Search

This letter proposes a switched capacitor (SC)-based continuously adjustable modular bidirectional dc–dc converter. The structure of the proposed converter consists of three types of modules, series–parallel SC converter module, regulating module, and resonant SC converters module. A basic configuration of three modules working in buck operating mode is analyzed in detail. The boost mode operation is symmetrical to the buck mode. The regulation module provides all regulation capability, and the other two modules operate at fixed duty cycle and provide the main conversion ratio. A prototype of the basic configuration was built to verify the theory. The peak efficiency of the prototype is 97.15%. [ABSTRACT FROM AUTHOR]

This article presents a deep analysis of the low-frequency ripple transferred from the bus voltage to the light-emitting diode (LED) current in integrated two-stage power converters, operating as offline LED drivers. This analysis presents a design methodology to select the optimum power control stage converter to the LED load and to reduce the bulk capacitance. The main focus is to analyze the ripple transfer ratio of the three main nonisolated dc–dc converters, namely buck, boost, and buck–boost. Moreover, this article presents a step-by-step case study for an existing converter and the proposed converter supplying a 26.9-W Luxeon 3014 LED load. The experimental results show that the integrated buck and boost converter requires a bus capacitance of 1200 μF, whereas in the integrated buck and buck–boost converter, the capacitance is reduced to 680 μF by applying the method proposed. This represents that the replacement of a boost converter by a buck–boost converter on the second stage allows a 50% reduction of the bus capacitance while keeping the same current ripple. [ABSTRACT FROM AUTHOR]

In this article, a high-power-density off-line light-emitting diode (LED) driver is proposed. The proposed ac–dc driver is the novel integrated buck and boost converter (IBBC). Besides the high-power-density, the converter shows a high power factor (PF), and a low total harmonic distortion (THD). The IBBC is a two-stage driver that features just one controlled switch, which leads to high PF and low THD operation ensuring high efficiency, and size and cost reduction. Moreover, the switch current is minimized as it conducts the higher of the buck or boost converter, but not the addition of both as in other integrated converters. Moreover, for a further increase of the power-density, a magnetic integration is made by integrating the two inductors of both the buck and boost converters in one core. Thus, the proposed converter has been named as fully integrated buck and boost converter (FIBBC). In this paper, the IBBC is analyzed, and a design methodology is proposed. Also, this article presents a magnetic analysis of the novel FIBBC. In addition, a comparison between two prototypes is presented, one for the IBBC and another for the FIBBC, both of them supplying an LED luminaire of 46 V/ 0.575 A. The FIBBC shows a high PF equal to 0.994, very small THD of 10%, output current ripple of 6%, and efficiency of 92.62%, which represents a landmark on the efficiency of integrated converters. [ABSTRACT FROM AUTHOR]

In this paper, a dual half-bridge LLC resonant converter with magnetic control is proposed for the battery charger application. The primary switches are shared by two LLC resonant networks, and their outputs are connected in series. One of the LLC resonant converters is designed to operate at the series resonant frequency, which is also the highest efficiency operating point, and the constant output voltage characteristic is achieved at this operating point. The second LLC resonant converter adopts magnetic control to regulate the total output current and voltage during both constant current charge mode and constant voltage charge mode. Meanwhile, the function decoupling idea is adopted to further improve the system efficiency. The significant amount of the power is handled by the LLC resonant converter operating at the series resonant frequency, whereas the second LLC resonant converter fulfills the responsibility to achieve closed-loop control. By carefully designing the resonant networks, the zero-voltage switching for primary switches and zero-current switching for secondary diodes can be achieved for whole operation range. A 320-W experimental prototype is built to verify the theoretical analysis, and the maximum efficiency is measured about 95.5%. [ABSTRACT FROM AUTHOR]

