LED Lighting Module Research Articles

Direct Design of Thin and High-Quality Direct-Lit LED Backlight Systems

The direct-lit LED backlight is a key component in large-area LCD displays. The existing methods which rely on point source assumption and irradiance feedback are less effective in compact designs in near field, and designing thin and high-quality back-lit LED backlights still remains a challenging issue. In this paper, we develop a direct method for designing thin and high-quality back-lit LED backlight systems. The étendue of LED light sources is considered in the numerical calculation of the lens profiles without cumbersome Monte Carlo ray tracing, which allows us to obtain compact LED lighting modules and achieve accurate control of the near-field irradiance distribution of the backlight system. Two examples are presented to demonstrate the elegance of this method in designing thin and high-quality back-lit LED backlights.

Influence of Light Spectra on the Production of Cannabinoids

In recent years, more attention has been paid to cannabis from both medical and political points of view. This study investigates the influence of 5 different light spectra on the active substance content in THC-poor hemp of the Alessia chemotype II variety. The focus is on comparing conventional growing under metal halide lamps with growing under high-pressure sodium (HPS) vapor lamps with regard to different spectra of LED lighting modules. Growing was carried out in 10 growing boxes under controlled and mostly identical conditions for all boxes. The photoperiod during the vegetative phase was 18 h light and photosynthetic photon flux density ∼520 μmol⋅m⁻² s⁻¹. The flowering phase was 12 h light and ∼540 μmol⋅m⁻² s⁻¹. During the experiment, CO₂, temperature, and humidity were measured and logged. Additionally, weekly measurements of chlorophyll, electric conductivity of the fertilizer, activity measurement (salt content) of the soil, and pH value of the soil were checked. The content of cannabinoids was measured by high-performance liquid chromatography (HPLC). Plant height and growth were monitored during the whole experiment by cameras taking pictures every 30 min and loading them onto a cloud storage platform. Cannabinoid content was measured using HPLC. Plant wet weight was determined at the end of the experiment and showed that plants under the high pressure lamp treatment had less flower weight than those under the LED treatment. In conclusion, it could be shown that certain LED spectra can considerably increase the amount of cannabinoids with respect to conventional illumination (HPS).

효율적인 LED 제어를 위한 다윗 스타 마방진 알고리즘

In this paper, we propose efficient LED lighting control algorithm using a David star magic square. Such algorithms increases the power reduction, the heat efficiency and LED life cycle and the efficiency of the LED lighting control consumption. Lighting system using existing Magic square algorithm could be reduced to increase the heat efficiency of the LED because the LED lighting time of the reduced cross-lighting. but it has a limit to the lighting control. If should apply the this proposed algorithm, can reduces power consumption and increases LED life-cycle, heat efficiency of LED lighting module and efficiency of the lighting control of the LED. This paper proposed that algorithm is by using a David star magic square on the LED Matrix. Divided into twelve areas to move the pattern in constant time interval, to perform the cross rotation and inversion techniques to thereby light up. In this paper proposed algorithm of this paper was compared with existing Magic square approach. As a result, power consumption and heat-value and luminous flux was reduced as the conventional lighting system. And, the LED lighting control increase the efficiency.

Developing a dermatological photodiagnosis system by optical image analyses and in vivo study

Dermatological photodynamic therapy (DPDT) involves using systematic photosensitizers in combination with light irradiation treatment to eliminate cancer cells. Therefore, a noninvasive fluorescence photodiagnosis system is critical in DPDT for diagnosing target tissues and demarcating the margin of normal tissues. This study proposes a 375-nm ring LED light module in fluorescence imaging for DPDT applications. Image reproducibility (I.R.) and image interference (I.I.) analysis were performed. The results showed that the I.R. value of this fluorescence diagnostic system was higher than 99.0%, and the I.I. from external light sources was lower than 3.0%. In addition, the result of an in vivo study showed that the Chlorin e6 red fluorescence and the scope of distribution of B16-F10 melanoma cells in a mouse ear’s vein could be measured clearly using our device; however, the comparison studio with 395-nm LED lights could not focus or capture the red fluorescence effectively.

Effects of Diode Voltage and Thermal Resistance on the Performance of Multichip LED Modules

This paper investigated the thermal characteristics of multichip LED modules under varying chip distances, driving currents, and number of chips in both parallel and series connections. The experimental results showed that, under the same input power, the thermal resistance and junction temperature were higher in series than in parallel due to the different diode resistances of individual chips. The deviations increase with increasing input power. Diode resistance variations significantly affected the current distributions in LED modules due to the restricted constant forward voltage in parallel connections. Nonlinear incremental increases in thermal resistance also enhanced the temperature nonuniformity in the LED module with increasing driving current. The theoretical approach substantially underestimates the junction temperature for two-chip and four-chip modules in both parallel and series connections, especially when the input power is high. The results are helpful for designing high-performance and long-term reliability multichip LED lighting modules.

