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This paper presents a new highly integrable hybrid step-down converter that merges switched-inductor and switched-capacitor operations and significantly reduces onboard loss by using the input cable's parasitic inductance as its main inductor. This converter has the inductor placed at the input with a smaller voltage swing, leading to possible use of a smaller inductor and low-voltage rating switches that generally translate to reduced conduction losses. Analyses of converter operation and losses to reveal its original characteristics and design guidelines are presented to facilitate the components optimization. The converter architecture is verified by a proof-of-concept 15-W inductor-less lithium-ion battery charger prototype that uses a 1-m USB 3.0 cable as inductor. The converter, switched at 2 MHz from a 5-V input, experimentally achieves 89.7% peak efficiency and 6% higher efficiency at full load than a Buck converter counterpart. This high efficiency and zero onboard inductor yield a relative 45.7% onboard loss reduction at full load, promising excellent integration feasibility and superior system thermal management. [ABSTRACT FROM AUTHOR]

This paper proposes a novel isolated high step-down conversion circuit, called an integrated buck and modified push−pull (IBMPP) converter, which is able to lower the voltage level on the primary side of the ideal transformer, resulting in a lower turns-ratio and decreased leakage inductance. The IBMPP converter is able to prevent the duty cycle from operating in extremely low conditions. Furthermore, the proposed converter adopts active-clamp techniques to recycle leakage energy and to suppress voltage spikes, so that the conversion efficiency can be effectively improved. The advantages of the IBMPP converter are its simple topology, easy control mechanism (which requires only two signals with a 180-degree phase shift), high conversion ratio, low component counts for power switches, and less voltage stress on some of the switches on the high-voltage side. The operation principle, steady-state analysis, design considerations, and experimental results of the proposed IBMPP converter are presented in detail. The feasibility of the IBMPP is verified by hardware implementation. The full-load efficiency at 250 W is 81.44%, and the input and output voltages are 380 and 5 V, respectively. [ABSTRACT FROM AUTHOR]

This paper presents the circuit design and magnetic integration of push–pull class-E inverters for wireless power transfer (WPT) up to megahertz. The design criterion for achieving zero-voltage switching (ZVS) of a class-E inverter with coupled windings is derived mathematically. The approaches of magnetic integration for push–pull class-E inverters are analyzed and compared. Then, a new magnetic structure with hybrid magnetic materials is proposed to build the integrated inductors with either coupled windings or uncoupled windings. A 3-MHz WPT system is built to verify the analysis. The detailed comparison of the class-E inverters with magnetic integration is presented in terms of switch voltage, efficiency, harmonic currents, and thermal distribution. In the optimized design example, the switches keep ZVS over the entire load range without using any closed-loop control. The system efficiency reaches 87.1% at 350-W output power. [ABSTRACT FROM AUTHOR]

Improving the power density of a power converter has many benefits for systems integration. Aspects such as thermal management, weight, conformation to mounting locations, and the footprint of the converter all become critical factors as systems continue to scale down in size. The flying capacitor multilevel converter topology is of interest because it has characteristics which contribute to high power density. This paper presents a quasi-square-wave zero-voltage switching (ZVS) multilevel dc–dc converter. ZVS greatly reduces switching losses and enables high-frequency operation of the converter. A hardware prototype is implemented, built on a flexible polyimide substrate circuit board. Experimental results show a peak system efficiency above 98.1%, an effective switching frequency of up to 3 MHz, and a power output of 250 W. [ABSTRACT FROM AUTHOR]

In this paper, two single-phase single-stage split-inductor buck–boost inverters are proposed: type-I and II. The proposed type-I is unity power factor inverter, while the proposed type-II inverter is suitable for any power factor. Both topologies remove the shoot-through problem. Furthermore, the reverse recovery issues for all switches are eliminated; therefore, mosfets are used to obtain higher efficiencies. The proposed inverters operated at higher switching frequencies confer the additional benefit of smaller passive components. The current stresses of the two switches in the proposed type-I and II inverters are lower of the conventional boost inverter. The dead time can be eliminated at both the high and line switching frequencies. In addition, the inductor conduction loss is minimized to improve efficiency. Moreover, the voltage stresses of the two switches in the type-I inverter can be much lower of its counterpart boost inverter. Most importantly, unlike the conventional high-reliability inverters, the magnetic volume of the proposed high-reliability type-I and II inverters is same of its counterpart boost inverter. The experimental results obtained for 500 W, 110 Vrms, 60 Hz hardware prototypes verify the analysis. [ABSTRACT FROM AUTHOR]

Analysis and design of a single-switch high step-up coupled-inductor boost converter are presented in this paper. With the aid of the coupled inductor, the proposed converter can achieve high-voltage gain without extreme duty cycle. Also, low switch voltage stress can be achieved, thus low-voltage-rating mosfet is allowed to lower the conduction loss. Moreover, the proposed converter features continuous input current, which is desirable and friendly to the battery, fuel cell, and photovoltaic applications. In addition, the reverse recovery problem of the diodes can be alleviated and leakage energy can be recycled. The operation principles and characteristics of the proposed converter are discussed. Experimental results are provided to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

When the interleaved boost power-factor correction (PFC) converter operates in a light load (<15% of nominal load), the phase-shedding control is commonly used to increase the converter's efficiency. If the inductors are coupled for high power density applications, because of the strong mutual effects of the coupled inductor, the switching of the operation phase may lead to a current flowing in the non-operation phase. In this paper, a two-phase interleaved boost PFC converter with a coupled inductor in the single-phase operation was analyzed. The operation modes of the converter in a switching cycle and a half line cycle were presented, and the modes’ variation with the load changes, as well as the power distribution, was provided. A 1-kW prototype was built to verify the analysis, and it was shown that the non-operation phase also delivers some power, which may worsen the converter's efficiency and distort the average input current waveform. [ABSTRACT FROM AUTHOR]

