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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%.

In this paper a research on magnetic control of DC-DC converters applied to LED drivers is presented. The proposed control method is based on the modulation of the effective inductance of the DC-DC converter operated in discontinuous conduction mode (DCM). Thus, by using a variable inductor (VI), the converter output can be controlled in order to regulate the current through the LED. This work demonstrates how the method of magnetic control can be effectively be used to control DC-DC converters with an LED load, as well as be combined with other control parameters as duty cycle or switching frecuency to improve the converter performance. An experimental prototype has been built to test the control method analysis and modeling methodology, and to verify its feasibility and possibilities.

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 paper introduces a megahertz-frequency resonant dc–dc converter that inherently achieves a load-independent output current while maintaining high efficiency across a wide output voltage range. These properties make the proposed converter well-suited for automotive light-emitting diode (LED) driver applications, where a varying number of LEDs need to be driven with a constant current. The proposed converter achieves load-independent output current by utilizing an LCL -T resonant network, and achieves high efficiency using a comprehensive design optimization methodology. This LCL -T resonant converter is also capable of regulating its output current at any desired value by utilizing phase-shift control. The performance of the LCL -T resonant converter is theoretically and experimentally compared with an LC 3 L and an LCLC resonant converter. For the experimental comparison, prototypes LCL -T, LC 3 L , and LCLC resonant converters are designed to operate at 2 MHz and across an output voltage range of 3.3–49.5 V while supplying a constant 0.5 A output current to the LEDs. The LCL -T resonant converter prototype achieves a peak efficiency of 91.1%, which is 0.6% and 1.8% higher than the peak efficiency of the LC 3 L and the LCLC converter prototypes, respectively. Furthermore, the LCL -T converter prototype maintains 0.8% and 1.6% higher average efficiency over its 15:1 output voltage range relative to the LC 3 L and the LCLC converter prototypes, respectively.

The high-brightness light-emitting diodes (LEDs) require an AC/DC converter with power factor correction (PFC). The large output electrolytic capacitor, which is used to minimize the low frequency ...

This paper proposes an efficient LED lamp converter circuit incorporating dimming feature and multiple lamp independent control. The converter consists of a half-bridge resonant converter in series...

This paper proposes a single-stage LED driver based on the CLCL resonant circuit and boundary conduction mode (BCM) boost circuit. The input voltage of an LED driver is categorized into two capacitors, which will reduce the input peak voltage by making a single-stage LED driver to work under maximum input voltage modes. The proposed CLCL resonant circuit contains a soft-switching feature where the major and minor area works under zero voltage and zero current phases, respectively. Moreover, this approach has reduced very small turn-off loss, turn-off current of a switch, which in turn proves the system efficiency. In this paper, the proposed BCM circuit, as well as CLCL resonant converter circuit, has been explained with five operational phases, and experimentation and analysis were made for proposed and existing methodologies. For validation of the proposed system, a 100 W investigational prototype is used, and experimental results were analyzed with the theoretical result.

Light-emitting diode (LED)-based lighting is the most dominant lighting solution in the current era since it is energy-efficient and long-lasting. Hence, performance analysis of the LEDs throughout its lifetime is of prime importance. The work presented in this article provides insight on degradation analysis of the LED luminaire inclusive of the LED driver in real operating ambient conditions and investigates the performance of both LED light engine and LED driver throughout the period of its lifetime. To represent the practical scenario of LED lighting system usage in commercial applications, analysis of switching cycles on the performance of LED luminaires is also studied. The outcome of this article suggests that LED luminaire under study tends to fail due to lumen degradation, followed by color shift represented by Duv and then lastly by driver failure. Scanning electron microscope and energy-dispersive spectroscopy (SEM-EDS) analysis suggests the corrosion of Ag mirror resulting in lumen output reduction and, thus, is the main reason for the failure of LED luminaire. This provides an insight into the LED manufacturing companies to have better estimate on lifetime of LED luminaires and also the necessity to improve the LEDs’ performance such that luminaires will have longer lifetime as claimed.

