can be provided to the LED lamps to extend the lighting time by 2.5 h.

Influence of Ambient Temperature on Optical Characteristics and Power Consumption of LED Lamp for Automotive Headlamp

In this study, the authors propose a method for evaluating the influence of ambient temperature (Ta) on the optical characteristics and power consumption of a LED lamp used for the automotive headlamp, which helps the designer to figure out the acceptable range of the ambient temperature for the LED lamps to work well in the practical case. The LED lamp was fixed on the test holder and placed in a fixed position in the air circulation temperature control oven to measure the illuminance, spectrum in three different directions, and power consumption under various Ta. The experimental results indicate that Ta has little effect on the correlated color temperature (CCT), chromaticity coordinates, and angular distribution of the emitting light. In contrast, Ta has a significant effect on the lamp’s resistance, thus affecting illuminance and power consumption. When the Ta increased from 30 °C to 60 °C, the illuminance of the low beam and high beam decreased on average by 16.6% and 21.7%, respectively, while the power consumption of the low beam and high beam decreased on average by 21.4% and 22.2%, respectively. The drop in the luminous flux output indicates the probability of originally qualified automotive LED headlamps becoming unqualified in high Ta.

Luminous output improvement in chip scale packaged Ce3+:YAG-based ceramic phosphors-converted white LEDs via laser assistance for application in automobile headlights

In this study, two kinds of composite ceramic phosphors, Ce3+:YAG/Al2O3 and Ce3+:Y(Gd)AG/Al2O3 were prepared via solid state reaction sintering in flowing pure oxygen at atmospheric pressure. The ceramic phosphors were packaged into chip-scale white light emitting diodes (w-LEDs), and laser assisted w-LED automobile headlight prototypes were assembled. The luminous flux output of the w-LEDs was significantly improved through additional blue diode laser excitation. Notably, the Al2O3 phase is able to impart an improvement in the luminescence saturation exhibited by Ce3+:Y(Gd)AG, which typically reaches saturation prior to Ce3+:YAG.

Temperature dependence correction method of LED filament lamp for total luminous flux calibration based on voltage measurement

Light-emitting diode (LED) standard lamps are interesting since the traditional incandescent standard lamps for photometry are difficult to obtain. Many of the National Metrology Institutes have started projects to study the use of LED standards for photometric comparison. The National Institute of Metrology, China, has developed a type of LED filament lamp for total luminous flux. The lamp mimics the 4π incandescent standard lamp and has no space for an active temperature control component. A temperature dependence correction method is reported using the coefficient of the lamp voltage to the output luminous flux. The luminous flux correction is derived from the lamp voltage value. By applying correction, the stability test of the LED filament lamp shows that the ageing effect was estimated to be less than 0.1%/210 days. The temperature dependence was suppressed to less than 0.1% for a range of 21 °C ± 2 °C, which could be due to possible temperature fluctuations of the lamp ambient temperature during measurement by the goniophotometer or integrating sphere.

Development of smart energy meter to measure energy saving of dimmable LED panel light

Conserving energy is important now more than ever. Dimming lamps to the required illuminance is one way to reduce the energy usage. Technological advancement in the form of new materials, sensors, and apparatus allows us to reduce the energy usage of an equipment. To obtain a clear understanding of consumer energy usage, a smart meter which is able to monitor and store energy usage characteristics can be a useful tool to have. This paper discusses the development of multi-points smart energy meter using ESP32, ZMPT101B voltage sensor, and SCT-013 current sensor. The measurements result of the meter developed has been validated using commercial energy meter. A 35 W dimmable LED panel light benefitting dimming function in QH7938 chip has also been constructed. The dimming characteristics were obtained, with the output luminous flux of 5644 to 950 lumen, and power input of 35 to 5.32 watt. Subsequently, the energy saving case scenario in 2.5 x 2.8 x 3 meters home office with various natural lighting condition were also presented.

