Dimmable LED Research Articles

Novel intelligent MPP tracker and sliding mode control for decentralized street lighting systems using photovoltaic energy

ABSTRACT This paper proposes a solution for powering an unlimited number of streetlight poles systems. Firstly, an intelligent MPPT battery charger incorporates battery state of charge monitoring and an Artificial Neural Network algorithm is incorporated to ensure optimal system performance. Secondly, an effective DC driver is proposed using a buck converter supported by a Sliding Mode Controller to achieve a smooth response under different loading conditions. Unlike traditional decentralised street lighting solutions, which focus mainly on LED dimming based on motion detection or basic MPPT algorithms, this paper proposes a hybrid approach that integrates an intelligent ANN-based MPPT battery charger with a robust SMC for load driving. The collected testing data are analysed to show effective MPPT battery charger and load driver using MATLAB/Simulink software. Simulation results demonstrate high performance of the proposed system, with accurate MPP location tracking by the ANN algorithm, achieving a Mean Square Error of 7.9467 × 10−5 and battery charging up to 80 % of SOC. The results also confirm an accurate controlling response of load driver with minimal voltage fluctuation of 0.25 mV and a low overshoot of 50 mV. The approach proposed enhances energy efficiency, making it ideal for large-scale, sustainable urban infrastructure.

A dimmable LED light source along the Planckian locus.

Multiple channels are designed for dimmable LED light sources with color temperatures ranging from 2,700 to 6,500 K. However, issues such as Delta uv (Duv) values <0, lower brightness, luminous efficacy, and color rendering index (CRI), lower power density, exceeding the standard deviation of color matching (SDCM), unconstant power, poor color consistencies, and high costs persist. We present a three-channel LED light source featuring an integrated chip-on-board (COB) package structure. The channels are separated by a white dam to reduce reabsorption problems and improve color consistencies between different color temperatures. Additionally, the complementary channel M uses layered phosphor excitation for more accurate and efficient spectral compensation during dimming. Ultimately, this solution enables dimming along the Planck curve with constant power, improving CRI, luminous efficacy, and brightness at intermediate temperatures, while being cost-effective and minimizing the impact on initial color temperatures, offering a high-quality dimmable LED option for intelligent applications.

Study on Lighting Energy Savings by Applying a Daylight-Concentrating Indoor Louver System with LED Dimming Control

Study on Lighting Energy Savings by Applying a Daylight-Concentrating Indoor Louver System with LED Dimming Control

Validation of Beam Angle Switching Method Using a LED Lumen Maintenance Testing Device

In today’s world, LED predominantly ousted all forms of light sources because of its long lifetime, reliability, very low power consumption, and excellent controllability. That is why, it became a necessity to find proper methods to examine all its characteristics. As directed in several standards, an accelerated life test (ALT) is a good method to predict LED’s lumen depreciation. In correspondence with these standards, to find that persistency of light output from a medium power LED, a prototype is developed, which has predefined data storage capacity with remote monitoring capability, at the Electrical Engineering Department’s Illumination Engineering Laboratory at Jadavpur University to measure the lumen maintenance factor, junction temperature, and ambient humidity in the defined test chamber. Besides, to test the device a particular case study is done to validate beam angle switching, a method for LED dimming. The case study reveals that the dimming method has no effect on the LED’s junction temperature or light output.

A Soft-Switching Proportional Dimming LED Driver Based on Switched Capacitor

This paper proposes a switched capacitor-based soft-switching proportional dimming LED driver to address color-mixing LED applications. The driver utilizes a half-bridge switch structure and incorporates a switched capacitor to regulate the dual resonant network. This configuration facilitates current sharing across each resonant network and enables fixed proportion dimming between them. The common inductance leveraged in this design results in fewer switching devices, thereby enhancing efficiency. Furthermore, all switches and diodes achieve soft switching, contributing to high efficiency. Finally, this paper built a 19 W experimental prototype, and the maximum efficiency reached 95.56%, which verified the correctness and feasibility of the driver.