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.

LED lighting market share shows an ever increasing trend. This is driven by some of the LED advantages, such as higher efficiency, wide range of colors, and longer lifetime. LED is a DC device, and to power it from AC supply, like in household or street lightings, a driver is required to convert AC to DC supply. In addition, LED driver is preferred to operate in constant current mode in order to avoid LED thermal runaway. Also the driver has to have high efficiency, low THD (total harmonic distortion), and comply with electromagnetic emission limits. In this paper, a prototype of primary-side-regulated AC-DC flyback LED driver has been implemented. It has a constant output current of 0.990A 0.012A across the output voltage 15.59V – 42.80V. Measurement results show that the achieved efficiency is up to 88.55%, current harmonics comply with IEC 61000-3-2, and conducted emission levels comply with CISPR 15.

Single-inductor-multiple-output (SIMO) light-emitting-diode (LED) drivers are attractive, practical solutions for lighting applications. An SIMO LED driver is usually constructed with conventional voltage-source-mode dc-dc converters. Current-source-mode (CSM) converters, though being highly suited for current driving, are less studied. Simple control, low cost and independent dimming function are among the advantages of CSM SIMO converters. The limiting factors of CSM SIMO converters, however, include the relatively low efficiency and the restricted number of outputs under low-frequency pulse-width modulation (PWM) dimming control. In this study, an adaptive current bus technique to the CSM SIMO converter is applied. Results show that a significant improvement in efficiency can be achieved. The low-frequency PWM dimming method is also analysed and redesigned. Also, we compare the voltage stress in the CSM SIMO converter with traditional input-series-connected structure. Results show that the CSM SIMO converter achieves a high-voltage step-down ratio without the use of transformers. This study presents detailed analysis and experimental results of the CSM SIMO converter with adaptive current bus.

This paper presents a genetic algorithm (GA)-based optimal configuration for multisegmented linear LED driver to achieve a maximized system efficiency. Based on the theoretical analysis of the turn-ON states, the system efficiency is derived and found to be highly dependent on the segment voltage and reference current parameters. GA with a fitness function of the system efficiency is introduced in detail for the case of a four-segmented LED voltage configuration. With an input voltage of 220 V (rms) and input current of $8\times $ , $10\times $ , $11\times $ , and $12\times $ reference for the four turn-ON states, the four optimal segment voltages are calculated to be 160, 80, 39, and 22 V. Saber simulation results show that the GA-based configuration can give a higher efficiency (96.5%) than other typical configurations (

This paper presents a light-emitting diode (LED) driver for street-lighting applications that uses a resonant rectifier as a power-factor corrector (PFC). The PFC semistage is based on a zero-current and zero-derivative-switching (ZCDS) Class-E current-driven rectifier, and the LED driver semistage is based on a zero-voltage-switching (ZVS) Class-D LLC resonant converter that is integrated into a single-stage topology. To increase the conduction angle of the bridge-rectifier diodes current and to decrease the current harmonics that are injected in the utility line, the ZCDS Class-E rectifier is placed between the bridge-rectifier and a dc-link capacitor. The ZCDS Class-E rectifieris driven by a high-frequency current source, which is obtained from a square-wave output voltage of the ZVS Class-D LLC resonant converter using a matching network. Additionally, the proposed converter has a soft-switching characteristic that reduces switching losses and switching noise. A prototype for a 150-W LED street light has been developed and tested to evaluate the performance of the proposed approach. The proposed LED driver had a high efficiency (>91%), a high PF (>0.99), and a low total harmonic distortion (THD i

This chapter introduces the topology and control methods for light-emitting diode for performance improvement, including efficiency, output current quality, and lifetime.

