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In this paper, a series-capacitor-based interleaving buck power factor correction (PFC) converter is proposed, the intermediate energy storage capacitance of which is operated at discontinuous capacitor voltage mode (DCVM), and automatic power factor (PF) correction for this converter is obtained. Moreover, the voltage across the series capacitor of the proposed PFC converter is clamped at the input voltage, and thus peak voltage stress existed in the traditional DCVM buck PFC could be relieved. By effectively regulating the charge/discharge time for the series capacitor, ultrahigh step-down conversion ratio of the proposed converter is achieved, the conversion ratio of which is independent of the duty cycle and only related to the switching frequency and circuit parameters. Therefore, high PF can be obtained due to very narrow deadtime of the input current. Meanwhile, the proposed PFC converter can realize the soft turn-on of part power switch and soft turn-off of part power diodes. In addition, comparing with the traditional discontinuous inductor current mode PFC, the input current of the proposed PFC converter is continuous so that the peak value and root-mean-square value of input current can be reduced. The operational principle, performance analysis, and parameter design principle are given in this paper. The analysis results show that the PF and total harmonic distortion are also independent of the duty cycle. Finally, a 220-Vac input, 60 W/15 V output experimental prototype is built to verify the validity of the theoretical analysis. [ABSTRACT FROM AUTHOR]

The extra-LC auxiliary-resonant-snubber-based converter (ELCARSC), as a soft-switching converter, has the advantages of low switching loss, low electromagnetic interference noise, and low-output distortion caused by the dead-time effect. However, the dead-time effect is still the main problem in a high-precision application. Besides, the traditional control and compensation methods rely on the accuracy of the circuit parameters, especially the junction capacitance, thus resulting in compensation error. Therefore, this paper proposed a novel high-precision control method through modulating the initial resonant current to eliminate the dead-time effect of ELCARSC. The method does not need complicated online calculation and reduces the dependence on the accuracy of the circuit parameters, especially the influence of the junction capacitances of the switches. In this paper, the dead-time effect of the ELCARSC is analyzed. The output voltage error with the conventional variable-timing control method is analyzed. Subsequently, the proposed modulated initial resonant current control is introduced. Finally, a prototype was developed that verified the effectiveness of the control method. The quality of the output current and voltage is improved by utilizing the proposed control method. However, the peak current of the auxiliary switch is increased. [ABSTRACT FROM AUTHOR]

In this paper, a new soft-switching bridgeless single-phase power factor correction (PFC) converter is presented and analyzed. Employing an auxiliary switch, the input current dead angle that is the main drawback of the existing buck-type PFCs is omitted, and thus, the power factor (PF) is improved, which is the main contribution of the paper. Proposed PFC converter operates under discontinuous conduction mode (DCM) and draws sinusoidal input current from power supply inherently. All switches and diodes are turnedonandoffunder soft switching, which leads to low switching losses and elimination of diode reverse recovery problems. Also, minimum numbers of semiconductor devices are in the power flow path that reduce the conduction losses. A 120-W laboratory prototype is implemented and experimental results verify the validity of theoretical analysis and show efficiency of 92.1%. In addition, total harmonic distortion (THD) of 3.3% is achieved and the input current harmonics complies with IEC61000-3-2 Class D requirements. [ABSTRACT FROM AUTHOR]

A high step-up dc–dc converter is proposed in this paper. The presented converter benefits from some advantages such as high voltage gain and continuous input current, which makes it suitable for the renewable energy applications. The presented converter is based on the SEPIC converter. However, the converter voltage gain is improved by employing a coupled inductor and two voltage multipliers. A passive clamp circuit is also added to the proposed converter that increases the voltage gain and reduces the voltage stress on the main switch. Thus, a switch with low $R_{{\text{DS(on)}}}$ will be needed that decreases the conduction loss. Besides, the voltage stress on the output diode in the proposed converter is reduced, which alleviates reverse recovery problem. The steady-state analysis of the proposed converter is discussed in this paper. The analysis is verified with experimental results under the output power of 245 W. [ABSTRACT FROM AUTHOR]

This paper proposes a new high-efficiency photovoltaic (PV) converter for grid connection through a high-leg delta transformer. The converter is composed of a symmetrically connected boost converter and three half-bridge inverters. One of the three half-bridge inverters is connected to the boost converter, and the others are directly connected to the PV terminals. As a result, this circuit configuration enables to reduce the power losses in both boost converter and inverters. This paper also proposes a new cooperative control method between the symmetrically connected boost converter and inverter. The control method can reduce the average switching frequency to 75% of that in a conventional one, resulting in a great reduction in the switching power loss. Experimental results confirm that the proposed circuit configuration makes it possible to improve its European efficiency from 91.6% to 94.5%. Moreover, system performance is evaluated on the assumption of maximum power point tracking operation. [ABSTRACT FROM AUTHOR]

In this paper, a new structure of nonisolated boost dc–dc converters based on voltage-lift technique is proposed. In comparison with conventional nonisolated boost dc–dc converters, the proposed converter generates higher voltage gain. In this paper, the relations between voltage and current of all elements in continuous conduction mode and discontinuous conduction mode are calculated as well as voltage gain in each mode. Then, the critical inductance and stress of switch current are extracted. Finally, the validity of given theories is examined by using the experimental results. [ABSTRACT FROM PUBLISHER]