This paper presents a self-adapting synchronized-switch harvesting (SA-SSH) interface circuit to extract energy from vibration-based piezoelectric energy harvesters (PEHs). The implemented circuit utilizes a novel switching technique to recycle optimum amount of harvested charge on piezoelectric capacitance to strengthen the damping force, and simultaneously achieve load-independent energy extraction with a single inductor. Charge recycling is realized by adjusting extraction time, and optimized through a maximum power point tracker based on charge-flipping dissipation. The circuit has been implemented using 180 nm HV CMOS technology with 0.9 × 0.6 mm2 active area. Self-adapting SSH circuit has been validated with both macro-scaled and MEMS PEHs with different inductor values. The interface circuit provides maximum energy extraction for the full storage voltage range of 1.8–3.7 V. The implementation harnesses have 500% more power compared to an ideal full-bridge rectifier, and output 3.4 μW for 2.24 V peak-to-peak open-circuit piezoelectric voltage from MEMS PEH excited at its resonant frequency. [ABSTRACT FROM AUTHOR]

This paper presents a delta-sigma modulation (DSM) control scheme for noninverting buck–boost (NIBB) converter that features a duobinary encoding for four power switch controls. The proposed scheme converts the single-bit output of the modulator into a 1.5-b signal to enable a three-phase operation comprising the charging, bypassing, and discharging phases. This control method reduces both switching and conduction losses by changing only two switches in each period, thus, achieving high conversion efficiency. A smooth mode transition is provided by the DSM controller, which automatically and continuously determines the operating mode of the converter. Thus, the dead zone can be effectively released with improved transient responses. Furthermore, the spurious tones in the output are effectively eliminated by the robust noise shaping capability of the modulator. The proposed DSM-based NIBB converter was implemented on a 180-nm CMOS. It regulated the output in the range of 2.0–4.6 V with input voltage of 2.5–5.0 V, and the maximal load current was 500 mA. The converter showed a peak efficiency of 94.8% at 90-mA load and the output voltage ripples were maintained under 18 mV. A low noise floor with the first spurious peak located –92 dBc below the signal was achieved across all mode operations. In addition, the converter occupied a small chip area of 1.51 mm2. [ABSTRACT FROM AUTHOR]

The discontinuous conduction mode boost power factor correction converter features zero-current turn-on for the switch, no reverse recovery in diode, and constant frequency operation. With traditional constant duty ratio control, the power transfer in each switching cycle exhibits great difference during a half-line cycle. Consequently, the peak and root mean square values of the inductor current are large, the same goes for the switch and diode. This increases not only the current stress of the power components but also the conduction and switching turn-off loss, and lowers the efficiency of the converter. Introducing third and fifth harmonics into the input current and varying the duty cycle correspondingly can reduce the aforementioned power transfer difference, and provide huge space for the increment of boundary inductance as well. An optimum boundary inductance control concerning limited power factor (PF) is proposed in this paper. For the maximum boundary inductance of the converter within wide input voltage range, the optimum harmonics amounts are analyzed and figured out. The proposed method brings about efficiency improvement, output voltage ripple reduction, and PF increase as well, especially at high input voltages. A prototype has been built and the experimental results are presented to show the validity of the scheme. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems having rechargeable batteries are prone to be complex and costly because multiple converters are necessary to individually regulate a load, PV panel, and battery. This paper proposes novel nonisolated multiport converters (MPCs) integrating a bidirectional pulsewidth modulation (PWM) converter and phase-shift-switched capacitor converter (PS-SCC) for standalone PV systems. A PWM converter and PS-SCC are integrated by reducing the total switch count, realizing the simplified system and circuit. In the proposed MPCs, two control freedoms of duty cycle and phase shift angle are manipulated to individually regulate the load, PV panel, and/or battery. The detailed operation analysis was performed to mathematically derive gain characteristics and zero voltage switching operation boundaries. For the battery discharging mode, in which the PV panel is not available and the MPC behaves as a single-input–single-output converter with two control freedoms available, the optimized control scheme achieving the lowest rms current is also proposed to maximize power conversion efficiencies. Various kinds of experimental verification tests using a 200-W prototype were performed to verify the theoretical analysis and to demonstrate the performance of the proposed MPC. [ABSTRACT FROM AUTHOR]

Boost-based converters are used in a variety of non-isolated step-up applications, such as power factor correctors, because of their simplicity. The power density of these converters can be increased in higher switching frequencies, which reduces the size of the magnetic elements. This increases the switching losses, but that can be solved by soft-switching techniques. This paper proposes a resonant bridgeless power factor correction converter that provides soft switching for all of the semiconductors. The proposed structure can provide zero voltage switching for the switches and zero current switching for the diodes. In the proposed structure, the input current is inherently sinusoidal with low total harmonic distortion, even with small inductances. Therefore, a high input power factor is achieved without requiring a current control loop in the circuit. This reduces the complexity of the control circuit. An experimental prototype has been constructed to investigate the validity of the claims. Experimental results show near-unity power factor, as well as $\text{2}\%$ efficiency improvement at full load when compared to a conventional interleaved boost converter with the same components. [ABSTRACT FROM AUTHOR]

In this paper, a new low-voltage ringing zero voltage transition (ZVT) cell is proposed for a family of non-isolated dc–dc converters. In the proposed converter, all semiconductor devices operate under soft-switching condition at both turning on and off. The proposed ZVT cell resolves the issues appeared in the previous works: no online calculation required to achieve ZVS turn-on of the main switch; no extra voltage stress imposed on the main or snubber components; no floating gate driver required for the main and snubber switches; low component count of the ZVT cell; operation principles and design guideline of the boost converter with the proposed ZVT cell are presented. Also, three different positions of a snubber diode considering its junction capacitor are analyzed to clarify the advantage of the proposed ZVT cell. A 2-kW laboratory prototype of the boost converter with the proposed ZVT cell operating at 100 kHz is built and tested to verify the theoretical analysis. Finally, a comparative analysis is given to demonstrate the superiority of the proposed converter. [ABSTRACT FROM AUTHOR]