In the first part, this paper aims to analyze the optical and electronic performance of advanced drivers for LED lighting applications, taking into account the financial aspects. Consequently, for two price classes (low- and high-cost), we investigate the power conversion efficiency, their grid impact, lighting characteristics, and finally the cost-benefit ratio. Experimental measurements on physical prototypes validate the simulations performed with real supplying conditions. The final part of the paper explains some optimization steps for price-performance ratio according to a multicriteria matrix or to the main criteria established by the beneficiary. The study should be a useful decision making tool for both the scientific community and the contracting authorities.

The main contribution of this paper is to show a new AC/DC converter based on the rearrangement of the flyback converter. The proposed circuit only manages part of the energy and the rest is delivered directly from the source to the load. Therefore, with the new topology, the efficiency is increased, and the stress of the components is reduced. The rearrangement consist of the secondary of the flyback is placed in parallel with the load, and this arrangement is connected in series with the primary side and the rectified voltage source. The re-arranged flyback is only a reductive topology and with no magnetic isolation. It was studied as a power supply for LEDs. A low frequency averaged analysis (LFAA) was used to determine the behavior of the proposed circuit and an equivalent circuit much easier to analyze was obtained. To validate the theoretical analysis, a design methodology was developed for the re-arranged flyback converter. The designed circuit was implemented in a 10 W prototype. Experimental results showed that the converter has a THDi = 21.7% and a PF = 0.9686.

In this paper, an LLC light-emitting diode (LLC LED) driver based on the current-sharing capacitor is presented. In the proposed LED driver, the LLC resonant converter is used to step down the high input voltage, to provide galvanic isolation, to offer a constant current for LEDs. Moreover, the current-sharing capacitor connected to the central-tapped point of the secondary-side winding is used to balance the currents in two LED strings. By doing so, the voltage stress on this capacitor is quite low. Above all, the equivalent forward voltages of the two LED strings are generally influenced by the temperature and the LED current, and this does not affect the current-sharing performance, as will be demonstrated by experiment on the difference in number of LEDs between the two LED strings. In addition, only the current in one LED string is sensed and controlled by negative feedback control, while the current in the other LED string is determined by the current-sharing capacitor. Moreover, this makes the current control so easy. Afterwards, the basic operating principles and analyses are given, particularly for how to derive the effective resistive load from the LED string. Eventually, some experimental results are provided to validate the effectiveness of the proposed LED driver.

In this paper, a stacked half bridge converter with automatic current balance and soft-switching is proposed. Here, an LED driver is taken as an example to analyze. Based on the ampere-second balance principle, the proposed LED driver can realize automatic current balance. The proposed converter adopts a small inductor to form a resonant tank, which achieves zero current switching (ZCS) in the discontinuous operation mode (DCM) and zero voltage switching (ZVS) in the continuous operation mode (CCM). By using frequency doubling technology, switching losses are reduced by half under the same hardware conditions. A 15.8W experimental prototype with 100V input voltage and 25V output voltage is established in the laboratory, verifying the feasibility of the stacked half bridge converter.

A LED (Light Emitting Diode) driver operating under a DC input voltage and driving a series of high power LEDs, is presented in this paper. Different topologies of LED driver feeding a constant current into a LED load and their operation principles are analyzed and discussed in detail. Then, a laboratory prototypes of constant-current LED drivers based on DC-DC buck converter with full dimming capability is designed, implemented, and tested. Experimental results show good agreement with simulation results.

Valley switching is one of the most efficient methods to decrease the switching losses in DC/DC converters. It uses a resonance between the converter's inductor and parasitic output capacitance of a metal–oxide–semiconductor field-effect transistor. In this study, the drawbacks of the valley switching in buck light-emitting-diode (LED) drivers are investigated. It shows that in spite of decreasing the switching losses, the valley switching method reduces its efficiency in some conditions. Also, it is clarified that the valley switching method not only causes current fluctuation in boost power factor correction converters but also malfunctions the buck LED drivers' performance. In this study, a semi-valley switching and its implementation are introduced to solve these problems. In general, it is shown that the proposed method improves both the efficiency and the performance of the buck LED driver, simultaneously. The methodologies are implemented in an experimental prototype to verify the proposed method.