This paper proposes two coupled-inductors-based Z-source networks, called the modified series and tapped switched-coupled-inductors quasi-Z-source networks (mSSCL-qZSN and mTSCL-qZSN, respectively). These networks offer high voltage gains with less-than-unity winding turn ratios $(n < {\text{1)}}$ , resulting in a reduced inductive element size. Other advantages include a less number of active components and their lower ratings and a higher efficiency. In addition, a lower magnetic core size is required for the proposed ZSNs due to the lower peak magnetizing current. The performance principles and detailed comparative analysis are provided and confirmed through experiments on a 200-W dc–dc converter. [ABSTRACT FROM AUTHOR]

In recent years, modular multilevel converter (MMC) is considered for medium-voltage variable speed drives (VSD) due to its modularity and higher reliability. However, the major drawback of the MMC-based VSD is the higher capacitor ripple voltage at lower operating speeds. In literature, this ripple voltage is reduced by injecting a high-frequency circulating current into each arm. This additional circulating current increases the overall current rating of the devices, inductors, and capacitors. Alternatively, the capacitor ripple voltage can be reduced at the lower output frequency by reducing the dc-bus voltage. This paper proposes a new configuration using a multipulse diode-bridge rectifier to reduce the dc-bus voltage when the drive is operated at lower speeds. Therefore, the capacitor ripple voltage decreases without injecting any circulating current. In addition, a new technique is proposed to maintain the peak-to-peak value of the submodule capacitor ripple voltage constant at near-zero speed. The proposed converter with 24-pulse rectifier configuration is simulated in MATLAB/Simulink, and the experimental validation is carried out on a prototype with 12-pulse rectifier. [ABSTRACT FROM AUTHOR]

A new single-switch high step-up dc–dc converter is proposed, in this paper, for fuel cell vehicles. The proposed topology utilizes an L2C3D2 network to obtain high voltage gain and reduce the voltage stress on the power switch. Additionally, the proposed converter has a universal input voltage in order to suit the soft output characteristics of the fuel cell. Comprehensive analyses of the steady-state operation in continuous conduction mode and discontinuous conduction mode, and design considerations of the proposed converter are given. Finally, a 400 V/1.6 kW scaled-down prototype is developed to validate the effectiveness and feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

A simple buck–boost LED driver suitable for battery operated applications with limited input voltage level is presented in this paper. Soft switching performance is provided for the main switch via a resonant circuit to improve the converter efficiency. The incorporated auxiliary switch also performs under zero voltage switching condition. Both power switches can be driven with a simple gate drive circuit, so, the additional switch does not add any driving complexity. In addition, only one magnetic element is utilized in the proposed LED driver which contributes to circuit simplicity and lower weight and size. Also, all diodes turn off at zero current switching which eliminates the reverse recovery losses and improves efficiency. A laboratory prototype converting 12 V input voltage to 32 V output operating at 26 W output power is implemented and tested to verify the effectiveness of the proposed LED driver. [ABSTRACT FROM AUTHOR]

High step-down voltage conversion is necessary to bridge the voltage gap between main power converters and low-voltage auxiliary electronics in power conversion systems. Switched capacitor converters (SCCs) are an attractive candidate as a high step-down converter, but their poor voltage regulation capability may limit their applications. Pulsewidth modulation (PWM) SCCs with adjustable high step-down voltage conversion are proposed in this paper. The proposed PWM SCCs can be derived from traditional SCCs by replacing an energy transfer capacitor with a switched-capacitor-inductor (SCL) cell that comprises inductors, capacitors, and diodes to realize PWM-controllable voltage conversion. The voltage step-down ratio of the proposed PWM SCCs is not only PWM controllable but also adjustable with structures of SCCs and SCL cells. Two representative PWM SCCs were taken as examples to perform the operational analysis. The prototypes of both representative PWM SCCs were built and tested to demonstrate the proposed concept. [ABSTRACT FROM AUTHOR]

This paper proposes a Class-DEMtuned power amplifier. The proposed amplifier achieves zero-voltage switching (ZVS), zero-voltage derivative switching (ZVDS), and zero-current switching (ZCS) at turning-on, and ZVS, ZVDS, ZCS, and zero-current derivative switching at turning-off. Therefore, the switching losses are extremely low, which is suitable for high-frequency operation. Moreover, the switch voltage stress is low, which is no more than its input voltage. A proposed amplifier was designed, built, and tested. The measured power conversion efficiency was 93.2% under the condition of the main input voltage of 46.8 V, the operating frequency of 1 MHz, and the output power of 4.87 W. [ABSTRACT FROM AUTHOR]