Development of LED Module based on Adjustable AC Line Direct SMPS

In this paper, we perform an AC direct input using PA2200Q driver IC module to improve efficiency of LED. In consideration of durability of LED module and its light module and low cost, This LED light module without using any external capacitors and inductors can be adjust a current waveform automatically in order to accomplish a low noise and high power factor including temperature adaptability. There are also the advantages of not only providing wide range of input voltage (200-260VAC) with 50/60Hz but also improves EMI and power factor as well as decreasing harmonics with sequentially current tracking method.

A Direct AC Driver with Reduced Flicker for Multiple String LEDs

This paper proposes a method to reduce flicker when running an AC-power direct-drive type multiple string LED driver IC. The proposed method greatly decreases flicker using one capacitor and Ptype MOSFET transistor (PMOS). The flicker index (FI) was reduced by over 40% through experiments, and less than half of the conventional external components are used in the passive valley fill circuit, which gives an advantage in the cost and utilization in the design of LED lighting modules. The 0.35 um 700 V BCD process was used to manufacture this LED driver.

A study on growth of the Plant depends on PPFD and Wavelength of LED lighting module

A study on growth of the Plant depends on PPFD and Wavelength of LED lighting module

헬리컬 핀 구조를 가진 LED 조명용 히트싱크의 열 특성

In this paper, we design a helical fin structure for the heat sink for a high-power LED lighting module, and analyze its thermal properties. By means of the helical fin structure, we can obtain about 14% larger surface area for the limited volume and it can decrease the LED chip temperature by about 12%. Because this helical fin heat sink has 15% less total volume than a conventional one, we can also expect to reduce the production cost due to these structural properties.

Thermal characteristics for chip on metal package of LED lighting module

The insulator of the metal printed circuit board (PCB) area layer, where a chip is packaged in the metal PCB structure of the chip on board (COB) package, is removed in order to propose a chip on metal (COM) package that allows the direct packaging of the chip to the PCB metal layer. In order to analyze the thermal characteristics from the chip, both COB and COM packages were fabricated during the operation to measure the chip junction temperatures (Tj) and thermal resistances of both specimens. According to the Tj measurement result, Tj=34.64°C for the COM package with the removed insulator and Tj=45.28°C for the COB package, showing that the COM package had an approximately 10°C less thermal distribution. Similarly, the thermal resistance of the COM package was 0.7°C/W, which was about 1°C/W less than the COB package thermal resistance of 1.67°C/W. Also, by comparatively analyzing the changes in the spectrum, color coordinates, and speed of light according to the driving time, it was found that luminous color stabilization may have contributed to the luminescence properties of the COM package, which has lower thermal resistance, and the degradation of the chip and packaging material can be minimized.

Thin LED light module using the inclined edge and inhomogeneous pattern reflection of a light guide plate

A low-power, high-brightness, thin, and flat LED light module was fabricated. LED arrays attached to the four walls of the lower part of a light guide plate (LGP) were used as the light source. The LGP was composed of a lower part with dot patterns on the bottom side, an intermediate section with inclined edges for the reduction of the bezel area, and a light-exiting plate. The bottom sides of the inclined edges and lower plate were coated with metal films for light reflection. The dot patterns on the bottom side of the lower plate were more concentrated in the center to obtain uniform brightness by inhomogeneous reflection. The dimensions of the fabricated LED light module were 100 mm (L) × 100 mm (W) × 10 mm (T). The average brightness and luminous uniformity of the LED light module were 12,155 cd/m2 and 96.7%, respectively.

Effect of Thermal Dissipation by Adding Graphene Materials to Surface Coating of LED Lighting Module

The effect of thermal dissipation by adding graphene nano-platelets to two different commercially available thermal dissipation coatings (ceramic coating and powder coating) was studied. Steady state temperatures of each points of LED modules was monitored in a closed system, with an integral photo detection sphere where there is no external air flow. Having eliminated the contributions of thermal conduction and air flow convection, the module with a conventional heat dissipation coatings showed 8-16% enhancement of thermal dissipation compared to that of non-coated LED module. The addition of graphene is shown to have about 3% additional enhancement. By analyzing thermal resistance of each component of the LED module, the improved thermal conductivity of the graphene added coatings contributes to the enhancement of slight improvement with heat dissipation.

Design of a LED Module with Special Constraint

LED gradually replaces light source in many fields, it becomes more and more important. For the purpose of letting LED more effective, people usually use secondary optical lens to improve the optical quality. In this research, reflector and lens are used to compose a LED light module. In this study, a LED module is designed to meet the specific requirement of the illumination. It was found that changing lens thickness and lens position can improve the uniformity and the size of light patch. As a result, we found parameters about lens for best results. In the design process, we realized that uniformity can be increased by decreasing D10 value of the light. The best result of simulation was found (which are in the form of point data). We used polynomials to fit the contour of LED module of point data and used it to extend the reflector contour of calculated results. The size of light patch of LED contour with reflector-masked and point data is much smaller than with polynomials.