This paper presents a high power factor (PF), low total harmonic distortion (THD) light-emitting diode (LED) driver with dimming capability. In addition, the proposed technique ensures a high PF and low THD at any dimming level. The driver is implemented by using an interleaved capacitor, which is placed between the rectifier and the integrated buck flyback converter (IBFC). In this way, the line current conduction angle is increased, which in return increases the PF and decreases the THD. The operation of the proposed converter ensures that one diode of the conventional IBFC will not conduct, so that it can be removed. Moreover, owing to the continuous power flow, the proposed technique makes a significant reduction of the converter output ripple. The paper presents a prototype of the proposed converter supplying an LED luminaire of 37 V/ 0.67 A. The prototype shows a high PF of 0.997, small THD of 2.5%, output current ripple of 6%, and an efficiency of 80%. [ABSTRACT FROM AUTHOR]

This paper presents a fast fuzzy logic control algorithm for a Takagi–Sugeno–Kang fuzzy controller, which is applied to integrated \textLED drivers with the purpose of getting a good dynamic response and the reduction in the low-frequency (120 Hz) ripple. The algorithm uses the high-speed mathematical engine of a digital signal controller \text(DSC) that is capable to achieve fast multiplications during a common one-cycle instruction. Therefore, the execution time of the controller is improved with the use of a \textDSC. A scaling procedure is included in the program in order to use and to improve the accuracy of the multiplications and divisions in the \textDSC mathematical engine. A low-range \textDSC was used to program the proposed controller; therefore, the cost is affordable for \textLED driver applications. The fuzzy control curve was approximated to the sliding mode control \text(SMC) curve with the purpose of getting some of the good advantages of the \textSMC strategy like a good dynamic performance. The proposed controller is used to regulate the \textLED current. Simulation and experimental results are shown [ABSTRACT FROM PUBLISHER]

A traditional flyback LED driver is limited by its low performance, which usually does not meet the power factor (PF) and total harmonic distortion requirements according to Energy Star or IEC61000-3-2. The control loop from the secondary side to the primary side has low reliability and employs more components, which reduces the power density of the system and increases the cost. In this brief, based on single-stage single ended primary inductor converter (SEPIC) and flyback converter, a primary-side-regulated LED driver is proposed to improve the performance of the system. Working in DCM, the SEPIC circuit realizes the PF correction naturally. For the flyback converter, the proposed primary-side-regulated method improves the power density and guarantees accurate control of the output current. A 100-W prototype based on SEPIC-flyback was built to verify the analysis and the experimental results coincided with the analysis results satisfactorily. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

A single-stage offline power supply for LED lighting applications, based on the integration of a buck power factor corrector (PFC) and a tapped buck dc/dc converter, is presented in this paper. In addition to the high step-down capability and the output current regulation, the proposed topology effectively provides PFC to comply with the harmonic injection and energy-saving standards EN 61000-3-2 and Energy Star. The low bus voltage level, resulting from the use of an input step-down PFC stage, actually allows the use of film technology capacitors, instead of short lifetime electrolytic capacitors, to filter the bus voltage and reduce the LED current ripple component at twice the line frequency. Due to the high reliability, the simple structure, the good line-side spectral performance, and the low component count, the proposed topology effectively results to be very suitable for medium-power solid-state lighting applications, as in the case of LED downlighting. The issues related to the operation of the presented solution and to its design optimization will be carefully discussed. A prototype of the proposed ac/dc converter has been built and tested. The main experimental results will be described. [ABSTRACT FROM PUBLISHER]

This paper proposes an offline single-stage light-emitting diode (LED) driver based on a novel approach to reduce low-frequency ripple in LED arrays supplied from mains, while assuring high input power factor (PF). The proposal employs a series resonant dc–dc converter integrated into a bridgeless boost power factor correction (PFC) stage. The resonant stage works to reduce the low-frequency ripple transmitted from the output of the PFC stage to the LEDs with only small power losses. This solution achieves three main goals: 1) reduction of the bulk capacitance used at the dc bus, allowing for the use of long-life film capacitors; 2) increase in the overall efficiency of the LED driver owing to the low switching and conduction losses in the shared switching network; and 3) assuring high input PF. Experimental results of a driver without electrolytic capacitors for a 100-W street lighting LED luminaire are presented, showing overall efficiency in excess of 92%, input PF greater than 0.97, and line current harmonic content in compliance with the IEC 61000-3-2 standard. [ABSTRACT FROM AUTHOR]

