High-efficiency DC-DC Converter Research Articles

A 1 W 104 dB SNR Filter-Less Fully-Digital Open-Loop Class D Audio Amplifier With EMI Reduction

This paper presents the design and implementation of a high-performance fully-digital PWM DAC and switching output stage which can drive a speaker in portable devices, including cellular phones. Thanks to the quaternary pulse-width modulation scheme, filter-less implementation are possible. A pre-modulation DSP algorithm eliminates the harmonic distortion inherent to the employed modulation process, and an oversampling noise shaper reduces the modulator clock speed to facilitate the hardware implementation while keeping high-fidelity quality. Radiated electromagnetic field emission of the class D amplifier is reduced thanks to a clock spreading technique with only a minor impact on audio performance characteristics. Clock jitter effects on the audio amplifier performance are presented, showing very low degradation for jitter value up to a few nanoseconds. The digital section works with a 1.2 V power supply voltage, while the output switching stage and its driver are supplied from a high-efficiency DC-DC converter either at 3.6 V or 5 V. An output power of 0.5 W at 3.6 V and 1 W at 5 V over an 8 Ω load with efficiency (digital section included) of about 79% and 81%, respectively, has been achieved. The total harmonic distortion (THD) at maximum output level is about 0.2%, while the dynamic range is 104 dB A-weighted. The active area is about 0.94 mm2 in a 0.13 μm single-poly, five-metal, N-well digital CMOS technology with double-oxide option (0.5 μm minimum length).

High-efficiency bidirectional DC-DC converter with coupled inductor

This study presents a novel soft-switching bidirectional dc-dc converter with a coupled inductor. Transformer-based circuit topologies are commonly employed in conventional bidirectional converters and soft-switching techniques, including zero-voltage switching (ZVS) or zero-current switching (ZCS), are frequently applied to mitigate switching losses. Unfortunately, the use of more than four switches and several diodes in these transformer-based schemes increase production costs and reduce conversion efficiency. This work presents a coupled-inductor bidirectional converter scheme that utilises four power switches to achieve the goal of bidirectional current control. The high step-up and step-down ratios enable a battery module current with a low-voltage level to be injected into a high-voltage dc bus for subsequent utilisation. Experimental results based on a 24 V/200 V 800 W prototype are provided to verify the effectiveness of the proposed bidirectional converter. Since the voltage clamping, synchronous rectification and soft-switching techniques are utilised in the proposed circuit topology and the corresponding device specifications are adequately fulfilled, the proposed converter can provide highly efficient bidirectional power conversion in a wide range on the low-voltage side.

New architecture for high efficiency DC-DC converter dedicated to photovoltaic conversion

Abstract The latest researches on photovoltaic energy conversion clearly show that the next generation systems will be both smarter and efficient, with insurance of greater security and modularity. They are clearly oriented nowadays on the multi-point conversion, based on a parallel high voltage bus, with photovoltaic panels owner of their individual Maximum Power Point Tracker (MPPT) connected to an integrated DC-DC converter managing a global Maximum Power Point. This structure allows to avoid shadowing problems. We have studied in this paper the possibility to have a small universal DC-DC converter able to work in a large input voltage range (10 - 40 volts), and producing an output voltage up to around 300 volts with a global efficiency better than 96%. In this paper we describe an original Step-Up converter architecture tested on a standard inverter i.e. including its own MPPT. We also discuss the possibility to use high voltage parallel bus to improve the electro-magnetic compatibility and electro-magnetic pulse robustness by the low surface of wirer loops, which also represents an interesting way to decrease wiring prices. The global efficiency improvement of this architecture has been estimated for + 15 to 20% compared to classic ones. This structure allows the use of numerous technologies (amorphous, poly, mono.. . cells) working together on a single HVDC bus in an optimal efficiency. Finally, it is possible to migrate sequentially and progressively from an old standard technology towards this new one as described before.

