High‐power‐factor single‐switch AC to DC converter for LED lighting

In this paper, we report a novel single‐switch AC to DC step‐down converter suitable for light emitting diodes. The proposed topology has a buck and a buck–boost converter. The circuit is designed to operate in the discontinuous conduction mode in order to improve the power factor. In this topology, a part of the input power is connected to the load directly. This feature of the proposed topology increases the efficiency of power conversion, improves the input power factor, produces less voltage stress on intermediate stages, and reduces the output voltage in the absence of a step‐down transformer. The theoretical analysis, design procedure, and performance of the proposed converter are verified by simulation and experiment. A 36 V, 60 W prototype has been built to demonstrate the merits of this circuit. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A single‐stage integrated bridgeless AC/DC converter for electrolytic capacitor‐less LED lighting applications

In this paper, a single‐stage integrated bridgeless AC/DC converter is proposed. As compared to its counterpart that is composed of totem‐pole boost power factor correction (PFC) cascade fly‐back DC/DC converter, the studied circuit has less components number while overcoming the limits of the totem‐pole type. Thus, it is suitable to the low‐power LED lighting applications. Furthermore, when both PFC inductors L_b and magmatic inductance L_m of the transformer TR1 operate at discontinuous current mode, the bus voltage v_CB can be used to decouple the ac input and constant dc output power. Thus, the approach of increasing bus voltage ripple is employed to eliminate electrolytic capacitors and obtain long operation lifetime. Additionally, it is able to be compatible with our studied twin‐bus configuration for increasing the overall efficiency. A 50‐W hardware prototype has been designed, fabricated, and tested in the laboratory to verify the proposed converter validity. Copyright © 2014 John Wiley & Sons, Ltd.     

A novel single‐stage AC–DC converter with quasi‐resonant zero‐voltage‐switching for high power factor and high efficient applications

A new single‐stage‐isolated ac–dc converter that can guarantee both high efficiency and high power factor is proposed. It is based on a new dc–dc topology that has prominent conversion ratio similar to that of boost topology so that it is adequate to deal with the universal ac input. In addition, since it utilizes the transformer more than others based on the general flyback topology, the size of whole power system can be reduced due to the reduced transformer. Moreover, the voltage stresses on the secondary rectifiers can be clamped to the output voltage by adopting the capacitive output filter and clamp diode, and the turn‐off loss in the main switch can be reduced by utilizing the resonance. Furthermore, since this converter operates at the boundary conduction mode, the line input current can be shaped as the waveform of a line voltage automatically and the quasi‐resonant zero‐voltage switching can be obtained. Consequently, it features higher efficiency, lower voltage stress, and smaller sized transformer than other topologies. A 100 W prototype has been built and tested as the validation of the proposed topology. Copyright © 2010 John Wiley & Sons, Ltd.     

An improved single‐stage Flyback PFC converter for high‐luminance lighting LED lamps

This paper presents a high‐performance LED lamp driver with an improved single‐stage Flyback configuration. A constant current control method is used to regulate the lamp current and brightness. A laboratory prototype has been built and tested. With the prototype, high efficiency, high power factor, and constant lamp current can be achieved under different pieces of LED series connection. Copyright © 2007 John Wiley & Sons, Ltd.     

A single‐stage LED streetlight driver with PFC and digital PWM dimming capability

This paper proposes a single‐stage light‐emitting diode (LED) driver that offers power‐factor correction and digital pulse–width modulation (PWM) dimming capability for streetlight applications. The presented LED streetlight driver integrates an alternating current–direct current (AC–DC) converter with coupled inductors and a half‐bridge‐type LLC DC–DC resonant converter into a single‐stage circuit topology. The sub‐circuit of the AC–DC converter with coupled inductors is designed to be operated in discontinuous‐conduction mode for achieving input‐current shaping. Zero‐voltage switching of two active power switches and zero‐current switching of two output‐rectifier diodes in the presented LED driver decrease the switching losses; thus, the circuit efficiency is increased. A prototype driver for powering a 144‐W‐rated LED streetlight module with input utility‐line voltages ranging from 100 to 120 V is implemented and tested. The proposed streetlight driver features cost‐effectiveness, high circuit efficiency, high power factor, low levels of input‐current harmonics, and a digital PWM dimming capability ranging from 20% to 100% output rated LED power, which is fulfilled by a micro‐controller. Satisfying experimental results, including dimming tests, verify the feasibility of the proposed LED streetlight driver. Copyright © 2016 John Wiley & Sons, Ltd.     

A single‐stage LED lamp driver with low DC bus voltage for general lighting applications

In this paper, we study the feasibility of a single‐stage lighting LED lamp driver with low DC bus voltage. The operating principles and design considerations for the LED lamp driver in this study are analyzed and discussed in detail. A laboratory prototype has been built and tested. Using the prototype, high efficiency, high‐power factor and LED current control were achieved using a wide AC input voltage range from 90 to 270 V. Copyright © 2010 John Wiley & Sons, Ltd.     