This paper presents a modeling approach for FL ballasts and LED drivers with adjustable topology and feedback control of switching converter stages suitable for flicker sensitivity studies. The driver model is based on switch-averaging modeling principle. Together with a generalized lamp model it can be used to estimate flicker level of given driver and lamp combination. Out of eight driver classes identified in related literature, the model is fitted – and thus verified – on two classes, the first corresponding to a current-controlled DC-DC converter and consisting of one active, closed-loop controlled, converter stage, the latter corresponding to two stage closed-loop controlled driver.

Highly efficient passive Light Emitting Diode (LED) driver configurations are studied and examined in this paper. The technology based on the LED becomes a promising lighting technology to exchange inefficient energy lamps. For outdoor applications, the LED drivers based on passive elements are appropriate in extreme weather conditions. A comparison of LED driver configurations is presented. Each LED driver configuration is validated through simulation, and their waveform characteristics are examined and analyzed.

Two-photon (2P) microscopy is a cornerstone technique in neuroscience research. However, combining 2P imaging with spectrally arbitrary light stimulation can be challenging due to crosstalk between stimulation light and fluorescence detection. To overcome this limitation, we present a simple and low-cost electronic solution based on an ESP32 microcontroller and a TLC5947 LED driver to rapidly time-interleave stimulation and detection epochs during scans. Implemented for less than $100, our design can independently drive up to 24 arbitrary spectrum LEDs to meet user requirements. We demonstrate the utility of our stimulator for colour vision experiments on the in vivo tetrachromatic zebrafish retina and for optogenetic circuit mapping in Drosophila.https://github.com/BadenLab/LED-Zappelin

This paper presents a novel driver topology to accurately control the current through LEDs by using a current sink, a switch mode pre-regulator, few interface components and a microcontroller employing an algorithm that controls and predicts the output state in normal and fault modes without directly measuring the output parameters. The topology is easily scaleable to realize multichannel LED drivers, supports wide range of LED loads, provides superior drive current accuracy and is modulation and flicker free. In this paper we provide an overview of the shortcomings of the commonly used multichannel topologies and demonstrate how the proposed architecture and control logic can solve those shortcomings. Experimental results are also provided to validate the operation of the proposed topology in both normal and abnormal load conditions.

Due to the use of electrolytic capacitor, the life span and operating temperature range of traditional light emitting diode (LED) drivers are limited. In order to solve these problems, many researchers focus on electrolytic capacitor-less design. In this paper, a new electrolytic capacitor-less LED driver with power factor correction (PFC) function is proposed. By using a coupled inductor, a single-stage topology with optimized energy-flow-path and higher efficiency is proposed. With this new topology, electrolytic capacitor can be replaced by film capacitor with lower capacitance value and longer lifetime so that the life span of the LED driver can be prolonged. Simulation results are presented to verify the proposed design.

A novel passive integrated unit is proposed to increase the power density of a single-stage light-emitting diode (LED) driver in this paper. With the flexible multi-layer foil (FMLF) integration technique, such an integrated unit consists of two transformers, one resonant inductor and two resonant capacitors to reduce the volume of these passive components. The composition principle, flux analysis and parameter design of the proposes integrated device are introduced in detail, respectively. Finally, the validity and feasibility of the proposed ideas are proved by the simulation results of a Maxwell model and a prototype for a 100W-100kHz single-stage LED driver.

In this paper, a novel topology combining reconfigurability and hybridization is presented. Reconfigurability allows the proposed converter to operate in three different operating modes, yielding a wide range of step-up conversion ratios. The combination of two charge-pump cells and an inductor allows to reduce the average inductor current if compared to a standard equivalent boost converter. A prototype with integrated MOS, drivers, and logic but external passives was built. Experimental results show that with $\mathbf {f_{s} }=\text{300}\,$ kHz, $\mathbf {V_{in} = \text{6}}\,$ V, and $\mathbf {I_o = \text{70}}\,$ mA, the converter can cover conversion ratios in the range from $\text {2.5}$ to $\text {10}$ , with a maximum output voltage equal to $\text {60}\,$ V. Peak efficiency is $\text {91}$ %. When the output current is increased to $\text {100}\,$ mA peak efficiency is $\text {92.8}$ %.

