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This paper proposes an active technique to reconstruct and balance the phase currents in multiphase dc-dc converters implementing both of voltage- and current-mode controls. Only one current sensor at the dc link is required to measure and reconstruct the phase currents. Multiple current samples in the pulsewidth modulation switching period are synchronized with the carrier waveforms to actively reconstruct the phase currents using a simple active balancing algorithm that is implemented in a digital controller. The proposed technique improves system performance, stability, and efficiency, and prevents inductor saturation. A 5-kW four-phase dc-dc converter prototype for battery charging application is built to experimentally verify the proposed algorithm. [ABSTRACT FROM AUTHOR]

This paper proposes a novel transformerless grid-connected power converter with negative grounding for a photovoltaic generation system. The negative terminal of the solar cell array can be directly connected to the ground in the proposed grid-connected power converter to avoid the transparent conducting oxide corrosion that occurs in some types of thin-film solar cell array. The proposed grid-connected power converter consists of a dc-dc power converter and a dc-ac inverter. The salient features of the proposed power converter are that some power electronic switches are simultaneously used in both the dc-dc power converter and dc-ac inverter, and only two power electronic switches operate at high switching frequency at the same time (one is in the dc-dc power converter and the other is in the dc-ac inverter). The leakage current of the photovoltaic generation system is reduced because the negative terminal of the solar cell array is connected directly to the ground. Finally, a prototype was developed to verify the performance of the proposed grid-connected power converter. The experimental results show that the performance of the proposed grid-connected power converter is as expected. [ABSTRACT FROM AUTHOR]

Within the photovoltaic (PV) power-generation market, the ac PV module has shown obvious growth. However, a high voltage gain converter is essential for the module's grid connection through a dc-ac inverter. This paper proposes a converter that employs a floating active switch to isolate energy from the PV panel when the ac module is off; this particular design protects installers and users from electrical hazards. Without extreme duty ratios and the numerous turns-ratios of a coupled inductor, this converter achieves a high step-up voltage-conversion ratio; the leakage inductor energy of the coupled inductor is efficiently recycled to the load. These features explain the module's high-efficiency performance. The detailed operating principles and steady-state analyses of continuous, discontinuous, and boundary conduction modes are described. A 15 V input voltage, 200 V output voltage, and 100 W output power prototype circuit of the proposed converter has been implemented; its maximum efficiency is up to 95.3% and full-load efficiency is 92.3%. [ABSTRACT FROM AUTHOR]

This paper proposes a new method for stability analysis of a bidirectional dual full-bridge dc-dc converter with triple phase-shift control under arbitrary parameter changes. The present analysis makes the stability determination of these power converters more systematic and precise than the existing methods in this field, which are largely based on simulation. Nonlinear and periodic operation of the bidirectional converter is presented including the control circuit. Using the working theory, the converter operation is separated into several stages. Equivalent circuits and state equations are developed for each stage. The Lyapunov function method is used to determine the stability of the converter in every stage. Justification is provided for the absence of abrupt changes of the state variables or infinite noise at the interface of different stages. The stability of the bidirectional converter is determined theoretically by integrating these concepts. Some simulation results are provided to validate the developments. [ABSTRACT FROM AUTHOR]

The integration of photovoltaic (PV) modules in buildings causes problems with shadows that can strongly reduce the energy produced by these systems. Moreover, most PV modules are designed for stand-alone applications that have output voltage adapted to lead batteries. Indeed, this historical sizing of PV modules can be discussed in the case of grid-connected systems. In this paper, a cascaded dc/dc converter based on boost chopper is proposed. First, the advantages and the limits of this topology will be shown. Second, this topology will be optimized to maximize the efficiency or minimize the volume. The originality of this optimization is that the converters' parameters and the arrangement of the PV cells are variable parameters. Indeed, the optimization is done on the entire system. To realize these optimizations, semiempiric models of losses and volumes of different components of a boost chopper were developed. The optimization uses a successive quadratic programming algorithm. Considering the optimization results over the whole range of the specifications, a flexible solution is developed and experimental results are presented. Finally, optimized topologies connected to several PV are evaluated at different situations of typical shadows. [ABSTRACT FROM AUTHOR]

This paper presents an alternative to the traditional dc-dc converter interfacing the battery with the inverter dc bus in plug-in hybrid electric vehicle (HEV) traction drives. The boost converter used in commercial HEVs meets with obstacles when it comes to upgrading the power rating and achieving high efficiency while downsizing the converter. A four-level flying-capacitor dc-dc converter is explored that can overcome these drawbacks by dramatically reducing the inductance requirement. A special case of the four-level converter, the 3X dc-dc converter, operates at three discrete output/input voltage ratios, thus further reducing the inductance requirement to a minimal value (almost zero). When further compared to its switched-capacitor dc-dc converter counterparts, the 3X dc-dc converter can be operated at variable output/input voltage ratios without sacrificing efficiency, and it lowers the capacitance requirement by utilizing the parasitic inductance. The operating principle, current ripple analysis, the transient control to limit the inrush current, and power loss analysis are introduced. Experimental results of a 55-kW prototype are provided to demonstrate the principle and analysis of this topology. [ABSTRACT FROM AUTHOR]

