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This paper proposes a power-factor-corrected bridgeless (BL) switched-mode power supply (SMPS) for welding applications that possesses output voltage control and current limiting feature even during extreme overloading conditions at the output terminals. Eliminating an input diode bridge rectifier minimizes conduction losses and improves thermal utilization of semiconductor devices. The front-end of the proposed SMPS consists of a BL boost converter operating in a continuous conduction mode to attain unity power factor, while at the rear end a pulse width modulation isolated full bridge dc–dc converter is used to regulate the output voltage. The design and implementation of this BL arc welding power supply (AWPS) is presented showing its fast dynamic response to supply voltage and load variations. The performance of the proposed AWPS is examined in terms of power factor, total harmonic distortion of the supply current, efficiency, and output current limit over a wide range of line/load variations. Test results confirm the effectiveness of the proposed AWPS in maintaining an impeccable power quality at utility interface apart from achieving an excellent output voltage regulation and current limiting capability. [ABSTRACT FROM PUBLISHER]

In this paper, a built-in voltage gain extension cell is proposed to give a universal topology derivation on next-generation high step-up converters for large voltage gain conversion systems. Several improved single-switch high step-up converters with built-in transformer voltage multiplier cell are derived with some advantageous performance, which includes extremely large voltage conversion ratio, minimized power device voltage stress, effective diode reverse-recovery alleviation, and soft-switching operation. The turns ratio of the built-in transformer can be employed as another design freedom to extend the voltage gain, which shows great design flexibility. Compared with their active clamp counterpart, only one MOSFET is required to simplify the circuit configuration and improve the system reliability. The over resonance frequency and the below resonance frequency operation modes are studied to explore the circuit performance, and the key parameter design criterion is provided to show a valuable guidance for future industrial applications. Finally, the experimental results from a 500 W 36-380 V prototype are provided to validate the effectiveness of the main contributions in this paper. [ABSTRACT FROM AUTHOR]

This paper identifies the characteristics of a current source inverter operating in discontinuous conduction mode, and proposes a new multiobjective pulse-width modulation (PWM) method to mitigate voltage boosting and harmonic distortion effects. The method takes into account load impedance effects. Controls are also developed to enable transition between the multiobjective PWM method and conventional PWM as the current source inverter operates in discontinuous and continuous modes of operation. The concept is verified experimentally on a 3 kW test bed. [ABSTRACT FROM AUTHOR]

This paper presents an analytical and experimental comparison of a two-phase buck converter and a two-phase, series capacitor buck converter. The limitations of a conventional buck converter in high-current (10 A or more), and high-frequency (HF, 3–30 MHz) point-of-load voltage regulators with large voltage conversion ratios (10-to-1) are highlighted. The series capacitor buck converter exhibits desirable characteristics at HF, including lower switching loss, less inductor current ripple, automatic phase current balancing, duty ratio extension, and soft charging of the energy transfer capacitor. Analysis of the topologies indicates that switching loss and inductor core loss can dominate at HF. Results from side-by-side 12 V input, 1.2 V output hardware prototypes demonstrate that the series capacitor buck converter has up to 12 percentage points higher efficiency at 3 MHz and reduces power loss by up to 33% at full load (10 A). Some guidelines for inductor selection are provided, and a switch stress comparison reveals that the maximum converter switch stress is reduced by 30%. [ABSTRACT FROM AUTHOR]

Multiphase constant on-time current-mode control based on pulse distribution structure is widely used in voltage regulator application for microprocessor. To minimize ripple cancellation effect, external ramp compensation is used in commercial products. However, external ramp will introduce dynamic to the system and stability margin will be suffered without considering its effect. This paper first studies the effect of external ramp by deriving small-signal transfer function based on describing function method. It is found that external ramp brings additional dynamic, with time constant related with switching period. Then, a simple equivalent circuit model based on three-terminal switch concept is proposed, which considers the effect of external ramp by adding an additional R–L branch. The equivalent circuit model can be reduced to previous unified three-terminal switch model when external ramp is zero and can be reduced to model of constant on-time voltage mode control when external ramp is much larger than inductor current ramp. The proposed three-terminal switch model is a complete model, which can be used to examine all transfer functions and is accurate up to half of switching frequency. The analytical transfer functions are provided for easy reference. The model is verified by SIMPLIS simulation and experimental measurement. [ABSTRACT FROM AUTHOR]

