Showing papers on "Buck–boost converter published in 2010"

A 20 mV Input Boost Converter With Efficient Digital Control for Thermoelectric Energy Harvesting

Abstract: This paper presents a low power boost converter for thermoelectric energy harvesting that demonstrates an efficiency that is 15% higher than the state-of-the-art for voltage conversion ratios above 20. This is achieved by utilizing a technique allowing synchronous rectification in the discontinuous conduction mode. A low-power method for input voltage monitoring is presented. The low input voltage requirements allow operation from a thermoelectric generator powered by body heat. The converter, fabricated in a 0.13 ?m CMOS process, operates from input voltages ranging from 20 mV to 250 mV while supplying a regulated 1 V output. The converter consumes 1.6 (1.1) ?W of quiescent power, delivers up to 25 (175) ?W of output power, and is 46 (75)% efficient for a 20 mV and 100 mV input, respectively.

A DC-DC multilevel boost converter

Abstract: A DC-DC converter topology is proposed. The DC-DC multilevel boost converter (MBC) is a pulse-width modulation (PWM)-based DC-DC converter, which combines the boost converter and the switched capacitor function to provide different output voltages and a self-balanced voltage using only one driven switch, one inductor, 2 N -1 diodes and 2 N -1 capacitors for an Nx MBC. It is proposed to be used as DC link in applications where several controlled voltage levels are required with self-balancing and unidirectional current flow, such as photovoltaic (PV) or fuel cell generation systems with multilevel inverters; each device blocks only one voltage level, achieving high-voltage converters with low-voltage devices. The major advantages of this topology are: a continuous input current, a large conversion ratio without extreme duty cycle and without transformer, which allow high switching frequency. It can be built in a modular way and more levels can be added without modifying the main circuit. The proposed converter is simulated and prototyped; experimental results prove the proposition's principle.

Accurate Power Loss Model Derivation of a High-Current Dual Active Bridge Converter for an Automotive Application

Abstract: An accurate power loss model for a high-efficiency dual active bridge converter, which provides a bidirectional electrical interface between a 12-V battery and a high-voltage (HV) dc bus in a fuel cell car, is derived. The nominal power is 2 kW, the HV dc bus varies between 240 and 450 V, and the battery voltage range is between 11 and 16 V. Consequently, battery currents of up to 200 A occur at nominal power. In automotive applications, high converter efficiency and high power densities are required. Thus, it is necessary to accurately predict the dissipated power for each power component in order to identify and to properly design the heavily loaded parts of the converter. In combination with measured efficiency values, it is shown that conventional converter analysis predicts substantially inaccurate efficiencies for the given converter. This paper describes the main reasons why the conventional method fails and documents the different steps required to predict the power losses more accurately. With the presented converter prototype, an efficiency of more than 92% is achieved at an output power of 2 kW in a wide input/output voltage range.

DC/DC Converter Design for Supercapacitor and Battery Power Management in Hybrid Vehicle Applications—Polynomial Control Strategy

Abstract: This paper presents supercapacitor (SCAP) and battery modeling with an original energy management strategy in a hybrid storage technology. The studied dc power supply is composed of SCAPs and batteries. SCAPs are dimensioned for peak power requirement, and batteries provide the power in steady state. A bidirectional dc/dc converter is used between SCAPs and the dc bus. Batteries are directly connected to the dc bus. The originality of this study is focused on SCAP behavior modeling and energy management strategy. The proposed strategy is based on a polynomial (RST) controller. For reasons of cost and existing components (not optimized) such as batteries and semiconductors, the experimental test benches are designed in reduced scale. The characterized packs of SCAPs include two modules of ten cells in series for each one and present a maximum voltage of 27 V. The proposed strategy is implemented on a PIC18F4431 microcontroller for two dc/dc converter topology controls. Experimental and simulation results obtained from the polynomial control strategy are presented, analyzed, and compared with that of classical proportional-integral control.

