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Three LED drivers which can be used for illumination, but whose main task is the transmission of information (data) via the light of the LEDs, are explored in this paper. The converter circuits need no capacitors for the energy transformation and avoid an inrush current. The lack of necessity of electrolytic capacitors reduces cost and space. Dimming the illumination is also easy to achieve. The control concept of the converters and the generation of pulsing of the LEDs for transmitting the information (data) are explained. The converters can also be expanded to more stages to drive more LEDs with different types of information. All three converters are explained in detail; all presented circuits are built up and simulated with LTSpice. Several data transmission concepts are applied and demonstrated through simulations.

This article introduces a wide input range buck‐boost Light Emitting Diode (LED) driver designed for industrial and street lighting applications. The driver characterized by a continuous input current with less ripple and common ground between input and output featuring non‐inverting voltage at the output, suitable for green energy sources. The proposed topology achieves a high voltage conversion ratio which is a blend of quasi‐Z source boosting followed by conventional buck with enhanced step‐down voltage capability. Furthermore, the driver maintains a constant voltage at the load terminal for diverse source voltage variations by adapting the inherent buck‐boost nature. Also, the driver operates with low duty ratio results in lower voltage, current stresses and conduction losses. The steady state and design analysis of the proposed LED driver is carried out for an input voltage range from 24 to 96 V. An experimental prototype of 200 W/71 V LED driver is validated in the laboratory for wide input voltage. There is a high concordance exists between the theoretical analysis and experimental results of the proposed topology. [ABSTRACT FROM AUTHOR]

This paper proposed a single-stage AC-DC converter based on boost circuit and CLCL-T resonant converter for improving the performance of the LED driver. In practice, the two-stage LED driver is not suitable for low-power lighting applications. To overcome the problems, by integrating the boost power factor correction (PFC) circuit and CLCL-T resonant DC–DC converter, the proposed LED driver exhibits high efficiency and high reliability. The CLCL-T resonant converter can achieve soft-switching on the power switch and rectifier diode and reduce the switch losses at high frequencies. Operation principle, performance analysis and design considerations for the proposed LED driver are analyzed and discussed. The results indicate that the proposed single-stage LED driver is superior in terms of efficiency, volume and number of components. Finally, a 100-W experimental prototype is implemented, and the experimental results verify the effectiveness and feasibility of the proposed LED driver. [ABSTRACT FROM AUTHOR]

Three LED drivers which can be used for illumination, but whose main task is the transmission of information (data) via the light of the LEDs, are explored in this paper. The converter circuits need no capacitors for the energy transformation and avoid an inrush current. The lack of necessity of electrolytic capacitors reduces cost and space. Dimming the illumination is also easy to achieve. The control concept of the converters and the generation of pulsing of the LEDs for transmitting the information (data) are explained. The converters can also be expanded to more stages to drive more LEDs with different types of information. All three converters are explained in detail; all presented circuits are built up and simulated with LTSpice. Several data transmission concepts are applied and demonstrated through simulations. [ABSTRACT FROM AUTHOR]

Currently, various light-emitting diode (LED) lighting systems are being developed because LEDs are one of the most used lighting sources for work environments, buildings, homes, and public roads in terms of some of their applications. Similarly, they have low energy consumption, quick responses, and excellent optimal performance in their operation. However, these systems still need to precisely regulate lighting, maintain stable voltage and current in the presence of faults and disturbances, and have a wide range of operations in the event of trajectory changes or monitoring tasks regarding the desired voltage and current. This work presents the design and application of two types of robust controllers (structure-at-infinity control and geometric control) applied to an LED driver using a buck converter. The controllers aim to follow the desired trajectories, attenuate disturbances at the power supply input, and compensate for faults in the actuator (MOSFET) to keep the capacitor voltage and inductor current stable. When comparing the results obtained with the two controllers, it was observed that both present excellent performance in the presence of constant disturbances. However, in scenarios in which variable faults and path changes are implemented, the structure-at-infinity control method shows an overimpulse of output voltage and current ranging from 39 to 42 volts and from 0.3 to 0.45 A, with a margin of error of 1%, and it can generate a failure in the LED driver using a buck converter. On the other hand, when using geometric control, the results are satisfactory, achieving attenuating constant disturbances and variable faults, reaching the desired voltage (40 v to 35 v) and current (0.3 to 0.25 A) with a margin of error of 0.05%, guaranteeing a system without overvoltages or the accelerated degradation of the components due to magnetic conductivity. [ABSTRACT FROM AUTHOR]