The extended commutation cell is a four-port four-switch cell that allows for bidirectional energy transport in two orthogonal directions throughout the cell. By cascading multiple cells, a multilevel converter can be constructed with a high number of levels. The voltage across each cell capacitor can be adjusted independently of the load, resulting in high flexibility in output levels. This paper presents an improved method for capacitor voltage control, based on a system model and the measured output current. The proposed method is analyzed and verified on a 4.4\text-\mathrmk\mathrmW eight-level dc–ac converter. The obtained reduction in capacitor voltage ripple is more than $75\%$. [ABSTRACT FROM AUTHOR]

Current sharing controller/functionality is commonly utilized for multiphase converters to achieve current balancing between converter phases. Conventional current sharing control schemes generally require sensing the current of each phase, leading to increased size and cost in addition to issues associated with current sensing inaccuracies. A sensorless current sharing control scheme is proposed in this paper that utilizes the difference between the input capacitor voltage ripple values to indicate the phases' current distribution status. The duty-cycle value of each phase is autotuned in a way to minimize the difference between the input capacitor voltage ripple values based on a single voltage sensing point, which results in equal current sharing with no need for current sensing. In addition, the input capacitor voltage ripple sensing does not need to be very accurate, and the sinusoidal frequency component of interest of the ripple is obtained by using a low-cost bandpass filter for improved ripple sensing resolution and noise immunity. Experimental results obtained from a digitally controlled two-phase synchronous buck converter prototype are presented to validate the feasibility of the proposed concept. [ABSTRACT FROM PUBLISHER]

Hardware-in-the-Loop tests of components for high-voltage dc transmission grids, for example circuit breakers, require converter systems capable of generating a high output current with fast transients of the output signal at different output voltages. In this paper, a three-level buck converter (N3L) employing three different supply voltages to enable a wide voltage operation range is presented. The modulation of the converter is investigated in detail with special focus on ripple cancellation, the startup of the interleaved converter and the level shifting between different converter output voltages. A prototype system is designed and constructed, optimized for pulsed power operation and compared to a two level and to a neutral point clamped converter design. The system has been simulated numerically and the design boundaries are validated by measurements on the prototype system. [ABSTRACT FROM AUTHOR]

A single-stage, bidirectional, current-source converter (CSC) topology to interface a dc microgrid with an ac grid is reported in the literature. In this topology, under a balanced grid voltage condition, the dc-link inductor current can be regulated over a wide range—from zero to rated value—while the ac-side current has low harmonic distortion. However, unbalanced grid voltages result in second-harmonic pulsation in the current and power on the dc side of the converter. In addition, the ac-side currents will be unbalanced due to the presence of a negative-sequence component. This would result in undesired tripping of the converter if one of the phase currents exceeded its rated value. Various control loop structures for the operation of voltage-source converter under unbalanced grid voltage conditions are reported in the literature. However, use of similar control loop structures for CSC may lead to unstable operation. Therefore, a control scheme to inject balanced three-phase currents into the ac grid under an unbalanced grid voltage condition is proposed in this paper. The stability of the proposed control scheme is studied using a small-signal model of the converter. Performance of the proposed control scheme is studied using MATLAB/Simulink and is experimentally validated. [ABSTRACT FROM AUTHOR]

