Light-emitting Diode Module Research Articles

Main Directions of the Russian State Energy Saving Policy in the Field of Electric Power Engineering

The article describes the issues of strategic planning and legal regulation of activities aimed at energy saving and energy efficiency in the Russian Federation. The authors set the goal to determine the directions for strategic planning of the energy saving policy of the Russian Federation based on a comparative legal analysis in order to achieve the goals of sustainable development of an energy­saving economy. The article considers advanced technologies designed to ensure the most effective implementation of the provisions of legal acts adopted in the last decade in Russia. The methodology of this scientific research is the use of hermeneutics, interpreting legal texts and application of formal logical instruments within the system analysis of current Russian strategic planning acts for long­term (medium­term) period to coordinate the activities of economic entities and public authorities in the appropriate direction. Besides, it includes normative acts that establish the legal, economic and organizational basis for stimulating energy conservation and improving energy efficiency as well as legal documents of other countries that determine their policies in this area. The authors come to the conclusion that it is required to consult various specialists, including ophthalmologists, when creating norms of Russian legislation in the field of energy saving; to account for technical and technological characteristics of LED (light emitting diode) modules, chips, other light sources; to take into consideration the possibility of their use in various fields in order to achieve energy efficiency.

Single chip design for detection and recovery of series LED open/short fault tolerance circuit

Light emitting diode (LED) lighting is widely used in current. However, lighting robustness is low in a series loop since the lighting shuts down as one LED fails. This study proposes a power chip for fault detection and isolation for enhancement of LED's fault‐withstanding capability. The chip can automatically detect the failed LEDs and bypass them, and let others continue to work. The authors implemented four bypass loops using a power metal oxide semiconductor (MOS) on the single chip. This chip can drive 1 A with 4‐bit current dimming, which includes four bypass power P‐type MOSs, one power N‐type MOS, schedule controller, level shifter and over voltage protection. The schedule controller with a state machine can quickly find which one LED fail and recover it soon. The prototyping chip was designed using TSMC 0.25 μm, which is the second generator high‐voltage technology, and the resulting chip area with pads is only 1.3 × 1.7 mm2. The chip had been successfully implemented and measured to drive and bypass four LED components or modules.

Experimental investigation of heat transfer characteristics of the LED module using passive heat sinks

ABSTRACT Light-emitting diode (LED) has several advantages and applications due to energy efficiency, versatility, performance, and long life. LED converts only 20–30% of the power input into light, converting the remaining 70–80% of the energy into heat that must be conducted from the LED die to the underlying circuit board, heat sinks, and housings. Improper thermal management will lead to an increase in the junction temperature above the safe limit, thus leading to premature failure of the LED. The present investigation aims to study the variation of case and junction temperature for three types of heat sinks, namely, diagonal, cylindrical, and spiral using 16 W LED. Light output in terms of lux is measured. Experiments were conducted by varying currents from 100 to 300 mA. It was observed that the spiral heat sink has the least junction temperature and thermal resistance among the three heat sinks at all current ratings.

Enhancement of Heat Dissipation by Laser Micro Structuring for LED Module.

Optimization for heat dissipation plays a significant role in energy saving and high-efficiency utilizing of integrated electronics. In this paper, we present a study of micro structuring on polymer-based flexible substrate coupled with aluminum-alloy heat sink. The heat dissipation performance was investigated by temperature evolution of a heat sink under natural convection by infrared (IR) camera, and results showed that the heat dissipation enhancement could be up to 25%. Moreover, the heat dissipation performance of a typical heat sink in terms of light-emitting diode (LED) hip was investigated via both thermal transient measurement and the finite element analysis (FEA). The maximum LED chip temperature of the laser-textured heat sink was approximately 22.4% lower than that of the as-received heat sink. We propose that these properties accompanied with the simplicity of fabrication make laser surface texturing a promising candidate for on-chip thermal management applications in electronics.