This paper presents the results of the study of the parameters and characteristics of the developed high-performance electronic control circuits for special-purpose LED lighting systems based on a two-stage forward converter (driver) with an output power of more than 200 W. Operation of the developed driver in the output power range of 13 to 202 W and the supply voltage range of 160 to 250 V was investigated. The maximum efficiency of the developed power supply system at the voltage of 240 V and the output power of 140 W is 89.9%. For the chosen topology, further voltage increase may increase the efficiency, but lead to accelerated degradation of the driver components. The results of the experimental studies of the developed drivers showed the drivers efficiency in the range of 84 to 90% at a load of 52…202 W with a power factor above 0.97 and a nonlinear current distortion factor less than 23.4% over the entire studied range of supply voltages. The high efficiency of the developed driver in a wide range of output power suggests the possibility of using the driver in lighting systems that provide additional power supply to energy storage systems (batteries), including those ensuring operation in the absence of mains power supply. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a new light‐emitting diode (LED) driver based on full‐bridge series resonant converter (SRC) is presented. In the proposed converter LED, load is placed in between DC source and the input side of the full‐bridge inverter which reduces the rectifier components of the SRC. The proposed converter reduces the number of diodes used for rectification and ensures zero voltage switching of the power switches which improves the efficiency of the converter. LED lamp current is regulated with phase‐shift pulse width modulation (PWM) of full‐bridge. Lamp illumination is controlled with PWM dimming. The operation and mathematical analysis of LED driver is presented. To validate the proposed concept, a 40‐W laboratory prototype is developed. Experimental results are presented. Peak efficiency of 93% is obtained. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

DC-DC converters used in LED driver applications are desired to operate with high efficiency at high switching frequencies. Class-E resonant converter, which is simple in structure and easy to implement, is especially suitable for high-frequency and low-power applications because the directly grounded switch can operate under soft switching conditions. However, when the input voltage and output power vary over a wide range in variable frequency control, the soft switching conditions are lost. To eliminate this drawback, the class-E resonant converter with synchronous rectifier is proposed as an LED driver. Although designed to operate at the fixed switching frequency, this converter structure is controlled using a hybrid method in which variable and fixed frequency switching techniques are used together because the efficiency decreases as the load becomes lighter. The converter incorporates all the advantages of conventional class-E resonant converter, while the hybrid control highlights the advantageous aspects of both variable and fixed frequency switching. To verify the validity of the driver, a prototype circuit that can operate in the 25–50 V input voltage range and whose load is a 20 W LED module is constructed. A control algorithm where the operating parameters such as switching frequency, duty ratio and synchronization angle of the converter are estimated using the polynomial regression technique is developed for closed-loop control of the driver. The driver is dynamically tested against varying input voltage and reference current across a wide range. Test results confirm the validity and feasibility of the driver, and it is observed that the polynomial regression-based control algorithm effectively and robustly follows the reference current. Furthermore, while power control of the LED module is effectively carried out throughout the entire input voltage range from 0 W to 20 W, the power switches are turned on under soft switching conditions.

Regulating LED current and voltage is critical to maintaining a constant luminous flux in AC- or DC-powered LED lighting circuits. Today, users require constant current drivers that can provide a wide range of output voltages to drive different numbers of series-connected LED arrays. This work proposes an LED driver by combining an isolated SEPIC converter operating in the continuous conduction mode (CCM) and a modified Vienna rectifier. The proposed LED driver offers a single-switch control structure by adding a Vienna rectifier to the integrated SEPIC-FLYBACK converter. This driver structure provides many advantages over traditional bridge rectifier structures. The prototype circuit was tested in an 18 W continuous current mode (CCM) to verify its feasibility. As a result of the values obtained from both simulation and prototype circuit models, it has been shown to provide many of the following advantages: 95% high efficiency, high reliability, 4% low total harmonic distortion, 97% high power factor, and 70 V low switching voltage. This work meets class C 3-2 and IEC 61000 standards. [ABSTRACT FROM AUTHOR]

A novel hybrid Luo-Cuk converter designed for LED lighting systems combines elements from both Luo and Cuk topologies. By integrating the input branch of both topologies, the converter, employing a single switch, can generate two distinct types of outputs simultaneously. One output follows a Luo-type, while the other adopts a Cuk-type . Through a series connection of the outputs from Luo and Cuk topologies, the voltage gain of the converter has been notably enhanced. The converter's output can be effectively regulated using a single controller. To validate the consistency between the topology's performance and theoretical analysis, simulation and prototype results have been provided.

Light emitting diodes (LEDs) have become an effective lighting solution because of the characteristics of energy efficiency, flexible controllability and extended lifetime. They find use in numerous lighting systems for residents, industries, enterprises and street lighting applications. The efficiency and trustworthiness of the LED systems considerably based on the thermal mechanical loading improved several degradation schemes and respective interfaces. The complication of the LED systems limits the theoretic interpretation of the core reasons for the luminous variation or the formation of the direct correlation among the thermal aging loading and the luminous output. Therefore, this paper designs a new hybrid Henry gas solubility optimization with deep learning (HHGSO-DL) algorithm for LED driver system design. The presented HHGSO-DL technique mainly concentrates on the derivation of empirical relationships among the design parameters, thermal aging loading and luminous outcomes of the LED product. In the presented HHGSO-DL technique, bidirectional long short-term memory (BiLSTM) algorithm is executed for examining the empirical relationship and its hyperparameters can be tuned by the HHGSO algorithm. In this work, the HHGSO algorithm is derived by the integration of traditional HGSO algorithm with oppositional-based learning (OBL) concept. The performance of the HHGSO-DL technique can be investigated on LED chip packaging and LED luminaire with thermal aging loading. The extensive results demonstrate the promising performance of the HHGSO-DL technique over other state-of-the-art approaches. [ABSTRACT FROM AUTHOR]

