Showing papers on "Buck–boost converter published in 2006"

A Novel Soft-Commutating Isolated Boost Full-Bridge ZVS-PWM DC–DC Converter for Bidirectional High Power Applications

Abstract: A soft-commutating method and control scheme for an isolated boost full bridge converter is proposed in this paper to implement dual operation of the well-known soft-switching full bridge dc/dc buck converter for bidirectional high power applications. It provides a unique commutation logic to minimize a mismatch between current in the current-fed inductor and current in the leakage inductance of the transformer when commutation takes place, significantly reducing the power rating for a voltage clamping snubber and enabling use of a simple passive clamped snubber. To minimize the mismatch, the method and control scheme utilizes the resonant tank and freewheeling path in the existing full bridge inverter at the voltage-fed side to preset the current in the leakage inductance of the transformer in a resonant manner. Zero-voltage-switching is also achieved for all the switches at the voltage-fed side inverter in boost mode operation. The proposed soft-commutating method is verified through boost mode operation of a 3-kW bidirectional isolated full bridge dc/dc converter developed for fuel cell electric vehicle applications. The tested result verified the isolated boost converter can operate at an input voltage of 8.5–15V and an output voltage of 250–420V with a peak efficiency of 93% and an average efficiency of 88% at 55-kHz switching frequency with 72 $^circ$ C automotive coolant.

Three-level buck converter for envelope tracking applications

Abstract: This letter proposes a three-level buck converter for tracking applications such as envelope-tracking in radio frequency power amplifiers (RFPAs). It is shown that the three-level buck converter can offer advantages in terms of switching ripples, losses, bandwidth, or the size of magnetic components compared to a standard buck or a two-phase buck converter. Experimental results illustrate improved efficiency and ripple rejection in an RFPA envelope-tracking application representative for low-power battery-operated systems.

A ZVS Bi-Directional DC–DC Converter for Multiple Energy Storage Elements

Abstract: This letter presents a high-power-density multi-input dc-dc converter interfaced with energy storage elements such as a battery and an ultracapacitor. The converter consists of three half-bridges and a high-frequency multi-winding transformer. Bi-directional power flow between input and output is achieved by adjusting the phase-shift angles of the voltages across the two sides of the transformer. Soft-switching is implemented naturally by snubber capacitors and transformer leakage inductance. Operation principles are analyzed in detail. Simulation and experimental results are provided to verify the performance of the proposed converter

Analysis and design of a low-stress buck-boost converter in universal-input PFC applications

Abstract: In converters for power-factor-correction (PFC), the universal-input capability, i.e., the ability to operate from any ac line voltage world-wide, comes with a heavy penalty in terms of component stresses and losses, and with restrictions on the dc output voltage. In this paper, we propose a new two-switch topology, boost-interleaved buck-boost (BoIBB) converter, which can offer significant performance improvements over single-switch buck-boost converters (including flyback, SEPIC, or Cuk topologies) or other two-switch buck-boost converters in universal-input PFC applications. The paper presents an analysis of the converter operation and component stresses, as well as design guidelines. High efficiency (over 93%) throughout the universal-input ac line voltage range is demonstrated on an experimental 100-W, 200-V dc output, universal-input BOIBB PFC rectifier.

A Multilevel Modular Capacitor Clamped DC-DC Converter

Abstract: A novel topology of multilevel modular capacitor clamped dc-dc converter (MMCCC) will be presented in this paper. In contrast to the conventional flying capacitor multilevel dc-dc converter (FCMDC), this new topology is completely modular and requires a simpler gate drive circuit. Moreover, the new topology has many advantageous features such as high frequency operation capability, low input/output current ripple, lower on-state voltage drop, and bi-directional power flow management. This paper discusses the construction and operation of the new converter along with a comparison with a conventional converter. Finally, the simulation and experimental results validate the concept of this new topology.

Resistor Emulation Approach to Low-Power Energy Harvesting

Abstract: This paper presents an approach and associated circuitry for harvesting near maximum output from low power sources in the 100 μW range for miniature wireless devices. A set of converter topologies and control approaches are presented together with detailed efficiency analysis and a design example for a buck-boost based energy harvesting converter using commercially available discrete circuitry. Experimental results are presented for harvesting energy from miniature RF and wind power sources operating over a 10:1 input power range from 500 μW to 50 μW. A closed-system efficiency of 65 % at 50 μW output power is achieved, including all control and converter losses. The results demonstrate that useful energy, sufficient to power typical wireless sensors, can be harvested from miniature sources that output less than 100 μW at a few hundred mV.