Study of thermal modes of operation of SMD-LEDs in phyto-lamps

LED phyto-irradiators are promising for use in irradiation systems for growing plants in greenhouses using photoculture technology. Cases, when the thermal calculation of phyto-irradiators is performed incorrectly, have an overheating in the active area of the crystal. It results in faster degradation of the semiconductor, reduces the output luminous flux and the service life of the device. To evaluate and analyze scientific works studying thermal models of LED operating modes, examples of the application of modern methods for determining thermal resistances, to study local heating zones on phyto-irradiator boards when using different types of LEDs and modern thermal imagers to detect soldering defects. The authors classified and analyzed the collected materials according to application criteria and implementation prospects. In the course of the research the authors applied methods of systematic approach. To assess the effectiveness of dissipation of thermal energy released by a LED crystal, they calculate the following parameters: thermal resistance between p-n transition and housing, thermal resistance between housing and PCB, thermal resistance between PCB and the environment. The thermal resistance between the p-n junction and the housing is due to the design of the LED, other parameters are set by the thermal models of the developed lighting devices. The applied methods of cooling do not essentially influence the complexity of thermal models, liquid cooling allows to refuse radiator for the linear thermal model, that slightly raises the accuracy of measurements and simplifies the process of calculation of thermal resistance of transition-housing. The primary role in thermal management of luminaires with SMD elements lies in the following elements: power supply circuits, SMD LED soldering quality and materials used, LED locations, PCB dimensions and location in space, ambient temperature, adequate calculation of thermal resistance between the LED and the environment and selection of radiators.

Design and application of a cooling device based on peltier effect coupled with electrohydrodynamics

Miniaturization has become the development trend of light-emitting diodes (LEDs), which results in a significant increase in heat flux production and operating temperature. The accumulated heat should be dissipated effectively to ensure that the chip can work properly. The conventional cooling techniques have now reached their limits in heat removal rates. A new cooling device coupled thermoelectric cooling (TEC) with corona wind cooling (CWC) was proposed and optimized experimentally based on the second law of thermodynamics and the principle of entropy generation minimization. The results indicate that a better cooling effect and a high coefficient of performance value is obtained by turning on the TEC near the heat source firstly and adjusting the CWC power at the hot side. Increasing the input power of TEC and keeping the total cooling power unchanged, another 4.7% improvement is obtained with the highest heating power of 14 W. The target temperature can be maintained at an acceptable level (＜80 °C) if the TEC and CWC are well coupled. However, the coupling effect between TEC and CWC will be worse when the input power is large. A higher output luminous flux will be obtained when the LED chip works in the constant current mode due to the good coupling between CWC and TEC. The luminescence intensity and chromaticity properties are improved significantly. The principal component analysis (PCA) also indicates excellent comprehensive performance. The results verify the feasibility of a novel cooling device coupled TEC with CWC in cooling high heat flux electronics.

Comparison of the generation characteristics and application performance of nanomaterials-enhanced ionic wind

Ionic wind technology is a right candidate for the thermal management of electronic devices. However, some highly-oxidizing substances are produced during corona discharge, which can destroy the electrode and shorten its service life. In the present work, nanomaterials were coated on the surfaces of needles, which act as emitting electrodes. The generation characteristics of ionic wind and the working durability of an ionic wind generator (IWG) were compared experimentally. The generator modified by nanomaterials was subsequently used to cool high-power LED chips, and the changes in the optical properties of the chips were studied. The results indicate that the electric field intensity and corona current increased after the application of the nanomaterials. The nanomaterials-decorated IWG performed better in operating durability than the original prototype. When the nanomaterials-decorated IWG was applied to cool LEDs, the case temperature at a discharge power of 3 W was reduced by 5.8 °C compared with the original generator. The luminous flux output increased by 28 lm and took less time to reach a stable working state. The ionic wind velocity and the energy conversion efficiency of the system were also greatly improved. This study provides a potential solution for the efficient thermal management of electronic devices.

Ring Remote Phosphor Structure for Laser-Driven White Lighting

In this article, a ring remote phosphor (RRP) structure comprising an inverted-cone-lens encapsulant and a surrounding phosphor layer was developed and used for laser-driven white lighting. The inverted-cone-lens encapsulant in the structure redirects light from a blue laser diode (LD) to the surrounding phosphor layer, thus preventing intense light from hitting the phosphor layer on a small surface and, therefore, from considerably reducing luminous efficiency. The design of the inverted-cone-lens surface of the encapsulant was investigated, and 3-D ray-trace simulations were performed to confirm its light distributions. The RRP structure with an inverted-cone-lens encapsulant and a surrounding phosphor layer was fabricated to produce laser-driven white lighting, and the optical characteristics of the RRP structure with different phosphor concentrations were examined. The output luminous flux of the RRP samples increased with increased phosphor concentration, whereas the correlated color temperature (CCT) decreased with an increase in phosphor concentration. Therefore, the RRP structure can be used to generate efficiently high-brightness white light.