Currently, various light-emitting diode (LED) lighting systems are being developed because LEDs are one of the most used lighting sources for work environments, buildings, homes, and public roads in terms of some of their applications. Similarly, they have low energy consumption, quick responses, and excellent optimal performance in their operation. However, these systems still need to precisely regulate lighting, maintain stable voltage and current in the presence of faults and disturbances, and have a wide range of operations in the event of trajectory changes or monitoring tasks regarding the desired voltage and current. This work presents the design and application of two types of robust controllers (structure-at-infinity control and geometric control) applied to an LED driver using a buck converter. The controllers aim to follow the desired trajectories, attenuate disturbances at the power supply input, and compensate for faults in the actuator (MOSFET) to keep the capacitor voltage and inductor current stable. When comparing the results obtained with the two controllers, it was observed that both present excellent performance in the presence of constant disturbances. However, in scenarios in which variable faults and path changes are implemented, the structure-at-infinity control method shows an overimpulse of output voltage and current ranging from 39 to 42 volts and from 0.3 to 0.45 A, with a margin of error of 1%, and it can generate a failure in the LED driver using a buck converter. On the other hand, when using geometric control, the results are satisfactory, achieving attenuating constant disturbances and variable faults, reaching the desired voltage (40 v to 35 v) and current (0.3 to 0.25 A) with a margin of error of 0.05%, guaranteeing a system without overvoltages or the accelerated degradation of the components due to magnetic conductivity.

Summary: Light emitting diode (LED) driver systems are now moving toward reduced processing power to improve conversion efficiency in indoor and outdoor applications. LED drivers connected to a single‐phase supply must meet the requirements for power factor correction with lower input current harmonics to maintain the alternating current (AC) power grid's quality and maintain a constant current through the LED load to eliminate the flickering effect in the light output. An LED driver is required to fulfill these requirements. In this paper, a new reduced processing power LED driver is proposed. By splitting the output capacitor into two capacitors and with the help of hardware design, the processing power can be reduced by using fewer semiconductors than in earlier designs. The proposed driver employs a simple ripple cancellation control approach to eliminate the 100 Hz ripple in the LED load current. Using this principle, an LED driver was designed and tested. The experimental results demonstrated that the proposed LED driver achieved an input power factor close to unity with lower input current harmonics and 92.5% of peak efficiency when operating at full power. [ABSTRACT FROM AUTHOR]

For low-power applications, this paper presents the development and design of a compact and ultra-highly efficient half-bridge LLC resonant converter. By using Galium Nitride (GaN) devices and high-efficient magnetics, the efficiency and power density of resonant converters can be improved. Compared to Silicon MOSFETs, GaN high-electron-mobility transistors (GaN HEMT) have a lower output capacitance and gate charge, resulting in lower driving loss and shorter dead times. Consequently, the proposed LLC converter based on GaN devices has excellent performance characteristics such as ultra-high efficiency, low switching losses, compact size, high voltage endurance, high operating temperature and high operating frequency. Furthermore, the proposed resonant converter features soft switching properties that ensure that the switches and diodes on the primary side are always switched at zero voltage and current. By doing so, LLC resonant converter switching losses are significantly reduced by up to 3.1%, and an overall efficiency of 98.5% is achieved. The LLC resonant converter design with GaN HEMT has great advantages over Si MOSFET solution regarding efficiency, overall losses, switching loose and power factor correction. A 240 W, 240 V to 60 V half-bridge GaN HEMT LLC resonant converter is simulated with a switching frequency of 75 KHz, along with the comparative analysis of the Si metal oxide semiconductor field effect transistor (MOSFET) solution. Moreover, the design and analysis of highly efficient magnetics with a power factor of 0.99 at full load is presented. A 240-Watt single stage LED driver with power factor correction is also designed to verify and compare the performance of proposed LLC resonant converter. [ABSTRACT FROM AUTHOR]

Tunability of correlated color temperature (CCT) and dimmability are the two major sought after features of functional solid-state lighting. This paper presents a low-cost, efficient, single-inductor-dual-output buck driver that facilitates CCT-control and dimming of a light emitting diode (LED) module composed of cool-white and warm-white chips. The proposed driver is designed based on two familiar integrated circuits (ICs), namely LM2596 and NE556. LM2596 serves as the main switching regulator and amplitude modulation (AM) controller whereas NE556 serves as the constant-frequency, dual-output pulse-width-modulation (PWM) controller. The exponential model of LED is exploited for improved estimation of the design parameters of the LED module and the driver circuit. The developed driver prototype is tested for its electrical, photometric, and colorimetric performances. The driver offers a full-load efficiency of about 90% for a 12-W test LED module. Under different operating modes, the LED system can produce warm, cool, or neutral white light and at the same time, the produced illuminance can be varied over a wide range. Moreover, the light flicker is imperceptible since the PWM frequency is set according to IEEE-1789 guideline. [ABSTRACT FROM AUTHOR]

