Efficient DC-DC Converter Research Articles

A high efficiency, soft switching DC-DC converter with adaptive current-ripple control for portable applications

A novel control scheme for improving the power efficiency of low-voltage dc-dc converters for battery-powered, portable applications is presented. In such applications, light-load efficiency is crucial for extending battery life, since mobile devices operate in stand-by mode for most of the time. The proposed technique adaptively reduces the inductor current ripple with decreasing load current while soft switching the converter to also reduce switching losses, thereby significantly improving light-load efficiency and therefore extending the operation life of battery-powered devices. A load-dependent, mode-hopping strategy is employed to maintain high efficiency over a wide load range. Hysteretic (sliding-mode) control with user programmable hysteresis is implemented to adaptively regulate the current ripple and therefore optimize conduction and switching losses. Experimental results show that for a 1-A, 5- to 1.8-V buck regulator, the proposed technique achieved 5% power efficiency improvement (from 72% to 77%) at 100 mA of load current and a 1.5% improvement (from 84% to 85.5%) at 300 mA, which constitute light-load efficiency improvements, when compared to the best reported, state-of-the-art techniques. As a result, the battery life in a typical digital signal processing microprocessor application is improved by 7%, which demonstrates the effectiveness of the proposed solution.

モバイル機器用CMOS DC-DCコンバータの最適設計手法

In recent years, low output power CMOS DC-DC converters which integrate power stage MOSFETs and a PWM controller using CMOS process have been used in many mobile applications. In this paper, we propose the calculation method of CMOS DC-DC converter efficiency and report optimum design of CMOS DC-DC converter based on this method. By this method, converter efficiencies are directly calculated from converter specifications, dimensions of power stage MOSFET and device parameters. Therefore, this method can be used for optimization of CMOS DC-DC converter design, such as dimensions of power stage MOSFET and switching frequency. The efficiency calculated by the proposed method agrees well with the 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.

16.1: Low‐Power Integrated Circuit Technologies Using Low Temperature Poly‐Si TFTs for Mobile Device Applications

AbstractA 2.2‐inch diagonal, 176×(RGB)×220 pixels poly‐Si TFT transflective LCD with 262k colors has been developed for mobile‐device applications. This LCD includes a low‐power consuming level‐shifter system and a highly efficient DC‐DC converter, both integrated on a glass substrate using poly‐Si TFTs. The integrated circuitry allows us to reduce power consumption of the LCD panel down to 0.87 mW.

FeCoBN Magnetic Thin Film Inductor for MHz Switching Micro DC-DC Converters

In order to obtain higher efficiency of the micro switching dc-dc converter using thin film magnetic device, FeCoBN magnetic film for thin film inductor was newly developed, which had high saturation magnetization of about 1.7T, and high electrical resistivity over 3μ Ω•m. Consequently, a newly fabricated magnetic thin film inductor using the FeCoBN magnetic film had lower power loss due to the small eddy current loss. 5MHz switching buck and boost converters using the new thin film inductor had higher efficiencies than those of the conventional micro switching dc-dc converters.

Double-output Luo converters, an advanced voltage-lift technique

Mirror-symmetrical double-output voltages are specially required in industrial applications and computer periphery circuits. Double output DC-DC converters can convert the positive input source voltage to positive and negative output voltages by two conversion paths. Because of the effect of parasitic elements, the output voltage and power-transfer efficiency of DC-DC converters are limited. The voltage-lift technique is a popular method that is widely applied in electronic circuit design. This technique gives a good way of improving circuit characteristics, and has been successfully applied for DC-DC converters. As are single output (positive and negative output) Luo converters, double-output Luo converters are a series of new DC-DC step-up converters using only one switch. They are developed from prototypes using the advanced voltage-lift technique. These converters perform from positive to positive and negative DC-DC voltage-increase conversion with high power density, high efficiency and cheap topology in a simple structure. They are different from any other existing DC-DC step-up converters and possess many advantages including high output voltage with small ripples. Therefore these converters will be widely used in computer peripheral equipment and industrial applications, especially for high double-output voltage projects.

A planar 4.5-GHz DC-DC power converter

In this paper, we present two DC-DC converters that operate at a microwave frequency. The first converter consists of a class-E switched-mode microwave amplifier, which performs the DC-AC conversion, and two half-wave diode rectifier outputs. The class-E MESFET amplifier has a minimum power-added efficiency of 86%, corresponding drain efficiency of 95%, and 120 mW of output power at 4.5 GHz. The diode rectifier has a maximum conversion efficiency of 98% and an overall efficiency of 83%. The second converter consists of a high-efficiency class-E oscillator and a diode rectifier. The class-E oscillator has a maximum efficiency of 57% and maximum output power of 725 mW. The DC-DC converter is planar and compact, with no magnetic components, and with a maximum overall DC-DC conversion efficiency of 64% for a DC input of 3 V, and the output voltage across a 87-/spl Omega/ load of 2.15 V.

On the High-Speed Turn-Off of a Power Transistor by a Small Saturable Core

An effective method for reducing the size and weight of the switching dc-dc converter is to increase the switching frequency. To accomplish this with no deterioration in efficiency, it is necessary to suppress the switching loss per cycle by shortening the switching time. An efficient dc-dc converter operating at the megahertz region is presented. The turn-off time is shortened by using the current feedback and the core saturation. The turn-off mechanism is analyzed with the equivalent circuits. As a result, it is found that the excess carrier in the base region is discharged quickly by the large reverse base current, which flows when the energy stored in the base-emitter capacitance of the power transistor is transferred to the saturated inductance of the core with high frequency oscillation.