Surgical Training in Resource-Limited Settings: Cost-Effective, Portable and Reproducible Personal Laparoscopic Endotrainer

Introduction: Minimal invasive surgery (MIS) is standard of approach for many surgical pathologies. The best way to enhance the psychomotor skills for MIS is through the disciplined and structured time with the Endotrainer. The cost and portability of available Endotrainer is the main reason for surgeons and residents allocating minimal time for training. Our goal was to create cost-effective and portable Endotrainer that enables skill development at home and classroom setting. Methods: The framework of this Endotrainer was made-up of local plywood. The anterior surface was divided into nearly equal superior and inferior surface by horizontal plywood stick. A rectangular window was created at the anterior surface for mobile phone or tablet or iPad placement. Similarly, two 8 mm hole were drilled and padded with locally available rubber washer inferior and lateral to rectangular window as laparoscopic ports. For light commercially available mini dimmable LED was installed. The final trainer box was similar in shape and size of medium suitcase, which was portable and could house laparoscopic hand instruments and training pads. Conclusion: The Endotrainer was easy and cost-effective to assemble. Embodying the essence of portability and reproducibility, this trainer box offers a personal practice tool that empowers trainee to sharpen their skills at their home or classroom.

Design and Implementation of A LED Driver Circuit with Dimming Function without Burst Mode at Constant Switching Frequency

This paper presents a dimmable LED driver with a topology of combination of series and parallel resonant converter. In dimming operation, a variable resonant inductor controlled by a PWM signal at a low frequency, while proving DC output current approaches, switching frequency variation or conventional PWM technique is not used. The proposed technique is performed on a load that consists of 40 one-watt power LEDs connected in series. Switching frequency of circuit is kept constant at 60 kHz. According to experiments results, LEDs can be dimmed to a desired power level linearly within the range of nominal power to very low power without being in burst mode unlike of the conventional PWM technique.

Design and Performance Evaluation of an Automatic Dimmable Fault-Adaptive LED Driver Circuit

In this paper, an automatic, fault-adaptive, and dimmable LED driver circuit and LED lamp module is designed and simulated. The designed LED driver can automatically operate and dim (18–72) W LED modules assembled with unknown series-parallel combination of 3 W LED chips on universal AC input (Vrms=(90–265) V, 50/60 Hz). The unique feature of the modelled LED driver circuit is its ability to monitor and detect failure of any connected LED chip and then adapt to provide optimised light output from the LED modules under faulty conditions. The proposed LED driver circuit and LED lamp module are simulated in MATLAB Simulink environment to evaluate the electrical performance. The operation of the simulated LED driver circuit from 100 % to 30 % of rated light output and during occurrence of fault is satisfactory and in compliance with IEC61000–3–2:2014 and IEEE Standard P1789. Input power factor of the simulated LED driver ranges from 0.74 to 0.99, THD from 3.33 % to 30.63 %, and output current ripple from 4.6 % to 20 % under operation of all connected LED modules.

Bi-Level Dimmable LED Driver in Refrigerated Display Lighting Systems

Commercial refrigerated display lighting (RDL) systems require LED drivers to provide constant 24 V to multiple LED light bars connected in parallel, each with a built-in current regulator to maintain a constant output brightness. The system uses a passive infrared motion detector to detect approach of people and a dimmer controller to further reduce the power consumption of the LED light bars. RDL system typically requires 100% and 20% only brightness control, so the dimmer controller can be replaced by a 0-10 V dimmable LED driver. By connecting a fixed resistor to the 0-10 V dimming interface, the brightness output can be set to 20%. However, the wiring of this technique is complex. This brief presents a new bi-level dimmable LED driver design that uses an astable multivibrator and totem pole gate driver integrated PWM dimming circuit to achieve a 20 brightness output through a single dimming wire, simplifying system wiring. The driver’s dimming wire is connected to the 24 V output voltage through the AC-powered passive infrared motion detector’s built-in relay, turning on the PWM dimming circuit to generate a 20% duty square wave signal that drives the internal series MOSFET at a frequency higher than 1.25 kHz to avoid LED flicker. This new design has been proven to have the advantages of high efficiency, low cost and easy wiring, and it can replace dimmer controller and 0-10 V dimmable LED driver in RDL applications.