Considered in this paper are the parameters and characteristics of the developed highly efficient electronic control systems for powerful LED modules (drivers), built on the basis of a single-stage flyback converter with a nominal power close to 200 W. The results of experimental tests show that, at the nominal load, the minimum efficiency of the developed driver reaches 88.2% with the power factor above 0.97 and the coefficient of total harmonic current distortion close to 23.4%. With the maximum value of the efficiency factor of the developed system 90.3% and the supply voltage 240 V, the power factor is higher than 0.99, and the total harmonic current distortion is 3.6%. The values of current harmonics of the driver do not exceed the maximum allowable values defined by the current standards. Used driver construction topology enabled to reduce the cost of the final product due to the unification of the component base, which increases the availability and manufacturability of the design. The use of a modern element base made it possible to ensure the deviation of the output current from the set one by no more than 1% over the whole range of the operating voltage of the supply (180...250 V), which allows using the developed driver in intelligent lighting systems and lighting systems with a combined power supply. [ABSTRACT FROM AUTHOR]

This paper proposes a novel electrolytic-free quasi-Z-Source Ćuk LED driver for automotive applications. Compared to the traditional Ćuk converter, the first merit of the novel converter is higher gain, which makes it apt to switch between multiple applications. Secondly, the proposed converter combines the inherent characteristics of LED load to operate in a wide range in Continuous Conduction Mode (CCM), so the inductors can assist in energy storage, and only small capacitance is required. Thirdly, inductors can be integrated and use only one core, and capacitors are electrolytic-free, which will benefit integration and long life. All merits are important to automotive application. Detailed analysis and design steps are presented. Then, with the help of the simulation software Saber, several key parts of the converter are simulated. Finally, a prototype controlled by the micro control unit stm32f103c8t6 is built, and the feasibility is verified by the experiment results. [ABSTRACT FROM AUTHOR]

In this paper, the application and design of a high-power factor isolated Ćuk converter-based LED driver are realized for up to 50 W power. For the power switch of the PFC isolated Ćuk converter, traditional Si and silicon carbide (SiC) MOSFETs, which are wide bandgap semiconductors, are used and compared. The application is conducted using a dsPIC30F4011 microcontroller including PI voltage control. A current sensor is added to limit maximum current. Moreover, PI control parameters are selected by genetic algorithm to avoid a complex mathematical procedure for controller design. The power LED model derived in this paper is used for the PI parameter selection process. In addition, the input side inductor of the converter is operated in discontinuous conduction mode, and the switching frequency of the power switch is 57 kHz. With the experimental setup, the total harmonic distortion (THD) of grid voltage and current, power LED voltage and current, switch voltage, and input side inductor current are shown for both the SiC and Si MOSFETs and compared. It is concluded from the application that the SiC-based driver gives better results than the Si-based driver on the basis of THD and efficiency. Further, both applications provide limits of IEC61000-3-2 C class standard. [ABSTRACT FROM AUTHOR]

This paper proposes a life test method and a model to predict the time to failure of LED drivers with electrolytic capacitors at the output stage that experience cycled power/thermal conditions. Based on failure rate estimation methods and field studies, degradation of aluminum electrolytic capacitors can be considered a potential point of failure in LED drivers and other power electronic applications. It is essential to identify failure modes, causes, and precursors of failure of electrolytic capacitors to design reliable power electronic circuits and estimate the useful lifetime of the designed drivers for a given application. LED drivers are exposed to elevated temperatures, on-off switching, and cycled thermal conditions like other power electronic converters. Past studies have investigated the parametric degradation of electrolytic capacitors under constant thermal stresses but not under cycled thermal conditions commonly found in lighting applications. Therefore, temperature and thermal cycling were selected as acceleration factors to study the effects of power/thermal cycling on the life of electrolytic capacitors in LED drivers. The accelerated life test showed that the LED driver's useful life had an inverse exponential relationship to the operating temperature of the output capacitor. The thermally cycled conditions did not indicate additional failure mechanisms introduced due to thermal cycling within the tested temperature range. Based on the experimental results, we developed a mathematical modeling technique to estimate the time to failure of LED drivers due to the electrolytic capacitor's parametric degradation with different operating profiles. • Electrolyte evaporation is the main failure mechanism in LED driver electrolytic capacitors. • Cycled power/thermal impacts on capacitor life in circuits lack extensive prior research. • Studied effects of power/thermal cycling on LED driver output and overall lifespan. • Proposed a life test method for predicting LED driver capacitor failures under thermal cycling. • Developed a method to estimate failure time from capacitor degradation under various profiles. [ABSTRACT FROM AUTHOR]

Permanent emergency lighting is a safety device whose lamp is always on and continues to operate when a mains failure occurs. The circuit has to charge the battery and drive the lamp while the grid is present and keep the lamp running from the battery in case of mains failure. This might require up to three different converters: front-end converter, electronic ballast, and battery charger. Since an emergency lamp must be on for as long as the local regulations require during a grid failure, efficiency is key. This article presents a permanent emergency lamp based on a series resonant current regulator that operates both as a ballast and as a battery charger. In this circuit, the power converter is placed in series with the LED array, operating as a controllable nondissipative impedance. A methodology based on the study of energy balances during resonant operation intervals is presented, aiming to design and build a laboratory prototype with low component count and high efficiency. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A buck-type LED driver together with automatic current sharing and high step-down voltage conversion ratio but without complex control is proposed. The proposed LED driver can not only achieve zero voltage switching (ZVS) turn-on by adding only one resonant coupled inductor, which resonates with parasitic capacitors of active switches, but also can obtain lower voltage gain and better conversion efficiency. In this paper, the operating principles and design considerations of the proposed converter are discussed in detail. In addition, the number of LED strings can be extended to more than four channels. Finally, the theoretical analysis and performance of the proposed LED driver are verified by simulations and experiments using a field-programmable logic gate array (FPGA) named EP3C5E144C8N as a circuit control kernel. [ABSTRACT FROM AUTHOR]