In this paper, a new technique for controlling dc-dc resonant converters is investigated. A variable inductance is used to control and regulate the dc output voltage maintaining constant switching frequency for the half-bridge transistors. The output voltage characteristics of the series resonant and parallel resonant converters under the proposed magnetic control are obtained and analyzed. In order to evaluate the proposed technique, a laboratory prototype for a 48 V-input 5 V/10 A-output 500 kHz parallel resonant converter is presented. A methodology for obtaining the converter dynamic response using a step response test is carried out. From the dynamic response, a compensator for operating the converter at closed loop is developed and tested in the laboratory. The results prove that the proposed technique is suitable for controling resonant inverters at constant frequency using a low-cost half-bridge inverter. [ABSTRACT FROM AUTHOR]

Multiport dc/dc converters are widely employed in hybrid energy generation systems to provide stable power to key loads with high power density. In this paper, the switch duty cycle and the phase angle of the interleaved converters are employed as two control freedoms to achieve decoupled voltage regulation within a certain operating range among different ports, which is referred to as pulsewidth modulation plus phase angle shift (PPAS) control scheme. An interleaved bidirectional buck-boost converter and a full-bridge converter are integrated together to derive a combined three-port dc/dc converter for photovoltaic (PV)-battery hybrid energy systems, which is adopted as a typical example to explore the clear performance of the proposed PPAS control strategy. The bidirectional buck-boost converter and the full-bridge converter share the same power MOSFETs in the primary side, which simplifies the circuit structure and improves the power density. The duty cycle of the interleaved bidirectional buck-boost converter is adopted to realize the maximum power point tracking and the voltage balance between the battery and the PV cell in the primary side. Furthermore, the phase angle of the interleaved buck-boost converter is employed as another control freedom to achieve accurate secondary output voltage regulation. Finally, a 100-W PV-Battery energy system is designed and tested to verify the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

A new 16-phase interleaved bidirectional dc/dc converter is developed featuring smaller input/output filters, faster dynamic response and lower device stress than conventional designs, for hybrid vehicle applications. The converter is connected between the ultracapacitor (UC) pack and the battery pack in a multisource energy storage system of a hybrid vehicle. Typically, multiphase interleaved converters require a current control loop in each phase to avoid imbalanced current between phases. This increases system cost and control complexity. In this paper, in order to minimize imbalance currents and remove the current control loop in each phase, the converter is designed to operate in discontinuous conduction mode (DCM). The high current ripple associated with DCM operation is then alleviated by interleaving. The design, construction, and testing of an experimental hardware prototype is presented, with the test results included. Finally, a novel soft switch topology for DCM operation is proposed for future research, to achieve zero-voltage switching (ZVS), or zero-current switching (ZCS) in all transitions. [ABSTRACT FROM AUTHOR]

Power electronics systems are becoming larger and more complex, involving a wide variety of loads, power sources, and power conditioning equipment. Simple behavioral models are required to perform a system-level analysis. These models can be parameterized from simple measurements or data supplied by the manufacturer. One of the emerging power sources are the fuel cells, which are being used in different power levels and applications. Some commercial products include not only the fuel cell stack, but also a dc–dc converter to provide a regulated output voltage despite the operation conditions of the fuel cell. In this paper, a behavioral model of a commercial fuel cell with a built-in front-end dc–dc converter is developed, based on load step tests. Model identification is carried out from experimental measurements using well-known identification algorithms. A validation of the obtained model has been performed by means of applying the same current patterns to the model and the actual fuel cell: steps; pulses; and sinusoids. Moreover, a simple power system has been built in order to validate the proposed model. A good trade-off between simplicity and accuracy is achieved. [ABSTRACT FROM AUTHOR]

Maximum power transfer in solar microgrid applications is achieved by impedance matching with a dc–dc converter with maximum power point tracking by the incremental conductance method. Regulation and dynamic control is achieved by operating with continuous conduction. It can be shown that under stable operation, the required output inductor has an inductance versus current characteristic, whereby the inductance falls off with increasing current, corresponding to increasing incident solar radiation. This paper describes how a variable inductor whereby the inductor core progressively saturates with increasing current meets this requirement and has the advantage of reducing the overall size of the inductor by up to 75% and increases the operating range of the tracker to recover solar energy at low solar levels. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage circuit topology consisting of the association of a full-bridge isolated dc-dc converter and two input inductors and two input diodes connected to the mains network, in order to obtain an isolated ac/dc switch mode power supply, with sinusoidal input current. The proposed topology does not use an input bridge rectifier, common in similar applications. The current in the two input inductors can, therefore, flow in both directions. Consequently, the proposed topology equally distributes the current by the four-bridge transistors that provide four input parallel boost power factor correctors (PFCs). The use of the four-bridge transistors to obtain the PFC function and regulate the output voltage with galvanic isolation is a new technique that makes this topology unique, which also contributes to improve the converter efficiency. The definition of appropriate control strategies permitting the accurate simultaneous regulation of output voltage and input current is hereby described. The interdependency between these two conversion processes is completely analysed, allowing for useful design rules. Experimental results were obtained in a 650-W laboratory prototype to verify the theoretical study. A maximum efficiency of 94% was obtained. [ABSTRACT FROM AUTHOR]