This paper presents a new bridgeless buck–boost power factor corrector with the use of the active virtual ground technique, which is named as the Manitoba Rectifier. The proposed topology can convert the grid ac voltage into a wide range of voltage outputs within a single-stage circuit. It is in a bridgeless structure and simple in design. During the operation, an LC filter is generated at the system input, where continuous grid current is guaranteed in a buck–boost characteristic topology. In addition, the filter capacitor helps to clamp the voltage ripple between the grid and the output bus terminal. Both leakage current and common mode noise are kept in a relatively small value. Thus, a single-stage and low common-mode buck–boost converter system is built. The proposed topology is successfully implemented on an 800 W prototype, and the performance is experimentally verified, which shows good agreement with the theoretical findings. [ABSTRACT FROM AUTHOR]

In this paper, a new high voltage gain step-up dc–dc converter is proposed for interfacing renewable power generation. The configuration optimally integrates both the coupled-inductor and switched-capacitor techniques to achieve an ultra-high step-up gain of voltage conversion with low voltage stress and high efficiency. It consists of a voltage boost unit, a passive clamp circuit, and a symmetrical voltage multiplier network. The structure becomes modular and extendable without adding any extra winding for ultra-high step-up voltage gain. The proposed topology not only reduces the voltage stress on the main switch but also maintains it steady for the entire duty cycle range. Furthermore, the reverse recovery issue of the diodes is alleviated through the leakage inductance of the coupled inductor. The operation principle and steady-state analysis are presented in detail. Experimental evaluation validates the claimed advantages and demonstrates a well-distributed efficiency curve and the peak of 96.70%. [ABSTRACT FROM AUTHOR]

The three-level full-bridge (TLFB) dc−dc converter has been widely used in high-voltage, high-power applications. In the experimental test, the neutral-point voltage deviation appears; moreover, it has also been found out that if the flying capacitors are introduced, the input capacitor voltages could realize self-balance even if no active balancing solutions are adopted. In the previous publications, the role of flying capacitors is generally considered to extend the range of soft switching; however, the self-balance ability has not been mentioned or investigated in any publications thus far. In order to fill this gap, this paper provides the detailed mode operation analysis of the TLFB converter and reveals the cause of the imbalance. In addition, the mechanism of the self-balance ability provided by the flying capacitors is explained in detail, which gives a deep insight into the converter. At last, the influence factor of the voltage error in steady state has been analyzed, and the specific expression of the voltage error is also derived. The feasibility of the theoretical analysis is verified by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

Digital peak current mode (DPCM) control is widely used for dc–dc converters operating in continuous current mode. However, current tracking delay (CTD) in the system is normally neglected in the modeling stage, which leads to poor compensator design and degraded performance. This paper investigates CTD effect in boost converter with different DPCM controls. Based on dynamic relationship between the reference current and actual inductor current, the CTD transfer functions are derived, which improves the accuracy of small signal model. Since CTD degrades the phase margin of the system, equivalent migration of right half plane zero is proposed to model CTD effect. This method is very simple and straightforward, which facilitates the compensator design. Furthermore, two novel DPCM control strategies with minimized CTD are proposed, and they are based on duty cycle restriction and duty cycle extension, respectively. Both controls greatly reduce the CTD effect and improve the response speed. Besides, the duty cycle extension benefits from an extended pulsewidth modulation (ExPWM). This optimizes the calculation algorithm and speed, while improving the time margin for digital calculations. Combined with the proposed models and controls, the CTD effect is greatly reduced. The effectiveness is verified through detailed simulations and experiments. [ABSTRACT FROM AUTHOR]

A novel PWM full bridge (FB) dc–dc converter for large power industrial applications is proposed in this paper. The soft switching mode of the primary switches can be varied under different input and output conditions to achieve optimum system efficiency. In the zero-voltage and zero-current switching (ZVZCS) mode, the turn-on and turn-off switching loss can be optimized because the soft switching conditions of the turn-on and turn-off instants are well decoupled. In the zero-voltage switching (ZVS) mode, the turn-off switching loss can also be optimized because there is no requirement for light load operation in this mode. Four mosfets with ultra-low on-state resistance are used, thus, the added conduction loss is small. The auxiliary mosfets with high switching frequency are turned on with zero-current and off with zero-voltage, hence, the added switching loss can also be neglected. Furthermore, some drawbacks of the conventional ZVS and ZVZCS converters, e.g., narrow ZVS load range, high primary circulating current, incomplete reset of the primary current, and unreasonable VA rating of the added components, have been well solved. The operation principles and soft switching characteristics are discussed. Experimental results from an 18-kW prototype are provided to verify the proposed converter. [ABSTRACT FROM AUTHOR]

The inductance is an important parameter impacting current ripple calculation, usually with the assumption that the designed inductance performs ideally in most of voltage source inverters (VSIs) applications. However, the initial permeability of magnetic material usually descends when the winding current reaches or goes beyond the saturation limit. In such region of saturation, the implemented inductor does not perform as expected in design stages and its value varies with the bias current. In this paper, analysis and calculation of the current ripple are presented for a three-phase VSI with powder cores-based inductors, which reveals the calculation error of current ripple caused by the soft saturation nature of powder cores. Based on the equivalent single-phase model, the influence of inductance saturation on current ripple can be quantitatively evaluated. Then, a comparison of the current ripple calculation between considering and ignoring inductance saturation of implemented inductors is drawn in detail. Furthermore, under the condition of inductance saturation, the output current ripple peak-to-peak value of three phases is used as the constraint for variable switching frequency pulsewidth modulation (VSFPWM) design. A comprehensive method is developed to compensate the effect of inductance saturation in VSFPWM. At last, the effectiveness of the proposed strategy is verified by the detailed simulation and experiment. [ABSTRACT FROM AUTHOR]