The demand for lean protein is the main reason for raising domesticated birds in poultry farms for the purpose of farming meat or eggs for food. In these poultry farms, artificial lighting system is an essential factor for the success of the commercial production of egg layers and broilers. Lighting loads connected to the existing AC system requires DC power. Nearly 25% of the total power consumed in India is by lighting loads. Therefore, low-voltage DC distribution system is the new requirement of electrical network to improve energy conservation. In this paper, an energy efficient single-stage LED driver topology is proposed as a better alternative to fluorescent lights used in poultry farms. The proposed topology is a phase-shifted buck converter with reduced size of passive components. The converter is mathematically modelled and designed for a power of 24 W LED lights. An experimental prototype is developed for the proposed converter and the results are validated in terms of cost, energy savings, and energy efficiency with various other LED driver topologies like conventional buck converter and interleaved buck converter. Further to justify the outcome of the proposed LED driver, a case study is also done for poultry farms. [ABSTRACT FROM AUTHOR]

A flicker-free resonant LED driver with high power factor (PF) and passive current balancing is proposed and analysed in this paper. The proposed LED driver are composed a buck power factor correction (PFC) unit and a resonant dc-dc unit by sharing an active switch. Based on this topology, the low output current ripple can be achieved via small voltage ripple on bulk capacitor and fast voltage-mode control loop. By the charge balance for resonant capacitor, the output current of each LED string can be balanced. In a half line cycle, owing to the small voltage ripple on bulk capacitor of pre-stage output, the duty cycle of active switch is almost constant. Therefore, when the inductor current of buck PFC unit operates in discontinuous conduction mode, high PF can be realized. Moreover, as the resonance is existed between resonant capacitor and leakage inductor of transformer, the diodes in resonant dc-dc unit can achieve zero-current turn-off. Thus, the efficiency can be improved. Finally, an 82W LED driver prototype with three-output is built to verify the studied results.

This paper proposes a high-performance isolated single-ended primary inductor converter (SEPIC) that is integrated with a non-dissipative snubber for a light-emitting diode (LED) driver. The proposed LED driver employs the snubber circuit to minimize any switching overvoltage caused by parasitic leakage inductance of the high-frequency transformer in the isolated SEPIC converter. This paper also presents a detail theoretical analysis of the proposed LED driver including its operating modes and design calculation. The experimental results of the proposed LED driver at the rated power of 18 W shows that it has a high-power factor, low harmonics, employs non-electrolytic capacitors, low switching stress, high reliability and high efficiency.

This article presents a two-stage automotive LED driver architecture delivering independently regulated output currents to multiple LED strings. The system consists of a multiphase noninverting buck–boost front-end stage, which allows for a wide battery voltage range, followed by high-frequency immittance-network-based LCL-T resonant converters, which operate as current sources over wide output voltage ranges. The two-stage buck–boost + resonant (BB+resonant) architecture takes advantage of the buck and boost capability of both stages, and the flexibility in setting the intermediate bus voltage to minimize losses. Advantages of the BB+resonant architecture include the use of lower voltage rated devices and soft switching in the resonant stage, leading to reduced losses and size. Experimental results are provided for a prototype consisting of a 250-kHz two-phase front-end stage and 2-MHz LCL-T resonant stages delivering independently regulated 1 A currents to four LED strings with $N = 1$ $-$ 18 LEDs. The measured system efficiency is greater than 88% over wide input (8 $-$ 18 V) and output (3–50 V) voltage ranges, with a peak efficiency of 93%. [ABSTRACT FROM AUTHOR]

This work presents an analysis and a design methodology for a DC–DC LLC resonant converter applied to off-line LED driving. An investigation regarding the main design parameters that influence the LED low-frequency (LF) ripple has been carried out. The study was based on a mathematical analysis of the converter and employs numerical algorithms to solve a set of equations that accurately describe the converter behavior. Based on this analysis, a novel design methodology that allows for LF current ripple prediction has been devised. A numerical model has been developed to determine the LF current ripple transmission in DC–DC LLC resonant converters and provide a methodology for designing the bus capacitance in two-stage off-line LED power supplies. The work shows that the design of the LLC resonant converter for off-line LED driving is a trade-off between the converter efficiency and the LF ripple transmission. Experimental results were taken from two 46-W laboratory prototypes considering two different design goals: one for LF ripple reduction and another aiming at the highest converter efficiency and better power quality. Furthermore, the design of a two-stage LED driver based on an LLC converter taking into account the LF ripple transmission is also presented. [ABSTRACT FROM AUTHOR]

In this study, a digital primary-side controller for a flyback light-emitting diode driver with superior line regulation, high power factor (PF), and low total harmonic distortion (THD) was proposed. Conventional constant on-time control is hampered by input current distortion, leading to high THD. To achieve high PF and low THD, a digital switching frequency limiter with quasi-resonant control was proposed. In addition, owing to the turn-off delay of the MOSFET and propagation delay of the feedback signals, a primary-side-controlled flyback converter experiences poor line regulation. To achieve superior line regulation, delay compensation was proposed and analyzed. A digital controller was realized using a field-programmable gate array and was applied to an input voltage of 90-264 Vac and an output current of 1 A in a hardware prototype to verify the feasibility of the proposed control solution. The experimental results indicate that line regulation was within ±3%, PF was higher than 0.95, and THD was lower than 5% at universal input voltage.