This paper presents a new control method and a detailed project methodology for the optimized connection method of two converters, aiming to reduce the redundant power processing, in order to supply high-power light-emitting diodes (LEDs) with reduced capacitance and high efficiency, directly from the ac line. This connection method allows dealing with two major issues related to the LED driver: capacitance reduction and efficiency increasing. The first converter provides power factor correction, whereas the second converter controls the current through the LED. The basic idea consists in making the second converter to process only the low-frequency ripple (LFR) of the first converter, thus smoothing the LED current. In this way, the LFR is managed by the second stage, so that the capacitance of the first stage can be significantly reduced. The proposed control method can achieve better results for the low-frequency compensation. In addition to that, a high power factor and a low harmonic content are obtained, fulfilling the IEC 61000-3-2 Class C requirements. A laboratory prototype with a rated power of 75 W and an input voltage of 220 \Vrms/60 Hz was built in order to show the feasibility of the idea. The measured overall efficiency of the converter was 91%, and electrolytic capacitors were avoided. [ABSTRACT FROM PUBLISHER]

The fourteen papers in this special section focus on high performance light emitting diode (LED) drivers. In recent years, as the fourth generation of light source, light-emitting diodes (LEDs) have been widely used in many applications such as street lighting, automotive, and residential lighting because of their long lifetime, low maintenance requirement, and environment friendliness. As the performance of LEDs will be influenced obviously by the drivers, researchers have shown a growing interest in optimizing the drivers. Although these problems such as current balancing, eliminating electrolytic capacitor, and improving the topologies are not new, the high-frequency high-efficiency trend of LED drivers has given rise to additional challenges. These papers provide an insight on some of the newly emerging challenges and potential solutions to overcome those issues. [ABSTRACT FROM PUBLISHER]

This paper presents an electronic ballast for driving high intensity discharge (HID) lamps with low frequency square waveform from a dc supply. From the dc source (e.g., PFC rail), a flyback arrangement is inserted into a switching structure whose output provides low frequency voltage yet avoiding instability issues. Proposal's main advantage is the use of one single choke of simple assembly and only two active switches for current control and inversion. Converter design for DCM is presented in this work, besides an equivalent circuit from a control point of view. Small signal ac model is obtained and a feedback control loop is designed, based upon frequency response stability and performance analysis. HID dynamics is inserted into converter model, with feedback directly implemented. A prototype is presented and described in detail, consisting of a complete power and sensing circuit fully referenced to the switches common ground proposal. For design conformity, experimental and simulation results from Matlab and PSIM are presented, as well as discussions about the converter feasibility. [ABSTRACT FROM AUTHOR]

In this paper, an integrated double buck–boost (IDBB) converter is proposed as a high-power-factor offline power supply for power-LED lamps. The IDBB converter features just one controlled switch and two inductors and is able to supply a solid-state lamp from the mains, providing high power factor and good efficiency. In this paper, the IDBB converter is analyzed, and a design methodology is proposed. It is demonstrated that, with a careful design of the converter, the filter capacitances can be made small enough so that film capacitors may be used. In this way, the converter mean time between failures can be made as high as that of the solid-state lamp. A design example for a 70-W converter supplied from a 230 V/50 Hz mains for street lighting applications is shown. Finally, experimental results from a laboratory prototype are also presented. [ABSTRACT FROM AUTHOR]

In the above titled paper (DOI: 10.1109/TIE.2017.2652365), Figure 16 is incorrectly inserted two times, one in Figure 15 and another in Figure 16. The correct Figure 15 is the one uploaded in this letter. [ABSTRACT FROM PUBLISHER]