Hybrid Full-Bridge Three-Level LLC Resonant Converter—A Novel DC–DC Converter Suitable for Fuel-Cell Power System

Abstract: This paper proposes a novel hybrid full-bridge (H-FB) three-level (TL) LLC resonant converter. It integrates the advantages of the H-FB TL converter and the LLC resonant converter. It can operate under both three-level mode and two-level mode, so it is very suitable for wide-input-voltage-range applications, such as fuel-cell power systems. Compared with the traditional full-bridge converter, the input current ripple and output filter can be reduced. In addition, all the switches can realize zero-voltage switching from nearly zero to full load, and the switches of the TL leg sustain only half of the input voltage. Moreover, the rectifier diodes can achieve zero-current switching, and the voltage stress across them can be minimized to the output voltage. A prototype of 200-400-V input and 360-V/4-A output is built in our laboratory to verify the operation principle of the proposed converter

Voltage-source active power filter based on multilevel converter and ultracapacitor DC link

Abstract: A new topology for active power filters (APF) using an 81-level converter is analyzed. Each phase of the converter is composed of four three-state converters, all of them connected to the same capacitor dc link voltage and their output connected in series through output transformers. The main advantages of this kind of converter are the negligible harmonic distortion obtained and the very low switching frequency operation. The single-phase equivalent circuit is analyzed and their governing equations derived. The dc link voltage control, based on manipulating the converter's voltage phase, is analyzed together with the circuit's characteristics that determine the capability to draw or deliver active and reactive current. Simulation results for this application are compared with conventional pulsewidth-modulated (PWM) converters, showing that this filter can compensate load current harmonics, keeping better-quality sinusoidal currents from the source. The simulated configuration uses a 1-F ultracapacitor in the dc link, making it possible to store energy and deliver it during short voltage dips. This is achieved by applying a modulation control to maintain a stable ac voltage during dc voltage drops. A prototype of the filter was implemented and tested, and the obtained current waveforms showed to be as good as expected.

Method and apparatus for controlling power drawn from an energy converter

Abstract: Methods, apparatus, media and signals for controlling power drawn from an energy converter to supply a load, where the energy converter is operable to convert energy from a physical source into electrical energy. Power drawn from the energy converter is changed when a supply voltage of the energy converter meets a criterion. The criterion and the change in the amount of power drawn from the energy converter are dependent upon a present amount of power supplied to the load. The methods, apparatus, media and signals described herein may provide improvements to DC to AC maximum power point tracking in an energy conversion system such as a photovoltaic power generation system.

Analysis and Design of a New High-Efficiency Bidirectional Integrated ZVT PWM Converter for DC-Bus and Battery-Bank Interface

Abstract: This paper proposes a high-efficiency bidirectional integrated zero-voltage transition (iZVT) pulsewidth-modulation (PWM) converter for dc-bus and battery-bank interface. The proposed converter can operate as battery charger when the utility is within its acceptable voltage range and can supply energy to critical loads when the utility fails. The converter practically eliminates both low- and high-frequency current ripple on the batteries, thus maximizing battery life without penalizing the volume of the converter. Moreover, soft switching of all switches is achieved using the proposed integrated auxiliary commutation circuit (iACC). Just one iACC is used to provide soft-switching conditions for the three converters that compose the system: the preregulator (boost), the battery charger (bidirectional converter operating as a buck), and the backup converter (bidirectional converter operating as a boost). This auxiliary circuit has few components and low reactive energy, increasing the system's overall efficiency. Experimental results based on a 580-W prototype are presented to validate the analysis and the proposed design procedure and to demonstrate the performance of the proposed approach

Selection of a curved switching surface for buck converters

Abstract: A general procedure for the selection of a curved switching surface (SS) to control buck-type converters is presented in this letter. The analysis is based on the normalized representation of ideal SSs for different loading conditions. The normalization process leads to a unique representation of the SSs for any possible buck converter. A set of graphics in three dimensions is introduced to give a spatial sense of the behavior of the converter and its control requirements during transients. As a result of the investigation, a switching surface referred to in this letter as the natural unloaded SS is selected, providing excellent transient behavior and no overshoot during startup. For any buck converter with typical parameters, this control scheme produces, in one switching action, a minimum of 99% of the desired output voltage. The general concept of using second-order SS is also geometrically analyzed in this letter to clarify its characteristic features and disadvantages. Experimental results for a typical buck converter are presented to illustrate the transient behavior of the converter during startup and sudden load changes. The results confirm the virtues of the control scheme.

