Showing papers on "Buck converter published in 2009"

Three-Port Series-Resonant DC–DC Converter to Interface Renewable Energy Sources With Bidirectional Load and Energy Storage Ports

Abstract: In this paper, a three-port converter with three active full bridges, two series-resonant tanks, and a three-winding transformer is proposed. It uses a single power conversion stage with high-frequency link to control power flow between batteries, load, and a renewable source such as fuel cell. The converter has capabilities of bidirectional power flow in the battery and the load port. Use of series-resonance aids in high switching frequency operation with realizable component values when compared to existing three-port converter with only inductors. The converter has high efficiency due to soft-switching operation in all three bridges. Steady-state analysis of the converter is presented to determine the power flow equations, tank currents, and soft-switching region. Dynamic analysis is performed to design a closed-loop controller that will regulate the load-side port voltage and source-side port current. Design procedure for the three-port converter is explained and experimental results of a laboratory prototype are presented.

A Hybrid Fuel Cell Power System

Abstract: This paper proposes a hybrid fuel cell power system, which consists of a fuel cell, an isolated unidirectional converter, a bidirectional converter, an inverter, and a battery. The fuel cell and the battery are connected to the same voltage bus through an appropriate hybrid full-bridge LLC resonant unidirectional converter and a three-level buck/boost bidirectional converter, respectively. The battery is an auxiliary energy source, powers the load during the system's start state to make it easy for the system to cold start, and provides or absorbs the dynamic power when the load varies and the fuel cell cannot respond immediately, so the system dynamic characteristics are improved. Furthermore, the battery can also provide peak power at overload, so the power rating of the fuel cell can be decreased, which reduces the total system cost. In order to ensure that the system operates with high efficiency, this paper also proposes a power management control scheme, which controls the bidirectional converter operating under buck, boost, or shutdown mode according to the operation condition of the fuel cell and battery, so that the battery can be charged or discharged. The operation of the system during cold start and overload are analyzed in detail. A 1-kW fuel cell power system was built in the laboratory. Experimental results are shown to verify the theoretical analysis.

Evaluation of DSP-Based PID and Fuzzy Controllers for DC–DC Converters

Abstract: In this paper, digital proportional-integral-derivative (PID)-type and fuzzy-type controllers are compared for application to the buck and boost dc-dc converters. Comparison between the two controllers is made with regard to design methodology, implementation issues, and experimentally measured performance. Design of fuzzy controllers is based on heuristic knowledge of converter behavior, and tuning requires some expertise to minimize unproductive trial and error. The design of PID control is based on the frequency response of the dc-dc converter. Implementation of linear controllers on a digital signal processor is straightforward, but realization of fuzzy controllers increases computational burden and memory requirements. For the boost converter, the performance of the fuzzy controller was superior in some respects to that of the PID controllers. The fuzzy controller was able to achieve faster transient response in most tests, had a more stable steady-state response, and was more robust under some operating conditions. In the case of the buck converter, the fuzzy controller and PID controller yielded comparable performances.

A Novel Three-Phase Three-Leg AC/AC Converter Using Nine IGBTs

Abstract: This paper proposes a novel three-phase nine-switch ac/ac converter topology. This converter features sinusoidal inputs and outputs, unity input power factor, and more importantly, low manufacturing cost due to its reduced number of active switches. The operating principle of the converter is elaborated; its modulation schemes are discussed. Simulated semiconductor loss analysis and comparison with the back-to-back two-level voltage source converter are presented. Finally, experimental results from a 5-kVA prototype system are provided to verify the validity of the proposed topology.