A low-cost and realistic noisy light system for studying photosynthesis.

Unlike the light conditions commonly used to grow photosynthetic organisms in the research laboratory, the light intensity in real environments is dynamic. A simple and low-cost system is described in which a commercial dimmable LED panel is controlled to simulate a sinusoidal function representing daylight hours and overlaid with stochastic shading events. The output closely resembles light intensity measurements on Earth's surface on partly cloudy days or in lower levels of plant canopies. This tool may be useful to researchers studying photosynthetic acclimation responses.

An Energy-Efficient PAR-Based Horticultural Lighting System for Greenhouse Cultivation of Lettuce

This paper presents an intelligent horticulture lighting and monitoring system to achieve energy-efficient supplemental lighting while maintaining the light quality and intensity at desired levels in the photosynthesis spectrum. Energy-efficiency is achieved through delivering only the required net light intensity, consisting of sunlight and supplemental LED light, using an intelligent controller that does not depend on the lighting system model. To this end, an online neural-network learning control system is developed, comprised of low-cost light sensors for measuring the photosynthetic photon flux density (PPFD), dimmable LED light fixtures, cameras, and internet-of-things (IoT)-enabled firmware used for crop monitoring and performance evaluation. Experiments performed in a research greenhouse facility on the lettuce crop are presented which indicate that the system can deliver the desired Daily Light Integrals (DLIs) to the plants in the presence of changing daylight conditions. The proposed method can thus deliver the exact amount of light to a specific crop based on the required light recipes during different growth phases. The control performance is further compared with a conventional on-off time-scheduling method in terms of plant health, growth, and energy requirements. The experiments indicate that the proposed solution can reduce energy consumption per unit dry mass of lettuce by 28% when compared to existing time-scheduling methods.

True specs for dimmed and colour tuned LED luminaires

Colour tunable and dimmable LED lamps and LED luminaires are used increasingly in both domestic and professional lighting sector. The documentation of energy and light quality performance are often very limited for only for a single setting of multiple possible settings. Fifteen LED lamps and eight LED luminaires that are dimmable and tuneable white have been selected for demonstration of the variations in these parameters and possible errors in lighting design simulations. These have been tested in over twenty modes of operation including dimming from 100% to 25%, and correlated colour temperature (CCT) settings from 2200K to 6500K. The inherent standby power of these colour tuneable devices is measured, and the overall efficacy is evaluated in normal usage situations. In average for all tested LED lamps and luminaires 49% and 33% of the energy consumption is used in standby mode for 1h and 2h on time pr. day, respectively. The extensive set of test results show that there can be very large variations in e.g. the luminous flux, luminous efficacy and stroboscopic visibility measure (SVM), while others are very consistent over the modes of operation. The luminous flux shows variations of down to 22% of the maximum and rated value, and these lowest values occurs at the lowest CCT. The best performing has over 90% at all CCT settings. For the luminous efficacy most test results show a maximum value at 4000K or at the maximum CCT, and variations down to 20-50% of the maximum efficacy. The SVM is shown to increase to values over 1 and up to 2.4 at low dimming levels or low light output, demonstrating that stroboscopic effect will be visible for the majority of people and hence a problem in such settings. This is seen for approx. half the tested while the others have SVM < 0.4 for all settings and will not be visible over all settings. These results demonstrate the need for testing over the possible modes of operation to be able to correctly design and simulate a lighting installation using dimmable and colour tunable LED lamps and luminaires. The needed new dataformats and adoption of these from test laboratories to lighting software, in order for lighting designers and energy engineers to be able to make use of the extensive test results, are discussed.