This paper presents a new configuration of high gain (HG) single ended primary inductor converter (SEPIC) with a ripple-free input current to maximize the efficiency of the PV panel for standalone water pumping system (WPS). The ripple eliminating circuit combined with the HG SEPIC converter to achieve reduced ripples in photovoltaic (PV) current is independent to the duty cycle control and hence, it can be easily integrated to the main power circuit of configuration. This circuit does not need any active switches, control, or drive circuit for its execution. The ripple eliminating circuit yields a complete removal of the electrolytic capacitor connected across the PV array and significantly reduces the inductance of the HG SEPIC converter. It also improves the response and power density of the dc–dc converter. The large gain of dc–dc converter enables the use of low-voltage PV panel and minimizes the partial shading and parasitic capacitance effects on PV array source. Due to the substantial compatibility between natural characteristics of switched reluctance motor (SRM) drive and WPS, a four-phase SRM drive is utilized in the proposed scheme. In addition, a single current sensor based maximum power point tracking technique is utilized in the proposed system, which helps to reduce the cost and improve the accuracy of the overall system. Analytical, simulated, and experimental results of the developed system are presented to demonstrate the performance of the system. [ABSTRACT FROM AUTHOR]

A modular quasi-resonant bidirectional dc–dc converter composed of half-bridge gallium nitride modules (HBGM) with reduced switch voltage stress is proposed in this paper. By using an auxiliary capacitor, a resonant circuit is formed to shape the current and voltage so that zero-voltage switching at turn-on instant is achieved. Since the switching loss dominates the power losses in a high-frequency dc–dc converter, the soft-switching performance leads to a noticeable reduction in the total loss; so, the operating temperature will decrease, and consequently, size of the heatsink will be reduced. The proposed circuit takes advantage of enhancement-mode gallium nitride (eGaN) switches regarding their small on-resistance RDS(on), low gate charge, and fast switching speed to improve both efficiency and power density. The main performance issue of adopting GaN switches in a bidirectional dc–dc converter is the high voltage stress of GaN devices, which is handled by connecting the HBGM in the active-clamped stacked configuration, as well as optimizing printed circuit board layout design. Finally, a 1 kW, 600 V laboratory prototype operating at 100 kHz is implemented to validate the proposed concept. [ABSTRACT FROM AUTHOR]

Unipolar-pulsewidth modulation (UP-PWM) inverter takes advantages of high power efficiency and small output chokes which is widely used in the industry. However, UP-PWM inverters cannot be used in parallel operation due to a current unbalance problem. This paper studies the current unbalance problem of paralleled UP-PWM inverters with common dc bus and ac bus. First, the problem of unbalanced inductor current is defined and analyzed. Second, a technique to eliminate unbalanced currents is proposed. The proposed current balancing technique only requires one more current sensor in an inverter module rather than changing converter topology or modulation method, which makes it possible to apply UP-PWM inverters in parallel-operation while keeping the advantages of unipolar switching. The proposed current balancing method is verified by both simulation and hardware experiment. Experimental verification is performed on two 1 kW, 400 V input, and 120 V/60 Hz output prototypes, which shows a good agreement to the analytical study. [ABSTRACT FROM AUTHOR]

DC microgrid is gaining attraction and a recent trend in distribution power generation system due to penetration of renewables (especially photovoltaic or fuel cell). In this paper, a new triple-switch-triple-mode high step-up converter (TSTM-HS converter) is presented for dc microgrid applications. In the proposed converter, voltage lift technique is employed and range of duty cycle is extended by incorporating an additional switch in converter circuitry. By doing this, high voltage conversion ratio is achieved without using a transformer, coupled inductor, and multiple stages of switched capacitors. Moreover, the TSTM-HS converter operated in three modes with two types of the duty cycles to achieve low to high voltage conversion without using high duty cycle for each switch. The effects of difference in the inductance values on the regulation and operating behavior of the TSTM-HS converter are discussed. The continuous conduction mode and discontinuous conduction mode characteristics of the TSTM-HS converter are discussed in detail with steady-state analysis and boundary condition. The comparison is provided to highlight the benefits of the TSTM-HS converter. The selection of semiconductor devices and the design of reactive components are discussed for the TSTM-HS converter. The experimental results of the proposed converter are provided which validate the theoretical approach, performance, and feasibility of converter. [ABSTRACT FROM AUTHOR]

Parallel interleaved two-level (2L) three-phase voltage source inverters (VSIs) are widely used due to their distinct advantages of high power delivery, modularity, low current rating devices, etc. Along with these advantages, the parallel interleaved 2L VSIs could also be analyzed as a single three-level (3L) VSI. Conventionally parallel interleaved 2L VSIs are modulated using the 2L pulsewidth modulation (PWM) techniques. However, implementation of parallel interleaved 2L VSIs using the 2L PWM techniques may generate a higher ac side current ripple as compared to implementing the parallel interleaved 2L VSIs using 3L PWM techniques. This paper proposes a carrier-based method for implementing different 3L discontinuous PWM (DPWM) techniques for parallel interleaved 2L three-phase VSIs. Comparison of different 2L switching sequences for implementing a 3L DPWM switching sequence based on circulating current, line current ripple, and switching loss is also carried out. Simulation and experimental results are also displayed to validate the proposal. [ABSTRACT FROM AUTHOR]

Control-to-output transfer function of the classical boost converter in continuous conduction mode contains a right-half-plane (RHP) zero that limits its frequency response. In this paper, to eliminate this zero and enhance the dynamic performance, a forward path for energy transfer to output within the on interval of the power switch is provided using the magnetic coupling. This approach simply eliminates the RHP zero by introducing an inductor coupled to the boost inductor, a diode, and a capacitor into the classical boost topology. In addition, the provided forward path enhances the voltage gain, which makes it possible to achieve a smaller operating duty cycle and reduced voltage stress for the power switch in applications with large voltage conversion ratios. Using this approach does not complicate the control structure, and a traditional single-loop voltage control scheme can be used to regulate the output voltage. The proposed approach is analytically examined by obtaining the averaged state-space model of the resulting converter, and a criterion to eliminate the RHP zero is presented. Experimental results from an implemented laboratory prototype for 48- to 200-V voltage conversion and 100-W nominal power are provided. [ABSTRACT FROM AUTHOR]