Novel High Step-Up DC–DC Converter for Fuel Cell Energy Conversion System

Abstract: A novel high step-up dc-dc converter for fuel cell energy conversion is presented in this paper. The proposed converter utilizes a multiwinding coupled inductor and a voltage doubler to achieve high step-up voltage gain. The voltage on the active switch is clamped, and the energy stored in the leakage inductor is recycled. Therefore, the voltage stress on the active switch is reduced, and the conversion efficiency is improved. Finally, a 750-W laboratory prototype converter supplied by a proton exchange membrane fuel cell power source and an output voltage of 400 V is implemented. The experimental results verify the performances, including high voltage gain, high conversion efficiency, and the effective suppression of the voltage stress on power devices. The proposed high step-up converter can feasibly be used for low-input-voltage fuel cell power conversion applications.

VSC-HVDC Transmission with Cascaded Two-Level Converters

Abstract: SUMMARY The two-level converter valve together with series-connected press-pack insulated-gate bipolar transistors (IGBTs) is a reliable and proven technology for transmission-scale converters. This has been put to use in a further development of high-voltage dc (HVDC) transmission employing voltage-source converters (VSCs). A cascaded two-level (CTL) converter consisting of several smaller two-level building blocks, also called cells, enables the creation of a nearly sinusoidal output voltage from the converter. The development of the CTL is the subject for this paper. Using technology modules developed and refined during the last 15 years, it has been possible to create a converter that addresses and solves many of the limitations of VSC-HVDC transmission while retaining all operational functionality. The technology is scalable up to the highest transmission voltages. Losses are reduced to roughly 1% per converter through a combination of methods. A method for removing the need for external protective equipment and circuitry in the valves is presented. The main control of the converter has been reused, although the control bandwidth, i.e., the speed, has been further improved.

Power system with power converters having an adaptive controller

Abstract: A power system having a power converter with an adaptive controller. The power system is coupled to a load and includes a power system controller that receives a signal indicating a system operational state of the load and selects a power converter operational state as a function thereof. The power system also includes a power converter with a power switch that conducts for a duty cycle to provide a regulated output characteristic at an output thereof. The power converter also includes a controller that receives a command from the power system controller to enter the power converter operational state and provides a signal to control the duty cycle of the power switch as a function of the output characteristic and in accordance with the command, thereby regulating an internal operating characteristic of the power converter to improve an operating efficiency thereof as a function of the system operational state.

Three-Level Bidirectional Converter for Fuel-Cell/Battery Hybrid Power System

Abstract: A novel three-level (3L) bidirectional converter (BDC) is proposed in this paper. Compared with the traditional BDC, the inductor of the 3L BDC can be reduced significantly so that the dynamic response is greatly improved. Hence, the proposed converter is very suitable for fuel-cell/battery hybrid power systems. In addition, the voltage stress on the switch of the proposed converter is only half of the voltage on the high-voltage side, so it is also suitable for high-voltage applications. The operation principle and the implementation of the control circuit are presented in detail. This paper also proposes a novel bidirectional soft-start control strategy for the BDC. A 1-kW prototype converter is built to verify the theoretical analysis.

A High-Efficiency High Step-Up Converter With Low Switch Voltage Stress for Fuel-Cell System Applications

Abstract: In this paper, a novel high step-up converter is proposed for fuel-cell system applications. As an illustration, a two-phase version configuration is given for demonstration. First, an interleaved structure is adapted for reducing input and output ripples. Then, a C?uk-type converter is integrated to the first phase to achieve a much higher voltage conversion ratio and avoid operating at extreme duty ratio. In addition, additional capacitors are added as voltage dividers for the two phases for reducing the voltage stress of active switches and diodes, which enables one to adopt lower voltage rating devices to further reduce both switching and conduction losses. Furthermore, the corresponding model is also derived, and analysis of the steady-state characteristic is made to show the merits of the proposed converter. Finally, a 200-W rating prototype system is also constructed to verify the effectiveness of the proposed converter. It is seen that an efficiency of 93.3% can be achieved when the output power is 150-W and the output voltage is 200-V with 0.56 duty ratio.