The three-phase four-wire inverter with split dc-link capacitors can supply unbalanced loads. For the purpose of reducing the filter inductors, a neutral inductor could be introduced into the neutral line. This paper analyzes the operation principle of the three-phase four-wire inverter with split dc-link capacitors when a neutral inductor is introduced. It is illustrated that the neutral inductor can reduce the zero-sequence switching harmonics in the voltages between the phase-leg midpoints and the output neutral point, thus the filter inductors can be reduced. The optimized design of the neutral inductor and filter inductors is proposed with the considerations of the inductor current ripple, the ability of supplying unbalanced loads, and the total energy stored in the inductors. The equivalent circuits of the three-phase four-wire inverter with split dc-link capacitors and neutral inductor is derived in the α–β–0 frame, and the zero-axis voltage regulator is modified to suppress the third-order harmonic in the zero-sequence current caused by the deadtime of the drive signals for the power switches. Finally, the experimental results from a 9-kW prototype are provided to prove the effectiveness of the proposed optimized design of the neutral inductor and filter inductors and the control strategy of the inverter. [ABSTRACT FROM AUTHOR]

In this paper, a family of step-up resonant switched-capacitor converters (RSCs) with a continuously adjustable conversion ratio is proposed based on the Cuk dual-resonance core (DRC) featuring two resonant paths. By adopting the on-time fixed frequency modulation, the two resonant paths can conduct simultaneously and satisfy the charge balance of the flying capacitor during the overlapping period. As a result, the conversion ratio—upper bounded by two determined by the circuit configuration—can vary continuously and efficiently even at the light load condition (1/10 of the rated power). A comprehensive analysis—the operation principle, voltage-gain curve, and voltage/current stresses—about the DRC is given. In addition, the Cuk DRC was extended to the series–parallel switched-capacitor converter (SCC), Fibonacci SCC, and voltage doubler to form a family of step-up RSCs, whose voltage-gain curves of different topologies are derived. Moreover, a characteristic comparison between the Cuk DRC and the traditional “direct” and “indirect” resonant core is given. Then, a 48 to 62–94.6 V resonant core with peak efficiency 97.8% and maximum power 120 W under the open loop condition was built. The analyses were verified by both experimental and simulation results. [ABSTRACT FROM AUTHOR]

This paper presents an overview of resonant and hybrid switched-capacitor converters with a particular focus on multimode operation. The multimode approach is discussed as a tool to affect high efficiency and power density across a wide load range, provide variable regulation, and, as a general framework, to conceptualize the advantages and opportunities of the approach compared to more traditional dc–dc converters. A general analysis is provided to quantify the advantage of hybrid and resonant converters that factors in the tradeoffs between size and loss in the magnetic component and voltage stress on the active devices. A broader set of operating modes is presented that spans continuous and discontinuous conduction and includes resonant, quasi-resonant, and more traditional buck- or boost-like operation. A prototype flying-capacitor multilevel converter is presented to demonstrate the variety of operating modes and motivate important considerations such as voltage balance on the flying capacitors. [ABSTRACT FROM AUTHOR]

The trend toward higher switching frequencies and higher power densities in dc–dc conversion led the designers to rediscover resonant topologies. However, the analysis of these converters is often limited to a particular operating mode and/or topology. This paper wants to fill the gap by presenting a state-space-based analysis for a broad class of series-resonant converters including voltage-fed as well as current-fed topologies, either unidirectional or bidirectional. The proposed solution consists of a mathematical framework that solves the trajectory of state variables in the resonant tank, as well as the main characteristic functions such as voltage conversion ratio and transferred power. The matrix approach permits a flexible and compact formulation and easy implementation in computational tools such as MATLAB. The theoretical framework is applied to both voltage-fed and current-fed resonant topologies: the first is used to show the advantages of the proposed model respect to the first harmonic approximation, while a detailed analysis in terms of operating mode boundaries, delivered power, and voltage gain is provided for the second. Simulations and measurements on a 300-W prototype of the current-fed topology are used to validate the correctness of the proposed solution. [ABSTRACT FROM AUTHOR]

In this paper, a novel buck–boost dc–dc converter with continuous input current is proposed. The voltage gain of the presented converter is higher than conventional converters, such as buck–boost, single-ended primary-inductance converter, Cuk, and Zeta converters. This converter works only by one switch and voltage stress across the switch is low. Input current of the proposed converter is continuous so a large filter at the input is not needed. Furthermore, continuous input current has made this converter suitable for renewable energy and fuel cell applications. In this converter, noninverting output voltage is obtained and high gain of voltage is achieved as well. So it can operate at wide output voltage range only by changing the duty cycle of the power switch pulse. The presented converter can easily controlled in continuous conduction mode operation, because of using only one power switch. In the following, the principle of operation and the mathematical analyses of the proposed converter are explained, finally, validity of the proposed dc–dc converter is verified by the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a half-bridge (HB) converter, additionally employing a diode compared with the conventional modified duty-cycle-shifted (MDCS) HB converter, is proposed to achieve a high efficiency in wide-input-voltage and low-output-current applications. Since the proposed converter has symmetrical operation, it maintains the advantages such as no transformer dc-offset current, and identical and low-voltage stresses on the secondary diodes. Moreover, due to one additional switch connected in series, the zero-voltage-switching capability of the upper switch is improved. As a result, small resonant inductances are required, which reduces the duty cycle loss, thus the primary conduction losses decrease. In addition, since additional clamping diodes separate external resonant inductor from the resonance path, additional voltage stresses on the secondary diodes can be decreased. Therefore, its snubber loss can be reduced, and it can achieve higher efficiency than that of the MDCS HB converter. To confirm the operation, features, and validity of the proposed converter, a 310–400 V input and 50-V/250-W output laboratory prototype is built and tested. [ABSTRACT FROM AUTHOR]