An AC Input Inductor-Less LED Driver for Efficient Lighting and Visible Light Communication

This paper presents an ac-powered inductor-less light-emitting diode (LED) driver, which can simultaneously provide efficient illumination and data transmission capability by modulating light output. The proposed driver does not have passive components’ speed limitation compared to the conventional switching converter-based driving solutions for visible light communication (VLC). Besides this, harmful low-frequency flicker is mitigated with an accurate 1/ ${x}$ circuit and the dimming compensation method. In addition, the digitalized power stage and controller utilized in the proposed driver can achieve smooth transitions among multiple current paths, while the keep-and-restore technique and auxiliary turn-on switch help to further increase the VLC data rate. The integrated circuit of the proposed driver is implemented and fabricated with a 0.35- $\mu \text{m}$ , 120-V high-voltage CMOS process. Measurement results show that under a 110- $V_{\text {AC}}$ , 60-Hz input, the peak efficiency of the proposed design is over 89% and the low-frequency flicker is reduced to below 10%. The driver supports up to 8-Mb/s on–off keying non-return-to-zero data transmission for a 1-m distance between the LED module and the receiver.

Thermal Stress Analysis for High CRI LED Indoor Lighting Module

AbstractThis research is for developing a new light emitting diode (LED) indoor lighting module with high color rendering index greater than 95. When the LED is operated, electrical energy is generated and heat is released. The failing of heat dispersal degrades the performance and decreases the operating life. To manage the thermal problem effectively, several approaches have been tested in this research study. A heat sink is designed to absorb and transfer heat from the LED module. To analyze the heat flow and thermal stress of the designed LED products effectively, hexahedral mesh generation has been implemented. Heat transfer analysis was performed to find an optimal conductive material. The outcomes of this research study suggest the best material for LED products and show the result of thermal transfer simulation.

Photocatalytic oxidation of dairy effluent with UV lamp or UV light-emitting diode module and biological treatment processes

The objective of this study was to develop a novel and simple-operated treatment system for refining dairy farm effluent after conventional dairy wastewater treatment system. Experimental results showed that average removal efficiency of COD, BOD, and SS in the effluents of a dairy farm was 72, 98, and 79%, respectively, using a combined photocatalytic and biological reactors. Removal efficiency of calculated conductivity value seems to be closely related to the removal efficiency of NH4+, PO43−, and Mg2+ when using the photocatalytic UV lamp reactor only. However, average removal efficiency of COD, BOD, and SS in the dairy farm effluent was 53, 62, and 62%, respectively, with the photocatalytic UV LED reactor. In summary, removal efficiency of BOD, COD, SS, and EC in photocatalytically treated dairy farm effluent with UV lamp reactor was higher than that with photocatalytic UV LED reactor. In addition, removal efficiency of COD and BOD with a combined photocatalytic and biological treatment system was higher than that using a photocatalytic oxidation reactor only. Thus, the combined system can provide dairy cattle farmers to refine and recycle their effluents.

Analysis of a New Single-Stage Soft-Switching Power-Factor-Correction LED Driver With Low DC-Bus Voltage

A new isolated single-stage soft-switching power-factor-correction (S4 PFC) driver for supplying light-emitting diodes (LEDs) is introduced in this paper. In the proposed LED driver, the switches voltage stress and also the dc-bus voltage is limited to the peak of the line voltage. Hence, low voltage rated mosfet s and diodes can be used. The efficiency is improved because the switches are turned on under zero current switching (ZCS) condition and turned off under zero voltage zero current switching (ZVZCS) condition. Also, no current feedback is required since the converter provides an output current independent of output voltage. In this paper, operating principle of the proposed LED driver is presented and design considerations are discussed. To verify the theoretical analysis, a laboratory prototype of the proposed converter for supplying a 50 W/70 V LED module from 220 Vrms/50 Hz ac mains is implemented, and the experimental results are presented. Since current feedback is not used, dimming property and operation for universal voltage range is not achievable.

Aluminum nitride coatings using response surface methodology to optimize the thermal dissipated performance of light-emitting diode modules

This study optimizes the thermal dissipation ability of aluminum nitride (AlN) ceramics to increase the thermal performance of light-emitting diode (LED) modulus. AlN powders are deposited on heat sink as a heat interface material, using an electrostatic spraying process. The junction temperature of the heat sink is developed by response surface methodology based on Taguchi methods. In addition, the structure and properties of the AlN coating are examined using X-ray photoelectron spectroscopy (XPS). In the XPS analysis, the AlN sub-peaks are observed at 72.79 eV for Al2p and 398.88 eV for N1s, and an N1s sub-peak is assigned to N-O at 398.60eV and Al–N bonding at 395.95eV, which allows good thermal properties. The results have shown that the use of AlN ceramic material on a heat sink can enhance the thermal performance of LED modules. In addition, the percentage error between the predicted and experimental results compared the quadric model with between the linear and he interaction models was found to be within 7.89%, indicating that it was a good predictor. Accordingly, RSM can effectively enhance the thermal performance of an LED, and the beneficial heat dissipation effects for AlN are improved by electrostatic spraying.