Droop control is broadly used in dc power distribution systems, e.g., dc microgrids. Implementing droop control for switch mode power supplies requires the measurement of average current. Synchronous sampling is used in digital control systems to obtain the average of a triangular inductor waveform. However, the dead time, semiconductor turn-on and turn-off delays, and signal conditioning delays shift the sensed waveform and change the effective duty cycle, resulting in a misalignment and measurement error from the average value. This paper proposes a duty cycle weighted averaging method based on double sampling. By sampling twice per switching period and averaging the results using duty cycle as the weighting factor, the error due to waveform misalignment is theoretically eliminated. The result always equals the average value of the triangle. This method does not rely on the knowledge of circuit delays, making it easy to implement and robust to parameter variations. Simulations and experimental measurements validate the superior performance compared with conventional single and double sampling methods. The experiment on a droop-controlled dc–dc converter demonstrates a more accurate droop characteristic. [ABSTRACT FROM AUTHOR]

This paper proposes an interleaved totem-pole bridgeless boost power factor correction (PFC) converter with soft-switching capability. In the proposed converter, an inductor is added compared with the conventional interleaved totem-pole bridgeless boost PFC converter. The added inductor is located between two PFC converter units, and by utilizing the energy of the added inductor, all switches can achieve the zero voltage switching (ZVS). In addition, by applying the phase-shifting control between two PFC converter units, the proposed converter can control the magnitude of the current flowing on the added inductor as an optimal value. Therefore, the proposed converter can achieve the ZVS operation, while minimizing the additional conduction loss and core loss of the added inductor. As a result, the proposed converter can achieve the high efficiency. The feasibility of the proposed converter is confirmed with 180–264 Vrms input and 1.6 kW (400 V/4 A) output prototype. [ABSTRACT FROM AUTHOR]

The pulse-width modulated (PWM) switching rectification that can achieve a high power factor (PF) for increasing the energy transfer efficiency between an LC resonator and a rectifier and voltage step-up and -down conversion is proposed for a wireless power transfer (WPT) receiver. The proposed method can emulate the switching rectifier as a resistive load by using an inductor and integrated phase synchronizers. Additionally, similar to a switched-inductor converter that controls the duty cycle ratio (D), the proposed PWM rectifier can control the output voltage VOUT when the input is a rectified, wirelessly coupled voltage instead of a constant voltage. Thus, unlike a conventional PWM switching rectifier for ac mains, an additional voltage conditioning circuit would not be needed after the proposed rectifier for WPT. The proposed PWM switching rectification is implemented in the AMS 0.18 μm 1.8 V/5 V CMOS process. PF = 1 is measured, indicating the most efficient energy transfer, compared to only 0.55–0.65 in a peak detection rectifier. Additionally, 88.2% of peak power conversion efficiency of the switching rectifier is achieved, and the maximum output power is 80.3 mW at 500 kHz of the WPT frequency. Moreover, the measured voltage conversion ratios ranging between 0.73× and 2× are demonstrated in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes a high-step-down dc–dc converter with continuous output current which utilizes coupled-inductors. Another main feature of this converter is applying the same number of switches as the synchronous buck converter. The introduced converter is suitable for non-isolated low-voltage high-current applications, especially voltage regulator modules (VRMs) with 12-V-input. Owing to extension of the duty cycle, the main mosfet current stress and the synchronous rectifier switch voltage stress are significantly reduced. However, the discharge of the leakage inductance energy increases the main mosfet voltage stress. By employing a simple lossless clamp/snubber circuit the leakage inductance energy is recovered, the voltage spike across the main mosfet is clamped, and the turn-off switching losses are reduced. There is at least one inductor in all current paths which creates an intrinsic protection against current shoot-through and provides zero-current-switching (ZCS) turn-on for the main mosfet. High efficiency is attained by the proposed converter due to extended duty cycle, low number of switches, and soft switching operation while the converter driver is just like the conventional buck converter. Due to the single-phase structure of the proposed converter, this converter is a viable alternative to the buck VRM. Similar to the other converters using coupled-inductors, the complexity of coupled-inductors design and the space occupied by coupled-inductors can be considered as drawbacks. A prototype of the proposed converter is implemented to verify the converter operation and the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper describes a theory to synthesize nonisolated dc–dc converters. It uses the fundamental flux balance equation across the inductors of a converter as a starting point in this synthesis process. The flux balance equations are the linear equations of the input voltage, capacitor voltages, and duty cycle (D). The coefficients of these linear equations can be selected from a finite set of choices. These choices define the converter topologies that are subsequently used to synthesize a converter. The synthesis procedure applies to a converter of multiple order. All the possible converters are identified for a first-order topology. In the case of second-order converters, all the choices of the flux balance equation are defined. Based on these choices, three new quadratic topologies are derived and verified to demonstrate the effectiveness of the theory. The procedure to synthesize a converter from a given voltage conversion ratio is also outlined. [ABSTRACT FROM AUTHOR]

High step-up boost converters with coupled inductor have attracted much attention in the fuel cell or photovoltaic grid-connected generation system, however, there are few literatures elaborated on the construction ideas and derivation methods of them. Accordingly, in order to obtain a clear roadmap on the derivation and inner connection of these converters, a comprehensive review and analysis are presented in this paper. First, the basic boost converter with coupled inductor is regarded as the basic topology, and its merits and demerits are analyzed in detail. Then, in order to address these demerits, various step-up techniques are introduced, such as the rectifier circuit, the active-clamped circuit, the multi-winding coupled inductor, and the voltage doubler rectifier; and numerous new topologies are continuously proposed by combinations and equivalent simplifications. In addition to a detailed synthesis of each topology, a comparative and quantitative analysis among some important converters is presented, and the optimal one is chosen to build a 250 W prototype. Finally, based on comparisons and analysis, the main characteristics and inner connections of these high step-up boost converters with coupled inductor are identified and clarified. [ABSTRACT FROM AUTHOR]