Double Flying Capacitor Multicell Converter Based on Modified Phase-Shifted Pulsewidth Modulation

Abstract: Multilevel converters are very interesting alternatives for medium and high-power applications. The main reason is the increase in the number of output voltage levels and its apparent frequency. This paper presents a new configuration of flying capacitor multicell (FCM) converter. The main advantages of the proposed converter, in comparison with FCM and stacked multicell converters, are doubling the rms and the number of output voltage levels, improving the output voltage frequency spectrum, and canceling the midpoint of dc source. This progress is achieved by adding only two low-frequency switches to the conventional configuration of FCM converter while the number of high-frequency switches and capacitors, voltage ratings of capacitors and switches, and the number of high-frequency switchings during a full cycle are kept constant. This converter is controlled by a modified phase-shifted pulsewidth modulation, therefore, the self-balancing property of the flying capacitor converter is maintained in the proposed converter. The circuit is simulated using power systems computer-aided design/electromagnetic transients in DC systems (EMTDC) software and simulation results are presented to validate the effectiveness and advantages of the proposed configuration as well as its control strategy. Additionally, measurements taken from an experimental setup are presented in order to study the practical configuration.

Isolated Bidirectional Full-Bridge DC–DC Converter With a Flyback Snubber

Abstract: An isolated bidirectional full-bridge dc-dc converter with high conversion ratio, high output power, and soft start-up capability is proposed in this paper. The use of a capacitor, a diode, and a flyback converter can clamp the voltage spike caused by the current difference between the current-fed inductor and leakage inductance of the isolation transformer, and can reduce the current flowing through the active switches at the current-fed side. Operational principle of the proposed converter is first described, and then, the design equation is derived. A 1.5-kW prototype with low-side voltage of 48 V and high-side voltage of 360 V has been implemented, from which experimental results have verified its feasibility.

Nonisolated High Step-up Boost Converter Integrated With Sepic Converter

Abstract: For a nonisolated high step-up converter, the combination of a boost converter with a series output module is investigated in this paper. As a solution to supplement the insufficient step-up ratio and distribute a voltage stress of a classical boost converter, a sepic-integrated boost (SIB) converter, which provides an additional step-up gain with the help of an isolated sepic converter, is proposed. Since the boost converter and the sepic converter share a boost inductor and a switch, its structure is simple. Moreover, the SIB converter needs no current snubber for the diodes, since the transformer leakage inductor alleviates the reverse recovery. The operational principle and characteristics of SIB converter are presented, and verified experimentally with a 200 W, 42 V input, 400 V output prototype converter.

Voltage regulation of photovoltaic arrays: small-signal analysis and control design

Abstract: This study deals with the regulation of the output voltage of photovoltaic (PV) arrays. As a case study, the DC-DC buck converter is used as an interface between the PV array and the load, but other types of converters can be used for the same purpose. The input voltage of the converter is controlled in order to regulate the operating point of the array. Besides reducing losses and stress because of the bandwidth-limited regulation of the converter duty cycle, controlling the converter input voltage reduces the settling time and avoids oscillation and overshoot, making easier the functioning of maximum power point tracking (MPPT) methods. The voltage regulation problem is addressed with a detailed analysis that starts with the modelling of the PV array and the converter. This analysis is followed by study, design, simulation and practical experiments of three closed-loop control strategies for the buck converter. Control stability and implementation considerations are presented.

Space-Vector Modulated Multilevel Matrix Converter

Abstract: A matrix converter is an ac-ac power converter topology that has received extensive research attention as an alternative to traditional ac-dc-ac converter. A matrix converter is able to convert energy from an ac source to an ac load without the need of a bulky and limited-lifetime energy-storage elements. The indirect three-level sparse matrix converter (I3SMC) is a new topology from this family that can synthesize three-level voltage in order to improve the output performance in terms of reduced harmonic content. This paper discusses the operating principles and a space-vector-modulation scheme for this topology. Simulation and experimental results are shown to prove the ability of this topology to generate multilevel output voltages as well as to maintain a set of sinusoidal balanced input currents. The performance of the converter is compared with the conventional matrix converter and an alternative multilevel matrix-converter topology in order to demonstrate the advantages and disadvantages of the I3SMC.