Single-Inductor Multi-Output (SIMO) DC-DC Converters With High Light-Load Efficiency and Minimized Cross-Regulation for Portable Devices

Abstract: A load-dependant peak-current control single-inductor multiple-output (SIMO) DC-DC converter with hysteresis mode is proposed. It includes multiple buck and boost output voltages. Owing to the adaptive adjustment of the load-dependant peak-current control technique and the hysteresis mode, the cross-regulation can be minimized. Furthermore, a new delta-voltage generator can automatically switch the operating mode from pulse width modulation (PWM) mode to hysteresis mode, thereby avoiding inductor current accumulation when the total power of the buck output terminals is larger than that of the boost output terminals. The proposed SIMO DC-DC converter was fabricated in TSMC 0.25 mum 2P5M technology. The experimental results show high conversion efficiency at light loads and small cross-regulation within 0.35%. The power conversion efficiency varies from 80% at light loads to 93% at heavy loads.

Bidirectional, High-Power DC Transformer

Abstract: This paper studies a bidirectional dc-dc converter concept which is capable of achieving very high stepping ratios with MW level power transfers. The converter can find potential application in connecting high-power dc sources, interfacing to high-voltage dc transmission or to flexible ac transmission system elements. The converter is based on two resonant circuits which share a common ac capacitor. The topology is simple and utilizes thyristors with potentially all soft switchings. Complete analytical modelling is presented which enables systematic design procedure for the converter. The detailed digital simulation on PSCAD platform confirms satisfactory operation on a 5-MW test system, which connects 4-kV dc source to an 80-kV high voltage dc grid. The converter shows good responses to rapid changes in power magnitude/direction and it is concluded that robustness to terminal voltage disturbances is excellent. Since the highest-power phase-control thyristors are employed, the converter can potentially be used at much higher power levels. The passive components are of reasonable size.

An Interleaved Boost Converter With Zero-Voltage Transition

Abstract: This paper proposes a novel soft-switching interleaved boost converter composed of two shunted elementary boost conversion units and an auxiliary inductor. This converter is able to turn on both the active power switches at zero voltage to reduce their switching losses and evidently raise the conversion efficiency. Since the two parallel-operated elementary boost units are identical, operation analysis and design for the converter module becomes quite simple. A laboratory test circuit is built, and the circuit operation shows satisfactory agreement with the theoretical analysis. The experimental results show that this converter module performs very well with the output efficiency as high as 95%.

An Analytical Investigation of DC/DC Power Electronic Converters With Constant Power Loads in Vehicular Power Systems

Abstract: Stability of multi-converter power systems, which exist in advanced more electric vehicles, is of great importance. The stability issue is investigated in this paper, and design considerations and limitations of the methods that stabilize the open-loop converters are presented. By stabilizing the open-loop converter, it is shown that the feedback loop design is usually translated into a conventional feedback design task. The behavior of the unstable converter is also discussed, and a method for decreasing the amplitude of the output voltage oscillations is proposed. The model of a tightly regulated practical converter is presented. This model is used to decide how much damping should be added to make the feeder converter stable. Furthermore, because we have this information about the load converter, the feeder converter can be redesigned so that it does not see the load converter as a constant power load.

Insulator integrated power supply

Abstract: A power scavenging device attaches to an overhead power cable and a support pole. The power scavenging device includes a non-conducting outer body and a first capacitor and a second capacitor that are connected in series forming a voltage divider. A voltage source converter is electrically connected to the output of the power scavenging device. The voltage source converter outputs a regulated power.

KY Converter and Its Derivatives

Abstract: In this paper, a voltage-boosting converter, named KY converter (i.e., 1-plus-D converter), is presented. Unlike the traditional nonisolated boost converter, this converter possesses fast load transient responses, which is similar to the buck converter with synchronous rectification. In addition, it possesses nonpulsating output current, thereby not only decreasing the current stress on the output capacitor but also reducing the output voltage ripple. Besides, 1-plus-2D and 2-plus-D converters, derived from the KY converter, are presented based on the same structure but different pulsewidth-modulation control strategies. Above all, the main difference between the KY converter and its derivatives is that the latter ones possess higher output voltages than the former one under the same duty cycle. A detailed description of the KY converter and its derivatives is presented along with some simulated and experimental results.

