An Isolated PFC Zeta-forward Single-stage Single-switch for LED Driver Without Electrolytic Capacitor

Abstract

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 LED current ripple, degrades the operating lifetime of the LED driver. In order to increase the lifetime of an AC–DC LED driver, the electrolytic capacitor should be eliminated without significantly increasing the output current ripple. In this article, an isolated single-stage single-switch AC/DC high power factor LED driver without electrolytic capacitor is proposed in which a zeta power factor (PF) corrector is integrated with a forward converter. The detailed theoretical analysis and design procedure of the proposed single-stage PFC converter is presented. The experimental results of a 110 V_rms, 21?W prototype verify the theoretical analysis. The input PF is 0.99 in the proposed converter that complies with lighting equipment standards such as IEC-1000-3-2 for class C equipment.     

An electrolytic capacitor‐less LED driver with interleaving flyback topology

Here, we propose a single‐stage alternating current/direct current electrolytic capacitor‐less light‐emitting diode (LED) driver, which applies interleaving flyback topology to reduce the peak‐to‐average ratio of LED driving current. With this approach, the peak current through LEDs is reduced, so the lifetime requirement of LEDs can be satisfied for an electrolytic capacitor‐less LED driver. A new transformer with two interleaving auxiliary windings is applied to this driver. Based on this approach, compared with other electrolytic capacitor‐less LED drivers, an important advantage of this driver is that it can be easily created, without additional control circuits. We will explain the operation principle and control strategy of the proposed driver in detail and will use experimental results taken from a 24‐V 350‐mA prototype to demonstrate its performance. Copyright © 2015 John Wiley & Sons, Ltd.     

Output current ripple reduction of LED driver using ceramic‐capacitor‐input circuit and buck‐boost converter

This article proposes an LED driver that consists of a ceramic‐capacitor‐input rectifier and a buck‐boost converter. The LED driver has an advantage of long life because it does not contain any electrolytic capacitors. However, the issue with electrolytic capacitor‐less LED driver is that the ripple of the smoothed voltage becomes large due to insufficient capacitance of the smoothing capacitor. The proposed method, which uses the discontinuous current mode of a buck‐boost converter, reduces the output current ripple under such conditions. Experimental results using a 5.7 W LED driver prototype demonstrate that the proposed method reduces the output current ripple and that the percent flicker becomes 4.4%, which is smaller than the recommended upper limit of 8%.     

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.     

功率LED替代灯的新颖谐振式Buck镇流器

LED灯发光效率高,寿命长,因此具有巨大的应用前景,并有望取代白炽灯。LED灯是低压电流型器件,需要LED镇流器(驱动电路)将公共电网的高压交流电转换为适合LED的低压直流电。为了保证整个LED照明系统具有高效率和长寿命,LED镇流器必须具有以上特性。相比于采用变压器降压,无变压器的降压变换器可以达到更高的效率,但此类变换器,如Buck变换器,在低占空比时要承受长时间的二极管续流,导通损耗大,效率低。因此,本文提出一种新颖的谐振式Buck镇流器,利用谐振可实现高电压转换比,转换效率高,工作时间长,且可以与已有的白炽灯调光器配合工作,可直接安装在白炽灯具上。实验结果证明了该镇流器的有效性,且成本低,适合于目前LED替代灯场合。     

Dimmable MR16 LED drivers with low output ripple and wide duty ratio operating range

In this paper, a novel single‐switch DC–DC converter is proposed for dimmable MR16 light‐emitting diode (LED) drivers. The proposed driver can achieve very low output voltage ripple without using MHz switching frequency; therefore, small non‐electrolytic capacitors can be used to achieve longer lifetime and higher efficiency. Also, because of special merit of the proposed converter, it can be designed so that much wider duty ratio operating range can be achieved for LEDs. Hence, better digital dimming level resolution can be attained. Finally, a prototype driver for MR16 LED lamps is constructed to demonstrate the effectiveness of the converter. Experimental results show that a maximum efficiency of 92% can be achieved. Copyright © 2016 John Wiley & Sons, Ltd.     