LLC Resonant Converter With Adaptive Link-Voltage Variation for a High-Power-Density Adapter

Abstract: The output voltage of an adapter for a laptop computer should vary according to the load current in order to supply power to the computer To satisfy this requirement, an LLC resonant converter with an adaptive link-voltage-variation (ALVV) scheme is proposed in this letter The proposed ALVV scheme helps the LLC resonant converter to operate at a nearly constant resonant frequency and also allows for the optimal design of the converter High power density and high efficiency can therefore be obtained The proposed LLC resonant converter with the ALVV scheme is analyzed theoretically and verified experimentally

Multi-output DC-DC converters based on diode-clamped converters configuration: topology and control strategy

Abstract: This study presents a new DC-DC multi-output boost (MOB) converter which can share its total output between different series of output voltages for low- and high-power applications. This configuration can be utilised instead of several single output power supplies. This is a compatible topology for a diode-clamed inverter in the grid connection systems, where boosting low rectified output-voltage and series DC link capacitors is required. To verify the proposed topology, steady-state and dynamic analyses of a MOB converter are examined. A simple control strategy has been proposed to demonstrate the performance of the proposed topology for a double-output boost converter. The topology and its control strategy can easily be extended to offer multiple outputs. Simulation and experimental results are presented to show the validity of the control strategy for the proposed converter.

Interleaved-Boost Converter With High Voltage Gain

Abstract: This paper presents an interleaved-boost converter, magnetically coupled to a voltage-doubler circuit, which provides a voltage gain far higher than that of the conventional boost topology. Besides, this converter has low-voltage stress across the switches, natural-voltage balancing between output capacitors, low-input current ripple, and magnetic components operating with the double of switching frequency. These features make this converter suitable to applications where a large voltage step-up is demanded, such as grid-connected systems based on battery storage, renewable energies, and uninterruptible power system applications. Operation principle, main equations, theoretical waveforms, control strategy, dynamic modeling, and digital implementation are provided. Experimental results are also presented validating the proposed topology.

High Voltage Ratio DC–DC Converter for Fuel-Cell Applications

Abstract: Employing fuel cell (FC) as main source requires increasing and regulating its output voltage. In this paper, nonisolated dc-dc converter with high voltage ratio is proposed to interface between the FC and high-voltage dc bus. To take into account the low-voltage-high-density characteristics of power sources, a cascaded structure composed of two subconverters in cascade has been chosen and allows obtaining high voltage ratio. The choice of each subconverter is based on source requirements and its performances. Consequently, in this paper, a converter consisting of two-interleaved boost converter is chosen as first subconverter and a three-level boost converter is chosen as second subconverter. Control of the whole system is realized by energy trajectory planning based on flatness properties of the system. The design of trajectories is explained and allows respecting the fuel-cell constraints as main power source. To ensure correct design of the energy trajectories, a noninteger power-law function is used to model the static characteristic of the FC. This law allows investigating the effect of humidity and temperature on the dynamics of the proposed system. The control of both current and voltage balance across the output serial capacitors of the three-level boost converter is ensured by nonlinear controllers based on a new nonlinear model.

A review of single-phase PFC topologies based on the boost converter

Abstract: The need for solid-state ac-dc converters to improve power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input ac mains, and precisely regulated dc output have motivated the proposal of several topologies based on classical converters such as buck, boost, and buck-boost. Additionally, novel control techniques dedicated to PFC have also been introduced, motivating the manufacturing of commercial integrated circuits to impose sinusoidal currents in the front-end stage of switch-mode converters. Boost converters operating in continuous current mode (CCM) have become particularly popular because reduced electromagnetic interference (EMI) levels result from its utilization. Within this context, this work deals with a comprehensive review of some of the most relevant ac-dc singlephase boost converters for PFC applications. The evolution of the conventional boost converter is demonstrated in terms of improved characteristics achieved by other boost-based topologies. Besides, it seeks to establish a fast and concise guide on ac-dc boost converters to researchers and experts in power electronics by comparing the topologies.