Method and system for providing local converters to provide maximum power point tracking in an energy generating system

Abstract: A method for providing maximum power point tracking for an energy generating device (202) using a local buck-boost converter (206) coupled to the device (202) is provided. The method includes operating in a tracking mode, which includes initializing a conversion ratio for the buck-boost converter (206) based on a previous optimum conversion ratio. A device power associated with the initialized conversion ratio is calculated. The conversion ratio is repeatedly modified and a device power associated with each of the modified conversion ratios is calculated. A current optimum conversion ratio for the buck-boost converter (206) is identified based on the calculated device powers. The current optimum conversion ratio corresponds to one of a buck mode, a boost mode and a buck-boost mode for the buck-boost converter (206).

Dual-Buck Full-Bridge Inverter With Hysteresis Current Control

Abstract: This paper presents a dual-buck full-bridge inverter (DBFBI) to solve the shoot-through problem in conventional bridge-type inverters and reduce the voltage stress of the power device in the dual-buck half-bridge inverter (DBHBI). Hysteresis current control is used in the DBFBI. All switches and diodes operate at each half line cycle, and the freewheeling current flows through the independent freewheeling diodes instead of the body diodes of the switches, so the efficiency can be increased potentially. As the shoot-through problem does not exist in the DBFBI, dead time between the switches need not be set. The input-voltage utilization rate of the DBFBI is twice that of the DBHBI under the same output-voltage condition, i.e., the voltage stress of the power device in DBFBI is half that in the DBHBI. The operating principle, stability and relative stability analyses, and design guidelines and example are provided. Experimental results of a 1-kVA DBFBI verify the theoretical analysis. The comparisons among other inverters and the DBFBI show that the proposed inverter is very promising in 220-240-Vrms output-voltage and high-reliability applications, such as uninterruptible power supplies and grid-connected inverters.

Impact of Power Density Maximization on Efficiency of DC–DC Converter Systems

Abstract: The demand for decreasing costs and volume leads to a constantly increasing power density of industrial converter systems. In order to improve the power density, further different aspects, like thermal management and electromagnetic effects, must be considered in conjunction with the electrical design. Therefore, a comprehensive optimization procedure based on analytical models for minimizing volume of DC-DC converter systems has been developed at the power electronic systems laboratory of the Swiss Federal Institute of Technology (ETH Zurich). Based on this procedure, three converter topologies-a phase-shift converter with current doubler and with capacitive output filter and a series-parallel resonant converter-are optimized with respect to power density for a telecom supply (400 V/48 V). There, the characteristic of the power density, the efficiency, and the volume distribution between the components as functions of frequency are discussed. For the operating points with maximal power density, the loss distribution is also presented. Furthermore, the sensitivity of the optimum with respect to junction temperature, cooling, and core material is investigated. The highest power density is achieved by the series-parallel resonant converter. For a 5-kW supply, a density of approximately 12 kW/L and a switching frequency of ca. 130 kHz are obtained.

A Practical Switching Loss Model for Buck Voltage Regulators

Abstract: In this paper, a review of switching loss mechanisms for synchronous buck voltage regulators (VRs) is presented. Following the review, a new simple and accurate analytical switching loss model is proposed for synchronous buck VRs. The model includes the impact of common source inductance and switch parasitic inductances on switching loss. The proposed model uses simple equations to calculate the rise and fall times and piecewise linear approximations of the high-side MOSFET voltage and current waveforms to allow quick and accurate calculation of switching loss in a synchronous buck VR. A simulation program with integrated circuit emphasis (Spice) simulations are used to demonstrate the accuracy of the voltage source driver model operating in a 1-MHz synchronous buck VR at 12-V input, 1.3-V output. Switching loss was estimated with the proposed model and compared to Spice measurements. Experimental results are presented to demonstrate the accuracy of the proposed model.