High power pseudospark switches (PSSs) can control pulsed high voltage, high peak current discharges. In this paper, a PSS in series with a saturable inductor at the anode is investigated. The commutation process is analyzed with a time-resolved method. And the effects of the number of magnetic cores and anode voltages on discharge characteristics are studied experimentally. At the beginning of commutation process, when the anode voltage is 10.4 kV with four magnetic cores, the inductor is unsaturated, and there is a flat plateau of the forward voltage drop after the anode voltage drops rapidly to about 200 V, at the same time the current rise rate is 2.8 kA/ $\mu \text{s}$. When the inductor is saturated, there is a voltage spike that occurs at the end of the flat plateau, and the current simultaneously rises rapidly at the rate of 6.4 kA/ $\mu \text{s}$. The current sharp rise lags behind the voltage drop of the pseudospark gap, and the electrode erosion and energy dissipation reduce significantly. When the anode voltage is 15.6 kV, the commutation losses reduce by about 30% with seven cores in series at the anode. As a result, it is evident that the discharge process will speed up if the anode voltage is higher. And the trigger delay decreases by up to 8% when the anode voltage varies from 5.2 to 15.6 kV. Finally, in order to obtain a reproducible pseudospark discharge by the use of a saturable inductor, the number of magnetic cores has to be optimized for different anode voltages. [ABSTRACT FROM AUTHOR]

This paper describes a study on the high-voltage compact solid-state pulsed-power modulator for parallel reactor operation. The current capacity of the pulsed modulator has been improved to drive multiple reactors in parallel. The pulse discharge switch uses the IXYK120N120C3 (1200 V/120 A) insulated-gate bipolar transistor for a high current output. The gate driver has been improved according to the characteristics of the replaced switch. The output specifications of the modified pulsed-power modulator are a maximum output voltage of 40 kV, a maximum output current of 300 A, a pulsewidth ranging from 1.5 to $5~\mu \text{s}$ , a maximum repetition rate of 3 kHz, and an average power of 13 kW. The modulator has the dimensions of $450 \times 475 \times 600$ mm3, a maximum peak power of 12 MW, and a maximum power density of 93 kW/L. A resistive load experiment and a plasma reactor parallel drive test were performed. Four parallel reactors were driven using one modulator. In addition, a 50% reduction in the concentration of toluene was obtained through the experiment of the toluene gas treatment using only parallel plasma reactors. [ABSTRACT FROM AUTHOR]

In this paper, an integrated step-up inverter without transformer is investigated for photovoltaic (PV) power generation. The proposed topology can be derived by combining a traditional boost converter with a single-phase full bridge dc–ac converter. The main features of the integrated inverter are: First, the leakage current caused by the solar cell array-to-ground parasitic capacitance can be theoretically reduced to zero due to the characteristics of the converter configuration, which can improve the efficiency and the reliability of the PV generation system; second, the output ac voltage of the proposed inverter can be higher than the input dc voltage, which is capable of connecting low voltage PV panels to the grid; third, only five active switches are used in the presented inverter, and those switching devices can be synchronously driven by various sinusoidal pulsewidth modulation methods based on the carrier; therefore, the proposed inverter is compact and with curtailed cost. The working principle and analysis of the proposed integrated inverter are elaborated. Finally, simulation and experimental results are obtained in a lab prototype, which agree well with the theoretical analysis. [ABSTRACT FROM AUTHOR]

A novel high step-down dc–dc converter with voltage demultiplier cell is proposed in this paper, which is widely used in the high step-down applications such as electric vehicle and digital circuits. The combination of switched-capacitor and coupled-inductor is employed to build extended voltage demultiplier in the proposed converter, which makes a quite higher voltage conversion ratio than that of the existing counterparts. Thus, the proposed converter can achieve extremely low output voltage with an appropriate duty ratio, and the extreme duty cycle is avoided. Accordingly, voltage stress on power switches is greatly reduced. Then, mosfets with low conduction resistance could be utilized to reduce conduction loss. Importantly, zero-voltage switching could be achieved for the main switch, which promotes the conversion efficiency further. In addition, the coupled inductor operates not only as a filter inductor, but also as a transformer when the main switch is in the off state, which reduces the volume of the magnetic core and improves the power density of the converter. The operation principle, performance analysis, design considerations of the proposed converter and performance comparison with recent counterparts are discussed in detail, and finally, an experimental prototype is built to verify the theoretical analysis and performance of the proposed converter. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage single-switch soft-switching (S6) power factor correction (PFC) converter to enhance the current shaping performance and reduce the total harmonic distortion. This improvement is achieved by the aid of an auxiliary winding which is used to lower the input current harmonics and also achieve soft-switching condition. As a result, the switching losses are reduced and harmonic content of the input current is improved noticeably in comparison to the conventional S6 PFC converter. Also, the total number of semiconductor elements is reduced in the proposed topology which results in lower cost and higher efficiency. The operating modes of the proposed converter are discussed in detail and the design procedure is presented. A 200-kHz prototype of the proposed converter is implemented and the obtained results are provided to verify the converter theoretical analysis and operation. [ABSTRACT FROM AUTHOR]

This paper investigates an approach for achieving zero-voltage switching of an interleaved bi-directional buck–boost converter over a wide input–output voltage operating range by utilizing a coupled inductor with a variable coupling coefficient. The approach is based on regulating the value of the coupling coefficient by means of a direct current depending on the converter conversion ratio, thereby controlling the amplitude and duration of the resonant voltage transition. The impact of the controllable value of the coupling coefficient on the equivalent inductance, the zero-voltage transition period, and the resonant amplitude is analyzed in detail by applying analytical modeling. In comparison to the converter with a fixed coupled inductor operating over a wide input–output voltage span, the variable coupled inductor significantly improves the soft-switching range and reduces the circulating energy. Outside of the controllable resonant amplitude region, the converter with a variable coupled inductor still achieves reduction in the duration of the resonant transition period. To validate theoretical analysis, experimental results are recorded on the gallium nitride interleaved bi-directional buck–boost converter prototype. Improvements in efficiency at both full and half loads in comparison to the prototype with a fixed coupled inductor are achieved. [ABSTRACT FROM AUTHOR]