Single-Phase AC–AC Converter Based on Quasi-Z-Source Topology

Abstract: This paper deals with a new family of single-phase ac-ac converters called single-phase quasi-Z-source ac-ac converters. The proposed converter inherits all the advantages of the traditional single-phase Z-source ac-ac converter, which can realize buck-boost, reversing, or maintaining the phase angle. In addition, the proposed converter has the unique features that the input voltage and output voltage share the same ground and the operation is in the continuous current mode. The operating principles of the proposed converter are described, and a circuit analysis is provided. In order to verify the performance of the proposed converter, a laboratory prototype was constructed with a voltage of 84 Vrms/60 Hz. The simulation and experimental results verified that the converter has a lower input current total harmonic distortion and higher input power factor in comparison with the conventional single-phase Z-source ac-ac converter.

Digital Average Current-Mode Control of PWM DC–DC Converters Without Current Sensors

Abstract: This paper introduces a digital average current-mode control technique for pulsewidth modulation dc-dc converters which only rely on voltage sampling. The proposed approach is to estimate inductor current using first-order discrete-time low-pass filter; therefore, the controller can calculate average inductor current in every switching cycle. As a novel technique of predictive average current control, it has been investigated by choosing an appropriate duty ratio to regulate valley inductor current first and then eliminating error between the estimated average inductor current and a reference current in succedent switching cycle. The algorithm is based on a two-loop control structure to achieve an accurate voltage regulation and is derived for three basic converters: buck, boost, and buck-boost. The validity of the proposed approach has been demonstrated by simulation and experimental results on a dc-dc boost converter.

Modelling, simulation and analysis of a Modular Multilevel Converter for medium voltage applications

Abstract: The Modular Multilevel Converter (M2C) is an emerging multilevel converter for HVDC and FACTS as well as for future AC-fed traction vehicles or medium voltage drives (MVD). A suitable converter model of the Modular Multilevel Converter (M2C) is presented. A 7.2 kV, 7.5 MVA converter is taken as an example to analyze characteristic waveforms of the converter. The cause of the circulating currents — a phenomenon unique to this topology — is investigated. Furthermore, particular attention is paid to the current distribution in the converter cells for characteristic load phase angles.

Soft-Switched CCM Boost Converters With High Voltage Gain for High-Power Applications

Abstract: This paper proposes a new soft-switched continuous-conduction-mode (CCM) boost converter suitable for high-power applications such as power factor correction, hybrid electric vehicles, and fuel cell power conversion systems. The proposed converter achieves zero-voltage-switched (ZVS) turn-on of active switches in CCM and zero-current-switched turn-off of diodes leading to negligible reverse-recovery loss. The components' voltage ratings and energy volumes of passive components of the proposed converter are greatly reduced compared to the conventional zero-voltage-transition converter. Voltage conversion ratio is almost doubled compared to the conventional boost converter. Extension of the proposed concept to realize multiphase dc-dc converters is discussed. Experimental results from a 1.5-kW prototype are provided to validate the proposed concept.

Step-up DC-DC converter by coupled inductor and voltage-lift technique

Abstract: A DC-DC converter with high step-up voltage gain is presented. The proposed converter uses the coupled inductor and the voltage-lift technique to achieve high step-up voltage gain. Additionally, the voltage on the active switch is clamped, and the energy stored in the leakage inductor is recycled in the proposed converter. Therefore the voltage stress on the active switch is reduced, and the conversion efficiency is improved. Finally, a laboratory prototype circuit with input voltage 12-V, output voltage 100-V and output power 35-W is implemented to demonstrate the performance of the proposed converter.

Zero-Voltage and Zero-Current-Switching PWM Combined Three-Level DC/DC Converter

Abstract: This paper proposes a zero-voltage and zero-current-switching (ZVZCS) PWM combined three-level (TL) dc/dc converter, which is a combination of a ZVZCS PWM TL converter with a ZVZCS PWM full-bridge converter. The proposed converter has the following advantages: all power switches suffer only half of the input voltage; the voltage across the output filter is very close to the output voltage, which can reduce the output filter inductance significantly; and the voltage stress of the rectifier diodes is reduced too, so that the converter is very suitable for high input voltage and wide input voltage range applications. The converter also can achieve zero-voltage-switching for the leading switches and ZCS for the lagging switches in a wide load range to achieve higher efficiency. The design considerations and procedures are presented in this paper. The operation principle and characteristics of the proposed converter are analyzed and verified on a 400-800-V input and 54-V/20-A output prototype.