Electrohydrodynamic assisted droplet alignment for lens fabrication by droplet evaporation

Lens fabrication by droplet evaporation has attracted a lot of attention since the fabrication approach is simple and moldless. Droplet position accuracy is a critical parameter in this approach, and thus it is of great importance to use accurate methods to realize the droplet position alignment. In this paper, we propose an electrohydrodynamic (EHD) assisted droplet alignment method. An electrostatic force was induced at the interface between materials to overcome the surface tension and gravity. The deviation of droplet position from the center region was eliminated and alignment was successfully realized. We demonstrated the capability of the proposed method theoretically and experimentally. First, we built a simulation model coupled with the three-phase flow formulations and the EHD equations to study the three-phase flowing process in an electric field. Results show that it is the uneven electric field distribution that leads to the relative movement of the droplet. Then, we conducted experiments to verify the method. Experimental results are consistent with the numerical simulation results. Moreover, we successfully fabricated a crater lens after applying the proposed method. A light emitting diode module packaging with the fabricated crater lens shows a significant light intensity distribution adjustment compared with a spherical cap lens.

The influence of a soldering manner on thermal properties of LED modules

Purpose This paper aims to present the results of the influence of a manner of soldering light emitting diodes (LEDs) to the metal core printed circuit board on thermal parameters of the module LED containing these diodes. Design/methodology/approach Using the authors’ elaborated measuring method and the dedicated measurement set-up, transient thermal impedances of LED modules, mounted using different soldering processes and mounted to the heat-sink with different values of the moment of force, are measured. The obtained results of measurements are discussed. Findings It was shown experimentally that the manner of soldering could strongly influence efficiency of dissipation of heat generated in the module. The best thermal properties were obtained for soldering using vapour phase technology with vacuum and paste LFS-216LT. It was also proved that the moment of force used while mounting the considered modules on the heat-sink can result in a change of the value of thermal resistance of this module exceeding even 12 per cent. Research limitations/implications The investigations were performed for five LED modules operating at one, arbitrarily selected value of power dissipated in these modules mounted on the heat-sink of arbitrarily selected dimensions. Practical implications The obtained results of measurements could be usable for designers of mounting processes of power LED modules. Originality/value This paper presents the results of investigations of thermal properties of LED modules, in which different techniques of soldering are used. It was shown experimentally that the manner of soldering could strongly influence efficiency of dissipation of heat generated in the module. It was also proved that the moment of force used while mounting the considered modules on the heat-sink is important.

GaN-based mid-power flip-chip light-emitting diode with high -3 dB bandwidth for visible light communications.

By directly flip-chip soldering three mid-power light-emitting diode (LED) chips with periodic micro-via-holes on ceramic substrates, -3 dB modulation bandwidths of 49.9MHz, 58.8MHz, and 25MHz are obtained at the driving current of 170mA. To the best of our knowledge, these are the reported highest -3 dB bandwidth values for flip-chip power-type LEDs (FC-LEDs) at the low-bias current levels. Moreover, good radiant powers are also achieved: 180.2mW, 168.8mW, and 233.8mW at 150mA, respectively. With a gold wire-free feature, the fabricated FC-LEDs could offer an opportunity to miniaturize the package volume of a LED module for illumination and free-space high-speed VLC dual-usage applications.

RGB-Stack Light Emitting Diode Modules with Transparent Glass Circuit Board and Oil Encapsulation

The light emitting diode (LED) is widely used in modern solid-state lighting applications, and its output efficiency is closely related to the submounts’ material properties. Most submounts used today, such as low-power printed circuit boards (PCBs) or high-power metal core printed circuit boards (MCPCBs), are not transparent and seriously decrease the output light extraction. To meet the requirements of high light output and better color mixing, a three-dimensional (3-D) stacked flip-chip (FC) LED module is proposed and demonstrated. To realize light penetration and mixing, the mentioned 3-D vertically stacking RGB LEDs use transparent glass as FC package submounts called glass circuit boards (GCB). Light emitted from each GCB stacked LEDs passes through each other and thus exhibits good output efficiency and homogeneous light-mixing characteristics. In this work, the parasitic problem of heat accumulation, which caused by the poor thermal conductivity of GCB and leads to a serious decrease in output efficiency, is solved by a proposed transparent cooling oil encapsulation (OCP) method.