A soft-switching dc/dc converter with high voltage gain is proposed in this paper. It provides a continuous input current and high voltage gain. Moreover, soft-switching characteristic of the proposed converter reduces switching loss of active power switches and raises the conversion efficiency. The reverse-recovery problem of output rectifiers is also alleviated by controlling the current changing rates of diodes with the use of the leakage inductance of a coupled inductor. Experimental results obtained on 200W prototype are discussed. [ABSTRACT FROM AUTHOR]

A dual-output dc-dc converter based on the complementary pulsewidth modulation is proposed to overcome the cross-regulation problem between the outputs. Using a special-connected two transformers cell, one operational period is divided into two complementary parts. One output branch gets the pulsewidth and is regulated by the duty cycle; the other output branch gets the complementary pulsewidth and is regulated by the PFM. Only one full bridge and several passive components are needed, but both the two outputs have the fully regulated abilities even in the no-load situation. Moreover, a full zero-voltage-switching (ZVS) range is achieved in all the switches without auxiliary circuits. Therefore, the proposed topology has compact structure, high switching frequency, high-power density, and high efficiency. The operation principle, ZVS conditions, and design considerations are presented in the paper. The analysis is verified by a 300 V input, and 24 V/10A and 48 V/5 A outputs prototype. [ABSTRACT FROM AUTHOR]

This paper studies the power flow characterization of a bidirectional galvanically isolated high-power dual active bridge dc/dc converter. In experimental tests at the University of Michigan, we have observed three phenomena, which we term as internal power transfer, phase drift, and low system efficiency, that are present under certain operating conditions. These phenomena cannot be explained by conventional power transfer analysis. The authors develop a new model, based on a detailed analysis over a short time scale, that incorporates additional parameters, including the power semiconductor voltage loss and dead time. The new power flow model may be used to explain the observed phenomena and to characterize the power flow of the converter. Themodel may also be used to perform accurate power flow computations over a wide operating range, thereby supporting optimal hardware design, operating range selection, and power management strategy development. Experimental results are presented to illustrate the validity of the new model. [ABSTRACT FROM AUTHOR]

For recent voltage regulators powering microprocessors, the amount of space they use is the most challenging issue. Moreover, efficient energy management depends not only on heavyload efficiency but also on light-load efficiency. So far, to reduce the space taken near the microprocessor and to increase heavy-load efficiency, a two-stage voltage regulator has been proposed, and the adaptive bus voltage positioning (ABVP) control concept has been proposed to increase the light-load efficiency of the two-stage structure. In this paper, a ABVP control structure is proposed and is employed in the adaptive voltage positioning (AVP) system. For the proper design of this system, the system is modeled and analyzed, and the experimental results verify the analysis. [ABSTRACT FROM AUTHOR]

Various fast and efficient computation techniques for a power converter simulation have been researched. According to the conventional methods, a single step size for a whole circuit is selected for the numerical integration. A real-power electronic system, however, is multirate in that its currents and voltages nonumformly vary spatially and temporally, and its subcircuits have different transient rates. A simulation that selected an appropriate step size for each subcircuit independently would, therefore, be more efficient. Several multirate analysis techniques have already been proposed; this paper proposes a new method that divides the whole circuit into subcircuits by applying an explicit integration formula to series inductors and/or parallel capacitors, and then integrates subcircuits by applying an implicit formula with independent integration step sizes. As analysis examples, this method is applied to an ac-dc converter, a benchmark test circuit, and a dclink inverter control system. The proposed method's effectiveness at reducing computational steps and CPU times is investigated, and its performance and efficiency are validated. [ABSTRACT FROM AUTHOR]

Today, "black-box" behavioral models of power converters are becoming interesting for system level simulation of power electronics systems. These models can be used to evaluate the response of systems that are composed of commercial converters, since they can be fully parameterized by analyzing the actual converter response. To optimize the required computational resources, these models should be as simple as possible. Furthermore, the identification of the parameters should be carried out easily, looking for simple experiments and straightforward adjusting algorithms. Easy modeling and identification procedures, based on a transient response analysis, are proposed in this paper. Using this method,a large-signal "black-box" behavioral model of a power converter is composed of reduced-order transfer functions, which are identified by analyzing the step response of the converter. Both an actual commercial dc-dc converter and a line-commutated rectifier have been modeled and identified by means of this approach, in order to validate the proposed procedures. [ABSTRACT FROM AUTHOR]

