A Review of LED Drivers and Related Technologies Yijie Wang; Alonso, J. Marcos; Xinbo Ruan
IEEE transactions on industrial electronics (1982),
2017-July, 2017-7-00, 20170701, Letnik:
64, Številka:
7
Journal Article
Recenzirano
Light-emitting diode (LEDs) have a promising prospect because of its outstanding advantages: 1) long lifetime, 2) environmentally friendly, 3) flexibility of color mixing, 4) high illumination ...efficiency, etc. Based on the electrical characteristics of LEDs, a constant current driver is needed to support the LED working performance. With the wide applications of LEDs, many new technologies are presented. In this paper, advantages and disadvantages of different LED drivers are discussed. A detailed technology review is presented which is good for researchers and engineers to make right choices in design and selection of LED drivers.
The LLC resonant converters commonly adopt frequency modulation (FM) or combination of FM with phase-shift modulation to regulate its output voltage. However, in these control schemes, a variable ...switching frequency range is required, which makes the magnetic components design complicated. Therefore, in this article, magnetic control (or variable inductor control) is adopted to make the converter operating at constant switching frequency and constant duty cycle. The fundamental harmonic analysis is commonly used because of its characteristic of simplicity. However, the accuracy of this method is reduced and considerable errors occur when the switching frequency or output power changes. Therefore, an optimal design methodology based on time-domain analysis of the LLC resonant converter with magnetic control is proposed in this article. The proposed methodology can assure that the converter will operate in PO or OPO modes within the whole operating range, and zero voltage switching operation for primary switches and zero current switching operation for secondary rectifier will be guaranteed. In addition, by limiting the resonant tank root-mean-square current, the system efficiency is improved. A 200-W experimental prototype is built and the effectiveness of the proposed optimal design methodology is verified.
This article presents a simultaneous wireless power and data transfer (SWPDT) system based on double-sided inductor-capacitor-capacitor compensation topology and frequency-shift keying. A simplified ...method to analyze the power transfer, data transfer, and interference between them is proposed. To obtain higher data transfer gain and lower bit error rate, the data injection and extraction transformers are optimized. A laboratory prototype was built to verify the correctness of the analysis and the methodology. The proposed SWPDT system is less susceptible to interference between the power and data transfer. This is experimentally proven by high signal-to-noise ratio of 47 dB in the worst case. The power transfer efficiency is 90.5% under nominal conditions, and the data rate is 150 kb/s. The proposed system is robust against coupling variations, with effective data transfer even though the coupling coefficient is decreased by 95.3%.
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%.
In this paper, a methodology to develop SPICE-based models of complex magnetic devices is presented. The proposed methodology is based on a reluctance equivalent circuit, which allows the user to ...study both the magnetic and electric behavior of the structure under any operating conditions. The different elements required to implement the reluctance model, namely, constant reluctances, variable reluctances, and windings, are implemented using SPICE behavioral modeling. These elements can thus be used to build a complete model for any magnetic device. The modeling process is illustrated with a particular example for a variable inductor. Simulations and experimental results are presented and compared to evaluate the accuracy and usefulness of the proposed modeling procedure.
This paper presents a study of the losses in the integrated buck-flyback converter (IBFC) used as high-power-factor LED driver. The aim of the study is to investigate the possibilities of increasing ...the efficiency of the IBFC converter. The procedure of the improvement is done by obtaining the equations of the current through each component in terms of converter parameters. The current is found in an average value or rms value, depending on the type of the parasitic component, whether it is modeled by a parasitic forward voltage source or by a parasitic resistance, respectively. Using these equations and the parasitic model, the losses of each element of the converter are estimated. This paper proposes a technique to increase the efficiency of the IBFC by redesigning the converter parameters. Furthermore, this paper presents a case of study with a step-by-step efficiency enhancement process of an existing driver. The driver is operating under universal input conditions, and 38 V output, supplying an LED luminary of 26.5 W. The new design shows an improvement of the efficiency from 82% in the old design to 89% in the proposed one. Moreover, the new design shows an improvement in the power factor and the THD and a 50% reduction in the output current ripple. Furthermore, a reduction in the number of components has been achieved, as it is found by the analysis that by adjusting the converter parameters, one diode can be removed. Finally, the presented methodology is explained in detail so that it can easily be applied to other dc-dc converters.
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.
Energy efficiency plays a crucial role in the development of solar-powered standalone lighting systems, as it directly impacts both the system's autonomy and size, ultimately affecting the cost. In ...scenarios where a single converter simultaneously functions as both battery charger and LED driver, minimizing energy losses becomes challenging due to the different power levels processed in each mode. The use of gallium nitride (GaN) semiconductors in the converter helps achieving this goal as they allow for a wide range of switching frequencies, maintaining high efficiency even in light-load conditions. However, focusing solely on the converter's efficiency in each task may not necessarily minimize energy losses when considering its 24/7 operating characteristic and charger/driver time ratio. This study introduces a methodology tailored to select circuit components and switching frequencies within a GaN-based dual-purpose converter solution. The primary objective is to maximize system autonomy. A comprehensive analytical model of the converter's losses is paired with a search-based algorithm, enabling the evaluation of commercial components. This evaluation pinpoints the combination that minimizes energy consumption, ultimately leading to a more compact design that efficiently harnesses available resources. Experimental results are showcased for a system with a 30 W driver and 150 W charger, affirming the efficacy of the proposed design methodology. By meticulously selecting parameters, a high-efficiency converter can be realized. This achievement extends the system's autonomy by nearly an hour without necessitating changes to the battery pack's dimensions.
In this letter, a magnetically controlled single-stage ac-dc converter is proposed for low-power application which has the following features. First, single-stage operation is achieved by sharing ...switches between LLC resonant converter and totem-pole bridgeless power factor corrector (PFC) converter. Second, the power factor correction function is inherently achieved by designing the PFC converter to operate in discontinuous conduction mode. Third, the dc-link voltage is almost constant. Fourth, fixed switching frequency and duty cycle can be implemented for the switches, which simplifies the magnetic component and driver circuit design. Fifth, the LLC resonant converter is designed to operate at series resonant frequency, the highest efficiency operating point, so the converter can always achieve the maximum efficiency operation. Meanwhile, at this operating point, the converter output voltage is independent of the load so that it is functioning as a dc transformer; and finally, soft switching for all semiconductors is achieved. A 75-W experimental prototype is built to validate the proposed magnetically controlled single-stage ac-dc converter
This paper presents a literature review on magnetically-controlled devices, variable inductors (VI), and variable transformers (VT), and their applications to lighting gears for discharge lamps ...and/or LED lamps. These current-controlled devices are mainly characterized by nonlinear and non-uniform saturation of the magnetic core. The paper describes the fundamentals and basic operating principle of such devices and provides an overview of existing patents. These patents refer the devices, VIs or VTs, as useful or industrially applicable. Some present one or more claims regarding the construction of the device and behavioral characteristic; others refer to specific applications, such as voltage regulation or universal ballast operation. Afterwards, the paper focuses on the review of specific techniques and circuits taking advantage of the presence of a controlled inductance value, by covering recent applications regarding discharge and solid-state lamp drivers. These applications will show how these multi-winding devices, typically not considered due to their low efficiency, may fulfill an important role and add features to state-of-the-art lamp drivers.