A color compensation algorithm to avoid color distortion in active dimming liquid crystal displays

In LCD applications, various low power techniques, such as low voltage driving LEDs, high efficiency DC-DC converter circuitries, active backlight control schemes and the likes, have been applied to a backlight, which occupies the huge portion of total power consumption. Especially, it is a well-known fact that active dimming methods have accomplished considerable power reduction by as much as 20% up to 50% compared to the constant backlight method. However, the former technique may involve several artifacts such as color distortion, clipping, and so on. In this paper, color distortion in an active dimming LCD system caused by the mismatch between gamma values of pixel compensation algorithm and RGB sub-pixels, is analyzed and lowered by the proposed color compensation algorithm. This color compensation algorithm achieves the dramatic reduction on the color distortion without any loss of power saving performances. The maximum color difference ΔE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ab</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sup> has been measured for each test image with the previous pixel compensation approaches (method-1 and method-2), and the average value of ΔE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ab</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sup> has been obtained over 24 KODAK images. The resultant average value of a color compensated active dimming algorithm has been reduced to 0.413 and 0.478, compared to 24.595 and 9.527 of the conventional active dimming algorithms for method-1 and method-2, respectively.

Low price Fuel Cell Inverter System for 3[KW] Residential Power

This study proposed a high efficiency DC-DC converter with a new current doubler rectifier for fuel-cell systems for use with the Nexa(310-0027) PEMFC from the Ballard Co. The proposed high efficiency DC-DC converter for the fuel-cell system generated ZVS by applying partial resonance and using a phase shift PWM control method. Constantly switching frequency, loss of switching, peak current, and peak voltage were reduced by this system. In addition to this system, two inductors were attached to a rectifier circuit allowing it to be able to provide the direct current(DC) and DC voltage safely to a load with reduced ripple components. Also, by using the newly proposed current doubler rectifier, the high frequency DC-DC converter for the fuel cell system was capable of reaching a highest efficiency of 92[%] as compared to 88.3[%] efficiency in previous results, which means that efficiency increased 3.7[%]. The overall results were confirmed by a simulation and laboratory experiment.

High-Efficiency DC-DC Converter With High Voltage Gain and Reduced Switch Stress

In this paper, a high-efficiency dc-dc converter with high voltage gain and reduced switch stress is proposed. Generally speaking, the utilization of a coupled inductor is useful for raising the step-up ratio of the conventional boost converter. However, the switch surge voltage may be caused by the leakage inductor so that it will result in the requirement of high-voltage-rated devices. In the proposed topology, a three-winding coupled inductor is used for providing a high voltage gain without extreme switch duty-cycle and enhancing the utility rate of magnetic core. Moreover, the energy in the leakage inductor is released directly to the output terminal for avoiding the phenomenon of circulating current and the production of switch surge voltage. In addition, the delay time formed with the cross of primary and secondary currents of the coupled inductor is manipulated to alleviate the reverse-recovery current of the output diode. It can achieve the aim of high-efficiency power conversion. Furthermore, the closed-loop control methodology is utilized in the proposed scheme to overcome the voltage drift problem of the power source under the variation of loads. Some experimental results via an example of a proton exchange membrane fuel cell power source with 250-W nominal rating are given to demonstrate the effectiveness of the proposed power conversion strategy

Intelligent PV Module for Grid-Connected PV Systems

Most issues carried out about building integrated photovoltaic (PV) system performance show average losses of about 20%-25% in electricity production. The causes are varied, e.g., mismatching losses, partial shadows, variations in current-voltage (I-V) characteristics of PV modules due to manufacturing processes, differences in the orientations and inclinations of solar surfaces, and temperature effects. These losses can be decreased by means of suitable electronics. This paper presents the intelligent PV module concept, a low-cost high-efficiency dc-dc converter with maximum power point tracking (MPPT) functions, control, and power line communications (PLC). In addition, this paper analyses the alternatives for the architecture of grid-connected PV systems: centralized, string, and modular topologies. The proposed system, i.e., the intelligent PV module, fits within this last group. Its principles of operation, as well as the topology of boost dc-dc converter, are analyzed. Besides, a comparison of MPPT methods is performed, which shows the best results for the incremental conductance method. Regarding communications, PLC in every PV module and its feasibility for grid-connected PV plants are considered and analyzed in this paper. After developing an intelligent PV module (with dc-dc converter) prototype, its optimal performance has been experimentally confirmed by means of the PV system test platform. This paper describes this powerful tool especially designed to evaluate all kinds of PV systems

Low cost high efficiency DC-DC converter for fuel cell powered auxiliary power unit of a heavy vehicle