Influence of Encapsulated Silica Gel on Output Luminous Flux of Deep Sea LED Light Source

Influence of Encapsulated Silica Gel on Output Luminous Flux of Deep Sea LED Light Source

28.1: Invited Paper: What’s the Focus of Debate in IEC Standardization for the Measurement of Laser Projection Displays?

The projection displays which use lasers or laser hybrids as light sources have been widely applied in offices, homes, and theaters. The optical performance has been more enhanced recently with the development of the technologies, especially in light enhancement, color reproduction, luminance contrast, and dynamic range. The characterization and measurement for these projection displays become very important.The full‐frame projection technologies such as digital micromirror devices (DMDs), liquid crystal on silicon (LCOS), and liquid crystal display (LCD) projectors are typically concerned in the international standardization. The image quality of the projection system in graphics and video reproduction has been discussed in IEC WG10 “Working group of Laser Displays.“ In recent years, the IS (international standard)‐ IEC62906‐5‐1 Laser display and devices Part 5‐1 Measurement of Optical Performance for Laser Front Projection has been developed and reached the CDV stage. However, at this stage, there are some discussions among the expert’s group on the issues of the optical measurement method. The main issues are the two topics related to the CLO (Color Light Output) and CGV (Color Gamut Volume). There are two opposing views within the working group which is a very challenging topic. According to IEC/ISO rule, the consensus is difficult to be achieved for more 2/3 favor support and less 1/4 against.In the traditional projectors, due to the graphic display is mainly used for black and white usage in the office application, the luminous flux output of the full white field was used as the primary indicator in the specification of the standard product. The light output is directly dependent on the power of the projection source. Therefore, a white light enhancement method is employed in some projection display technologies, and in such cases, the brightness of a color display is often lacking. However, this is no longer the general case. Manufacturer use different ways to boost the white lumen value for the full white screen, but the saturated colors do not get the same boost in brightness. The lumen ratio between the full white and the colors is no longer maintained. In the new standard we recommend using a regional grid pattern to test the projector's light output, including white light output and color light output.Set of four colour tile test patterns used for projector characterizationfigureMoreover, the argue for color volume method is the derivative from the CLO/WLO issue. The main point is the argument between the applicability of CGV method (CIELAB usage) in HDR/SDR conditions. In this paper, we reviewed some of the most important aspects to provide a basic understanding the current development of laser projection display measurement in IEC standardization.Example of range in colors produced by a given display as represented by the CIELAB color spacefigure

Performance Improvement of GaN-Based Light-Emitting Diodes With a Microhole Array, 45° Sidewalls, and a SiO2 Nanoparticle/Microsphere Passivation Layer

The characteristics of GaN-based light-emitting diodes (LEDs) with a hybrid structure incorporating a microhole array, 45 sidewalls, and an appropriate SiO2 nanoparticle (NP)/microsphere (MSs) passivation layer are studied and reported. The use of a SiO2 NP/MSs passivation layer causes a remarkable reduction in reverse-biased leakage current. The employment of this hybrid structure leads to substantial enhancements in optical properties without any degradation in electrical performance. In addition, a lower content of SiO2 NP in the mixed SiO2 NP/MSs solution leads to enhanced optical behavior due to the improved transmittance. Experimentally, as compared with a conventional LED (Device A), the studied Device E shows 50.6%, 50.9%, 48.4%, and 49.9% enhancements in light output power, luminous flux, luminous efficacy, and wall-plug efficiency, respectively. These advantages are mainly attributed to the increased scattering probability and the opportunity to find photon escape cones as well as the reduced total internal reflection and Fresnel reflection effects. Therefore, the studied hybrid structure provides a promise for high-performance GaN-based LED applications.

Switched-Capacitor-Based Current Compensator for Mitigating the Effect of Long Cable Between PWM Driver and LED Light Source

It is sometimes unavoidable to have light-emitting-diode (LED) light sources and their pulsewidth modulation (PWM) drivers connected by long cables in large-scale illuminations. However, long-cable inductance delays the rate of rise of the driving current pulses and thus leads to the reduction of luminous flux output. It also causes the off-state voltage across the light sources negative, which would deteriorate the life expectancy of the LEDs. A switched-capacitor-based current compensator for correcting the wave shape of the driving current pulses is presented. The methodology is based on transferring the energy stored in the cable to a capacitor at the end of the current pulse and then momentarily boosting the voltage with the capacitor applying to the cable at the beginning of the next current pulse. Thus, the rise time of the current pulses can be shortened. The topological states and operations of the compensator will be described. A simplified design procedure will be given. A prototype for a 12-V, 3-A PWM driver has been built and evaluated. Performance comparisons between the proposed current compensator and prior art and between the systems with and without the compensators will be conducted.