The trend of utilizing light emitting diodes (LEDs) in some applications has attracted the attention of many researchers, to study its applications. This article investigates the performance analysis of the dc–dc converter systems based on analog and digital controllers for a low voltage dc–dc buck converter, to drive strings of LEDs at different conditions, to judge system’s robust performances. This converter comprises of a single controller, working with a voltage control feedback system, in a continuous conduction mode. The analog and digital type-3 controllers are designed for the said system while using standard frequency response techniques. Simulations are shown to validate the design and the response of these controllers under various dynamic load conditions.

The electrolytic capacitor (Al-Cap) is widely considered as one of the reliability-critical components in LED driver applications. A realistic lifetime prediction of Al-Caps would be beneficial to the sizing of capacitors to fulfill a specified design lifetime. This paper investigates the impact of electrolytic capacitor parameter shifts on the LED driver performance and the capacitor reliability. The operation condition, degradation, and tolerance are considered as the main reasons that deviate the parameters from nominal values. A method to model the degradation of Al-Cap parameter is introduced as well. In the case study of a flyback LED driver for street lighting, the contribution of parameter shifts to the electrical performance of LED drivers and Al-Cap core temperature is evaluated based on both theoretical analysis and simulation. A quantitative comparison of the estimated lifetime of Al-Cap in the LED driver is given with and without the consideration of capacitor parameter shifts within the service life. The proposed method enables a more realistic way for electrolytic capacitor lifetime prediction in LED drivers, which would otherwise have the risk of overestimation.

This paper presents the implementation of a two-stage light-emitting diode (LED) driver based on commercial integrated circuits (IC). The presented LED driver circuit topology, which is designed to drive a 150 W LED module, consists of two stages: AC-DC power factor correction (PFC) stage and DC/DC power converter stage. The implementation of the PFC stage uses IC NCP1608, which uses the critical conduction mode to guarantee a unity input power factor with a wide range of input voltages. The DC/DC power converter with soft-switching characteristics for the entire load range uses IC FLS2100XS. Furthermore, the design of an electromagnetic interference (EMI) filter for the LED driver and the dimming control circuit are discussed in detail. The hardware prototype, an LED lighting system, with a rated power of 150 W/32 V from a nominal 220 V/50 Hz AC voltage supply was tested to show the effectiveness of the design. The presented LED driver was tested for street lighting, and the experimental results show that the power factor (PF) was higher than 0.97, the total harmonics distortion (THD) was lower than 7%, and the efficiency was 91.7% at full load. The results prove that the performance of the presented LED driver complies with the standards: IEC61000-3-2 and CIRSP 15:2009.

This paper presents a 7.7-mm2 on-chip LED driver based on a DC/DC resonant hybrid-switched capacitor converter operating in the MHz range with and without output capacitor. The converter operation allows continuously dimming the LED while keeping control on both peak and average current. Also, it features no flickering even in the absence of output capacitor and for light dimmed down to 10% of the nominal value. The capacitors and switches of the LED driver are integrated on a single IC die fabricated in a low-cost 5 V 0.18-μm bulk CMOS technology. This LED driver uses a small (0.7 mm2) inductor of 100 nH, which is 10 times smaller value than prior art integrated inductive LED drivers, still showing a competitive peak efficiency of 93% and achieving a power density of 0.26 W/mm2 (0.34 W/mm3).

