Single-stage Driver Research Articles

A High-Efficiency Integrated Converter for LED Driver

Enhancing the efficiency in the light-emitting-diode (LED) drivers is a noteworthy issue as it not only helps saving energy but also causes the long life span of the drivers. In this paper, a new LED driver with improved efficiency is proposed. Efficiency improvement is achieved without using any active or passive component to perform soft switching conditions. In the proposed driver, buck and buck-boost converters are integrated. The freewheeling diodes and inductors - of the two converters - are replaced by one diode and one inductor. So, the proposed driver constitutes a single-stage driver with a simple structure that uses only one controlled switch, one freewheeling diode, and one inductor. Besides its simple structure, the driver works with a constant frequency, which leads to using a simple controller. Efficiency improvement is obtained by changing the inductor size and LEDs arrangement rather than using the active clamp or snubber circuits. To decrease the switching losses in the proposed driver, the average of the input current is kept constant while the peak of the pulsating input current - which passes from the switch and freewheeling diode - is decreased. Moreover, power losses of the semiconductor components in the proposed driver are investigated, and consequently decreased, leading to improvement in the system's overall efficiency. Finally, a 10 W experimental driver is built and tested. The experimental results are consistent with theoretical analysis.

Integrated Isolated AC/DC Converter Using IOFL for LED Driver Applications

Power factor correction, voltage and current ripple reduction and eradicating short-life electrolytic capacitors are challenging issues in state-of-the-art ac/dc Light-Emitting-Diode (LED) drivers. Conventional single-stage drivers need an electrolytic capacitor to ensure low output current flicker. However, electrolyte capacitors having a high failure rate, reduce the life-span of the LED driver. To cover these challenges, in this paper an integrated LED driver is proposed. The proposed driver, is combined of three dc/dc converters with only one active switch. It features high power factor, low current flicker, and due to using only one active switch its cost, volume, complexity and power loss is low. The driver is analyzed step by step to show the operation principles based on duty cycle variations. Dynamic analysis and control design of the proposed driver is presented based on nonlinear control by Input-Output Feedback Linearization (IOFL). The simulation and experimental results have been provided to verify the versatility of the proposed driver.

A Single-Stage LED Streetlight Driver with Soft-Switching and Interleaved PFC Features

This paper presents a single-stage driver with soft-switching and interleaved power-factor correction (PFC) features suitable for light-emitting diode (LED) energy-saving streetlight applications. The proposed LED streetlight driver integrates an interleaved buck-boost PFC converter with coupled inductors and a half-bridge LLC resonant converter into a single-stage power-conversion circuit with reduced voltage stress on the DC-linked capacitor and power switches, and it is suitable for operating at high utility-line voltages. Furthermore, coupled inductors in the interleaved buck-boost PFC converter are operated in discontinuous-conduction mode (DCM) for accomplishing PFC, and the half-bridge LLC resonant converter features zero-voltage switching (ZVS) to reduce switching losses of power switches, and zero-current switching (ZCS) to decrease conduction losses of power diodes. Operational modes and design considerations for the proposed LED streetlight driver are introduced. Finally, a 144 W (36V/4A)-rated LED prototype driver is successfully developed and implemented for supplying a streetlight module and operating with a utility-line input voltage of 220 V. High power factor, low output-voltage ripple factor, low output-current ripple factor, and high efficiency are achieved in the proposed LED streetlight driver.

An AC–DC PFC Single-Stage Dual Inductor Current-Fed Push–Pull for HB-LED Lighting Applications

An ac–dc single-stage driver for high-brightness light-emitting diodes (HB-LEDs) with galvanic isolation is presented in this paper. The driver is based on a dual inductor current-fed push–pull converter with each inductor operating in boundary conduction mode (BCM). The interleaving between the two inductors enables the converter to reduce the high input current ripple inherent to a BCM. Moreover, it is fully compliant with IEC 1000-3-2 Class C and it is able to achieve a high power factor (PF). Its low component count, simplicity, and overall outstanding characteristics make this current-fed topology suitable for medium power range HB-LED drivers in low-cost applications. The proposed topology has been tested on a 100-W prototype for the full range of the US single-phase line voltage, feeding several HB-LED strings, with an output voltage equivalent to 48 V at full load. The prototype achieves a maximum efficiency of 92% with a 0.99 PF, 8% total harmonic distorsion at full load while guaranteeing a good quality light.