This paper presents a new predictive power-factor-correction (PFC) controller for series-interleaved three-level boost (TLB) converters. Compared to the state-of-the-art TLB PFC controllers, where a two-cycle prediction and a detection of an operating region are necessary, the proposed controller achieves a low total harmonic distortion of the input current by using a single equation to predict the input current in all operating regions of the converter, in just one operating cycle. The average current control is achieved by sampling at the peak of the triangular carrier. The proposed PFC controller significantly reduces the distortion of the input ac current near the zero-crossing points, resulting in a low total harmonic distortion of the input current. The operation of the proposed controller was evaluated, and its stability and robustness to parameter changes was confirmed analytically. The controller operating principles were verified in simulations and validated by experiments on a medium-voltage 50-kW converter prototype. [ABSTRACT FROM AUTHOR]

The powder-core-based inductor has a wide inductance variation due to the soft-saturation nature when subjected to varying load current. Under such a condition, the current ripple is influenced, and the conventional inductor design principle may be inaccurate. Besides, the voltage of the inductor is distorted. Also, the bandwidth of the controller is hard to determine. In this paper, the current ripple under the condition of wide inductance variation is analyzed, and its change rule is revealed; then, a new inductance design principle is proposed. The harmonic components for the three-phase converter with the powder core inductor are investigated, and the harmonic characteristic of the input current is analyzed. According to the current harmonic characteristic, the resonance controllers are introduced to eliminate harmonics, and the quality of the current is improved. Besides, the bandwidth of the controller is found to vary with the output power. Then, a compensation method is proposed to eliminate the influence of inductance variation on the bandwidth. The experimental results verify the analysis. [ABSTRACT FROM AUTHOR]

A family of high-voltage-gain dc–dc converters derived from a generalized structure with two stages is introduced in this paper. On the input side, a two-phase interleaved boost stage boosts the dc input voltage to output a modified square-wave voltage that feeds the second stage. This output of the interleaved boost stage is rectified and further boosted using a voltage multiplier stage. As a result, a high voltage gain is achieved using the proposed converters. The two-phase interleaved boost stage on the input side makes it possible for the converters to be operated using a single source or two independent sources. If a single source is used, the input current drawn is continuous with a very small ripple. Owing to its generalized structure, the proposed family of converters includes both nonisolated and isolated converters with high voltage gains. The high voltage gain and low-ripple continuous input current make these converters appealing in applications like the integration of renewable sources such as solar, fuel cells, etc., on to a 400-V dc bus. [ABSTRACT FROM AUTHOR]

In this paper, a novel transformerless interleaved high step-down conversion ratio dc–dc converter with low switch voltage stress is proposed. In the proposed converter, two input capacitors are series-charged by the input voltage and parallel-discharged by a new two-phase interleaved buck converter for providing a much higher step-down conversion ratio without adopting an extreme short duty cycle. Based on the capacitive voltage division, the main objectives of the new voltage-divider circuit in the converter are for both storing energy in the blocking capacitors for increasing the step-down conversion ratio and reducing voltage stresses of active switches. As a result, the proposed converter topology possesses the low switch voltage stress characteristic. This will allow one to choose lower voltage rating MOSFETs to reduce both switching and conduction losses, and the overall efficiency is consequently improved. Moreover, due to the charge balance of the blocking capacitor, the converter features automatic uniform current sharing characteristic of the interleaved phases without adding extra circuitry or complex control methods. The operation principles and relevant analysis of the proposed converter are presented in this paper. Finally, a 400-V input voltage, 25-V output voltage, and 400-W output power prototype circuit is implemented in the laboratory to verify the performance. [ABSTRACT FROM PUBLISHER]

In this paper, dual-buck structured single-stage buck–boost inverters that use power MOSFETs to achieve high efficiency are presented. The proposed inverters require fewer switches, and half of the switches have reduced current stresses. They have no shoot-through problem; therefore, high system reliability can be obtained. The dead-time in PWM signals can be minimized or eliminated, which improving the quality of the output ac voltages and increasing the efficiency. In the proposed inverters, MOSFETs can be used without reverse-recovery issues of their body diodes to boost the efficiency and increase the switching frequency. To further improve the efficiency and stability of the proposed single-phase inverter, PWM strategies combining high- and low-frequency modulation are presented. A hardware prototype of the single-phase inverter was built and tested using resistive, inductive, and nonlinear loads. Experimental results for a 300-W prototype inverter show a 97.4% peak efficiency with a 25 kHz switching frequency. [ABSTRACT FROM AUTHOR]

