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This paper presents a high-power-density high-power-factor GaN-based two-stage electrolytic-free offline LED driver. The LED driver achieves high power density through the use of a hybrid film-ceramic stacked switched capacitor (SSC) energy buffer, and a comprehensive optimization methodology that evaluates various converter topologies and designs, and minimizes overall system volume while maintaining...
A capacitor-isolated structure with brightness and color controlling for multicolor LED strings is proposed. Such structure mainly plays the role of current-balancing and color mixing. Moreover, in order to decrease the color shift, the current amplitude of LED strings is controlled constant. The luminous flux and chromaticity coordinates are regulated through controlling the sum and ratio of duty...
This paper presents an AC-powered, boost-converter-based multi-segmented LED driver that maintains a high-power factor (PF) and accurate input current level, using a novel look-up table (LUT)-based digital control with background calibration and optimal switching mode selection schemes. The presented multi-segmented LED driver aims to reduce the costs of high-voltage capacitors and high-inductance...
Flyback type converters are widely used in various applications including small power LED drivers. However, they suffer from the losses from the snubber circuit. To beat this problem, previous studies investigated the lossless snubbers. However, they still have a limitation due to the additional components resulting in a high cost and low power density. In this paper, a new converter topology for...
The main of this paper is to present a new bridgeless AC/DC topology without electrolytic capacitor. The topology is described and studied by simulation. Experimental results on a LED driver demonstrator using bidirectional GaN transistor validate the proposed circuit.
This paper proposes a novel LED driver, which consists of an isolated single-switch AC-DC converter with power factor correction (PFC) suitable for streetlight applications. Theoretical analysis of operational modes for the presented LED driver is included. In addition, a 65W-rated prototype circuit of the proposed LED driver with an input utility-line voltage of 110 V has been implemented and tested...
This paper introduces a multi-string quasi-resonant driver for LED lighting applications. The proposed LED driver is operated with variable frequency, constant on-time control strategy. Key characteristics of the proposed driver under the proposed control method are reported. The theory is verified by simulation and experimental results.
A family of DC/DC step-down converters with quadratic voltage transformation rate with only one low-side active switch is presented. The most promising topology using coupled inductors with pronounced step-down ratio is analyzed in detail. The circuit is especially useful for higher input voltages when diodes are used, which have lower losses than the active switch. The current and voltage waveforms...
Light-emitting diodes (LEDs) have largely replaced conventional light circuits, and have been applied in household lighting, smart lighting, and commercial lighting systems. LED driver structures can be divided into single-stage or double-stage power management structures. Previously, systems with a single-stage power management structure, which featured a fixed-frequency structure, were commonly...
This paper presents a step-down converter with Resonant Switched Capacitor (RSC) that supplies high power light emitting diodes (LEDs), designed for DC nanogrids applications. The proposed converter differs from traditional RSC converters by ZVS (Zero Voltage Switching) turn-off and the stabilization of power delivered to the LEDs. A laboratory prototype of 10 W presented a maximum efficiency of 92...
In this paper, an architecture of a single-stage power factor corrected AC-DC converter controlled by a high voltage resonant controller IC L6598 is proposed as LED street lighting driver. The converter is formed by the integration of two boundary conduction mode (BCM) boost circuits and a half-bridge LLC resonant circuit. The converter adapts dual half-wave rectifiers at the output side that supply...
A two-stage quasi-resonant LED driver with digital control method is proposed in this paper. The first stage of this converter is a boost circuit with power factor correction (PFC) function and the second stage is a dual Buck circuit which works in quasi-resonant zero voltage switching (ZVS) state. Because of the soft switching characteristics of the converter, switching losses are reduced and efficiency...
Traditional flyback LED driver is limited by its low performance which usually dissatisfy the power factor (PF) and Total Harmonic Distortion (THD) according to Energy Star or IEC61000-3-2. The control loop from secondary-side to the primary-side has low reliability to reduce the working lifetime and employs more components, which reduces the power density of system. In this paper, based on single-stage...
This paper presents a Cuk converter fed power factor correction (PFC) based light emitting diode (LED) driver. It is designed for high brightness (HB) low voltage LED driving. A pulse width modulation (PWM) technique is used for current control to achieve different LED brightness level. The PFC Cuk converter is used to feed a dual output flyback DC-DC converter which supplies power to the forced cooling...
A simple and low cost quasi resonant LED driver is proposed. Prominent merits of the proposed topology are low line current distortion and reduced switch voltage stress. This paper presents the principle of operation of the proposed circuit, analysis of average power and switch voltage and current stress. Theoretical predictions are supported by simulation and experiment.
This paper proposes a capacitive current balancing method for multistring LED lighting system driven by a LCC resonant converter. Different from conventional current balancing methods, this method replaces the capacitor in the resonant tank by a switch-controlled capacitor (SCC) with which the output voltage can be regulated by modulating the frequency of the resonant tank instead of the switching...
This paper describes the topology and operation of a quasi-resonant driver for LED lighting applications. The proposed driver incorporates a current doubler rectifier and capacitive safety isolation barrier. Variable frequency constant on-time dimming strategy is employed. Capacitive isolation helps eliminating the isolation transformer. The proposed theory is suggested and verified by simulation...
In this paper, the 120W single stage PFC LED driver with a leakage energy recycling circuit is proposed. Three buck-boost derived converters are integrated and they utilize only one common active switch. The first buck-boost converter regulates the sinusoidal input current with unity power factor drawn from the grid. The second flyback converter controls essentially DC current supplied to the LEDs...
Switched-mode dc-dc converters are used to regulate dc voltages or currents at a certain desired level. Due to inherent switching action, currents and voltages in the circuit tend to oscillate around a given average value, as the output values present some ripple in steady-state condition. The low-frequency output current ripple (OCR) is a key parameter for design considerations when a light-emitting...
This paper presents a single switch soft switched buck-boost resonant converter for LED drive applications. Zero current switching condition results in high efficiency. The proposed circuit provides a constant average output current independent of output voltage which makes it suitable for LED drive applications. The average output current is independent of output voltage and is a function of switching...
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