Fast power converters are desired in microprocessors, audio, and servomotor power supplies. Fixed-topology dc-dc converters have a minimum time in which to respond to line, load, and control change. This response depends on converter control, topology, and circuit parameters. Minimum-time control (MTC) considers these three items when it predicts postdisturbance steady-state points and directs capacitor voltage and inductor current in the shortest time. In this paper a nonlinear model-predictive control steers energy using geometrical curved control surfaces derived from piecewise linear (PWL) and bilinear models. The MTC differs from previous work on the topic in that it considers lossy components (a cause for nontriangular ripple) and is an open-form solution (as originally proposed by LaSalle in 1959). The different approach revealed a quantitative link between the needed control surface memory and state/parameter resolution. Results are generalized for two-state dc-dc converters and all parameter/control disturbances. An unconventional digital method was devised to accommodate the open-form solutions. It involved a priori control surface calculations, A/D scaling, surface quantizing, and image compression. The final control executed no real-time arithmetic operations. MTC performance was compared with other pulsewidth modulation controls and time-optimal control in simulations, and tests were performed in hardware using synchronous buck and boost converters. [ABSTRACT FROM AUTHOR]

Recent progress in the identification of switching power converters using an all-digital controller has granted net- work analyzer functionality to the control platform. In particular, the cross-correlation technique provides a nonparametric identification of a converter's small-signal control-to-output frequency response. The literature shows the viability of this technique as well as a few improvements to the basic technique. This online network analyzer functionality allows new flexibility in the areas of online monitoring and adaptive control. In this paper, several improvements to the cross-correlation method of system identification are proposed that aim to further improve the accuracy of the frequency response identification, particularly at high frequencies near the desired closed-loop bandwidth frequency. Additionally, an extension to the cross-correlation method is proposed that allows measurement of the control loop gain without ever opening the feedback loop. Thus, performance and stability margins may be evaluated while maintaining tight regulation of the output. Simulation and experimental results are shown to verify the proposed improvements and extension. [ABSTRACT FROM AUTHOR]

An efficient active LC snubber for forward converters is proposed in this paper. The proposed active LC snubber can be used to reset transformer and suppress switching surge. Further, by storing surge energy in the proposed active LC snubber and then releasing it to the flyback auxiliary output, the converter can achieve high efficiency. For a forward converter with active LC snubber, 91.02%, the maximum output efficiency can be obtained. Because of the high performance on surge suppression and energy recovery, experimental results show that the output efficiency of this proposed converter is higher than that of active-clamped. based converters. Furthermore, for a synchronous rectification forward converter with this active LC snubber, the maximum output efficiency can be further raised to 94.72%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A multilevel modular capacitor-clamped dc-dc converter (MMCCC) will be presented in this paper with some of its advantageous features. By virtue of the modular nature of the converter, it is possible to integrate multiple loads and sources with the converter at the same time. The modular construction of the MMCCC topology provides autotransformer-like taps in the circuit, and depending on the conversion ratio of the converter, it becomes possible to connect several dc sources and loads at these taps. The modularity of the new converter is not limited to only this dc transformer (auto) like operation, but also provides redundancy and fault bypass capability in the circuit. Using the modularity feature, some redundant modules can be operated in by-pass state, and during some faults, these redundant modules can be used to replace a faulty module to maintain an uninterrupted operation. Moreover, by obtaining a flexible conversion ratio, the MMCCC converter can transfer power in both directions. Thus, this MMCCC topology could be a solution to establish a power management system among multiple sources and loads having different operating voltages. [ABSTRACT FROM AUTHOR]

This paper presents a DSP method that allows decomposing conducted electromagnetic interference (EMI) emissions from different sources in large power electronics systems. The estimation process is carried out by a number of Wiener filters (WFs), which represent all different converter states. These are determined by initial commutation event conditions and propagation paths layout. Filters are fed by a semiconductor power switch voltage or current waveforms regarded as sources of perturbation. The EMI emissions are measured on the line impedance stabilization network (LISN) terminals. Optimal filter adaptation is carried out in the frequency domain by measuring and computing input and cross-power signal spectra. Analysis of a parallel quasi-resonant dc-link voltage inverter (PQRDCLI) is outlined to distinguish filters assigned for inverter operation from those for external dc/dc converter interaction. Experimental results are given to illustrate the WF estimation quality. The possibility of detailed decomposition of the LISN-EMI waveforms is depicted in both time and frequency domains. Comparative analysis of frequency responses for PQRDCLI-link voltage changes is given. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel approach to the modeling and controller design of the synchronous step-down dc-dc converter. We introduce a hybrid converter model that is valid for the whole operating regime and captures the different modes of operation. Based on this model, we formulate and solve a constrained optimal control problem. This allows a systematic controller design that achieves the regulation of the output voltage to its reference despite input voltage and output load variations while satisfying the constraints on the duty cycle and the inductor current. The resulting state-feedback control law is of piecewise affine form, which can be easily stored and implemented in a lookup table. A Kalman filter is added to account for unmeasured load variations and to achieve zero steady-state output voltage error. Experimental results demonstrate the potential advantages of the proposed control methodology. [ABSTRACT FROM AUTHOR]

This paper presents an approach to improve dynamic responses of digitally controlled dc-dc converters using nonuniform analog-to-digital (A/D) quantization of the output voltage error. The nonuniform A/D quantizer parameters are selected to achieve improved step-load transient responses without compromising stability margins. The implementation, which includes a programmable A/D quantizer and a look-up table based discrete-time compensator, is simple and well suited for practical high-frequency digital pulsewidth modulation controllers. Simulation and experimental results are presented for a proof-of-concept point-of-load 5 V-to-1.3 V digitally controlled synchronous buck converter. [ABSTRACT FROM AUTHOR]

