High Power Factor Light-emitting Diode Driver on Digital Signal Processor Without Electrolytic Capacitor for High-power Lighting

Abstract—Electrolytic capacitor is a key factor that limits the life-time of the driver in a high-power light-emitting diode (LED) lighting. This article presents a high-power LED lighting driver on a digital signal processor without an electrolytic capacitor. The driver is composed of three stage circuits. The first stage is the boost power factor correction converter to achieve a high power factor. As it does not use an electrolytic capacitor, the output voltage ripple is larger, which directly affects the overall performance of the LED driver. Consequently, it must be optimized through the second and third stages. The second stage is the two-output LLC (Double inductance and capacitance) resonant converter, which is driven by a digital signal processor. This stage provides galvanic isolation and reduces voltage. The third stage is the two-input buck converter based on digital signal processor control that reduces the low-frequency ripple generated from the first two stages. Moreover, the regulation of each LED string current is achieved at this stage. The simulation and experimental results show that this LED lighting driver can achieve a high power factor and good constant current characteristics.     

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.     

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.     

A single‐phase buck‐boost PFC converter with output‐voltage,ripple‐reducing operation

This paper describes a new single‐phase buck‐boost power‐factor‐correction (PFC) converter with output‐voltage, ripple reducing operation. The converter consists of a conventional buck‐boost PFC converter and an additional switch to obtain a freewheeling mode of the dc inductor current, and is operated by two modulators. The first modulator controls the buck‐boost switch to obtain PFC. The other modulator controls the square value of the instantaneous dc inductor current to perform the output‐voltage‐ripple‐reducing operation. In the two modulations, the time integral value of the input and output currents in each modulation period are controlled directly and indirectly, respectively. Thus, modulation errors or undesirable distortions of the input current and output voltage ripple are eliminated even if the dc inductor current produces large ripple in a low‐frequency range. The theories and combination techniques for the two modulators, implementation, and experimental results are described. © 1998 Scripta Technica, Electr Eng Jpn, 126(2): 56–70, 1999     

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.     

Current‐fed isolated PFC pre‐regulator for multiple LED lamps with extended lifetime

To emit high‐quality LED light, one or a bin of LED lamp(s) is normally driven by a PWM‐controlled constant current source to minimize device variation and achieve accurate brightness control. Powered from offline AC mains, the front‐end power converters should provide a relatively low DC voltage bus for the inputs of post‐end LED current regulators. To match the long lifetime of LEDs, the whole LED driver (ballast) should work as durably as the LEDs. However, the lifetime of the driver is usually limited by the high‐voltage electrolytic charge storage capacitors used in conventional PFC pre‐regulators. In this paper, our previously proposed resonant current‐fed isolated PFC pre‐regulator is extended to operate in discontinuous conduction mode (DCM). It allows the use of the low‐voltage storage capacitors on the transformer secondary, and therefore extends the overall lifetime of the LED lighting system. A detailed procedure for finding the expected lifetime of the low‐voltage electrolytic capacitor is given. As before, the high‐voltage stress on the main switches, which is typical in current‐fed isolated converters, is reduced substantially by taking advantage of the transformer leakage inductance necessary for resonance. Additionally, high efficiency is ensured by the use of dual non‐cascading structures. Steady‐state state‐space averaging analysis is performed for designing the converter in DCM operation. A prototype converter is built to verify performance of the proposed PFC LED pre‐regulator. Copyright © 2011 John Wiley & Sons, Ltd.     

Single‐Inductor Dual‐Output DC–DC Converter Design Using RC Ripple Regulator Method

In this paper, we have proposed Single‐Inductor Dual‐Output (SIDO) buck–buck and boost–boost dc–dc converter using improved RC ripple regulator control. The proposed SIDO buck–buck converter has the characteristics of low‐ripple and high control frequency. RC ripple regulator control cannot be applied to SIDO boost–boost converter because RC ripple regulator undergoes self‐excited oscillation and two self‐excited oscillating controllers make the SIDO converter unstable. Thus we proposed the priority circuit for RC ripple regulator control. The proposed control circuit improves response characteristic and simplicity of the control circuit. Simulations are performed to verify the validity of the proposed SIDO converter. Simulation results indicate good performance of the proposed SIDO converter.     