Single‐stage single‐switch PFC converter for wide‐input extreme step‐down voltage applications

This paper presents a new single‐stage single‐switch high power factor correction AC/DC converter suitable for low‐power applications (< 150 W) with a universal input voltage range (90–265 V_rms). The proposed topology integrates a buck–boost input current shaper followed by a buck and a buck–boost converter, respectively. As a result, the proposed converter can operate with larger duty cycles compared with the existing single‐stage single‐switch topologies, hence, making them suitable for extreme step‐down voltage conversion applications. Several desirable features are gained when the three integrated converter cells operate in discontinuous conduction mode. These features include low semiconductor voltage stress, zero‐current switch at turn‐on, and simple control with a fast well‐regulated output voltage. A detailed circuit analysis is performed to derive the design equations. The theoretical analysis and effectiveness of the proposed approach are confirmed by experimental results obtained from a 100‐W/24‐V_dc laboratory prototype. Copyright © 2011 John Wiley & Sons, Ltd.     

Fast‐scale bifurcation in single‐stage PFC power supplies operating with DCM boost stage and CCM forward stage

This paper describes the fast‐scale bifurcation phenomena of a single‐stage single‐switch power‐factor‐correction (PFC) regulator comprising a boost stage operating in discontinuous conduction mode (DCM) and a forward stage operating in continuous conduction mode (CCM). The two stages combine into a single stage by sharing one main switch and one control loop. Using ‘exact’ cycle‐by‐cycle computer simulations, the effects of various circuit parameters on fast‐scale instabilities are studied. The results are qualitatively verified by experimental measurements. This work provides a clear picture of how the variation of certain practical parameters can render such a circuit fast‐scale unstable. Copyright © 2006 John Wiley & Sons, Ltd.     

基于反激变换器的无频闪LED驱动电源

为解决具有功率因数校正(PFC)功能的发光二极管(LED)AC/DC驱动电源存在的工频闪烁问题,提出了一种Flyback-Buck LED驱动电源。它由一个双输出绕组反激(Flyback)PFC变换器和一个Buck变换器构成,Flyback PFC变换器的辅助绕组作为Buck变换器的输入,Buck变换器的输出与Flyback PFC变换器的输出串联。通过Buck变换器有效补偿二次工频纹波,消除了LED频闪。Flyback-Buck大部分功率只经Flyback PFC单级变换,与两级变换拓扑相比,该拓扑具有较高的效率。最后,通过一台0.7 A/50W的实验样机,验证了理论分析的正确性。     

A power decoupling control method for an isolated single‐phase AC‐to‐DC converter based on a high‐frequency cycloconverter

This paper proposes a new power decoupling method for a high‐frequency cycloconverter which converts the single‐phase line‐frequency ac input to the high‐frequency ac output directly. The cycloconverter consists of two half‐bridge inverters, two input filter capacitors, and a series‐resonant circuit. The proposed power decoupling method stores the input power ripple at double the line frequency in the filter capacitors. Therefore, the proposed method achieves a unity power factor in ac input and a constant current amplitude in the high‐frequency output without any additional switching device or energy storage element. This paper theoretically discusses the principle and operating performance of the proposed power decoupling method, and the viability is confirmed by using an experimental isolated ac‐to‐dc converter based on the high‐frequency cycloconverter. As a result, the proposed power decoupling method effectively improved the displacement power factor in the line current to more than 0.99 and reduced the output voltage ripple to 4% without any electrolytic capacitor.     

A single‐stage phase‐shifted full‐bridge AC/DC converter with variable frequency control

This letter presents a single‐stage soft‐switched full‐bridge AC/DC converter for low‐voltage/high‐current output applications. A phase‐shifted method with a variable frequency control is used to regulate the DC bus voltage and the output voltage of the single‐stage AC/DC converter. The proposed circuit topology and control scheme exhibit superior performances (i.e. high power factor, high‐efficiency, and ring‐free features). Correspondingly, a laboratory prototype, 500 W 5V/100A AC/DC converter, is implemented to verify the feasibility of the proposed design. Copyright © 2009 John Wiley & Sons, Ltd.     

A universal‐input high‐power‐factor power supply without electrolytic capacitor for multiple lighting LED lamps

The AC–DC power supply for LED lighting application requires a long lifetime while maintaining high‐efficiency, high power factor and low cost. However, a typical design uses electrolytic capacitor as storage capacitor, which is not only bulky but also with short life span, thus hampering performance improvement of the entire LED lighting system. In this article, a SEPIC‐derived power factor correction topology is proposed as the first stage for driving multiple lighting LED lamps. Along with a relatively large voltage ripple allowable in a two‐stage design, the proposal of LED lamp driver is able to eliminate the electrolytic capacitor while maintaining high power factor and high efficiency. To further increase the efficiency of LED driver, we introduced and used the twin‐bus buck converter as the second‐stage current regulator with Pulse Width Modulation (PWM) dimming function. The basic operating principle and the deign consideration are discussed in detail. A 50‐W prototype has been built and tested to verify the proposal. Copyright © 2011 John Wiley & Sons, Ltd.     