This paper introduces an approach to near time- optimal control for synchronous buck dc-dc converters. The proposed proximate time-optimal digital (PTOD) controller is a combination of a constant-frequency pulsewidth modulation (PWM) controller employing a linear PID compensator close to a reference point, and a linear or nonlinear switching surface controller (SSC) away from the reference, together with smooth transitions between the two. A hybrid capacitor current estimator enables switching surface evaluation and eliminates the need for current sensing. The SSC, which is implemented as a small Verilog HDL module, can be easily added to an existing digital PWM controller to construct the PTOD controller. In steady state, the controller operates exactly the same as a standard constant-frequency PWM controller with a linear PID compensator. Simulation and experimental results are shown for a 6.5 V-to-1.3 V, 10 A synchronous buck converter. [ABSTRACT FROM AUTHOR]

This paper presents a closed-loop self-tuning technique for digitally controlled dc-dc switched-mode power supplies (SMPS) based on proportional-integral-derivative (PID) regulators, which derives from the more general model reference autotuning techniques. After briefly discussing an open loop, model-reference based tuning technique, a closed-loop solution is presented in which a perturbation frequency generated digitally is injected into the control loop and superimposed to the duty cycle command. The tuning is performed elaborating the signals right before and right after the injection point, and adjusting the PID parameters until predefined bandwidth and phase margin targets are obtained. The proposed approach allows for a robust and repeatable tuning, mainly because of the high resolution and dynamics available at the signal injection point. Moreover, the tuning is performed maintaining the closed-loop configuration, thus ensuring voltage regulation even during the PID adjustment, this being a fundamental constraint for most electronic equipments. The proposed technique is simple from the signal processing point of view, since it requires a few integrations, multiplications and phase-shift; further simplified implementations by employing nonsinusoidal perturbation waveforms like square-wave or triangular signals are also proposed. The approach is first discussed for two-parameters PI and PD regulators, and successively extended to PID structures, for which two possible implementations are proposed. The effectiveness of the tuning approach is verified by means of computer simulations and experimental tests carried out on a digital signal processor platform interfaced with a prototype point-of-load converter. The complexity of an HDL-implementation of the tuning hardware for field programmable gate array platforms is also discussed. [ABSTRACT FROM AUTHOR]

This paper presents a novel technique and system for increasing the efficiency of dc-dc converters that supply dynamic electronic loads, such as modern audio and video equipment and other devices whose power consumption largely depends on the digital data they process. The optimization does not require a current-measurement circuit and is well-suited to portable applications. It is based on a real-time prediction of the dc-dc converter output current from easily accessible digital data streams present in the targeted loads. The result of the prediction is used for dynamic adjustment of the power-stage transistor size and/or for switching into pulse-frequency-mode of output voltage regulation, in order to maximize the instantaneous converter efficiency on-the-fly. The use of a segmented power-stage allows the effective power-transistor size to be changed on-the-fly, and the tradeoff between the gate-drive and rms conduction losses is continuously optimized over the full range of operation. The effectiveness of the optimization is demonstrated on an experimental system, including a 1-W digitally controlled 4-MHz, 3.6 V-1.8 V buck converter with an integrated segmented power-stage and a digital high-fidelity class-D audio amplifier acting as the digital load. The results show a good agreement between the digitally predicted and actual dc-dc converter load current, as well as a reduction in total energy consumption of up to 38%. [ABSTRACT FROM AUTHOR]

Fuel cell systems have not significantly penetrated the low-power (< 50 W) portable energy source market, largely due to complexity of control and the balance-of-plant systems required. Even though the fuel cell and fuel container may scale down well, the pumps, blowers, and power converters required may dominate the system mass. This paper focuses on the tradeoff between efficiency and converter mass, and achieving the design objective of minimum mass of both converter and fuel. The effect of desired run-time, or mission duration, on the optimal dc-dc converter design was explored in detail. The effort focused on boost converters; however, the methodology can be applied to any converter topology. In an example case, at a mission length of 100 h, the optimized converter saved 91 g of system mass when compared to an off-the-shelf dc-dc converter. [ABSTRACT FROM AUTHOR]

Single-ended and two-ended bidirectional capacitor multipliers for providing on-chip compensation, soft-start, and fast transient mechanisms are proposed in this paper. The bidirectional current mode capacitor multiplier technique can effectively move the crossover frequency toward to the origin in the start-up period for a smoothly rising of the output voltage. Besides, the small time constant is set by the fast transient control circuit in order to get a higher crossover frequency. Thus, the output voltage can be regulated to its stable value as fast as it can when large load current changes. A test chip fabricated by the Taiwan Semiconductor Manufacturing Corporation (TSMC) 0.35-μm process verifies the correctness of the bidirectional current mode capacitor multiplier technique. Experimental results demonstrate the transient speed by our proposed technique is faster than that by conventional control by about 2 times, and there is only about 76% dropout voltage of the conventional design with off-chip compensation. The proposed circuits consume more quiescent current about 10 μA in single-ended capacitor multiplier and 20 μA in two-ended capacitor multiplier. With the proposed bidirectional current mode capacitor multiplier technique, the performance of dc-dc converters is improved significantly and the external pins and footprint area are minimized. [ABSTRACT FROM AUTHOR]