This study indicates a converter based on change condenser to drive a high power light emitting diodes LEDs. Unlike standard steady current DC drivers, change condenser provides the current pulse. The recommended approach varies from the classical switch capacitor as it utilizes a little inductor to improve the swapping performance of the converter. The impact of condensers on the chosen regulator is demonstrated and examined based on the charging control analysis. A 3 W, 220 V experimental prototypes has been implemented when the outcomes are reported and explained in order to show that the proposed converter is practically feasible and can be used as LED driver.

A light-emitting diode (LED) driver circuit of warning lighting with a photovoltaic (PV) panel is proposed in the paper. To efficiently utilize PV power, the LED driver employs a partial power regulator (PPR) for tracking the maximum power point (MPP) and simultaneously matching the dimming feature. A laboratory LED driver with a 54-W PV panel is designed for a 40-W LED warning-light formed by 36 LEDs. Experimental results have demonstrated that the LED driver can perform the dimming control of the warning-light and at the same time accomplish the MPP tracking of the PV panel in a wide operation region. A high efficiency can be achieved by processing a small part of the generated PV power with partial power regulation.

In this paper, a critical study on the improvement of energy efficiency on the commercial light emitting diode (LED) driver along with the development of power conversion technique over the last two decades was conducted. A new classification of LED driver was proposed based on the new technologies and construction invented recently, and the past classifications of LED driver used. The corresponding energy efficiency on different types of LED drivers was studied accordingly. A new effective labeling scheme of energy efficiency on LED driver that will be suitable in Hong Kong from 2019 to 2029 was proposed based on the recent situation and the new classification. This proposed labelling scheme can be used as reference by the manufacturers of LED driver on the selection of power conversion techniques with various levels of energy efficiency.

An auto-zero-voltage-switching (ZVS) quasi-resonant LED driver with gallium nitride (GaN) FETs for general lighting applications is presented. The proposed LED driver switches at high frequency to minimize the inductors to microhenry range. ZVS can be automatically achieved with the proposed controller to eliminate switching loss. The GaN FETs enable high-frequency operation and improve the power efficiency. A fully integrated LED shunt protector is proposed to bypass the failed LEDs in series-connected LED strings. The overall lifetime of the LED strings can be improved, and the maintenance cost can be reduced. The characteristics of the ZVS quasi-resonant LED driver with small inductors and the conditions for ZVS are also discussed in detail. The LED driver is fabricated with a 0.35- $\mu \text{m}$ 120-V high-voltage process. It can provide up to 25-W power to the LED with $2 \times 3.3\,\,\mu \text{H}$ inductors and achieves 91.4% peak efficiency and a 0.973 peak power factor from 60-Hz 100- to 120- $\text{V}_{\mathrm {ac}}$ input.

This paper proposes a novel single-stage light-emitting diode (LED) driver with interleaved power-factor corrections (PFC) suitable for energy-saving streetlight applications. The presented circuit...

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.

A buck-type light-emitting diode (LED) driver is proposed herein. The proposed LED driver automatically possesses current sharing and high step-down voltage gain. Without complex control, the proposed LED driver, with a single input and multiple outputs, can achieve automatic current sharing of four-channel LED strings, even under the different number of LEDs of each LED string. Furthermore, as compared with the traditional four-phase interleaved buck converter with a single input and a single output having current sharing required, the proposed circuit has the duty cycle up to 0.5, not 0.25, meaning that under the same input voltage the latter has a wider output voltage range than that of the former. Above all, if the proposed circuit with N outputs, then it still has the duty cycle up to 0.5, not one over N as shown traditionally. Moreover, as compared with the current sharing based on the differential-mode transformer, the proposed circuit has no magnetic resetting loop required. In this paper, the operating principles and design considerations of the proposed converter are discussed. Finally, the theoretical analyses and performances of the proposed LED driver are verified by simulation and experiment.