Step-up DC-DC converter for megawatt size applications

Abstract: This study describes a novel DC-DC converter concept which is capable of achieving very high step-up gains with megawatt (MW) level power transfers. The converter is based on two four-switch bridges around a LC circuit and does not utilise iron core transformers. The converter topology is simple and utilises thyristors as switches, with potentially soft switching operation. The high-voltage circuit does not suffer from excessive switch stresses or reverse recovery problems. The analytical modelling indicates that loading, and not the voltage gain, determines the converter size and the control input magnitude. For a given converter, the gain and either loading or operating frequency can be arbitrary selected. The converter shows good controllability with a linear characteristic if the operating frequency is used as the control input. The detailed digital simulation on PSCAD platform confirms conclusions from theoretical analysis on a 5 MW test system, which connects 4 kV source to 80 kV high voltage DC grid. The simulation studies of loses, with realistic internal resistances, indicate that efficiencies of around 95% could be expected.

Method and system for providing maximum power point tracking in an energy generating system

Abstract: A method for providing a maximum power point tracking (MPPT) process for an energy generating device (202) is provided. The method includes coupling a local converter (204) to the energy generating device (202). A determination is made regarding whether the local converter (204) is operating at or below a maximum acceptable temperature. A determination is made regarding whether at least one current associated with the local converter (204) is acceptable. When the local converter (204) is determined to be operating at or below the maximum acceptable temperature and when the at least one current associated with the local converter (204) is determined to be acceptable, the MPPT process is enabled within the local converter (204).

Buck boost function based on a capacitor bootstrap input buck converter

Abstract: A buck boost voltage converter circuit has a capacitor pump circuit for boosting an input voltage in a first mode of operation when an input voltage is below a desired voltage level A buck converter circuit provides the output voltage responsive to the boosted input voltage from the capacitor pump circuit in the first mode of operation and provides the output voltage responsive to the input voltage in a second mode of operation when the input voltage is above the desired voltage level

Optimal Pulsewidth Modulation of Nine-Switch Converter

Abstract: Nine-switch converter is a recent reduced semiconductor topology proposed in place of the back-to-back 12-switch converter. Like its precedence, the nine-switch converter can either operate at a single common frequency (CF) or different frequencies (DFs) at its two sets of three-phase terminals, but because of its reduced-switch configuration, some compromises cannot be avoided. In particular, the nine-switch converter is more restricted in its total attainable amplitude and phase shift between its two terminal sets, which means that when migrating standard modulating theories to the nine-switch converter, more concerns have to be addressed. These concerns are now investigated in the paper, before knowledge on how to avoid unintentional distortion and appropriate modulation schemes are formulated for operating the nine-switch converter in its CF and DF modes. Explanation, simulation, and experimental results are all presented in the paper for verifying the conceptual standing and practicality of the proposed modulation schemes.

Hybrid Digital Adaptive Control for Fast Transient Response in Synchronous Buck DC–DC Converters

Abstract: This paper presents a hybrid digital adaptive (HDA) control for fast step-load transient responses in synchronous buck DC-DC converters. The proposed HDA controller results in near-time-optimal step-load transient responses even when the output voltage is sampled using a relatively low-resolution, narrow-range window A/D converter. The controller is a combination of a standard constant-frequency pulsewidth-modulated (PWM) control in the vicinity of steady-state operating point and a bank of switching surface controllers (SSCs) away from the reference. The switching surface slope is adaptively selected by a supervisor based on an inductor current estimate. Furthermore, the controller is capable of taking into account a maximum inductor current limitation. A large-signal stability analysis is presented for all possible cases during transients when one of the SSCs is active. Experimental results demonstrate fast transient responses for a 1.3 V, 10 A synchronous buck converter over a wide range of step-load transients.