This paper proposes an integrated magnetic dc-dc converter suitable for high input voltage application. The converter is based on a coupled input-series and output-parallel dual interleaved Flyback converter concept. All the center and outer legs are gapped, and the transformers are integrated into one magnetic core with not so tight coupling. The gap is beneficial for suppressing current spike caused by the voltage mismatch between the windings. The two transformers are inversely coupled, and current ripple reduction can be achieved with suitable coupling design. A prototype with 350–450-V input and 24-V/4-A output is built. Experimental results verify the performance of the new topology. [ABSTRACT FROM AUTHOR]

This paper introduces a new method and system for parameter extraction and automated controller adjustment, suitable for low power digitally controlled dc-dc switch-mode power supplies (SM PS). The system allows closed-loop calibration throughout regular converter operation. During a short-lasting test phase, SMPS parameters, such as output capacitance and load, are estimated by examining the amplitude and frequency of intentionally introduced limit cycle oscillations in duty ratio control variable as well as from its steady state value. Accordingly, a digital compensator is automatically constructed to provide fast dynamic response and good output voltage regulation. In addition, the load estimation data are used for improving efficiency of a converter having segmented transistors. It is performed through a selection of driving sequence resulting in minimized sum of switching and conduction losses. The effectiveness of the system is demonstrated on an experimental 400 kHz, 9 V-to-3.3 V, 10 W, digitally controlled synchronous buck converter. [ABSTRACT FROM AUTHOR]

This paper presents a novel switching sequence design for the space-vector modulation of high-power multi- level converters. The switching sequences are optimized for the improvement of harmonic spectrum and the minimization of device switching frequency. Compared to other commonly used switching sequences, the output spectrum of the proposed design shows higher inverter equivalent switching frequency. Meanwhile, the device switching frequency is reduced by using a flexible switching pattern. The proposed switching sequence has been simulated and experimentally tested on a 5-level neutral point clamped H-bridge based inverter. The results from both simulations and experiments consistently verify the above-mentioned features. [ABSTRACT FROM AUTHOR]

This paper evaluates the capability of SiC power semiconductor devices, in particular JFET and Schottky barrier diodes (SBD) for application in high-temperature power electronics. SiC JFETs and SBDs were packaged in high temperature packages to measure the dc characteristics of these SiC devices at ambient temperatures ranging from 25 °C (room temperature) up to 450 °C. The results show that both devices can operate at 450 °C, which is impossible for conventional Si devices, at the expense of significant derating. The current capability of the SiC SBD does not change with temperature, but as expected the JFET current decreases with rising temperatures. A 100V, 25W dc-dc converter is used as an example of a high-temperature power-electronics circuit because of circuit simplicity. The converter is designed and built in accordance with the static characteristics of the SiC devices measured under extremely high ambient temperatures, and then tested up to an ambient temperature of 400 °C. The conduction loss of the SiC JFET increases slightly with increasing temperatures, as predicted from its dc characteristics, but its switching characteristics hardly change. Thus, SiC devices are well suited for operation in harsh temperature environments like aerospace and automotive applications. [ABSTRACT FROM AUTHOR]

This paper presents the theoretical analysis of the three-phase zero voltage switching pulsewidth modulation dc-dc converter associated with a double Wye connected rectifier, delta primary, using a special switching scheme in order to maintain equilibrium among the currents through the output filters. The operating stages are described and the simulation and experimental results of a 6-kW prototype are presented. [ABSTRACT FROM AUTHOR]

The series parallel resonant converter (SPRC) is known to have combined the merits of the series resonant converter (SRC) and the parallel resonant converter (PRC). However, the series PRC (SPRC) has a three-element LCC structure with complex transient dynamics and without control of the resonant circuit's dynamics, the converter's closed loop bandwidth to switching frequency ratio will be much reduced compared to that of pulsewidth modulation converters. In this paper, the generalized optimal trajectory control (GOTC) for the SPRC is presented. It allows the nonlinear resonant circuit of the SPRC having an arbitrary starting state to reach a desired steady state in one cycle with two optimally controlled switching instances. It is a generalized form of optimal trajectory control (OTC) [11] which is restricted to transitions between steady states. Based on GOTC, a traditional controller with inner current and outer voltage state-feedback is designed for an SPRC based dc-dc converter. The GOTC based feedback controller allows use of higher feedback gains compared with one using OTC or frequency control and gives higher closed loop bandwidth. This results in either better disturbance rejection for the converter or the possibility of reducing output filter sizing. Experimental results confirm the theoretical claims. [ABSTRACT FROM AUTHOR]