Uncertainty Quantification for Junction Temperature of Automotive LED With Die-Attach Layer Microstructure

Junction temperature is a critical metric for reliability evaluation of light-emitting diodes (LEDs) as light sources for automotive lamps. While numerous researchers have quantified the junction temperature accurately, uncertainty factors including electrical–thermal–mechanical boundary conditions and the die-attach layer (DAL) microstructure in automotive LEDs have not been addressed; the propagation of these variables degrades the precision of the junction temperature quantification. In this paper, a junction temperature uncertainty quantification framework involving finite element modeling, the evolution separation spectrum, and Monte Carlo simulation is introduced to build 3-D stochastic finite element models for automotive LEDs with stochastic DAL microstructures. Evolution of the statistical junction temperature probability for three types of automotive LEDs subjected to electrical–thermal–mechanical loadings is discussed and the failure risk is predicted. The results show that the temperature-mechanical displacement coupling of the DAL plays a major role in the junction temperature with regard to automotive boundary loadings, and the thermal power load is more likely to cause junction temperature deterioration of LED with DALs having voids. The automotive LED failure rate is dependent upon the boundary conditions, the DAL microstructures, and the LED numbers. The failure rate for LED modules with DALs having voids is higher than that for modules with uniform DALs; the failure rate is higher in aged LED modules; the failure risk at the given junction temperature threshold increases with increasing LED numbers in the module; and when operating at lower junction temperatures, the voids in LED DALs may not increase the module failure risk.

Unusual carbon nanomesh constructed by interconnected carbon nanocages for ionic liquid-based supercapacitor with superior rate capability

The exploration of various porous nanocarbon materials with an extraordinary electrochemical capacitive performance in ionic liquid (IL) electrolytes is urgently needed for development of the next-generation energy storage devices. Significant improvements in energy density have been achieved, however, supercapacitors with IL electrolytes usually suffer from issues related to low power density and large IR drop. Herein, we report an unprecedented carbon nanomesh that is made up of interconnected densely-packed carbon nanocages with ultrathin partially graphitic shells. The large specific surface area and well-developed mesopores combined with its unique structural features, make it a very competitive material for high-performance supercapacitor in IL electrolyte. Notably, this unique nanosheets morphology with lots of in-plane nanopores on their surface can provide fast cross-plane ion diffusion pathways, and meanwhile, the carbon nanocages with partially graphitic shells ensure the rapid electron transfer. The supercapacitor assembled with the optimized sample can deliver a high specific capacitance (up to 194 F/g at 1 A/g), superior rate capability (68% capacitance retention at 70 A/g), low IR drop (0.685 V at 70 A/g). Moreover, benefiting from the wide working voltage and high-rate capability, the energy densities can maintain at 56.1 Wh/kg even at an ultrahigh power density of 61.250 kW/kg. Strikingly, the as-assembled supercapacitor can successfully power a light-emitting diodes (LED, 2.2 V) module with 53 red LED lights demonstrating its great potential for practical applications in energy storage devices.

Arithmetic and experimental approach to effect of visible light absorption on silicone plate in high-power LED module

In a light emitting diodes (LEDs), the effect of visible light absorption on silicone encapsulant temperature has largely been overlooked by the scientific community. In this paper, we develop a new optical energy model to calculate the absorption power of a silicone plate in a remote phosphor LED module. In addition, we introduce a unique experiment for visible light absorption. Three types of silicone plate are investigated – a transparent silicone plate in a blue LED and two phosphor-mixed silicone plates (YAG:Ge, yellow phosphor) in white LEDs. We discover that by mixing phosphor with transparent silicone, the absorption coefficient is increased to 2.5 times in the case of 3 wt% phosphor-mixed silicone, and 5.9 times in the case of 30 wt% phosphor-mixed silicone compare with transparent silicone plate. Moreover, we find that visible light absorption only is able to increase silicone plate temperature by 7.3 °C in the case of transparent silicone, 18.7 °C in the case of 3 wt% phosphor-mixed silicone, and 43.3 °C in the case of 30 wt% phosphor-mixed silicone.