An Energy-Efficient Subthreshold Level Converter in 130-nm CMOS

Abstract: This brief presents a fast energy-efficient level converter capable of converting an input signal from subthreshold voltages up to the nominal supply voltage. Measured results from a 130-nm test chip show robust conversion from 188 mV to 1.2 V with no intermediate supplies required. A combination of circuit methods makes the converter robust to the large variations in the current characteristics of subthreshold circuits. To support dynamic voltage scaling, the level converter can upconvert an input at any voltage within this range to 1.2 V.

Analysis and Design of a Nonisolated Bidirectional ZVS-PWM DC–DC Converter With Coupled Inductors

Abstract: A new zero-voltage-switched bidirectional dc-dc converter with coupled inductors is proposed in the paper. The proposed converter can operate with a steep conversion ratio, soft switching, a continuous inductor current, and fixed switching frequency. It can also operate with the switch stresses of a conventional pulsewidth-modulation-tapped/coupled-inductor converter regardless of the direction of power flow and without any voltage spikes across the switches during turn-OFF. These features are due to a very simple auxiliary circuit that is operational regardless of the direction of power flow and absorbs energy from the leakage inductance of the coupled inductors during switch turn-OFF. In the paper, the operation and design of the converter are discussed and its feasibility is confirmed with experimental results obtained from a prototype.

Zero-Voltage- and Zero-Current-Switching Full-Bridge Converter With Secondary Resonance

Abstract: A zero-voltage- and zero-current-switching full-bridge (FB) converter with secondary resonance is presented and analyzed. The primary side of the converter is composed of FB insulated-gate bipolar transistors, which are driven by phase-shift control. The secondary side is composed of a resonant tank and a half-wave rectifier. Without an auxiliary circuit, zero-voltage switching (for leading-leg switches) and zero-current switching (for lagging-leg switches) are achieved in the entire operating range. To implement the converter without an additional inductor, the leakage inductance of the transformer is utilized as the resonant inductor. Due to its many advantages, including high efficiency, minimum number of devices, and low cost, this converter is attractive for high-voltage and high-power applications. The analysis and design considerations of the converter are presented. A prototype was implemented for an application requiring a 5-kW output power, an input-voltage range varying from 250 to 350 V, and a 350-V output voltage. The experimental results obtained from a prototype verify the analysis. The prototype's efficiency at full load is over 95.5%.

Issues on Solar-Generator Interfacing With Current-Fed MPP-Tracking Converters

Abstract: The large-scale harvesting of solar energy is an important action to decelerate the observed climate changes. Reliably operating solar-energy systems composing of solar arrays and their interfacing converters are of prime importance to maximize solar-energy harvesting. The paper investigates the solar-generator interfacing in terms of current-fed (CF) maximum-power-point (MPP) tracking converter. The investigations show that the CF converter under input-voltage control can usually operate from the short-circuit to open-circuit conditions of the solar generator without stability problems. When the output voltage or current has to be controlled constant, the converter may become unstable at the MPP due to the negative incremental resistance appearing at its input terminals. In practice, this means that the operating range of the CF converter has to be limited to the voltages less than the MPP voltage, when the output-voltage or current control is active. Practical evidence is provided based on a CF superbuck converter derived from the corresponding voltage-fed converter applying duality-transformation methods and supplied by an actual solar panel.

Light-Load Efficiency Optimization Method

Abstract: In this paper, a method of maintaining high power-conversion efficiency across the entire load range and its circuit implementations are described. The proposed method substantially increases the conversion efficiency at light loads by minimizing switching and driving losses of semiconductor switches, as well as core losses of magnetic components. These losses are minimized by periodically turning off and on the power converter, and by controlling the converter so that when the converter is on, it operates at the power level that exhibits the maximum efficiency. The performance of the proposed method was evaluated on a 500-W, 400-V/12-V dc-dc converter and a 1-kW ac-dc boost power-factor-correction front-end.