The parallel three-phase grid-connected converters sharing dc and ac bus can increase the system power level effectively. However, the zero sequence circulating current (ZSCC) will occur inevitably under space vector pulse width modulation or discontinuous pulse width modulation (DPWM). In this paper, the mechanism and the mathematical model of ZSCC are studied. Then, a hybrid PWM (HPWM) strategy is proposed to suppress the ZSCC based on the same zero sequence voltage injected, which is dependent on the common grid information. The dc voltage utilization of HPWM can be extended compared with sinusoidal PWM (SPWM). The number of parallel modules can be infinity theoretically by using HPWM. It is noted that there is no internal commutation among modules (expect the dq current reference). Finally, the feasibility and the effectiveness of the proposed method are verified by experiments. [ABSTRACT FROM AUTHOR]

This paper proposes an isolated single-ended primary-inductor converter (SEPIC) dc–dc converter with ripple-free input current and lossless snubber. The proposed converter is based on a conventional isolated SEPIC converter to enable electrical isolation and high voltage gain using a coupled inductor. The input current ripple is significantly reduced by utilizing an auxiliary circuit that also functions as a lossless snubber circuit with an additional diode. Moreover, the maximum switch voltage stress is clamped to a low voltage by the snubber circuit. Therefore, a low voltage rating mosfet that has low $R_{{\rm{DS(on)}}}$ can be utilized as a main switch device. Hence, the total power efficiency is improved. Experimental results from a 100 W prototype, which are presented to verify the theoretic analysis and performance of the proposed converter. [ABSTRACT FROM PUBLISHER]

In this paper, a power factor correction (PFC)-based switched reluctance motor (SRM) drive is proposed. Generally, the SRM drive is fed with a simple diode bridge rectifier followed by a bulky capacitor, which draws peaky current at low power factor and high-input-current total harmonic distortion (THD). Here, a dual output converter is proposed to control the SRM and to provide power quality improvement as well. This converter is a combination of Cuk and SEPIC converters, which produces two equal output voltages with neutral point N, to feed a midpoint converter of the SRM drive. The converter is designed to operate in discontinuous conduction mode of operation to obtain inherent PFC at supply side. The motor control is attained by regulating dc link voltage over a wide range. Test results on a prototype of the SRM drive demonstrate the excellent performance with high power factor and reduced input current THD. The observed power quality indices depict the improved power quality as per the standard IEC 61000-3-2. [ABSTRACT FROM PUBLISHER]

In this paper, a new type of matrix converter (MC) also called a single-phase high-frequency transformer isolated (HFTI) buck MC is proposed. The proposed converter can provide step-down operation of the input voltage with various types of output voltages such as in-phase and out-of-phase output voltages, rectified (or positive) output voltage, and output voltage with step-changed frequency. By incorporating HFT isolation, the proposed MC saves an extra bulky line frequency transformer, which is required for the conventional MCs to provide electrical isolation and safety, when used in application such as dynamic voltage restorers, etc. Two different circuit variations of the proposed HFTI MC are presented with and without continuous output currents, with the latter having less passive components. The safe-commutation strategy is also employed for the proposed HFTI MC to provide current path for the inductor during dead-time, which avoids switch voltage spikes without adding any snubber circuits. The operation principle and circuit analysis of the proposed MC are presented, and switching strategies are also developed to obtain various output voltages. Moreover, a prototype of the proposed MC is fabricated, and experiments are performed to produce in-phase/out-of-phase and rectified output voltages, and output voltage with step-changed frequency. [ABSTRACT FROM PUBLISHER]

This paper presents a new buck–boost converter. Unlike the single-switch buck–boost converter, the proposed converter has low-voltage stresses on semiconductors. Moreover, although both the conventional two-switch buck–boost (TSBB) and the proposed converters have the same number of passive and active components, and the proposed converter can reduce the conduction loss as a result of having fewer conducting components. Therefore, the proposed converter obtained a higher efficiency than the TSBB converter. A 48-V output voltage and 150-W output power prototype was fabricated to verify the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper presents a primary-side regulation constant current constant voltage (CC-CV) Flyback ac–dc converter characterized by high efficiency and high precision of constant current control. In CC mode, a novel ring detection and demagnetization portion control technique is proposed, with which the ending time of demagnetization can be accurately determined and the portion of demagnetization in switching periods remain precisely the same, which enable the accuracy of constant current output that can reach a level as high as ±0.8%. In CV mode, a power stage model based on steady-state analyzing method is established, according to which the expression of static power loss is first obtained. After that total power loss expression including switching loss is derived as well. By MATLAB simulation, power loss mechanism is revealed and analysis is made in detail. According to which, optimized parameters of Flyback converter system and an effective CV regulation strategy are obtained eventually. Simulation as well as experimental results verifies the efficiency of the ac–dc converter system after optimization that can be more than 84.7% at 5 V/1 A application. [ABSTRACT FROM PUBLISHER]