Current programmed control of a single-phase two-switch buck-boost power factor correction circuit

Abstract: This paper presents a new current programmed control (CPC) technique for a cascaded two-switch buck-boost converter suitable as a low-cost power factor correction (PFC) rectifier in a variable speed motor drive. This new CPC technique, which is an extension of the conventional CPC method, enables the variable output dc voltage, and is therefore suitable in a pulse amplitude modulated (PAM) motor drive or as a universal input-power supply. The CPC method is very simple and requires only a constant-current reference without any changes in the transition between boost and buck operating mode, and the line current is practically unaffected by the topology-mode shift. Simulations and experimental results verify the presented control technique. Compliance with IEC-61000-3-2 class A is achieved. The experimental setup is based on a commercial CPC integrated circuit (IC) for dc-dc converters. This new control technique enables a simple low-cost control circuit for the two-switch buck-boost converter, which complies with IEC-61000-3-2, and the PFC circuit has inherent in-rush and overcurrent protection.

Topological and Modulation Design of Three-Level Z-Source Inverters

Abstract: This paper presents the development of two three-level cascaded Z-source inverters, whose output voltage can be stepped down or up unlike a traditional buck three-level inverter. The proposed inverters are designed using two three-phase voltage-source inverter bridges, supplied by two uniquely designed Z-source impedance networks. These three-phase bridges can either be cascaded at their dc sides to form a dc-link-cascaded Z-source inverter or at their ac outputs using single-phase transformers to form a dual Z-source inverter. The dc-link-cascaded inverter has the advantages of not using any clamping diodes and transformers, but does not have redundant switching states within a phase leg for equalizing switching losses among the power devices. This constraint limits the modulation options for the dc-link-cascaded inverter, and indeed, it can only be controlled using the modified carrier disposition technique with appropriate ldquoZ-source shoot-throughrdquo states inserted for achieving balanced voltage boosting and optimal ldquonearest-three-vectorsrdquo switching. On the other hand, the dual Z-source inverter with transformer isolation can be controlled using different modulation approaches due to the presence of redundant switching states within a phase leg. Particularly, using a modified phase-shifted-carrier (PSC) scheme with shoot-through states inserted, it is shown that the dual inverter can be implemented using only a single Z-source network, while still achieving the correct volt-sec average and switching loss equalization. This represents a significant reduction in cost, and can more than compensate for the slightly degraded spectral characteristics of the PSC scheme. To verify the theoretical concepts discussed, experimental testing has been performed with the captured results presented in a later section of the paper.

Multiple output power supply that configures itself to multiple loads

Abstract: A two stage multiple output power supply device is capable of outputting programmable DC voltages onto multiple outputs. The first stage receives an AC supply voltage and outputs a DC supply voltage. The second stage includes a DC-ID controller and multiple DC-to-DC converters, each DC-to-DC converter receiving the DC supply voltage and capable of outputting a programmable DC voltage onto a conductor of a power cord to power an electrical device. For each DC-to-DC converter, the DC-ID controller receives information in an AC signal on the conductor, the information indicating the voltage and current requirements and the polarity of an electrical device connected to the power cord for that DC-to-DC converter. In response to the information, the DC-ID controller controls the DC-to-DC converter to set a magnitude, a polarity and a current limit for the programmable DC voltage that will be output by the DC-to-DC converter.

Implementation of a hybrid AC/AC direct power converter with unity voltage transfer ratio

Abstract: This paper presents a novel hybrid direct power converter (HDPC) which overcomes the two main disadvantages of matrix converters: limited voltage transfer ratio and low immunity to grid disturbance. The proposed converter is formed by integrating a reversible auxiliary boost converter in the dc link of the two-stage matrix converter. Therefore, the HDPC can provide unity voltage transfer ratio even in the case where the supply voltage is highly unbalanced. The proposed converter also preserves most of the inherent advantages of the conventional matrix converter such as: controllable input power factor, sinusoidal supply currents, and bidirectional power flow. A novel predictive current control technique for the HDPC is also proposed for minimum energy storage in the converter. Important aspects of design, control, and implementation of the new HDPC are presented including theoretical analysis and simulations. Experimental waveforms at unity voltage transfer using a laboratory prototype are presented to confirm the viability of the proposed idea.

A digitally controlled switch mode power supply based on matrix converter

Abstract: High power telecommunication power supply systems consist of a three-phase switch mode rectifier followed by a dc/dc converter to supply loads at -48 V dc. These rectifiers draw significant harmonic currents from the utility, resulting in poor input power factor with high total harmonic distortion (THD). In this paper, a digitally controlled three-phase switch mode power supply based on a matrix converter is proposed for telecommunication applications. In the proposed approach, the matrix converter directly converts the low frequency (50/60Hz, three-phase) input to a high frequency (10/20kHz, one-phase) ac output without a dc-link. The output of the matrix converter is then processed via a high frequency isolation transformer to produce -48V dc. Digital control of the system ensures that the output voltage is regulated and the input currents are of high quality under varying load conditions. Due to the absence of dc-link electrolytic capacitors, power density of the proposed rectifier is expected to be higher. Analysis, design example and experimental results are presented from a three-phase 208-V, 1.5-kW laboratory prototype converter.