Visible light-driven degradation of Acid Orange 7 by light modulation techniques

The impact of light modulation on the decolorization of Acid Orange 7 (AO7) in aqueous solution was examined in this paper. A fixed bed batch photocatalytic reactor with a flat plate geometry, irradiated by 240 white-light LEDs, was used. A successful transfer of visible active photocatalyst (N-TiO2) in powder form on a polystyrene (PS) transparent plate was realized. The structured photocatalyst was characterized through SEM–EDX, Raman and UV-DRS analyses, evidencing the formation of a coating of N-TiO2 in the anatase phase, with a band-gap energy of 2.5 eV, and almost uniform distribution on the PS surface. Different LED dimming techniques, with fixed and variable duty-cycle values, were tested, and four types of light modulation were compared: fixed duty cycle (constant irradiation), sinusoidal variable duty cycle (sinusoidal variable irradiation), triangular variable duty cycle (triangular variable irradiation), and square wave variable duty cycle (square wave variable irradiation). The resulting responsiveness/efficiency of the LED versus the current intensity was evaluated, and the stability of the photocatalyst activity and the influence of optimized irradiation waveforms were examined in the decolorization of 400 mL of 10 ppm AO7 solution. The sinusoidal modulation, with current between 50 and 100 mA and 10 s as the period, shows the highest value of the apparent pseudo-first-order kinetic constant, resulting equal to 0.0044 min−1, at parity of total transmitted photons. An energy saving with the application of sinusoidal irradiation is highlighted with respect to the literature.Graphical

MACHINE LEARNING MODEL FOR GLARE PREDICTION IN OFFICES WITH SIMPLE ARCHITECTURAL FEATURES

ABSTRACT Daylight glare index (DGI), daylight glare probability (DGP) and glare-sensation (GS) predictive models are the widely used glare indices for the assessment of occupant visual comfort in daylit spaces. This paper presents the development and implementation of Machine Learning models to predict these glare indices. The training and validation data sets were collected from sensors incorporated in the test room with motorized Venetian Blinds and dimmable LED luminaires. Predictor and response data were obtained from conventional sensors, digital cameras, and the EVALGLARE Software. The regression models predict DGI and DGP, whereas the classification model predicts GS. In addition to standard statistical error evaluation metrics, the hypothesis test assesses the performance of regression/classification models. The results reveal that Ensemble Tree (ET) models are highly accurate at predicting glare indices. The proposed technique attempts to simplify the existing traditional Glare Index(GI) estimation method. The combination of real-time daylight glare prediction and suitable window shading control increases occupant visual comfort. A high dynamic image-based system is employed to verify the measurements made using traditional sensors.

A Deep Learning-Assisted Visible Light Positioning Scheme for Vehicles With Image Sensor

Visible light communication (VLC) based on image sensor (IS) as the receiver is one of the supplementary technologies of radio frequency communication. By combining with image processing technology, VLC has various applications in smart home, underwater communication and intelligent transportation system (ITS). In the paper, it focuses on the vehicle positioning service provided by VLC in ITS. For the weak image spatial separability caused by long-distance VLC transmission between the vehicle and the infrastructure, it will lead to serious deterioration in communication and positioning performance. Thus, a deep learning-assisted IS-based visible light positioning (VLP) scheme is proposed and experimentally demonstrated. At the transmitter, a novel coding method is proposed to support both short-distance and long-distance communication based on VLC in ITS. Meanwhile, it can meet the dimming requirements of LED road infrastructure. In addition, in the proposed VLP scheme, it uses an artificial neural network (ANN) to predict the location of the vehicle. It is demonstrated that long-distance communication, high-accuracy positioning, and LED dimming can be realized simultaneously. The results show that, by using the proposed scheme, as the transmission distance is 2 m, the bit error rate (BER) of system is 1.25 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> . And the average positioning error is 19.8 mm at the maximum simulated distance of 30 m.