In this paper, an averaged model for a recently pro- posed novel three-phase transformer-isolated phase-shift dc-dc converter is derived. Fuel cell static and dynamic characteristics are used for the converter power stage design consideration. The controller is then designed based upon the power stage parameters and system dynamic requirements. The entire system has been designed, fabricated, and tested using a commercial 1.2-kW proton exchange membrane fuel cell. The experimental results match the simulation results fairly well on both fuel cell source dynamic and step load transient responses. [ABSTRACT FROM AUTHOR]

In recent years, interest in natural energy has grown in response to increased concern for the environment. Many kinds of inverter circuits and their control schemes for photovoltaic (PV) power generation systems have been studied. A conventional system employs a PV array in which many PV modules are connected in series to obtain sufficient dc input voltage for generating ac utility line voltage from an inverter circuit. However, the total power generated from the PV array is sometimes decreased remarkably when only a few modules are partially covered by shadows, thereby decreasing inherent current generation, and preventing the generation current from attaining its maximum value on the array. To overcome this drawback, an ac module strategy has been proposed. In this system, a low-power dc-ac utility interactive inverter is individually mounted on each PV module and operates so as to generate the maximum power from its corresponding PV module. Especially in the case of a single-phase utility interactive inverter, an electrolytic capacitor of large capacitance has been connected on the dc input bus in order to decouple the power pulsation caused by single-phase power generation to the utility line. However, especially during the summer season, the ac module inverters have to operate under a very high atmospheric temperature, and hence the lifetime of the inverter is shortened, because the electrolytic capacitor has a drastically shortened life when used in a high-temperature environment. Of course, we may be able to use film capacitors instead of the electrolytic capacitors if we can pay for the extreme large volume of the inverter. However, this is not a realistic solution for ac module systems. This paper proposes a novel flyback-type utility interactive inverter circuit topology suitable for ac module systems when its life- time under high atmospheric temperature is taken into account. A most distinctive feature of the proposed system is that the decoupling of power pulsation is executed by an additional circuit that enables employment of film capacitors with small capacitance not only for the dc input line but also for the decoupling circuit, and hence the additional circuit is expected to extend the lifetime of the inverter. The proposed inverter circuit also enables realization of small volume, lightweight, and stable ac current injection into the utility line. A control method suitable for the proposed inverter is also proposed. The effectiveness of the proposed inverter is yen- fled thorough P-SIM simulation and experiments on a 100-W prototype. [ABSTRACT FROM AUTHOR]

Abstract-This paper presents a novel single-stage push-pull boost converter with improved integrated magnetics and a better low-ripple input current. Most of the reported single-stage power factor corrected (PFC) rectifiers cascade a boost-type converter with a dc-dc converter. It is found that the push-pull converter, when the duty cycles are greater than 50%, can simplify the front end of the boost-type converter to a novel single-stage converter. Coupled inductor techniques provide a method to reduce the converter size and weight and to achieve a ripple-free current. All the magnetic components including the input filter inductor and the step-down transformer are integrated into a single El core. The proposed integrated magnetic structure has a simple core structure, a small leakage inductance, and low core losses. The prototype is built to demonstrate the theoretical prediction. [ABSTRACT FROM AUTHOR]

In this paper, a single-stage high-power-factor high-efficiency electronic ballast for compact fluorescent lamps is presented. The proposed topology uses two voltage sources connected in series to feed the inverter ballasting the lamp, one of them consists in the rectified line voltage and the other in a dc-dc converter operating in discontinuous conduction mode. In this way, the converter processes a lower energy than the nominal power of the lamp. The proposed topology presents simplicity, high-power-factor, low current crest factor, and high efficiency. [ABSTRACT FROM AUTHOR]

Reduced-order averaged modeling and analysis of soft-switching dc-dc converters employing active clamping techniques are presented in this paper. A general modeling method based on time-scale separation of converter state variables is used to develop large-signal averaged models that accurately represent the converter dynamics up to half the switching frequency. The fast-changing resonant variables of the active clamping circuits are eliminated in the modeling process, resulting in reduced-order models that are much simpler than existing full-order models. A method is also presented to account for the effects of switching-frequency ripple on converter dynamics in the low-frequency region. A transformer-coupled active-clamp single-ended primary inductance converter (SEPIC) is studied in detail to demonstrate the application of the method. Numerical simulation and experimental measurement of frequency responses of a experimental SEPIC converter are presented to validate the developed models. Additionally, an active-clamp flyback converter is briefly studied to demonstrate the general applicability of the method to other active-clamp converter topologies. [ABSTRACT FROM AUTHOR]

In this paper, a short circuit phenomenon when dc-dc modules with self-driven synchronous rectifier (SR) run in parallel is described. Three existing driving schemes are analyzed and compared. A novel driving scheme for SR maintains the performance of SR as a self-driven scheme, while solving the problem of a short circuit when modules run in parallel. In addition, the amplitude of an SR driving voltage can be adjusted by using the proposed scheme. Therefore, the scheme is more attractive in the applications of comparatively high-voltage output. The principle of operation and the characteristics of the scheme are analyzed and verified fled on a 36-75 V input 1.8-V/60-A output experimental prototype, whose size is 1/4 brick and efficiency is above 90% under rating conditions. [ABSTRACT FROM AUTHOR]