Switching power converter employing pulse frequency modulation control

Abstract: A method for controlling a switching power converter provides an efficient algorithm for controlling the output voltage across loads that are relatively light with small transients. When the output voltage is at or below a predetermined first magnitude, a determination is made of the charge required for one or more pulses to increase the output voltage to a predetermined second magnitude which is greater than a target output voltage. Corrective action is taken to raise the output voltage to the second magnitude and the system takes no further corrective action until output voltage is determined to be at or below the first magnitude. The method is useful with synchronous or non-synchronous power converters of buck, boost, buck/boost or other topologies. The method further provides a simple means for determining the amount of charge removed from a battery.

A new PWM ZVS full-bridge converter

Abstract: A soft-switched full-bridge (FB) converter that features zero-voltage-switching (ZVS) of the bridge switches over a wide range of input voltage and output load is introduced. The proposed converter achieves ZVS with substantially reduced duty-cycle loss and circulating current. The control of the proposed converter can be implemented either with the phase-shift (PS) or pulse-width-modulated (PWM) technique. The performance of the proposed topology was verified on a 2-kW (48-V/40-A) experimental PWM FB converter prototype operating at 120 kHz from a 380-V dc input.

Primary side constant output voltage controller

Abstract: A lower-cost and more precise control methodology of regulating the output voltage of a flyback converter from the primary side is provided, which works accurately in either continuous voltage mode (CCM) and discontinuous mode (DCM), and can be applied to most small, medium and high power applications such cell phone chargers, power management in desktop computers and networking equipment, and, generally, to a wide spectrum of power management applications. Two highly integrated semiconductor chips based on this control methodology are also described that require very few components to build a constant voltage flyback converter.

Implementation of Single-Phase Matrix Converter as a Direct AC-AC Converter with Commutation Strategies

Abstract: This paper is concerned on investigations in implementations of the Single-Phase Matrix Converter (SPMC) as a direct AC-AC converter subjected to passive load conditions. The output voltage was synthesized using the well-known Sinusoidal Pulse Width Modulation (SPWM) technique. A Xilinx Field Programmable Gate Array (FPGA) was used to implement the controlling algorithm with IGBTs as power switching device. Prior to hardware implementation, simulations were performed to predict the behaviour. A laboratory model test-rig of the SPMC was then developed to experimentally verify the result. Good agreement was obtained between simulations and experiments.

Small-signal analysis and control design of asymmetrical half-bridge DC-DC converters

Abstract: This paper presents the small-signal modeling, dynamic analysis, and control design of the asymmetrical half-bridge dc-dc converter that employs a clamp capacitor and a magnetizing inductor to accommodate pulsewidth-modulated operation with asymmetrical duty ratios. The circuit averaging technique is applied to extract the small-signal dynamics of the power stage, and a graphical loop-gain method is used to design the feedback compensation and analyze the closed-loop performance of the converter. The distinctive power-stage dynamics of the converter are addressed and design guidelines for voltage feedback compensation are established. The results of the control design and closed-loop analysis are substantiated by experiments using an experimental converter.

Power converter with reduced common mode voltage

Abstract: An improved power converter that produces reduced-levels of common-mode voltages, or even entirely eliminates such voltages, is disclosed herein, along with a method of reducing common-mode voltages. In at least some embodiments, the improved power converter is equipped with common-mode filter inductors and a link coupling input and output ports of the power converter with one another to communicate a ground point associated with the input ports of the converter (and the source) to the load. Further, in at least some embodiments, the method includes providing common mode filter inductors as part of the converter, where the inductors are connected at least indirectly to at least one of a rectifier and an inverter of the converter, and communicating a grounded neutral from input ports of the converter to output ports of the converter by way of at least one additional linkage.

Buck converter with inductor pre-energizing

Abstract: Circuits and methods to achieve a buck-boost converter, capable to achieve a constant output voltage by pre-charging of an inductor if the input voltage is close to the output voltage has been achieved. The prior art problem of output voltage variations occurring while the input voltage is close to the output voltage is avoided. In case the input voltage is lower than a defined threshold voltage or the duty cycle exceeds a defined maximum allowable level, the inductor of the converter is pre-charged followed by boosting of the energy of the inductor to the output of the converter. In both modes the control loops of the buck converter can be used for buck duty cycle control. The duration of the pre-charge depends upon the level of the input voltage, the lower the input level is the longer is the pre-charge performed.