A Single-Stage High-Power-Factor Light-Emitting Diode (LED) Driver with Coupled Inductors for Streetlight Applications

This paper presents and implements a single-stage high-power-factor light-emitting diode (LED) driver with coupled inductors, suitable for streetlight applications. The presented LED driver integrates an interleaved buck-boost power factor correction (PFC) converter with coupled inductors and a half-bridge-type series-resonant converter cascaded with a full-bridge rectifier into a single-stage power conversion circuit. Coupled inductors inside the interleaved buck-boost PFC converter sub-circuit are designed to operate in discontinuous conduction mode (DCM) for achieving input-current shaping, and the half-bridge-type series resonant converter cascaded with a full-bridge rectifier is designed for obtaining zero-voltage switching (ZVS) on two power switches to reduce their switching losses. Analysis of operational modes and design equations for the presented LED driver are described and included. In addition, the presented driver features a high power factor, low total harmonic distortion (THD) of input current, and soft switching. Finally, a prototype driver is developed and implemented to supply a 165-W-rated LED streetlight module with utility-line input voltages ranging from 210 to 230 V. Experimental results demonstrate that high power factor (>0.99), low utility-line current THD (<7%), low-output voltage ripples (<1%), low-output current ripples (<10%), and high circuit efficiency (>90%) are obtained in the presented single-stage driver for LED streetlight applications.

Design and Implementation of a Single-Stage Driver for Supplying an LED Street-Lighting Module With Power Factor Corrections

This paper proposes a novel single-stage light-emitting diode (LED) driver for street-lighting applications with power factor corrections (PFC). The presented driver integrates a modified bridgeless PFC ac-dc converter with a half-bridge-type LLC dc-dc resonant converter into a single-stage conversion circuit topology. The proposed ac-dc resonant driver provides input current shaping, and it offers attributes of lowered switching losses to the soft-switching functions obtained on two power switches and two output-rectifier diodes. The proposed driver features cost-effectiveness, high circuit efficiency (>92%), high power factor (>0.99) and low input current total harmonics distortion (<;8%). A prototype driver is developed for supplying a 144-W-rated LED street-lighting module with utility-line input voltages ranging from 100 to 120 V, and experimental results demonstrate the functionalities of the proposed LED driver.

Single‐stage LED driver with low bus voltage

A single-stage driver is proposed. The LED driver is obtained by integrating an interleaved boost circuit and an LLC resonant converter. Since the interleaved circuit is adopted here, the input voltage is divided into two parts, each part sharing with one switch of the LLC resonant converter forms a boost circuit in discontinuous mode, and the power factor correction function and low bus voltage are realised. Since the LLC resonant converter is adopted, the converter works in soft switching state, which increases the efficiency of the system. A 100 W prototype is achieved to prove the analysis of the LED driver, and the efficiency of the LED driver is as high as 91% in full load.

Single-stage driver for supplying high-power light-emitting-diodes with universal utility-line input voltages

The conventional two-stage non-isolated driver for high-power light-emitting diodes (LEDs) is composed of a power-factor-correction (PFC) converter with a non-isolated flyback converter for regulating the output voltage/current for supplying LEDs. However, large numbers of circuit components are required and the total efficiency is limited because of two-stage power conversion. This study proposes a high-power LEDs driver based on a single-stage topology. The presented driver combines a buck-boost PFC converter with a non-isolated flyback converter with two output windings connected in series into a single-stage power-conversion circuit. The proposed driver offers high power factor, high efficiency, low total-harmonics-distortion (THD) of input utility-line current, cost-effectiveness and a constant-output voltage along with limited-output-current control scheme. Finally, a prototype driver is developed and tested in order to supply a 100 W LED light bar module with universal utility-line input voltages for indoor or outdoor general lighting applications. Operational analysis, design equations, a design example and experimental results provided by examining three LED light bar modules demonstrate the feasibility of the proposed circuit.

Tritium Pellet Injector for TFTR

The tritium pellet injector (TPI) for the Tokamak Fusion Test Reactor (TFTR) will provide a tritium pellet fueling capability with pellet speeds in the 1- to 3-km/s range for the TFTR deuterium-tritium (D-T) phase. The existing TFTR deuterium pellet injector (DPI) has been modified at Oak Ridge National Laboratory (ORNL) to provide a four-shot, tritium-compatible, pipe-gun configuration with three upgraded single-stage pneumatic guns and a two-stage light gas gun driver. The TPI was designed to provide pellets ranging from 3.3 to 4.5 mm in diameter in arbitrarily programmable firing sequences at speeds up to approximately 1.5 km/s for the three single-stage drivers and 2.5 to 3 km/s for the two-stage driver. Injector operation is controlled by a programmable logic controller. The new pipe-gun injector assembly was installed in the modified DPI guard vacuum box, and modifications were made to the internals of the DPI vacuum injection line, including a new pellet diagnostics package. Assembly of these modified parts with existing DPI components was then completed, and the TPI was tested at ORNL with deuterium pellet. Results of the limited testing program at ORNL are described. The TPI is being installed on TFTR to support the D-D run period in 1992.more » In 1993, the tritium pellet injector will be retrofitted with a D-T fuel manifold and secondary tritium containment systems and integrated into TFTR tritium processing systems to provide full tritium pellet capability.« less