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A buck-type light-emitting diode (LED) driver is proposed herein. The proposed LED driver automatically possesses current sharing and high step-down voltage gain. Without complex control, the proposed LED driver, with a single input and multiple outputs, can achieve automatic current sharing of four-channel LED strings, even under the different number of LEDs of each LED string. Furthermore, as compared with the traditional four-phase interleaved buck converter with a single input and a single output having current sharing required, the proposed circuit has the duty cycle up to 0.5, not 0.25, meaning that under the same input voltage the latter has a wider output voltage range than that of the former. Above all, if the proposed circuit with N outputs, then it still has the duty cycle up to 0.5, not one over N as shown traditionally. Moreover, as compared with the current sharing based on the differential-mode transformer, the proposed circuit has no magnetic resetting loop required. In this paper, the operating principles and design considerations of the proposed converter are discussed. Finally, the theoretical analyses and performances of the proposed LED driver are verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

This paper is concerned with the derivation of a discontinuous conduction mode boost PFC rectifier as a driver for high-power LED lighting applications. The proposed driver is operated in the current mode regime while emulating a resistance towards the line, thus attaining a near unity power factor and low total harmonic distortion of the line current. Theoretical analysis is reported and conditions for the low LED flicker are derived. A method of design for minimum THD is also suggested. Simulation and experimental results are reported. [ABSTRACT FROM AUTHOR]

In this paper, an LLC light-emitting diode (LLC LED) driver based on the current-sharing capacitor is presented. In the proposed LED driver, the LLC resonant converter is used to step down the high input voltage, to provide galvanic isolation, to offer a constant current for LEDs. Moreover, the current-sharing capacitor connected to the central-tapped point of the secondary-side winding is used to balance the currents in two LED strings. By doing so, the voltage stress on this capacitor is quite low. Above all, the equivalent forward voltages of the two LED strings are generally influenced by the temperature and the LED current, and this does not affect the current-sharing performance, as will be demonstrated by experiment on the difference in number of LEDs between the two LED strings. In addition, only the current in one LED string is sensed and controlled by negative feedback control, while the current in the other LED string is determined by the current-sharing capacitor. Moreover, this makes the current control so easy. Afterwards, the basic operating principles and analyses are given, particularly for how to derive the effective resistive load from the LED string. Eventually, some experimental results are provided to validate the effectiveness of the proposed LED driver. [ABSTRACT FROM AUTHOR]

This paper presents a tightly regulated multi-output isolated converter that employs only an independently regulated synchronous Single-Switched Post-Regulator (SSPR). The proposed converter is a highly accurate single-ended secondary side post-regulator based on a Series Resonant Converter (SRC); furthermore, it has a voltage-doubler characteristic. The proposed post-regulator requires only one auxiliary switch, in contrast with a bulky and expensive non-isolated DC–DC converter. Moreover, the added voltage-doubler can tightly regulate the slave output current. In addition, the voltage-doubler can improve electromagnetic interference characteristics and reduce switching losses arising from the Zero Current Switching (ZCS) operation of all power switches. The validity of the proposed converter is verified using experimental results obtained via a prototype converter applicable to an LED 3D TV power supply. [ABSTRACT FROM AUTHOR]

In this study, a light emitting diode (LED) driver containing an integrated transformer with adjustable leakage inductance in a high-frequency isolated LLC resonant converter was proposed as an LED lighting power converter. The primary- and secondary-side topological structures were analyzed from the perspectives of component loss and component stress, and a full-bridge structure was selected for both the primary- and secondary-side circuit architecture of the LLC resonant converter. Additionally, to achieve high power density and high efficiency, adjustable leakage inductance was achieved through an additional reluctance length, and the added resonant inductor was replaced with the transformer leakage inductance without increasing the amount of loss caused by the proximity effect. To optimize the transformer, the number of primary- and secondary-side windings that resulted in the lowest core loss and copper loss was selected, and the feasibility of the new core design was verified using ANSYS Maxwell software. Finally, this paper proposes an integrated transformer without any additional resonant inductor in the LLC resonant converter. Transformer loss is optimized by adjusting parameters of the core structure and the winding arrangement. An LLC resonant converter with a 400 V input voltage, 300 V output voltage, 1 kW output power, and 500 kHz switching frequency was created, and a maximum efficiency of 97.03% was achieved. The component with the highest temperature was the transformer winding, which reached 78.6 °C at full load. [ABSTRACT FROM AUTHOR]

In order to reduce the cost and improve the reliability, real-time performance, and installation convenience of remote-controlled light-emitting diode (LED) lighting systems, a networked LED driving technology based on the direct current (DC) grid power line carrier is proposed. In this system, an alternating current (AC)/DC bus converter converts the mains into a DC bus with multiple distributed LED drive powers on the DC bus. The AC/DC bus converter receives the user's control command and modulates it into the DC bus voltage. The DC bus waveform changes to a square wave containing the high and low changes of the address information and command information. The LED drive power of the corresponding address receives energy from the DC bus and demodulates the commands, such as turning the lights on and off, dimming, etc., and performs the action. In order to make the waveform of the AC/DC bus converter have better rising and falling edge, this paper adopts the half-bridge topology with variable modal control. In the modulation process, the circuit works in buck mode and boost mode. Distributed LED drivers have DC/DC circuits and very simple demodulation circuits that dissipate energy and information from the DC bus. Through experiments, the technology not only simplifies the use of communication technology in application, but also reduces the application difficulty. [ABSTRACT FROM AUTHOR]

This paper deals with a design and experimental verification of 400-W class light-emitting diode (LED) driver with cooperative control method for two-parallel connected DC/DC converters. In the cooperative control method, one DC/DC converter is selected to supply the output current for the LED, based on the reference value of the LED current. Thus, the proposed cooperative-control strategy achieves wide dimming range operation. The discontinuous current conduction mode (DCM) operation improves the total harmonic distortion (THD) value on the AC side of the LED driver. The standard of Electrical Applications and Materials Safety Act in Japan has defined the flicker frequency and minimum optical output. The smoothing capacitors are designed by considering the power flow and LED current ripple for satisfying the standard. A prototype LED driver is constructed and tested. Experimental results demonstrate that a wide dimming operation range from 1 to 100% is achieved with a THD value less than 10% on the AC side, by the proposed control strategy. The authors compare the power conversion efficiency between Si- and SiC-metal-oxide-semiconductor field-effect transistors (MOSFETs) based LED driver. The maximum power conversion efficiency by using SiC-MOSFETs based LED driver is 91.4%. Finally, the variable switching frequency method is proposed for improving the power conversion efficiency for a low LED current region. [ABSTRACT FROM AUTHOR]