In this paper, a design method is proposed for finding the equivalent inductance and capacitance of the single-ended primary-inductor converter (SEPIC). The relations of the output voltage ripple (OVR) of the SEPIC converter are obtained in complete inductor supply mode–continuous conduction mode (CISM-CCM), incomplete inductor supply mode-CCM (IISM-CCM), and IISM-discontinuous conduction mode (IISM-DCM). The maximum of OVR (MOVR) is investigated for a specified range of the input voltage and load resistance. This value of the MOVR is obtained for the minimum values of input voltage and load resistance. In this paper, the minimum values of the equivalent inductance and capacitance are calculated in obtaining the minimum value of the MOVR. One of the other performed studies in this paper is calculation of the switch peak current in CCM and DCM. In addition, the converter is designed based on the minimum values of the MOVR and stress of the switching current. Experimental and simulation results are used to prove the validity of the presented theoretical subjects. [ABSTRACT FROM PUBLISHER]

This paper proposes a pulse-width modulation three-level converter with reduced filter size using two transformers. The proposed converter has many advantages. All switches sustain only the half of the input voltage and since the secondary rectified voltage is a three-level waveform, the output filter inductor can be reduced. Also, because of the power sharing of transformer and reduced output inductor, high efficiency can be obtained. The operational principle, analysis, and design considerations of the proposed converter are presented in this paper. The validity of this study is confirmed by the experimental results from a prototype with 600 W, 500-600 V input, and 60 V output. [ABSTRACT FROM AUTHOR]

A new low-power single-stage ac-dc converter is proposed in the paper. The outstanding feature of the converter is that it can operate with a sinusoidal input current and a low primary-side dc bus voltage that is much less variable than that found in other single-stage converters. The operation of the converter is discussed in the paper and its various modes of operation are explained in detail. An analysis of the converter's steady-state characteristics is performed and the results are used in the design of the converter. Experimental results obtained from a prototype converter are also presented. [ABSTRACT FROM AUTHOR]

This paper presents a new formulation of a finite control set model-predictive control (FCS-MPC) algorithm, allowing to determine the best commutation instant in order to optimize the converter current tracking. This algorithm, mixing properties of FCS-MPC method and time resolution related to pulse width modulation schemes, is illustrated in a parallel flying capacitor converter. The parallel association of classical commutation cells is a good solution for increasing the output current driven by the converters, while the standard semiconductor technology is used. The control strategy used with this type of connection must be able to ensure not only a good distribution of the output current among the different legs, but also the balancing of the floating capacitor voltages. [ABSTRACT FROM PUBLISHER]

The two-switch cascade converter is the most appropriate solution for efficient high-power applications among the existing converter topologies. However, the cascade structure and the nonlinear dc gain of boost circuit are more likely to cause severe oscillations if the criterion for the selection of the operation mode is chosen improperly during step-up/step-down transition. A novel high-power input-parallel output-series buck-half-bridge (IPOSBHB) converter is proposed in this paper. The circuit structure, operating principles, and basic relations are analyzed. Comparisons between IPOSBHB and two-switch cascade converter are also elaborated on with respect to voltage and current stress, total volume of magnetic components, and efficiency. In addition, the inconformity of the transfer functions, the discontinuity caused by the switching time delay, and the disturbance of input voltage are analyzed. Methods for compensation are also proposed. The proposed converter can achieve satisfactory comprehensive performance when the step-up ratio is low. The combinational control strategy and the compensation methods proposed in this paper are easy to carry out in order to achieve effective control at steady state, smooth transition at mode change, and reduction of the adverse effect caused by the disturbance of input voltage. A 15-kW prototype is used to validate the proposed theory. [ABSTRACT FROM AUTHOR]

In this paper, a new three-level single-stage power-factor-corrected ac/dc converter is presented. The proposed circuit integrates the operation of a boost power factor correction converter and a three-level dc/dc converter into one converter. It does not have the problem of high component stress due to high rising intermediate bus voltages at light load conditions that other single-stage converters have because of its three-level structure. It can operate over a wider load range with significantly less output inductor current ripple; moreover, its input current has little distortion. In the paper, the operation of the new converter is explained in detail and analyzed, its steady-state characteristics are determined, and its design is discussed. Experimental results obtained from a prototype are presented to confirm the feasibility of the new converter. [ABSTRACT FROM AUTHOR]

Resistance emulation using one cycle control (OCC) has been used extensively in single-phase full-bridge boost rectifiers. This paper proposes a new control strategy called dual comparison OCC (DC-OCC), which eliminates the limitations of OCC. The advantages of the proposed control strategy is that it ensures the average current is equal to grid voltage scaled by emulated resistance, in each switching cycle. This eliminates issues such as dc offset due to the peak current comparison in OCC. It also ensures that there is no distortion in current when the converter is lightly loaded. It is analytically shown that the proposed DC-OCC does not have the light load instability concerns of conventional OCC. The proposed method is also shown to achieve unipolar pulse-width modulation without sensing the grid voltage resulting in lower effective switching frequency. The proposed control requires only one additional comparator and additional logical elements for implementation. Detailed simulation and experimental studies are carried to validate the proposed control and the high performance that can be obtained. [ABSTRACT FROM PUBLISHER]