For high-voltage and high-power bidirectional dc–dc converters, soft switching of all active power devices is mandatory to ensure the high efficiency and reliability. This paper describes a control technique for wide-range zero-voltage switching (ZVS) implementation of dual-bridge series-resonant dc–dc converters. The proposed control technique integrates variable-frequency modulation (VFM) and phase-shift modulation (PSM), in which the former effectively achieves the ZVS for both step-down and step-up operation, while the latter is employed to further extend the power transmission capability. The proposed technique is built on the time-domain analysis of the ZVS condition. A closed-form solution is formulated that guarantees the sufficient ZVS commutation current at switching instants, accounting for the presence of switches parasitic and/or snubber capacitances, while maintains the rms tank current at near-to-minimum levels. Furthermore, a compensation strategy for the effect of conduction losses is presented achieving better switching behavior and higher efficiency. Compared with the minimum rms current trajectory modulation, lower switching losses, enhanced efficiency, and mitigated voltage ringings are obtained. Effectiveness of the proposed technique is verified by means of a 800 W experimental prototype. Closed-loop operation with the proposed VFM+PSM controller is also implemented and experimentally tested. [ABSTRACT FROM AUTHOR]

This paper presents a method that overcomes the problem of the confusion during fast irradiance change in the classical maximum power point tracking (MPPT) as well as in model predictive control (MPC)-based MPPTs available in the literature. The previously introduced MPC-based MPPTs take into account the model of the converter only, which make them prone to the drift during fast environmental conditions. Therefore, the model of the photovoltaic (PV) array is also considered in the proposed algorithm, which allows it to be prompt during rapid environmental condition changes. It takes into account multiple previous samples of power, and based on that is able to take the correct tracking decision when the predicted and measured power differ (in case of drift issue). After the tracking decision is taken, it will be sent to a second part of the algorithm as a reference. The second part is used for following the reference provided by the first part, where the pulses are sent directly to the converter, without a modulator or a linear controller. The proposed technique is validated experimentally by using a buck converter, fed by a PV simulator. The tracking efficiency is evaluated according to EN50530 standard in static and dynamic conditions. The experimental results show that the proposed MPC-MPPT is a quick and accurate tracker under very fast changing irradiance, while maintaining high tracking efficiency even under very low irradiance. [ABSTRACT FROM AUTHOR]

This paper proposes a voltage-source parallel resonant Class E inverter. The proposed circuit has a shunt capacitor including parasitic capacitance of a switching device and achieves zero-voltage switching and zero-voltage derivative switching at turning-on like a classical Class E inverter. Therefore, high power conversion efficiency is achieved under high operating frequency. Unlike the other Class E inverters, the proposed circuit has no choke inductor or dc blocking capacitor. Moreover, it has a parallel resonant tank unlike the classical Class E inverter. Thus, a circuit protection is not required in a wireless power transfer system. Circuit analysis, circuit simulations, and circuit experiments were carried out. The experimental circuit performed the desired operation and the power conversion efficiency was 93.2% with the output power 4.76 W at the operating frequency 1 MHz. [ABSTRACT FROM AUTHOR]

In order to provide high and extendable power levels for inductive power transfer (IPT) system, a parallel multi-inverter system based on modular inverter is presented. Various power requirements can be implemented by an adjustment of the number of paralleled inverters, which provides a high modularity. A master−slave scheme is employed for the switching-driver signals of parallel inverters, where one acts as a leader while others act as followers. Despite the master−slave scheme, the proposed circuit topology has natural robustness because of the equality in terms of the hardware configuration of each modular inverter. For proper parameters, the output phase (current lagging corresponding voltage) of an inverter is lower than the average of output phase of all inverters, when its output voltage lags behind others, and vice versa. Based on this approach, PI controllers are designed to implement phase synchronization for output voltages of all inverters. An IPT prototype supplied by the proposed parallel multi-inverter with three inverters was designed, built, and tested. Experiments show that the proposed parallel multi-inverter system has not only good circulating current suppression capacity but also excellent performance of phase synchronization. The maximum dc−dc efficiency was 94% at a 35.1 kW receiving power. This paper is accompanied by a Matlab/Simulink file demonstrating phase synchronization control. [ABSTRACT FROM AUTHOR]

This paper presents a multi-period frame transient switching control (MP-TSC) scheme for buck converter with a controlled coupled inductor, aiming at improving the load transient response. The proposed buck converter utilizes a controlled coupled inductor as the output inductor. During a load transient, the coupled inductor is controlled as a small equivalent inductance so as to achieve fast transient regulation. While in the steady state, the coupled inductor behaves as a large inductance to reduce the output current ripple. Furthermore, on the basis of the proposed variable inductance circuit, an MP-TSC control scheme is proposed and implemented in a digital form. With the proposed control scheme, the load transient event is divided into n + 1 sub-periods, and in each sub-period, the capacitor-charge balance principle is used to determine the switching time sequence. Moreover, the control principle design and transient response index analysis are provided. Furthermore, its feasibility is validated in simulation and experiment with a 12–3.3V low-voltage high-current synchronous buck converter. Experimental results demonstrate that the voltage deviation of the proposed MP-TSC scheme (coupled coefficient of the controlled coupled inductor is 0.52) has improved by more than 79% compared to that with the auxiliary circuit disabled. [ABSTRACT FROM AUTHOR]

An improved bridgeless (BL) Cuk converter-based electric vehicle (EV) battery charger with high power factor and increased efficiency is designed and developed in this paper. It provides low cost and high-power-density-based charging solution for the EV. This charger incorporates less number of devices operating over one switching cycle, which reduces the additional conduction loss incurred by a diode bridge rectifier of the conventional charger. Hence, it improves the charger's efficiency. The added advantage of the proposed topology is that the unwanted capacitive coupling loop is removed, as well as the unwanted conduction through the body diode of the inactive switch in the previously developed BL Cuk converter is avoided. This significantly improves the charger's efficiency. For the constant current and constant voltage charging, the commands are synchronized by a flyback converter. The proposed charger draws a sinusoidal current from ac mains and the total harmonic distortion in the supply current is reduced to the limits specified by the IEC 61000-3-2 guidelines. The improved efficiency and power quality indices of the proposed charger are investigated to demonstrate its satisfactory charging operation at all operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents a novel switch current stress reduction technique for a single switch boost-flyback high step up dc–dc converter. Coupled inductor-based converters do not have a sufficiently higher inductance value of their windings. This creates current surge during transient and steady state, which in turn increases current stress at main switch. To compensate this difficulty in coupled inductor-based boost flyback converter, an inductor–diode parallel combination has been connected in series with the switch. This technique increases the effective inductance of the coupled inductor primary winding during switch turn-on operation and helps to reduce current stress. Steady-state operating principle with the proposed technique is analyzed in continuous conduction mode. The current reduction technique is discussed with a proper mathematical derivation. To verify theoretical findings, simulation study is carried out in MATLAB/Simulink R2014b. Finally, a laboratory-based 40-W prototype converter is designed to show the effectiveness of the proposed switch current reduction technique. [ABSTRACT FROM AUTHOR]