基于Cuk变换器的无桥LED驱动电源

针对传统发光二极管LED（light-emitting diode）驱动电源因低频整流桥导致效率不高的问题,提出了一种基于Cuk PFC变换器的无桥LED驱动电源。该电源由2个共用输出的Cuk变换器并联而成,不仅保留了Cuk变换器输入输出电流脉动小、可实现升降压的优点,而且相较于现有LED驱动电源,避免了大体积变压器的使用,尤其适合空间狭小的大功率照明场合。详细分析了断续导电模式DCM（discontinuous conduction mode）下无桥LED驱动电源的工作原理及电路工作特性,最后通过仿真和实验搭建的20 W样机证明了所提拓扑的正确性。     

A long lifetime passive LED driver with power factor correction

In this paper, a novel single stage passive ac to dc converter is first proposed for LED drivers. No controlled active switch, electrolytic capacitors and auxiliary power supply are required in the proposed LED driver. The advantages of the proposed driver include long lifetime, high efficiency and recyclability. In addition, application of the proposed quasi‐resonant circuit enables one to use much smaller capacitance and inductance for the capacitors and inductor to achieve high power factor and compact size. Theoretical analysis of the proposed LED driver is made, and some design guidelines are provided. Finally, a prototype system of 50‐W rating is constructed. Experimental results confirm the validity of the proposed LED driver. It can be seen that the proposed driver is robust to variations of input voltage, frequency and output load. The features of low cost, long lifetime, robustness and without EMI problem render the proposed driver a very attractive alternative for outdoor applications. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

基于LLC变换器的多路LED自动均流策略研究

针对大功率LEDSg动电源需要实现多路均流输出的特点,提出1种新型的具有多路LED均流功能的磁集成LLC变换器,将LLC变换器中的变压器与均流耦合电感集成在1个磁芯上,并通过加入均流电容实现多路输LED自动均流。详细分析磁集成LLC变换器的集成方案及均流原理。设计1台80W4路均流输出的LED-~动电源,实验结果验证了所提方案是可行的。     

Series resonant high‐voltage DC–DC converter with reduced component count

This paper proposes a novel zero‐current‐switching series resonant high‐voltage DC–DC converter with reduced component count. The series resonant inverter in the proposed topology has two power switches (insulated‐gate bipolar transistors, IGBTs), two resonant capacitors, and only one high‐voltage transformer (HVT) with center‐tapped primary windings. The power switches are connected in the form of a half‐bridge network. The leakage inductances of the transformer's primary windings together with the resonant capacitors form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with interleaved half switching cycle. The secondary winding of the HVT is connected to a bridge rectifier circuit to rectify the secondary voltage. The converter operates in the discontinuous conduction mode (DCM) and its output voltage is regulated by pulse frequency modulation. Therefore, all the power switches turn on and off at the zero‐current switching condition. The main features of the proposed converter are its lower core loss, lower cost, and smaller size compared to previously proposed double series resonant high voltage DC–DC converters. The experimental results of a 130‐W prototype of the proposed converter are presented. The results confirm the excellent operation and performance of the converter. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

一种单级无电解电容LED驱动电路

基于Flyback的单级LED驱动电路的隔离变压器漏电感严重影响了驱动电路的工作效率,同时由于电解电容的存在,缩短了LED驱动电路的寿命。研究了一种带漏电感能量回馈通路的Buck-Boost+Flyback单级PFC驱动电路,利用一个二极管作为变压器漏电感能量回馈通路,消除开关管上的电压尖峰。建立了一定输出功率条件下中间级电容两端上限电压与电容值之间的函数关系,根据关系曲线选取合理的瓷片电容取代电解电容。研制一台输入130~260 V,输出为33 V/150 mA的实验样机验证了理论的正确性。     

Application of duality principle to synthesis of single‐stage power‐factor‐correction voltage regulators

The duality principle is applied to derive new single‐stage power‐factor‐correction (PFC) voltage regulators. This paper begins with an application of duality transformation to conventional discontinuous‐conduction‐mode buck, buck‐boost and boost converters. The resulting dual converters operate in the discontinuous capacitor voltage mode. These new converters provide the same PFC property, but in the dual manner. It is proved that in the practical case of the input being a voltage source, the mandatory insertion of inductance between the voltage input and the ‘dual PFC converter’ does not affect the power‐factor‐correcting property. A new single‐stage PFC regulator is derived by taking the dual of a well‐known circuit based on a cascade of conventional boost and buck converters. Analytical design expressions are derived, illustrating the relation between current stress and component values. Experiments are performed to confirm the operation of the circuit and its power‐factor‐correcting capability. Copyright © 2003 John Wiley & Sons, Ltd.     