In this paper, a new dc-dc converter for solid oxide fuel cell (SOFC) powered auxiliary power unit (APU) is proposed. The proposed converter does not consider the leakage inductance of the transformer as a parasite and uses it for energy transfer, thus avoiding problems of low efficiency and difficulty in control, caused by leakage inductance. The need for a separate filter inductor is also eliminated. Soft switching is done for some of the switches of the proposed converter, thereby further increasing the efficiency of the converter. Thus, the achieved low cost and high efficiency of the proposed converter make it suitable for SOFC powered APU applications. Simulation and experimental results are presented to verify the proposed dc-dc converter. The achieved cost and efficiency of the prototype are 50.8$/kW and 90%, respectively

High-efficiency Voltage-clamped DC-DC converter with reduced reverse-recovery current and switch-Voltage stress

This paper investigates a high-efficiency clamped-voltage dc-dc converter with reduced reverse-recovery current and switch-voltage stress. In the circuit topology, it is designed by way of the combination of inductor and transformer to increase the corresponding voltage gain. Moreover, one additional inductor provides the reverse-current path of the transformer to enhance the utility rate of magnetic core. In addition, the voltage-clamped technology is used to reduce the switch-voltage stress so that it can select the Schottky diode in the output terminal for alleviating the reverse-recovery current and decreasing the switching and conduction losses. Furthermore, the closed-loop control methodology is utilized in the proposed scheme to overcome the voltage-drift problem of power source under the variation of loads. Thus, the proposed converter topology has a favorable voltage-clamped effect and superior conversion efficiency. Some experimental results via an example of a proton-exchange-membrane fuel cell (PEMFC) power source with a 250-W nominal rating are given to demonstrate the effectiveness of the proposed power-conversion strategy.

High-efficiency DC-DC converter chip size module with integrated soft ferrite

This letter describes a power supply module with an ultrathin, high-efficiency switching dc-dc converter system in order to meet increasing demand for smaller, thinner and lighter devices in portable electronic equipment. Usually, the inductor is the largest passive components in a converter system. We formed inductors on ferrite wafers as a substrate to mount an IC chip using thin film technology. This realized a significantly small and thin module. The external size of the module is 3.5 mm /spl times/ 3.5 mm /spl times/ 1.0 mm. Its maximum output power is 1 W, and its efficiency is up to 93.4%. A high power density of 81.6 W/cc was realized.

Active clamped ZVS forward converter with soft-switched synchronous rectifier for high efficiency, low output voltage applications

The analysis, design, and implementation of an active clamped ZVS forward converter equipped with a soft-switched synchronous rectifier (ACFC-SR), proposed for high-efficiency low output voltage DC-DC converter applications, is presented. The converter efficiency is maximised due to soft switching of the main, active clamp, synchronous rectifier, and freewheeling MOSFET switches. The operating principles of the ACFC-SR are analysed in detail, and the converter performance is compared with that of alternative forward converter schemes employed in low output voltage DC-DC converters, in view of their power conversion efficiency. Experimental results are presented for a 50 W ACFC-SR converter with a DC input voltage of 48 V, an output voltage of 5 V, and operating at a switching frequency of 120 kHz. In general, good agreement is observed between the theoretical and experimental results.

Reducing DC-DC power

High efficiency DC-DC converter designs are vital for high efficiency power consumption. Designers of power supplies for battery driven products face the challenge of selecting the right integrated switched mode converter chips from an ever increasing number of vendors. Each vendor of course claims to offer the best solution for their application. Having selected the right product, the designer then has to make the right tradeoffs between certain design parameters. One of the most critical of these is the system's power consumption. Designing for the highest efficiency is therefore discussed in this article using the TPS6103x boost converter IC family from Texas Instruments as an example in the design of a power supply for a portable digital audio and video system.

DC to DC Converters with High-Frequency AC Link

The properties of a dual thyristor are advantageously used for the development of very high-efficiency dc-dc converters. A new device named ``dual thyristor'' having static and dynamic characteristics dual to that of a thyristor has been recently reported. The development aspects of a dual thyristor based high-efficiency dc-dc converter with an intermediate ac link using a high-frequency inverter is described. The output voltage is regulated by varying the frequency of operation of the inverter. In spite of the relatively high-frequency operating range of this device between 30 kHz and 100 kHz, high efficiency of operation of the converter is obtained due to the use of lossless snubbers. Further, the selfprotective nature of the device against overcurrents enables a high reliability of operation of the dc-dc converter.