A new transformerless bidirectional buck-boost converter is proposed in this paper. The proposed converter has a simple circuit structure, low component count, low voltage stress on the power transistors, and a wide voltage gain range. This makes it applicable in the energy storage charge/discharge systems, such as electric vehicles (EV), microgrids and nanogrids with energy storage units, and uninterruptible power supplies. In addition, synchronous rectification between the complementary transistors is employed to improve the converter efficiency. A comprehensive analysis of the steady-state operation, small-signal model, component parameters design, and efficiency analysis of the proposed converter operating in a continuous conduction mode is given. Finally, a 1.6-kW scaled-down prototype was built using Silicon Carbide MOSFETS to validate the effectiveness and feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, a novel noncoupled inductor high voltage gain single-ended primary-inductor converter (SEPIC) is presented. The proposed converter has various advantages, such as lower voltage stress on the switches, noninverting output voltage, high efficiency, and high voltage gain. Also, the introduced converter has a continuous input current which makes it suitable for renewable energy and fuel cell applications. Moreover, high voltage gain is achieved without using any transformer and coupled inductor, thus there is not any voltage overshoot for the switches during the turn-off process. This effect allows low conduction losses by using lower voltage rating switches and also additional clamping circuit is not needed. The control system of the presented converter is simple and the converter can be easily controlled in continuous conduction mode mode operation. Because, the gating pulses for both of the switches are the same and wide output voltage range is achieved only by changing the duty cycle. Furthermore, the number of the components compared to the other noncoupled inductor, SEPIC-based converters which provide near voltage gain to the proposed converter, is reduced. The detailed operation of the introduced converter and design considerations are discussed. Experimental results are presented to verify the performance of the proposed dc–dc converter. [ABSTRACT FROM AUTHOR]

In this paper, a cooperative triple-phase-shift (CTPS) control for the isolated dual active bridge dc–dc converter is proposed first to eliminate the dual-dc side flow back currents. Furthermore, the current characteristics of the proposed CTPS control with the main variable (the primary side inner phase shift) tuned in two different regions are derived in detail and compared with each other. The tuning region of the main variable with the optimal current characteristics is finally determined based on the comparison results. As a result, the current stress is reduced and the efficiency is enhanced. The detailed experimental results of CTPS control verify its validity and practicability. The advantages of CTPS control are also highlighted by comparing it with some conventional phase shift controls. [ABSTRACT FROM AUTHOR]

This paper discussed an active-bridge-active-clamp (ABAC) topology that is suitable for highpower more-electric-aircraft applications. Though conventional modulation techniques can be applied to ABAC converters, they present drawbacks, such as increased low-voltage (LV) current ripple and limited power transfer capability. To address these problems, a phase-shift-modulation (PSM) scheme is proposed to provide clean dc terminal current at the LV side while maintaining high power transfer capability and efficiency in a wide operating range. The proposed PSM has a complete switching harmonics cancellation on the LV terminals independent of the operating conditions. This results in high quality power without any ac components, thus minimizing passive filtering. In addition, when terminal voltages vary from their nominal values, the proposed PSM can improve the maximum power transfer capability of the ABAC converter compared to the conventional approach. The theoretical claims are validated by both simulation and experimental results on a 10-kW 270-V/28-V ABAC converter. [ABSTRACT FROM AUTHOR]

In this paper, a new zero-voltage zero-current transition (ZVZCT) boost converter using coupled inductors is proposed. The feature of this topology is: the main switch can be switched on with ZVZCT, and off with zero-voltage switching, without any voltage and current stress. The auxiliary switch is turned on with zero-current switching. Other semiconductor devices can also achieve soft switching (SS). Due to the existence of the coupling effect, the current impact of the auxiliary switch is completely suppressed when it is turned off. Lower input current and output voltage in the interval of the switch-off for the auxiliary switch are just equivalent to running at a low power level, which is an additional advantage of the coupled inductor ZVZCT solution. Another advantage of the topology is that the SS condition of the main switch for each specific load can be effectively optimized just by setting the ratio of coupling inductance corresponding to the circuit design and application load. Thus, the topology design can be improved to adapt to different load types. A 100 kHz experimental prototype has been verified, different load for 1 and 0.4 kW optimization comparison has been presented, and the case without optimization is also observed. [ABSTRACT FROM AUTHOR]

In the applications such as mixed-color light emitting diode (LED) lighting system, LED drivers are always required to provide constant current for each LED string and each current should be controlled independently. For this purpose, a single-stage series-type LED driver with independent control of N-channel output currents is proposed in this paper. The function of power factor correction can be realized inherently to obtain high power factor. N active output units, each one made up of a power switch, a diode, and an output filter capacitor, are series-connected to form the series-type N-channel outputs structure. According to different current reference values, N-channel output currents can be independently regulated just by sampling each output current to adjust the duty cycle of each secondary output-switch automatically. The operating principle and independent closed-loop control strategy of the proposed LED driver with N = 3 are analyzed as an example in detail. Finally, the quantitative parameter design method for a 120 W prototype is elaborated. And, the experimental results are presented to verify the effectiveness of the LED driver and the correctness of parameter design method. [ABSTRACT FROM AUTHOR]