One important test for the formation and grading of a lithium-ion battery is to confirm the performance of the battery while discharging it down to zero volts. In this paper, a novel soft-switching charge/discharge converter with the zero voltage discharge function is proposed. The proposed converter is able to discharge a battery until its voltage reaches zero volts. The phase-shift full-bridge method is used to charge the battery and the current-fed push–pull method with bidirectional switches is used for the discharge. Zero voltage switching (ZVS) of the switches is achieved at turn-on during the charge operation. ZVS turn-on and zero current switching turn-off of the switches are achieved during the discharge operation. The charge/discharge controllers are designed taking into account the internal impedance of the battery. The performance of the system is verified by the experiments using lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A novel high step-up dc–dc converter with a quasi-active switched-inductor structure for a renewable energy system is presented in this paper. The proposed converter is composed of two coupled inductors which can be integrated into one magnetic core, two capacitors, two active switches, and three diodes. The primary sides of coupled inductors are charged in parallel by the input source, and the secondary sides of coupled inductors are discharged in series with the input source and two capacitors to achieve high step-up voltage gain with an appropriate duty ratio. The two sets of diode–capacitor circuits not only help to lift the voltage conversion gain but also alleviate voltage spike affected by the leakage inductance to limit the voltage stress across the power switch effectively. Therefore, the two low on-state resistance switches can be adopted to reduce conduction loss. Furthermore, the two diodes have no reverse-recovery problem due to turn off naturally, the reverse-recovery problem of the output diode is also alleviated by the leakage inductor and lower part count is needed; therefore, the power conversion efficiency can be further improved. The operating principles and steady-state analyses are discussed in detail; then, the performance of the proposed converter is compared with existing converters. Finally, a prototype is established in the laboratory, and the experimental results are given to verify the correctness of the analysis. [ABSTRACT FROM AUTHOR]

Conventional matrix converters (MCs) have limited voltage gain that is less than 0.866, whether for direct MC (DMC) or indirect MC (IMC). Existing Z-source (ZS)/discontinuous quasi-Z-source (qZS) DMCs and ZS IMCs achieved larger than 0.866 voltage gain; however, the former inherited the complex commutation from DMC, and the latter involved a ZS network in dc link and led to non-all-silicon solution. In this paper, ZS and discontinuous qZS networks of existing ZS/qZS DMCs are used for an IMC topology for simplifying commutation and having high voltage gain, but they require extra input filter to reduce current harmonics. A new continuous qZS IMC is proposed, where a qZS network integrates the filtering function of the grid side; hence, additional input filter is avoided in the proposed continuous qZS IMC. Three new IMCs are compared in detail, in terms of voltage gain, current ripple, voltage ripple, inductor current and capacitor voltage stresses, ZS/qZS switch current and voltage stresses, filtering function, input current total harmonic distortion (THD), output voltage THD, and efficiency. Their control and modulation methods are presented to achieve the desired performances. Experimental comparisons verify the theoretical analysis and that the proposed continuous qZS IMC is a promising topology. [ABSTRACT FROM PUBLISHER]

Affected by the equivalent series resistance (ESR) of the devices in the circuit, the voltage-conversion ratio of traditional boost converter is limited. Various topologies have been developed to provide a high step-up voltage gain. An inherent high voltage gain can be achieved in a dual-switch converter with the advantages of low voltage and current stress on the switches. However, this converter has a strict requirement of the parameters' consistency. This paper discusses the steady-state operation principle of the converter in detail under the condition that the parameters are inconsistent and then illustrates the solutions to balance the voltage on the switches and suppress the resonance with passive lossless clamping. Finally, a prototype has been established in the laboratory, and simulation and experimental results have been given to verify the analysis and the effectiveness of clamping method. [ABSTRACT FROM PUBLISHER]

This paper presents a novel direct current-fed interleaved phase-modulated single-phase unfolding inverter for fuel-cell applications. Two active-clamped zero-voltage switching current-fed half-bridge isolated converters are interleaved in parallel input and series output configuration. Phase modulation is proposed to control these two converter cells, which generate a rectified sinusoidal pattern at the dc link. A simple H-bridge unfolding dc–ac inversion is used to produce single-phase sine voltage at line frequency switching using square-wave control. This not only simplifies the inversion stage in terms of modulation but also reduces the switching losses. Direct front-end current-fed based unfolding inverter is not reported in literature yet. Detailed analysis and design of the proposed direct current-fed single-phase unfolding inverter has been presented. Simulation waveforms using PSIM 9.0.4 are given to verify the presented analysis and design. Experimental results on a laboratory prototype rated at 200 W are demonstrated to support the investigation, to validate the accuracy of the proposed analysis and design, and to test the performance. [ABSTRACT FROM PUBLISHER]

Considering the tradeoff between efficiency and output ripple over a wide load range, a monolithic dc–dc buck converter with switch-on-demand modulation (SODM) and switch size control (SSC) is presented in this paper. SODM achieves a hybrid mode of pulse skip and pulse width modulation (PWM) without mode detection circuit. The converter's on time is adaptively adjusted with the load demand, achieving low output voltage ripple. Detecting the output of the error amplifier by a comparator, the SSC circuit can select appropriate switch size according to load current for reducing switching loss in a light load. The threshold level of the comparator varies with respect to the amount of slope compensation, which maintains a substantially constant switch size changing point. Experimental results show that the fabricated converter with the proposed scheme achieves high efficiency from 83% to 96% over a wide load range from 10 mA to 5 A. The switch size is 1/4 of the maximum value when load current is below 1 A with 0.5-A hysteresis. Also, the measured maximum output ripple is less than 10 mV. [ABSTRACT FROM PUBLISHER]