Bi-directional inductive power transfer

Abstract: A method, apparatus, and system are provided which enables the control of contactless power transfer in an inductive power transfer system using a phase control technique. The method comprises adjusting the phase of a secondary-side converter output voltage with respect to that of a primary-side converter. The magnitude of power transfer is determined by the relative phase angle, and the direction of power transfer is determined by whether the secondary converter output voltage leads or lags the input converter voltage, thereby enabling bi-directional power transfer between the primary and secondary sides of the system. According to alternative embodiments, the method may also be used for uni-directional power transfer only, and/or the secondary converter may be operated to maintain a constant relative phase angle.

Digital Combination of Buck and Boost Converters to Control a Positive Buck–Boost Converter and Improve the Output Transients

Abstract: A highly efficient and novel control strategy for improving the transients in the output voltage of a DC-DC positive buck-boost converter, required for low-power portable electronic applications, is presented in this paper. The proposed control technique can regulate the output voltage for variable input voltage, which is higher, lower, or equal to the output voltage. There are several existing solutions to these problems, and selecting the best approach involves a tradeoff among cost, efficiency, and output noise or ripple. In the proposed method, instead of instantaneous transition from buck to boost mode, intermediate combination modes consisting of several buck modes followed by several boost modes are utilized to distribute the voltage transients. This is unique of its kind from the point of view of improving the efficiency and ripple content in the output voltage. Theoretical considerations are presented. Simulation and experimental results are shown to prove the proposed theory.

Energy Management in a Fuel Cell/Supercapacitor Multisource/Multiload Electrical Hybrid System

Abstract: In this paper, a flatness-based nonlinear control method is proposed to control a multisource/multiload electrical hybrid system (EHS). The EHS is composed of a fuel cell and a supercapacitor-bank (SCB) as the main and auxiliary sources. They supply two independent loads, connected to a dc-bus through unidirectional buck converters. The proposed method is able to control the fuel cell output power and its dynamics. It also allows limiting the current of an SCB during charging and discharging processes. The proposed control strategy has the advantage of not requiring any commutation between different control algorithms when the operating mode of the system changes (from the normal mode to the overload mode, for example). As the fuel cell output characteristic (FCOC) varies with the physical and environmental parameters, an observer is also proposed and designed to estimate either the fuel cell voltage-power (V-P) output characteristic or voltage-current (V -I) output. The use of the proposed observer allows achieving an efficient control of the system and avoiding overcharging or discharging of an SCB. Experimental results demonstrate the operation of the proposed control strategy and observer in all situations. Experimental test on a system is done with two separated loads of 5 and 12 V, via a dSPACE platform.

Analysis and simulation of the P&O MPPT algorithm using a linearized PV array model

Abstract: This paper shows that the performance of the perturb and observe (P&O) maximum power point tracking (MPPT) algorithm is improved when the electronic converter is correctly controlled. A linearized photovoltaic (PV) array model is used to obtain the transfer function of the electronic converter and to design a voltage compensator for the converter input voltage. A buck converter is used in this work.

Design of a Solar Power Management System for an Experimental UAV

Abstract: The design of a solar power management system (SPMS) for an experimental unmanned aerial vehicle (UAV) is summarized. The system will provide power required for the on-board electronic systems on the UAV. The power management system mainly consists of the maximum power point tracking (MPPT), the battery management, and the power conversion stages. The MPPT stage attempts to obtain the maximum power available from the solar cell panels. The battery management stage monitors and controls the charge and discharge processes of the Li-ion polymer battery modules. The last stage is for power conversion that consists of dc/dc synchronous buck converters to generate +5 V and +12 V powers for the on-board computers and other electronic circuitries.

Two Types of KY Buck–Boost Converters

Abstract: A novel voltage-bucking/boosting converter, named as KY buck-boost converter (i.e., 2D converter), is presented herein. Unlike the traditional buck-boost converter, this converter possesses fast transient responses, similar to the behavior of the buck converter with synchronous rectification. In addition, it possesses the non-pulsating output current, thereby not only decreasing the current stress on the output capacitor but also reducing the output voltage ripple. Furthermore, it has the positive output voltage, different from the negative output voltage of the traditional buck-boost converter. Above all, there are two types of KY buck-boost converters presented herein. In this paper, the basic operating principles of the proposed converters are first illustrated in detail, and second, some experimental results are offered to verify the effectiveness of the proposed topologies.