Ionic Wind Development in Corona Discharge for LED Cooling

The working temperature of an LED chip has a great influence on its photoelectric properties. It is urgently necessary to develop an adaptive cooling device for LEDs’ heat management. This paper proposes a “multi-needle-to-mesh” ionic wind generator for enhanced heat transfer in high-power LEDs (HPLED). Experiments were conducted to evaluate the cooling performance of HPLEDs under multiple working conditions. The electric field intensity (EFI) distribution, the charge density, and the dynamic pressure of ionic wind were measured. We also investigated the thermal resistance, the mean heat transfer coefficient, and the output luminous flux of HPLEDs. The results indicate that the EFI distribution is inhomogeneous and there was a reduction in EFI from the needle tip to the collecting electrode of up to 90%. Furthermore, the density of discharges was proportional to the overvoltage but inversely proportional to the square of the discharge gap. The ionic wind velocity was proportional to the overvoltage but inversely proportional to the discharge gap. An approximately 34% reduction of thermal resistance was observed as well. The final reducing rate of HPLED output luminous flux was 9.3%under the action of ionic wind.

Optical and electrical properties of a spiral LED filament * * Project supported by the National Nature Science Foundation of China (No. 51302171), the Science and Technology Commission of Shanghai Municipality (CN) (No. 14500503300), the Shanghai Municipal Alliance Program (No. Lm201547), the Shanghai Cooperative Project (No. ShanghaiCXY-2013-61), and the Jiashan County Technology Program (No. 20141316).

This paper introduces a new type of spiral white light-emitting diodes (WLED) filament with high luminous efficiency and uniform optical performance. The optical and thermal properties of the flexible filament were investigated at different stretching heights, namely 0, 1, 2, and 3 cm. The results indicated that the filament showed the best optical characteristics at the stretching height of 2 cm, because of good heat dissipation. In addition, the radiation temperature of the filament was inversely proportional to the output luminous flux. The reliability of the filament at a stretching height of 2 cm was also evaluated after 1000 h of use. The result demonstrated that the luminous flux decay of the bulb was only 0.85%. The flexible spiral WLED filament exhibiting high luminous flux and good reliability could be adapted to promote industrial development in the near future.

Proposed integration of a photovoltaic solar energy system and energy efficient technologies in the lighting system of the UTA-Ecuador

This research assesses the current fluorescent lighting system of the Faculty of Civil and Mechanical Engineering (FICM), Technical University of Ambato (UTA), Ecuador. The aim of this study is to present the main results obtained from an efficient lighting project to be implemented at FICM, UTA, and also proposes the integration of an existing photovoltaic solar energy system (PVSE-S) to supply the proposed efficient lighting system. In this study, the Society of Light and Lighting (SLL) Code for Lighting 2012 is used to determine the spacing or maximum distance between measurement points in classrooms. Lighting levels (lux) of 14 available classrooms are measured to estimate illuminance by using 70 measurements. DIALux software is applied to simulate three scenarios of proposed luminaries based on LED (lighting emitting diode) system. RC660B LED is selected due to the highest values of luminous flux, light efficiency and light output at minimum required power and area of installation. RC660B additionally denotes a considerably low value of Limit Value of Energy Efficiency (VEEI-Spanish acronymic) in comparison to fluorescent lamps (FL). Finally, this study proposed the use of a PVSE-S to power 2898 VA (volt-amperes) of the selected LED luminaries of seven classrooms in the FICM building.

PWM Dimming for High Brightness LED Based Automotive Lighting Applications

In recent years, the use of high brightness LEDs has become increasingly accepted as light sources in mainstream vehicles. However, they are semiconductor devices and their electrical characteristics are completely different to the traditional lamps. The output luminous flux of an LED is determined by the forward current running through it. Hence they cannot be powered directly from the automotive battery using the conventional driving techniques. They require specialised driving circuits which can respond to the changing needs of the LEDs as their electrical properties change, while maintaining the uniform brightness.<strong> </strong> This paper discusses the importance of dimming for LED based automotive lighting applications. A boost type DC-DC switching converter with pulse width modulated (PWM) dimming control has been proposed. MATLAB/Simulink simulation package has been used to verify the theoretical predictions hence to provide a useful guide for design engineers and researchers.