Cascaded boost-buck PFC (CBBPFC) converters offer a wide voltage conversion ratio and a near-unity power factor but require a large output electrolytic capacitor, leading to poor reliability and power density. In this paper, a coordinated two-stage operation and control strategy is proposed to significantly minimize the capacitor requirement without any other hardware changes. In a conventional CBBPFC converter, the boost and buck stages either operate independently nor complementally. In contrast, the proposed method operates the two stages in a concerted manner, so it is possible to use the dc-link capacitor with certain voltage fluctuation to buffer the power imbalance between the AC input and DC output. A new coordinated control strategy and a fluctuation-ratio based design consideration are developed to coordinate the operation of the two stages, further complement the system design. A 200W CBBPFC prototype based on the design concept exhibits a maximum reduction of the output capacitor by 83%, a peak efficiency of 95.8%, and a power factor of 0.99.

The lightning surge robustness of a light-emitting diode (LED) driver based on a flyback converter has been experimentally investigated. It is demonstrated that the surge failure in the driver results from the burnout of the super-junction vertical double-diffused MOS (SJ-VDMOS). The high residual surge voltage causes the SJ-VDMOS to go into breakdown, resulting in a large number of impact ionizations. It is also shown that the impact ionization centers in the device are enlarged and shifted toward the bottom of trench gate with the increased surge stress. As a result, the generated holes preferentially flow along the p-body region near trench gate, finally triggering the parasitic BJTs and destroying the device. Next, a low-cost protection scheme that includes both a first-stage discharge network and a novel SJ-VDMOS with higher surge robustness is proposed to improve the lightning surge capability of the LED driver, increasing the robustness by more than a factor of 10. [ABSTRACT FROM AUTHOR]

This paper presents a new hybrid dual-loop control system for the DC/DC LLC resonant converter, operating as a downstream DC/DC converter in a two independent stage offline LED driver. The outer loop employs a PI controller to maintain the average LED current regulated at the reference value and reject parametric variation. The inner loop implements an adaptive periodic disturbance rejection (APDR) subsystem, thus conceiving the hybrid PI\&APDR controller. The APDR subsystem is designed to strictly reject the bus voltage ripple and limit its transmission to the LED current. Experimental results show the proposed controller feasibility in achieving good tracking behavior, reduced output current ripple under different bus voltage ripple amplitude and frequency, robustness against parametric variations, and simple implementation and design. For the sake of completeness, the proposed PI&APDR is compared with the conventional proportional resonant controller employing experimental results and extra analysis based on simulations.

This article presents a Photoplethysmography (PPG) sensory system for continuous health monitoring. The PPG chip is fabricated using $0.35~\mu \text{m}$ standard CMOS technology and occupies 2.3 mm $\times$ 1.7 mm. The average power consumption of the receiver analog front-end (AFE) is $50.75~\mu \text{W}$ , the LED driver is power $29.3~\mu \text{W}$. The consumed power is dramatically reduced due to the using of both low duty cycle for LED lighting and automatic light control (ALC). The PPG sensor has a low input noise current of 41.3 pA and can reject a DC photocurrent up to $24~\mu \text{A}$ because of the integrated background light cancelation (BLC) loop. 12-b SAR-ADC and Serial Peripheral Interface (SPI) are integrated for communication with MCU used for signal processing and results display. Readings of 9 subjects show mean absolute error (MAE) and standard deviation (SD) of 1.95±2.13 beats per minute (BPM), 6.00±4.18mmHg, and 6.13±3.93mmHg, for heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP), respectively. [ABSTRACT FROM AUTHOR]

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Summary: A multicolor light‐emitting diode (LED) module comprises LED chips of more than one type or color and is frequently used for spectrally tunable lighting applications. In this paper, electrical models of such multicolor LED modules are formulated taking two basic circuit configurations into account, namely, (i) conventional, where a parallel string is made of one particular LED type, and (ii) nonconventional, where a parallel string is composed of different LED types. For deriving the model equations, the basic exponential model of a single LED chip has been applied, which is experimentally found to be the suitable option out of the four existing models, namely, linear, parabolic, exponential, and modified Shockley models. The formulated models are experimentally validated, results of which show maximum deviations of 4.71% and 4.19% from the measured data in the nonlinear and the linear operating regions, respectively. The formulated models are utilized to design dimmable, isolated LED drivers for red‐green‐blue (R‐G‐B) LED module. Performance evaluation of the drivers is conducted in Matlab‐Simulink. The results reveal the satisfactory operation of the LED modules in terms of current and power regulation, branch current matching, and fast response and thus establish the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