用于大功率LED驱动的单端反激恒流源设计

大功率发光二极管(Light Emitting Diode,简称LED)是一种可取代传统光源的新型光源,适合采用恒流驱动方式。设计了一种由220 V/50 Hz交流电供电的单端反激恒流源电路,对该恒流源电路进行了概要介绍,分析了电路的恒流原理并设计了反馈回路。该恒流源可为大功率LED提供恒定的电流,具有开路限压保护功能,满足对大功率LED的驱动要求。实验结果表明,采用该单端反激恒流源可驱动大功率LED。     

一种高可靠无源恒流LED驱动电源

针对如何提高发光二极管(LED)驱动电源的使用寿命以及可靠性等问题,提出一种新型高可靠无源恒流LED驱动电源,并对其工作原理和性能特点进行了分析。由于该电源内部不含有电解电容,因此克服了由电解电容引起的LED驱动电源与LED理论使用寿命不匹配的问题。该电源内部不含有任何有源开关器件以及相关驱动、控制电路等,因此电路简单可靠。在工频交流电压输入时,其输出电流值近乎恒定,与所接负载LED串联颗数无关。最后,制作了一台220 V工频交流电压输入,输出电流平均值为350 mA,额定输出功率为42 W的试验样机,在负载LED颗数发生变化时,其输出电流识误差在10%以内,输入功率因数接近1,效率达到93.3%,实验结果验证了理论分析的正确性。     

基于SEPIC变换器的高功率因数LED照明电源设计

针对LED驱动电源功率因数低的问题,依据LED照明电源的特点,选择SEPIC电路作为主电路拓扑实现功率因数校正(PFC)和LED电流控制。传统的SEPIC电路用于功率因数校正时都工作在断续模式下,通过对SEPIC电路的分析,证明了临界连续模式下SEPIC电路也可以实现PFC,并推导出输入输出电压比和功率因数关系的公式,得出当输入输出电压比很小时,功率因数值很高。该电源用单级电路同时实现功率因数校正和LED电流控制,相对两级功率因数校正电路,所用器件少,损耗低,尺寸小,尤其适合空间狭小的照明电源电路。通过实验证明理论分析的正确性。     

基于单级PFC无频闪无电解电容的LED电源驱动设计

在矿用大功率照明应用中,电解电容将指数级降低驱动电路寿命。通过分析Boost-Flyback不同电压下的不同工作状态及其约束条件,提出基于电压的分段控制策略,建立了不同电压下的动态小信号模型。最后通过仿真验证了此控制策略下单级PFC去除电解电容的可行性。     

A new single‐phase high‐power‐factor converter with buck and buck–boost hybrid operation

In recent years, a wide variety of high‐power‐factor converter schemes have been proposed to solve the harmonic problem. The schemes are based on conventional boost, buck, or buck–boost topology, and their performance, such as output voltage control range in the boost and buck topology or efficiency in the buck–boost topology, is limited. To solve this, the authors propose a single‐phase high‐power‐factor converter with a new topology obtained from a combination of buck and buck–boost topology. The power stage performs the buck and buck–boost operations by a compact single‐stage converter circuit while the simple controller/modulator appropriately controls the alternation of the buck and buck–boost operation and maintains a high‐quality input current during both the buck and buck–boost operations. The proposed scheme results in a high‐performance rectifier with no limitation of output voltage control range and a high efficiency. In this paper, the principle and operation of the proposed converter scheme are described in detail and the theory is confirmed through experimental results obtained from 2‐kW prototype converter. © 2000 Scripta Technica, Electr Eng Jpn, 131(3): 91–100, 2000     

基于反激变换器的高功率因数LED驱动电源设计

针对传统的发光二极管(LED)驱动电源功率因数不高的问题,在需要隔离的场合选择反激电路作为主电路拓扑实现功率因数校正(PFC)和LED电流的控制.通过对反激电路的分析,证明了工作在临界连续模式下的反激电路可以实现PFC.该电源是采用反激电路为主电路的单级PFC电路,能同时实现PFC和LED电流控制,相对2级功率因数校正...     

光伏LED照明系统中双向变换器研究

研究设计了一种应用于光伏LED照明系统的改进型Zeta/Speic双向变换电路,该电路兼顾MPPT控制、蓄电池充放电控制、LED恒流控制及隔离保护控制等多种功能,与传统光伏LED照明系统中的常规变换器相比,具有结构简单灵活、成本低、效率高等优点.详细分析了电路组成及工作模式,并通过实验进行了测试,测试结果验证了该变换器...     

无电解电容无频闪的LED驱动电源

新型光源要符合以下四个条件:高效、节能、无污染及模拟自然光,发光二极管(LED)就具有这样的优点。采用脉动电流驱动大功率LED可以去除驱动电源中的电解电容,大大提高驱动电源的寿命。但是LED中存在两倍工频的频闪。本文在此基础上,提出一种无电解电容、无频闪的新型LED驱动电源,既去除了电解电容,提高了LED驱动电源的使用寿命,又解决了脉动电流驱动带来的LED频闪的问题。