Boost型无频闪谐振降压式LED驱动电源分析与设计

传统的二次型Boost功率因数校正变换器只能实现升压输出,在一定程度上限制了其在LED驱动电源中的应用。本文基于二次型Boost变换器提出了一种Boost型无频闪谐振降压式LED驱动电源,并分析了其工作原理及特性。该LED驱动电源利用一个有源开关管将二次型Boost变换器与一个谐振网络进行整合。与传统的二次型Boost变换器相类似,该LED驱动电源可以实现高效率和高功率因数。此外,该LED驱动电源可实现低电流纹波和降压变换输出。最后,搭建了一台84W的实验样机,最高效率可达到92.88%,验证了理论分析的正确性及可行性。     

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.     

基于LNK403EG的大功率LED照明电源设计

设计了一种采用LNK403EG为核心驱动芯片的带功率因数校正的LED驱动电源。该电源输入交流电压范围为90～265V,可以驱动输入电压为18V、电流为0.38A的大功率LED光源;电路中没有使用电解电容,延长了LED驱动器在高温下的工作寿命。     

A simple control scheme for a single stage flyback LED driver

This study proposes a simple control scheme for using single‐stage flyback (SSF) converters in lighting source applications for LEDs. Among the advantages of the average current mode is an I/O current ripple that is only one‐half of the critical conduction mode (CRM). This condition helps extend the output capacitor lifetime while lowering the input EMI capacitance input EMI capacitance. The SSF converter proposed in this study operates in continuous conduction mode (CCM). In addition, two sample‐and‐hold (S/H) circuits are placed at the output voltage loop and feed‐forward path, respectively. Since these S/H circuits access the average output current and average feed‐forward voltage, the LED driver is unaffected by the 120‐Hz ripple noise, the total harmonic distortion (THD) is reduced, and the transient response of the output current is improved. Finally, the operation principles and design considerations of the studied LED driver are analyzed and discussed. A laboratory prototype is also designed and tested to verify the feasibility. Copyright © 2014 John Wiley & Sons, Ltd.     

LED驱动电路及多路均流技术探讨

介绍了不同功率级别的LED驱动器常用的几种电路拓扑,探讨了几种去电解电容的LED驱动电路方案以避免电解电容带来的寿命限制,并针对多路LED驱动存在的均流问题,分析了现有的主要均流方法。     

一种无电解电容的单级复合LED驱动电路

近年来为了提高LED驱动电路转换效率和减小输出纹波,单级复合型电路得到深入研究与应用。针对辅助绕组支路上串联Buck电路的单级反激LED驱动电路,研究了一种输出电流谐波注入方案,以减小输出电容,使得输出电解为高频容所代。首先,介绍单级复合电路的工作原理,推导输出电压纹波与负载电流的关系,分析脉动电流的相位对电容电压纹波的影响,给出负载电流谐波注入方案的设计依据;其次,给出所述方案的实现方式与电路;最后,研制了一台150 W实验样机,验证方案的可行性与有效性。     

无电解电容的改进型SEPIC LED照明驱动

高功率白光LED因其高光效、长寿命、环保及小体积等优点,已经引起学术界和工业界的广泛关注,有望成为第四代照明光源。通常LED照明的供电电源除了要求高效率、高功率因数、低成本外,还必须具有高功率密度。然而作为储能的电解电容不但体积较大,而且寿命短,不但影响了电源功率密度的提高而且降低了LED驱动的使用寿命。因此本文在研究分析了现有LED照明驱动的基础上,提出了一种改进型SEPIC变换器,并以此为基础,提出了一种新的LED照明驱动。该LED照明驱动以Twin-Bus Buck变换器作为LED电流调节器,改进型SEPIC PFC作为预处理级。该驱动在满足输入功率因数不低于0.96时,消除了电解电容。一台50W的SEPIC PFC的实验样机的测试结果表明了设计的合理性和可行性。