A high-efficiency LED driver with the pulse frequency modulation (PFM) control method to generate nearly consistent illuminance is demonstrated in this investigation. The illuminance consistency is achieved by sensing the feedback voltage and the temperature to modulate the on time of power devices such that automatic illuminance regulation is carried out. The recommended LED driver using the PFM control method is featured with an up-and-coming illuminance equalizer. Thus, it does not need any compensation circuit. Utilizing a 0.5- μ m High Voltage CMOS process, the prototype has successfully fabricated, occupying 3.2 mm 2 of chip area. The measurement outcomes of the chip demonstrate that the current error remains within 1% when the LED output current set at 20 mA. Moreover, the variation in illuminance is exceptionally low, measuring a mere 0.5%. Furthermore, the efficiency reaches 91% verified by the measurement results. [Display omitted] • The LED Driver uses pulse frequency modulation (PFM) control technique. • Implemented on a single chip using TSMC 0.5- μ m HV CMOS process. • Illuminance variation is 0.5% through on-silicon measurement. • High efficiency of 91% in the measurement results. • Measurement results show an Illuminance Uniformity of 0.85. [ABSTRACT FROM AUTHOR]

One of the most efficient lighting technology is based on light-emitting diodes (LEDs). Common LED drivers with AC-input (50-60Hz) usually require a bulk electrolytic capacitor to decrease low-frequency ripple in the output. However, the critical element that limits the lifespan of the LED driver is the electrolytic capacitor. An isolated off-line LED driver is proposed in this paper, in which the required output capacitance is reduced so that the electrolytic capacitor can be omitted from the driver structure. The driver’s configuration and controlling method provide a high input power factor. Just a single switch and therefore a single controlling IC have been used in the proposed structure. The input power factor correction is implemented utilizing a boost-based method, and a novel structure is introduced for dc/dc conversion section. Power factor correction and dc/dc conversion are performed employing a simplistic and single controlling system. The output current feeding the LEDs is a high frequency pulsating current. Calculations, simulations and experimental waveforms of a laboratory prototype are presented to confirm the validity of the proposed driver.

In the field of non-isolated light-emitting diode (LED) driver, the omnipresent buck-based LED constant current driver shows poor efficiency in occasions of high step-down ratio due to the marginal operating duty cycle. In order to overcome such drawback and to provide an alternative topological scheme for an LED driver, a Watkins-Johnson topology-based solution is proposed in this paper, by improving the original circuit structure into a dual low-side power switch version and introducing a feedback network for regulating the output current to a constant level. Theoretical analysis, including accurate model construction, steady-state analysis, dynamic analysis, and design consideration, is conducted. Also, an experimental prototype is realized to drive all kinds of LED arrays for acquiring electrical parameters and evaluating performance. The innovative points include invoking the low-side-ize approach to realize the power circuit transformation, and furthermore, theWatkins-Johnson topology is first applied to the constant current power supply. The proposed LED driver holds salient features of low-terminal current ripple, ease of driving, high-voltage conversion ratio tolerance, and inherent energy recovery functionality. The application scope covers low-voltage dc input or automotive lighting use.

In energy efficient system designs, LED lighting leads to reduction in global energy demand. This paper proposes a high brightness, high efficiency, dimmable LED driver based on linear current regulator technology for DC grid distribution systems. The proposed driver has excellent characteristics like highest lumen per watt, long lifetime, high reliability, compact, low cost, both environmental and user friendly which makes it suitable for lighting applications. Steady state and small signal model of the proposed driver are performed which helps in minimizing ground current and accurate compensator design, respectively. These two modelling approaches result in the optimization of both footprint and cost of the driver. The performance of the proposed 20W driver is modeled using real-time simulation in spice software. Experimental prototype is developed to validate the performance of the proposed driver for different dimming levels and achieves a maximum efficiency of 97%.

A buck-type LED driver together with automatic current sharing and high step-down voltage conversion ratio but without complex control is proposed. The proposed LED driver can not only achieve zero voltage switching (ZVS) turn-on by adding only one resonant coupled inductor, which resonates with parasitic capacitors of active switches, but also can obtain lower voltage gain and better conversion efficiency. In this paper, the operating principles and design considerations of the proposed converter are discussed in detail. In addition, the number of LED strings can be extended to more than four channels. Finally, the theoretical analysis and performance of the proposed LED driver are verified by simulations and experiments using a field-programmable logic gate array (FPGA) named EP3C5E144C8N as a circuit control kernel.