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

Abstract: 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

A High Step-Up DC-DC Converter Based on Three-State Switching Cell

Abstract: A new non-isolated boost converter with high voltage gain is proposed on this work This converter is suitable for applications with a high voltage gain between the input and the output In this converter, for a given duty cycle, the output to input voltage ratio can be raised by adding transformer turns Another important feature of this converter is the lower blocking voltage across the controlled switches compared to similar circuits, which allows the utilization of MOSFETs switches with lower conduction resistances RDS(on) In order to verify the feasibility of this topology; principle of operation, theoretical analysis, and experimental waveforms are shown for a 1 kW assembled prototype

Dual Z-source Inverter with Three-Level Reduced Common Mode Switching

Abstract: This paper presents the design of a dual Z-source inverter that can be used with either a single dc source or two isolated dc sources. Unlike traditional inverters, the integration of a properly designed Z-source network and semiconductor switches to the proposed dual inverter allows buck-boost power conversion to be performed over a wide modulation range, with three-level output waveforms generated. The connection of an additional transformer to the inverter ac output also allows all generic wye-or delta-connected loads with three-wire or four-wire configuration to be supplied by the inverter. Modulationwise, the dual inverter can be controlled using a carefully designed carrier-based pulsewidth-modulation (PWM) scheme that will always ensure balanced voltage boosting of the Z-source network while simultaneously achieving reduced common-mode switching. Because of the omission of dead-time delays in the dual-inverter PWM scheme, its switched common-mode voltage can be completely eliminated, unlike in traditional inverters, where narrow common-mode spikes are still generated. Under semiconductor failure conditions, the presented PWM schemes can easily be modified to allow the inverter to operate without interruption, and for cases where two isolated sources are used, zero common-mode voltage can still be ensured. These theoretical findings, together with the inverter practicality, have been confirmed in simulations both using PSIM with Matlab/Simulink coupler and experimentally using a laboratory-implemented inverter prototype.

A new interleaved isolated boost converter for high power applications

Abstract: Isolated boost converter is desirable in the low-to-high dc/dc application where isolation is required or a large step up is in a need. The challenge of designing such a converter for high power applications is how to handle the high current at the input and high voltage at the output. An effective way is to parallel the inputs and series the outputs of the isolated boost converters. Based on this concept, a new interleaved and isolated boost converter is proposed in this paper that has two inductors in parallel at the input to share the current and two capacitors in series at the output to share the voltage. The current stresses and voltage stresses of the converter are both alleviated. The two boost converter cells realize demagnetizing by helping each other, which simplifies the transformer structures. With interleaved operation, the current ripple is smaller; therefore, it is possible to use smaller capacitors at the input and output of the converter. All these features make the new interleaved isolated boost converter desirable for high power low-to-high dc/dc applications. The proposed interleaved isolated boost converter is presented based on the basic isolated boost converter, but the interleaved structure is applicable to other isolated boost converters including the full-bridge converter, the push-pull converter, and the L-type half-bridge converter. The theoretical analysis is verified by a 200W prototype.

Reduced Switch Count DC-Link AC–AC Five-Leg Converter

Abstract: This paper investigates a reduced switch count dc-link ac-ac five-leg converter for three-phase power conversion. The converter provides both an input rectifier and an output inverter by sharing a leg in order to reduce the number of power switches. Scalar and vector pulsewidth modulation techniques are presented and the concepts of local and global apportioning factors are introduced. A control technique that aims at maximizing the utilization of the dc-link voltage is proposed. A hysteresis current controller that allows operating with one leg being shared by the load and grid sides is developed. In addition, several relevant characteristics of the converter are addressed, such as voltage capability, harmonic distortion, shared-leg and capacitor currents, and power rating. The features of such a converter are compared to those of the six-leg and four-leg converters. Selected experimental results are presented

A new soft-switched PFC boost rectifier with integrated flyback converter for stand-by power

Abstract: This paper presents a magnetic integration approach that reduces the number of magnetic components in a power supply by integrating magnetic components in two conversion stages. Specifically, in the proposed approach, a single transformer is used to implement the continuous-conduction-mode boost power-factor-corrected (PFC) converter and the dc/dc flyback converter. The integrated boost and flyback converters offer soft switching of all semiconductor switches including a controlled di/dt turn-off rate of the boost rectifier. The performance of the proposed approach was evaluated on a 150-kHz, 450-W, universal-line range boost PFC converter with 12-V/2.2-A integrated stand-by flyback converter.