Thermal transient measurement and modelling of a power cycled flip-chip LED module

Reliability testing has become a major focus for light emitting diode (LED) systems to predict its lifetime. One common type of testing methods, which was investigated in this study, is the supply switching test (SST), also called power cycle test. In this paper, reliability testing was used to analyze failure modes appearing within a flip chip LED module. The characterization of the LED module was done by thermal transient measurement and radioscopic imaging. It was shown that the thermal transient measurement was sensitive enough to observe structural changes induced by the SST. To supply the experiments, a finite volume simulation of the LED module was carried out to analyze which physical structures in the LED module caused the changes in the measurements. Furthermore, the simulation enabled the thermal heat path to be visualized within the module via isotherms. To understand the changes seen in the measurement, two different failure type scenarios were implemented in the simulation. The effects of solder joint degradation and delamination in the printed circuit board (PCB) were analyzed and depicted by their isotherms. Conclusions about the failure roots could be drawn by comparing thermal transient measurements of a stressed LED module with its corresponding simulation of an integrated failure.

A Single-Stage Single-Switch Soft-Switching Power-Factor-Correction LED Driver

This paper proposes a new isolated single-stage single-switch soft-switching power-factor-correction (S6-PFC) driver without electrolytic capacitors for supplying light-emitting diodes (LEDs). In the proposed LED driver, all the semiconductor devices are soft-switched without employing any extra active switch. The leakage inductance of transformer acts as a resonant component so that the leakage energy is recycled. Soft-switching operation of the semiconductor devices together with absorption of the leakage energy improve the proposed driver efficiency. Furthermore, input current of the driver has very low harmonics resulting in high power-factor. Operating principles of the proposed S6-PFC LED driver as well as its design guidelines are presented. Also, experimental results of a laboratory prototype for supplying a 21 W/30 V LED module from 220 V/50 Hz ac mains are provided to verify the theoretical analysis. The presented results show that the implemented prototype has an efficiency of 92% under full-load condition and its input current total harmonic distortion is as low as 2.6%.

Rearrangeable and exchangeable optical module with system-on-chip for wearable functional near-infrared spectroscopy system.

.We developed a system-on-chip (SoC)-incorporated light-emitting diode (LED) and avalanche photodiode (APD) modules to improve the usability and flexibility of a fiberless wearable functional near-infrared spectroscopy (fNIRS) system. The SoC has a microprocessing unit and programmable circuits. The time division method and the lock-in method were used for separately detecting signals from different positions and signals of different wavelengths, respectively. Each module autonomously works for this time-divided-lock-in measurement with a high sensitivity for haired regions. By supplying of power and base and data clocks, the LED module emits both 730- and 855-nm wavelengths of light, amplitudes of which are modulated in each lock-in frequency generated from the base clock, and the APD module provides the lock-in detected signals synchronizing with the data clock. The SoC provided many functions, including automatic-power-control of the LED, automatic judgment of detected power level, and automatic-gain-control of the programmable gain amplifier. The number and the arrangement of modules can be adaptively changed by connecting this exchangeable modules in a daisy chain and setting the parameters dependent on the probing position. Therefore, users can configure a variety of arrangements (single- or multidistance combinations) of them with this module-based system.

Preliminary Study on Development of Ship-Rolling-Motion-Adaptive LED Fishing Lamp System

This paper presents a preliminary study on the development of a Light-Emitting Diode (LED) fishing lamp system that can maintain a stationary irradiation region despite ship rolling motions. The proposed system is composed of three modules which include a main control module, a fishing lamp module, and a sensor module. The main control module collects both the operating condition setting of the fishing lamp via the input panel and the tilt angle information of a fishing boat from the sensor module. It provides the conditions and information to the fishing lamp module for controlling the LED modules that maintain a stationary irradiation region. One fishing lamp module is composed of 22 LED modules, a lamp controller, and a temperature sensor. The sensor module is used for measuring the tilt angle of the fishing boat. Tests were carried out to verify the reliability of the LED module driver and the sensor module. The tests showed that the LED modules were reliably controlled, in accordance with the rolling motion of a fishing boat.