Comparative analysis of the energy efficiency of dimmable LED lamps with different types of luminous flux control

The article presents the results of experimental studies of the energy efficiency of dimmable LED lamps with different types of regulation. It has been established that CCR-controlled LED lamps pollute the electrical network less with current harmonics, which reduces power losses and loads the electrical network less. When the supply voltage changes, the energy characteristics of CCR-controlled LED lamps are generally less subject to negative changes than PWM-controlled LED lamps.

Dimmable LED Driver with Precise Power Metering

Dimmable LED Driver with Precise Power Metering

Determination of Speed-Dependent Roadway Luminance for an Adequate Feeling of Safety at Nighttime Driving

The purpose of this work is to determine as a function of velocity the minimal roadway luminance that is required to be judged as being bright enough for a driver to perform a nighttime driving task with an adequate feeling of safety. In this context, it shall also be evaluated which areas of the vehicle forefield are most crucial for the driver’s general brightness perception. A field study with 23 subjects and dimmable LED headlights was conducted, in which the subjects were given the task to assess their perceived brightness for different luminance levels caused by the headlights’ low-beam distribution in the vehicle’s forefield on a 5-step rating scale. The experiments were repeated for three different driving velocities of 0 km h−1 (static case), 30 km h−1, and 60 km h−1, respectively. Results for the static case indicate that, for the roadway to be perceived as bright enough by 50% of the subjects, an average roadway luminance of 0.88 cd m−2 is required in an area up to 32 m in front of the vehicle. Furthermore, a significant effect of driving speed is observed. For example, at 60 km h−1, the luminance must be increased to 1.54 cd m−2 to be still perceived as sufficiently bright by 50% of the subjects.

Low-cost smart solutions for daylight and electric lighting integration in historical buildings

Research have shown that the correct integration of daylight and electric lighting reduces the energy use in buildings, while improving visual comfort. Smart shading systems, especially those electrically controlled, play an important role to control solar radiation. Similarly, smart and dimmable/tunable lighting can help to adjust the artificial light to the real users’ needs. This paper presents preliminary results of an ongoing living lab study investigating how artificial lighting systems can be integrated with shading systems, placing human comfort at the heart of the study and yet saving energy. A manually controlled, commercial and low-cost smart system integrating two motorized shading devices and six dimmable LED luminaires with a different selection of CCT were installed in a private office in a historical building. Indoor and outdoor lighting conditions and energy consumption associated to the lighting system are constantly monitored to assess how the people use shading and lighting upon varying the boundary conditions.. Preliminary results highlight that users prefer to maximise daylight on the work plane as well as they generally use both shading and electric lighting systems in response to boundary conditions that cause serious discomfort.

Bridgeless Isolated AC LED Driver

A novel bridgeless isolated AC LED driver is developed, which improves LED utilization and application flexibility due to a coupled inductor inserted between the bidirectional switch and the LED module without any output electrolytic capacitor. By reducing the turns ratio of the coupled inductor, the voltage across the secondary side will be decreased so as to lessen the voltage across the LED strings and hence reduce the number of LEDs, thereby making the load design of the AC LED driver more flexible. It is noted that the coupled inductor plays a role of not only galvanic isolation but also inductor behavior as well as transformer behavior. Therefore, during the turn-on period of the bidirectional switch, the coupled inductor can transfer the energy to one LED string and store the energy simultaneously, whereas during the turn-off period of the bidirectional switch, the coupled inductor can release the stored energy to the other LED string. That is, two LED strings are conducted over a pulse-width-modulated (PWM) period for any half-cycle, implying that LED utilization is upgraded. As for LED dimming, it is realized by directly tuning the control signal for the bidirectional switch without any dimming circuit. Eventually, the basic operating principles and theoretical deductions are given along with some experimental results provided to verify the effectiveness of the proposed AC LED driver topology.