In conventional isolated half-bridge dc-dc converters, the leakage-inductance-related losses degrade converter efficiency and limit the ability to increase the converters' switching frequencies. In this paper, a novel active-clamp snubber circuit for half- bridge dc-dc converters is proposed to recycle the energy stored in the leakage inductance by transferring this energy to a capacitor with zero-voltage zero-current-switching switched auxiliary switches, such that body-diode conduction of primary-side main switches are prevented and primary side ringing are attenuated resulting in improved converter efficiency. Principles of operation and simulation analysis are presented and supported by experimental results that show significant improvement in efficiency. [ABSTRACT FROM AUTHOR]

The fast response double buck (FRDB) dc-dc converter was presented like a low output voltage dc-dc converter with fast transient response, in order to feed devices such as microprocessors and digital signal processors (DSPs). The topology of the FRDB is composed of two buck converters connected in parallel, each one of them with different features and aims, and controlled by means of the novel linear-non-linear (LnL) control. In this paper, the topology, the control strategy and the operation principle are shown. Finally, experimental results in different prototypes are presented to show both, the transient response and the recovery time when these prototypes are subjected to load current steps, and the influence of the output filter on these parameters. [ABSTRACT FROM AUTHOR]

This paper begins by reviewing current bus converters and exploring their limitations. Next, a family of inductor-less bus converters is proposed to overcome the limitations. In the new bus converters, magnetizing current is used to achieve zero-voltage-switching (ZVS) turn-on for all switches. The resonant concept is used to achieve nearly zero-current-switching (ZCS) turn-off for the primary switches and no body diode loss for the synchronous rectifiers (SRs). Meanwhile, the self-driven method can be easily applied to save drive loss of SRs. Based on these concepts, a full-bridge bus converter is built in the quarter-brick size to verify the analysis. The experimental results indicate that it can achieve 95.5% efficiency at 500-W, 12-V/45-A output. Compared with industry products, this topology can dramatically increase the power density. These concepts are also applied to nonisolated dc/dc converters. As an example, a resonant Buck converter is proposed and experimentally demonstrated. [ABSTRACT FROM AUTHOR]

The aim of this paper is to introduce a dc-dc converter that can be used in an online uninterruptible power supply (UPS). The proposed converter provides uninterrupted, reliable power and voltage regulation for critical loads, as well as power factor correction in supply systems. Operating principles, theoretical analysis, and control strategy are described. Digital simulation and experimental results are included, supporting the validity of the concept. [ABSTRACT FROM AUTHOR]

Power electronics is finding increasingly more applications in high temperature environments where power density is also a driving factor. The engine compartment of a passenger vehicle is one such example. In this paper, an integral thermal, electrical, and mechanical design of a high power density dc/dc converter operating in the thermally harsh automotive environment is discussed. The interactions and interdependencies between the three design disciplines are considered. It is illustrated how these interactions can be manipulated and used to an advantage In meeting the harsh temperature and high power density requirements of the automotive converter. Packaging and circuit techniques are identified that can be used to this end. Two case studies of a 2kW 14-V/42-V dc/dc converter for application in the automotive environment are considered. The first prototype achieved a power density of 170 W/in3 while the second prototype, operating with a higher environmental temperature achieved a power density of 120 W/in3. The experimental structures and practical results are presented. Technology issues concerning the three-dimensional construction of the prototypes that need research attention are also identified. [ABSTRACT FROM AUTHOR]

The high installation cost is the major obstacle of the commercialization of the solid oxide fuel cell for distributed power generation. This paper presents a new low cost 10-kW converter system to overcome this obstacle. The proposed system consists of an isolated dc-dc converter to boost the fuel cell voltage to 400 V dc and a pulse-width modulated inverter with filter to convert the dc voltage to two split-phase 120-V ac. The dc-dc converter uses phase shifting to control power flow through a transformer with a metal oxide semiconductor field effect transistor full bridge on the low voltage side and a voltage doubler on the high voltage side. One IPM is used to realize the voltage doubler and the dc-ac inverter. Compared to the existing fuel cell converter systems, the proposed circuit has low cost, less component count, smaller size, and reduced dc-dc converter peak current. Simulation and experimental results are demonstrated. [ABSTRACT FROM AUTHOR]

New residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single dc-ac inverter connected to a series string of pv panels, or many small dc-ac inverters which connect one or two panels directly to the ac grid. This paper proposes an alternative topology of nonisolated per-panel dc-dc converters connected in series to create a high voltage string connected to a simplified dc-ac inverter. This offers the advantages of a "converter-per-panel" approach without the cost or efficiency penalties of individual dc-ac grid connected inverters. Buck, boost, buck-boost, and Cúk converters are considered as possible dc-dc converters that can be cascaded. Matlab simulations are used to compare the efficiency of each topology as well as evaluating the benefits of increasing cost and complexity. The buck and then boost converters are shown to be the most efficient topologies for a given cost, with the buck best suited for long strings and the boost for short strings. While flexible in voltage ranges, buck-boost, and Cék converters are always at an efficiency or alternatively cost disadvantage. [ABSTRACT FROM AUTHOR]