In this paper, the concept of built-in transformer voltage doubler cell is derived to generate an improved interleaved high step-up converter for distributed photovoltaic generation applications. The proposed built-in transformer voltage doubler cell is composed of three transformer windings, two voltage doubler diodes, and two voltage doubler capacitors. The voltage doubler capacitors are charged and discharged alternatively to double the voltage gain. The switch duty cycle and the transformer turns ratio can be employed as two controllable freedoms to lift the voltage ratio flexibly. The power device voltage stress can also be reduced to improve the circuit performance. Furthermore, the active clamp scheme is adopted to recycle the leakage energy, absorb the switch turn-off voltage spikes, and achieve zero-voltage switching (ZVS) operation for all active switches. Meanwhile, the diode reverse-recovery problem is alleviated by the leakage inductance of the built-in transformer. All these factors benefit the circuit performance improvements in the high step-up and large current applications. Finally, a 1-kW prototype with 40-380 V conversion is built and tested to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

The LLC resonant converter has drawn much attention for high efficiency. However, its light-load efficiency still cannot meet the ever increasing requirements. This paper proposes a novel burst-mode control for the LLC resonant converter to improve the light-load efficiency. Based on the state-plane trajectory analysis, during the burst-on time, a three-pulse switching pattern is implemented. By optimizing the first pulse width, the state variables are settled to the steady state of the highest efficiency load in the minimal time, and then, the next two pulse operation follows this steady-state trajectory to achieve high burst efficiency. Moreover, when the load changes, the burst-on time with the optimal three-pulse switching pattern is maintained, but the burst-off time is modulated. As a result, the output-voltage low-frequency ripple minimally keeps constant, and no additional filter is needed. Experimental results validate the proposed techniques. [ABSTRACT FROM AUTHOR]

This paper is devoted to the step-up dc/dc converter family with a cascaded quasi-Z-source network (qZS-network). The cascaded (two-stage) qZS-network could be derived by the adding of one diode, one inductor, and two capacitors to the traditional quasi-Z-source inverter (qZSI). The proposed cascaded qZSI inherits all the advantages of the traditional solution (voltage boost and buck functions in a single stage, continuous input current, and improved reliability). Moreover, as compared to the conventional qZSI, the proposed solution reduces the shoot-through duty cycle by over 30% at the same voltage boost factor. Theoretical analysis of the two-stage qZSI in the shoot-through and non-shoot-through operating modes is described. The proposed and traditional qZS-networks are compared. A prototype of a step-up dc/dc converter with the cascaded qZS-network was built to verify the theoretical assumptions. The experimental results are presented and analyzed. Finally, a further optimization method of the cascaded qZS-network is proposed, and some practical design issues are discussed. [ABSTRACT FROM PUBLISHER]

In this paper, A single-phase improved active clamp coupled-inductor-based converter with extended voltage doubler cell is proposed for large-voltage conversion ratio applications. The secondary winding of the coupled inductor is inserted into the half-wave voltage doubler cell to extend the voltage gain dramatically and decrease the switch voltage stress effectively. By combining the coupled inductor and voltage doubler cell structure, the disadvantage of the potential resonance between the leakage inductance and the diode stray capacitor is cancelled, and the unexpected high pulsed current in the voltage doubler cell is decreased due to the inherent leakage inductance of the coupled inductor. Meanwhile, the active clamp scheme is employed to recycle the leakage energy, suppress the switch turn-off voltage spikes, and implement zero-voltage-switching turn-on operation. In addition, there is only one magnetic component in the proposed converter and the coupled inductor operates not only as a filter inductor, but also as a transformer when the main switch is in the ON state, which reduces the volume of the magnetic core and improves the power density of the converter. A 500 W prototype operating at 100 kHz with 48 V input and 380 V output is built to verify the analysis. The maximum efficiency of the prototype is nearly 97% and the efficiency is higher than 96% over a wide load range. [ABSTRACT FROM AUTHOR]

A novel interleaved boost converter with zero-voltage switching (ZVS) and zero-current switching (ZCS) characteristics is proposed in this paper. By using the interleaved approach, this topology not only decreases the current stress of the main circuit device but also reduces the ripple of the input current and output voltage. Moreover, by establishing the common soft-switching module, the soft-switching interleaved converter can greatly reduce the size and cost. The main switches can achieve the characteristics of ZVS and ZCS simultaneously to reduce the switching loss and improve the efficiency with a wide range of load. This topology has two operational conditions depending on the situation of the duty cycle. A driving circuit is designed for the proposed topology to determine the two conditions automatically. The operational principle, theoretical analysis, and design method of the proposed converter are presented. Finally, simulations and experimental results are used to verify the feasibility and exactness of the proposed converter. [ABSTRACT FROM AUTHOR]