An MC3 LLC resonant light-emitting diode (LED) driver is a multi-channel constant current (MC3) output solution based on LLC resonance. Through an effective combination of multiple transformers and a DC block capacitor, this driver allows constant current outputs in multiple channels when the LED channels are unbalanced. This study considers a fuzzy self-tuning proportional integral derivative (PID) control strategy that allows for the self-tuning of PID parameters according to fuzzy inference rules designed using the relationship between the current gain and the switching frequency. Thus, when LED channels are unbalanced, the system allows a constant current output for each of the channels and controls the input voltage disturbances well. Simulation and experimental verifications are carried out, and a 20 W 4-channel constant current power supply design based on LLC resonance is obtained for the LED driver. This realizes soft-switching of the switching device, which reduces system loss and improves system efficiency. Moreover, the adjustment time of the proposed method is half that of fixed-parameter control methods, and the overshoot of the proposed method is smaller than that of fixed-parameter control methods. When compared with PID controllers with fixed parameters, the proposed method is more robust. When a system is disturbed, it recovers faster and has a smaller range of current fluctuation with the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, current-mode boundary conduction mode (BCM) of a high-efficiency LED driver with high power factor, utilizing low-voltage film capacitors, is presented, and its theoretical design and considerations are discussed. The 1.5-stage driver consists of a forward-flyback and buck converter. Higher efficiency was reached using the reduced redundant power processing approach. Most of the processed energy is transferred to the output through flyback, while the rest removes the low harmonic ripple in the output current through the forward-buck path. An acceptable amount of odd harmonics is injected into the input current by using current-mode BCM control method, further reducing bus capacitance. To validate these principles, a laboratory prototype has been built and experimental results of a high-current 85 W (29.5 V/2.9 A) lamp with 50 Hz, 185–255 V power supply are provided. The results show that output current ripple is low, and the input current harmonics are within the standard regulations. [ABSTRACT FROM AUTHOR]

This paper shows the status of the ethernet-based communication solutions, focused on optical links, for the automotive industry. First, the implementation of a product compatible with the 1000BASE-RHC according to the IEEE Std 802.3bv is presented, which is the first able to transmit 1 Gbps over POF (Plastic Optical Fiber) for automotive. Second, a new architecture to achieve up to 25 Gbps for automotive is described. The proposed Multi-Gigabit system leverages existing technologies, as VCSELs (Vertical-cavity surface-emitting laser), multi-mode fibers and photodiodes already developed for the data centers industry. [ABSTRACT FROM AUTHOR]

The accurate and effective reliability prediction of light emitting diode (LED) drivers has emerged as a key issue in LED applications. However, previous studies have mainly focused on the reliability of electrolytic capacitors or other single components while ignoring circuit topology. In this study, universal generating function (UGF) and physics of failure (PoF) are integrated to predict the reliability of LED drivers. Utilizing PoF, lifetime data for each component are obtained. A system reliability model with multi-phase is established, and system reliability can be predicted using UGF. Illustrated by a two-channel LED driver, the beneficial effects of capacitors and MOSFETs for the reliability of LED drivers is verified. This study (i) provides a universal numerical approach to predict the lifetime of LED drivers considering circuit topology, (ii) enhances the modelling and reliability evaluation of circuits, and (iii) bridges the gap between component and circuit system levels. [ABSTRACT FROM AUTHOR]

In order to reduce the number of switching devices and the switching loss of the LED driver, this paper presents a novel single-stage AC-DC LED driver based on LCLC resonant converter. The topology can reduce the number of switching devices by combining the power factor correction converter with the resonant converter. On the other hand, it can reduce the switching loss by using LCLC resonant converter, which can realize ZVS and ZCS simultaneously. In this paper, the structure is analyzed in detail and the LTspice IV software is used on the simulation. Finally, the correctness of the analysis is verified by experiment.

In order to reduce the size and cost of a medium-power light-emitting diode (LED) driver, a novel single-stage LED driver integrating a boost converter with a half-bridge LLC resonant converter has been proposed. This topology is composed of a boost power factor correction circuit operating in a discontinuous conduction mode and an isolated LLC circuit unit with soft-switching characteristics. The proposed LED driver only adopted two switch components, thus benefiting from control simple and without employing an extra switch driver and a control circuit. The operating principle and characteristics of the proposed LED driver are analyzed in detail. In addition, experimental results of a laboratory prototype for supplying a 100-W/70-V LED lighting systems from 220-V/50-Hz ac line voltage are presented to verify well the correctness of the theoretical analysis and parameters’ design.

Multiple output LED drivers are necessary to achieve better performance and higher reliability in street lighting, tunnel lighting and LCD background lighting applications. Based on LCL-T constant-current characteristics, a modular multiple output LED driver is proposed in this paper. The LCL-T rectifiers are connected to the same voltage bus and work like current sources. However, since there are much higher voltage harmonics in the AC square bus voltage, it is very important to quantitatively analyze how these harmonics influence the precision of the output currents. In addition, all of the switches can achieve Zero Voltage Switching (ZVS) by proper design of the LCL-T network. Finally, a 200-W prototype with five channels is established with an efficiency of 92.25%. [ABSTRACT FROM AUTHOR]

A low flicker dimmable four-channel LED driver with precise current balancing is proposed in this paper. It is able to achieve highly linear dimming and low lighting flicker at the same time by utilizing a new matrix-style digital pulsewidth modulation (DPWM) along with LED string rotation. Only one LED string needs to be modulated to reduce the total LED current variation and switching loss. To avoid color shift and reduce the effect of subharmonic flicker, a fourth-order common centroid layout is applied to match the current-controlling MOSFETs for precise current balancing. Low-voltage and high-temperature protection circuits as well as a temperature-compensated relaxation oscillator are all integrated to complete the driver design and reduce the overall cost for practical applications. The chip is designed in a TSMC 0.25- $\mu \text{m}$ 1P3M 60-V high-voltage CMOS process with a chip size of $1.76\times1.37$ mm2. The current mismatch among LED strings is measured to be only ±0.28% along with four times reduction in lighting flicker. [ABSTRACT FROM AUTHOR]