Modeling and Analysis of Coupled Inductors in Power Converters

Abstract: This paper describes a new approach to the analysis of switched mode power converters utilizing coupled inductors and presents a novel canonical circuit model for N-winding coupled inductors. Waveform and ripple of the winding current in a coupled inductor converter can be easily determined using the developed model similar to those obtained in an uncoupled inductor converter. Influence of coupling coefficient on converter steady state and transient performances is readily predicted by the proposed model and a comparison of coupled and uncoupled inductor converters is provided. It is found that coupling among windings effectively alters the phase node voltage waveforms driving the coupled inductors. Through coupling, a converter is capable of responding faster to load transient depending on the coupling coefficient and control mechanism, and this dependency is analytically revealed in the paper. Some design constraints regarding coupling coefficient are also discussed for two-winding and multi-winding coupled inductors in power converter applications. Finally, a two-phase buck regulator is experimentally tested to verify the proposed model.

A Simple Current-Balancing Converter for LED Lighting

Abstract: In this paper, a current-balancing converter is proposed herein and applied to driving LED strings paralleled, so as to make the required current shared among LED string. There are two stages of the proposed current-balancing converter. The first stage is one buck converter under constant current control and transfers DC current to AC current, whereas the second stage is passive AC-DC rectifiers with front-end current-balancing transformers. Some experimental results, together with a simple mathematical derivation, are provided to verify the proposed scheme.

Analysis of LLC Resonant Converter considering effects of parasitic components

Abstract: Nowadays the trend of power supply market is more inclined to high switching frequency, high efficiency and high power density. To meet this trend, resonant power supply holds more attraction, because it can be operated in high switching frequency with high efficiency. There are many resonant power supplies such as Series-Resonant Converter (SRC), Parallel-Resonant Converter (PRC) and Series-Parallel Resonant Converter (SPRC). Among them, LLC Resonant Converter has a lot of advantages over the conventional SRC and PRC considering relatively narrow switching frequency variation over wide input and load variation and Zero-Voltage-Switching for entire load range. Therefore, the LLC Resonant Converter has been widely used and discussed. However, the conventional analysis of LLC Resonant Converter with Fundamental Harmonic Approximation (FHA) can not explain the practical operation of LLC Resonant Converter. To overcome this limitation, in this paper, analysis and design of the LLC Resonant Converter including parasitic components which are affecting converter operation are proposed using a traditional analysis based on FHA. The effect of each parasitic component is analyzed with simulation results and the design guideline standing on this analysis will be described. Moreover, the experimental results of prototype designing on the basis of the analysis are shown to demonstrate the proposed analysis and design guideline.

A Single-Inductor Step-Up DC-DC Switching Converter With Bipolar Outputs for Active Matrix OLED Mobile Display Panels

Abstract: A single-inductor step-up DC-DC switching converter with bipolar outputs is implemented for active-matrix OLED mobile display panels. The positive output voltage is regulated by a boost operation with a modified comparator control (MCC), and the negative output voltage is regulated by a charge-pump operation with a proportional-integral (PI) control. The proposed adaptive current-sensing technique successfully supports the implementation of the proposed converter topology and enables the converter to work in both discontinuous-conduction mode (DCM) and continuous-conduction mode (CCM). In addition, with the MCC method, the converter can guarantee a positive output voltage that has both a fast transient response of the comparator control and a small output voltage ripple of the PWM control. A 4.1 mm2 converter IC fabricated in a 0.5 mum power BiCMOS process operates at a switching frequency of 1 MHz with a maximum efficiency of 82.3% at an output power of 330 mW.