The reliability of a LED luminaire depends on the reliability of each of its subsystems. Experience suggests that, of these subsystems, it is the LED driver that tends to fail earliest. Any LED driver has an electrolytic capacitor to limit the ripple current, which helps the luminaire to function appropriately. This paper describes the effects on ripple current of changes in the capacitance and thus on LED luminaire performance. A capacitor bank is developed containing electrolytic capacitor combinations to obtain 27 capacitance values in the range 0.017 to 1570 µF. Two commercially available LED downlighter luminaires of the same model and manufacturer were used for this study. The ripple current and lumen output values are observed after connecting each capacitance from the bank, and the percentage flicker is calculated. LED light output shows visible flicker for low capacitances up to 0.1 µF with percentage flicker above 100%, while percentage flicker for capacitors up to 100 µF is more than 50%. For capacitance values of 220 µF and more, the percentage flicker is less than 50%. For the LED driver the capacitor decides the amount of ripple in the output current, so this work helps in formulating metrics for determining the service life of LED luminaires.

This paper is concerned with the derivation of a discontinuous conduction mode boost PFC rectifier as a driver for high-power LED lighting applications. The proposed driver is operated in the current mode regime while emulating a resistance towards the line, thus attaining a near unity power factor and low total harmonic distortion of the line current. Theoretical analysis is reported and conditions for the low LED flicker are derived. A method of design for minimum THD is also suggested. Simulation and experimental results are reported.

In this paper, an integrated LED lamp with an electrolytic capacitor-free driver is considered to study the coupling effects of both LED and driver’s degradations on lamp’s lifetime. An electrolytic capacitor-less buck-boost driver is used. The physics of failure (PoF) based electronic thermal simulation is carried out to simulate the lamp’s lifetime in three different scenarios: Scenario 1 considers LED degradation only, Scenario 2 considers the driver degradation only, and Scenario 3 considers both degradations from LED and driver simultaneously. When these two degradations are both considered, the lamp’s lifetime is reduced by about 22% compared to the initial target of 25,000 h. The results of Scenario 1 and 3 are close to each other. Scenario 2 gives erroneous results in terms of luminous flux as the LED’s degradation over time is not taken into consideration. This implies that LED’s degradation must be taken into considerations when LED and driver’s lifetimes are comparable.

In this paper, a Double Frequency Buck Driver (DFBD) using SiC diodes for LED lighting systems is presented. This topology enhances the efficiency of the Double Frequency Buck Converter (DFBC) by minimizing the switching losses in power diode. The design procedure, mathematical equations and efficiency calculations of the DFBD are discussed. A prototype of the Conventional Buck Converter (CBC) with Si and SiC diode, DFBC with SiC diode and Si diode is implemented for 10W LED in hardware. Experimental results are presented for the four different topologies to imply that the efficiency of the system increases with SiC diodes. In addition, the cost analysis and energy savings for a multi-storeyed official building are estimated for the DFBC with SiC topology and validated with the other topologies.

This paper proposes a new 48-V dc-fed dimmable LED driver based on a resonant-switched-capacitor topology (RSCT), where the analog-based dimming feature is accomplished by means of a variable inductor (VI). The proposed topology is based on the classic RSCT step-up double mode converter and it provides a simple and cost-effective solution while guaranteeing a wide dimming range. In order to implement an analog-based dimming, the control of the dc current in the LED lamp is required. This technique proposes to replace the resonant inductor by a VI, which will control the rms value of the resonant current, and, therefore, the mean value of the LED lamp current. In order to evaluate the feasibility and performance of this method, a 22-W LED lamp and driver prototypes were built. The most relevant experimental results are presented and briefly described.

LED is a promising new generation of green lighting with the advantages of high efficiency, good optical performance, long lifetime and environmental friendliness. A pulsating current can be used to drive LEDs. However, current with a high peak-to-average ratio is unfavorable for LEDs. A novel control scheme for the ac-dc critical conduction mode (CRM) flyback LED driver is proposed in this paper. By using the input voltage, output voltage and average output current to control the turn-on time of the switch, the peak-to-average ratio of the output current can be reduced. The operation principle is analyzed and an implementation circuit is put forward. Experimental results show the effectiveness of the proposed scheme.