The Fluorescence Image of Portable System Enhanced by Asynchronous Trigger UV-LED Excitation

Fluorescence is widely used to detect the biochemical effect and some substance containing certain dye. In general, the formation of fluorescent reaction is that an organism or dye, excited by UV light, emits a specific frequency of light; the light is usually a visible or near infrared light. Practically, the fluorescence of object can be excited by continued UV light, but the contrast and sharpness of fluorescence image decrease readily with stray light from the surrounding. In this study, we connect a trigger LED light module to a portable camera system and to perform the fluorescence inspection. When the fluorescent object is excited by asynchronous trigger UV-LED light, the extra intensity of fluorescence can be obtained. In the experiment of security organic dye (BL-ORT), the relative intensity of fluorescence acquired by 30 fps CCD can be increased by more than 11 %. In addition, when the fluorescent dye (chlorine e6) is injected into the tail vein of nude mouse, if its tail excited by the 375nm asynchronous trigger and continuous UV-LED are processed, the average relative intensity is 56.5 % and 49 %, respectively. Therefore, an added relative fluorescence of 15.3 % can be obtained from asynchronous triggering method. Furthermore, the ratio of extra intensity increases with the increase of frame rate of camera.

An Isolated Dual-Input Converter for Grid/PV Hybrid Power Systems

An isolated dual-input power converter for a grid/photovoltaic (PV) hybrid power indoor lighting system is proposed in this paper. The proposed converter can be operated in single power supply mode or hybrid power supply mode. While the available PV power is insufficient for the load demand, the proposed dual-input converter will automatically deliver the complement power from the grid. The power complementing is achieved by two independent control loops of the PV power and the grid power. Finally, a prototype for a 36W LED lighting module is constructed to verify the validity of the proposed converter. From the experimental results, it can be seen that a smooth 24V/1.5A output power for the LED lighting module can be provided even while the PV power is insufficient or unavailable.

A 36 W Wireless Power Transfer System with 82% Efficiency for LED Lighting Applications

This paper presents the design and implementation of an LED lighting module powered by a wireless power transfer system. The overall system achieves an efficiency of 82% with an output power of 36 W when the load resistance in the receiver is 30 Ω, which is the turn-on resistance of the LED lighting module. The transmitter of the system adopts ClassE power amplifier structure instead of Class-D, to decrease the number of transistors and its cost. The coils of the system are designed by electromagnetic coupling methodology and realized by Litz wire to reach high efficiency. Matching circuits between the system blocks are also discussed in this paper in order to obtain the excellent system performance.

A Novel Optimization Approach Applied in Injection Molding of a Led Lighting Module

A Novel Optimization Approach Applied in Injection Molding of a Led Lighting Module

Experimental study of microrectangular groove structure covered with multi mesh layers on performance of flat plate heat pipe for LED lighting module

The paper presents a novel concept for a coronary-stent-like model to solve the problem of compactness between wick and copper mesh, which can enhance the performance of the hybrid structure flat plate heat pipe (FPHP) of LED lighting modules. The various wick structures combine axial rectangular grooved structures, manufactured in aluminum extraction, and the concept of a coronary-stent-like model, which provides a supportive copper mesh and wick structure. In this study, the performance of FPHP was experimentally measured at different inclination angles and heating areas. The axial rectangular groove structure and copper mesh layer structures have different permeabilities and capillary pumping forces, and combining these two structures could be beneficial for pumping the required operational fluid across the axial groove structure and from the condenser to the evaporator under different inclinations of the flat plate heat pipe. The exterior wall temperature of the FPHP was measured to evaluate the thermal resistance and vapor heat transfer coefficient at the condenser and evaporator for 31×31 and 10×10mm2 heating areas. The experimental result showed that the FPHP has better performance in both the junction temperature of the LED light module and the uniformity of the substructure temperature. The highest FPHP temperature was decreased by 28%, as compared to a commercial substrate. In addition, a 200W LED light module, running for 9h with FPHP, maintained luminance at about 2080 lux due to its low thermal resistance and high capillary force.

Design of the Liquid-Cooling System for High Power LED Modules Using Taguchi Analysis

To optimize thermal dissipation efficiency for cooling high power LED modules is studied and analyzed using ANSYS CFX software and Taguchi method. In liquid-cooling system, four control factors are tested and compared in order to find the best cooling arrangement that are pump flow rate, fan power, cooling liquid type and k- value of thermal compound. The experimental results show that the importance of these cooling parameters applied to high power LED module are k-value of thermal compound, fan power, liquid type and pump flow rate in sequence. For a constant heating power of 90W from an LED lighting module, an optimal thermal resistance of 0.563K/W is obtained that shows a significant improved result then the conventional LED module’s. It has high potential in future high power LED applications.

TRIAC 디밍제어방식을 적용한 실내 LED 조명기기의 전도성 잡음 저감에 관한 연구

This paper analyzes the noise sources of an LED lighting module with TRIAC dimming control and proposes an improved EMI filter design for the reduction of conducted noise emission. TRIAC dimming invokes problems of input oscillation and capacitor overvoltage at the lighting module. The proposed double LC filter reduces high noise level from the circuit. The experimental and simulation results show that this approach can make significant contributions to the reduction of conducted noise emission from an LED lighting module with TRIAC dimming control.