Implementation of parallel zero‐voltage switching converter with series‐connected transformers

This paper presents a parallel zero‐voltage switching (ZVS) DC–DC converter with series‐connected transformers. In order to increase output power, two transformers connected in series are used in the proposed converter. Two buck‐type converters connected in parallel have the same switching devices. The primary windings of series‐connected transformers can achieve the balanced secondary winding currents. The current doubler rectifiers with ripple current cancellation are connected in parallel at the output side to reduce the current stress of the secondary winding. Thus, the current ripple on the output capacitor is reduced, and the size of the output choke and output capacitor are reduced. Only two switches are used in the proposed circuit instead of four switches in the conventional parallel ZVS converter to achieve ZVS and output current sharing. Therefore, the proposed converter has less power switches. The ZVS turn‐on is implemented during the commutation stage of two complementary switches such that the switching losses and thermal stresses on the semiconductors are reduced. Experimental results for a 528‐W (48 V/11 A) prototype are presented to prove the theoretical analysis and circuit performance. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

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.     

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     

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。     

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 systematic approach to designing a wide‐current range,MOS capacitor‐based switched‐capacitor DC‐DC converter with an augmenting LDO

Switched‐capacitor DC‐DC converters (SC DC‐DC) are analyzed for loss sources, voltage regulation integrity, start‐up latency, and ripple size, while the trade‐offs between these metrics are derived. These analyses are used to design a SC DC‐DC that achieves high efficiency in a wide load current range. Four‐way interleaving was employed to reduce the output ripple and efficiency loss due to this ripple. The design can be reconfigured to achieve gains of 1/3 and 2/5 for inputs ranging between 1.4 and 3.6 V to generate output voltage range of 0.4 to 1.27 V and can supply peak load current of 22 mA. It uses thin‐oxide MOS capacitors for their high density and achieves 75.4% peak efficiency with an input frequency of 100 MHz and a load capacitor of 10 nF. An augmenting LDO that only regulates during sudden load transients helps the converter respond fast to these transients. The chip was implemented using a 65‐nm standard CMOS process.     

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.     

Dimmable integrated CMOS LED driver based on a resonant DC/DC hybrid‐switched capacitor converter

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).     

Analysis and implementation of a high‐efficiency zero‐voltage‐zero‐current‐switching DC–DC converter

A high‐efficiency zero‐voltage‐zero‐current‐switching DC–DC converter with ripple‐free input current is presented. In the presented converter, the ripple‐free boost cell provides ripple‐free input current and zero‐voltage switching of power switches. The resonant flyback cell provides zero‐voltage switching of power switches and zero‐current switching of the output diode. Also, it has a simple output stage. The proposed converter achieves high efficiency because of the reduction of the switching losses of the power switches and the output diode. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed and its experimental results are presented for validation. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance analysis and calculation of critical inductance and output voltage ripple of a simple non‐isolated multi‐input bidirectional DC‐DC converter

In this paper, a simple non‐isolated multiple input (MI) bidirectional DC‐DC topology is proposed which can operate in buck, boost, or buck‐boost modes. The proposed topology utilizes a battery pack to realize the bidirectional power flow operation especially when the input sources are non‐storable ones. The excess energy of input sources can be stored in the battery and be injected to the load, when required. Simultaneous or independent power transfer of input sources is also provided. For better evaluation, the proposed topology has been compared with several recently presented novel topologies, from view point of number of inductors, capacitors, switches, and diodes. Comparison results show that the proposed topology utilizes less number of components (switches, inductors, capacitors, and current sensors) which can reduce the size, cost, and complexity of converter. Different operational modes of the proposed topology (unidirectional buck, boost, buck‐boost modes, and bidirectional mode) have been presented. Also, boost mode of the proposed topology has been investigated in detail, from design point of view, and generalized relationships have been proposed for calculation of critical inductance (CI) and output voltage ripple (OVR) of proposed n‐input boost topology. To validate proposed theoretical concepts, the proposed topology has been modeled and simulated in PSCAD/EMTDC software, and the 3‐input boost version has been experimentally implemented. Simulation and experimental results confirm appropriate performance of the proposed topology.     

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.     

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。