This paper presents an average current mode buck dimmable light-emitting diode (LED) driver for large-scale single-string LED backlighting applications. The proposed integrated current control technique can provide exact current control signals by using an autozeroed integrator to enhance the accuracy of the average current of LEDs while driving a large number of LEDs. Adoption of discontinuous low-side current sensing leads to power loss reduction. Adoption of a fast-settling technique allows the LED driver to enter into the steady state within three switching cycles after the dimming signal is triggered. Implemented in a 0.35-μm HV CMOS process, the proposed LED driver achieves 1.7% LED current error and 98.16% peak efficiency over an input voltage range of 110 to 200 V while driving 30 to 50 LEDs. [ABSTRACT FROM AUTHOR]

Subharmonic oscillation is widely studied in switching converters under current mode control (CMC). Its boundary of occurrence in the design parameter space is well known in the case of an infinite-bandwidth current sensor. However, in a practical implementation, either a limited-bandwidth current sensor or an additional filter is used. This could have an effect on the system dynamics particularly for relatively high switching frequencies. This paper discusses the effect of the additional dynamics due to the finite-bandwidth current sensor or the additional filter on the stability and subharmonic oscillation boundaries in switching converters under CMC. It is shown that a simplified model, taking into account the dynamics of the inductor current and the sensor/filter, is enough to obtain accurate results concerning the prediction of the occurrence of subharmonic instabilities in switched converters. Design-oriented equations describing the occurrence of subharmonic oscillations are used to show some problems related to the additional dynamics on the ramp compensator design in a single-switch dc–dc converter working in continuous conduction mode. Some proposed solutions are also discussed. Numerical simulations and experimental measurements corroborate the theoretical predictions. [ABSTRACT FROM PUBLISHER]

High-performance buck converters are often required in modern power electronic applications. An augmented buck converter (a main buck converter with augmentation circuits) can achieve fast transient recovery and small output voltage deviation. Compared with other augmentation circuits, a resonant augmentation circuit offers potential electromagnetic interference reduction due to the relatively low $di/dt$ value and compacts the circuit through a reduced inductance for resonance. In this paper, the performance analysis of an augmented buck converter constructed with the resonant circuit are described in detail in terms of voltage-deviation band and power loss. A circuit design and control principle is also proposed for achieving the required voltage deviation for a given transient-detection delay. A 12-to-5-V converter prototype is built to verify the analysis and effectiveness of the proposed methodology. It is demonstrated that the voltage deviation is reduced from 360 to 200 mV using the proposed resonant augmentation circuits and control scheme. The efficiency study shows that the power loss varies from 0.02 to 0.72 W, when the repetition frequency of 5-to-10-A transients changes from 100 to 5 kHz. [ABSTRACT FROM AUTHOR]

In this paper, a three-phase current-fed dual-active-bridge (DAB) bidirectional DC-DC converter is presented. Compared to the voltage source DAB converter, the proposed converter allows low RMS current and maintains zero voltage switching (ZVS) in the whole operating range by keeping the ratio between primary side and secondary side DC-link voltage constant, leading to high efficient energy conversion over a wide input voltage range. In addition, the ZVS conditions can be maintained using small DC inductors and the input current ripple still remains small because of high DC inductor current ripples being alleviated by three-phase interleaving structure. Furthermore, the proposed topology with Y-Y connected transformers is proven to have better current sharing capability compared with other three-phase topologies with different transformer connections. The operation mode analysis, soft switching conditions, and hardware design guidelines are derived in this paper. A 6-kW hardware prototype with input voltage range of 24~48 V and rated 288 V output voltage is developed and tested in the laboratory. The experimental results verified that the proposed converter could maintain high efficiency over a wide input voltage and power range. [ABSTRACT FROM AUTHOR]

This paper shows two applications for using vacuum circuit breakers (VCBs) in flexible ac transmission systems in the high-voltage (HV) power grid. This is first a mechanically switched reactor, which is series connected to a thyristor-controlled series compensator in order to enhance the inductive working range. Nevertheless, the switching frequency of VCBs is limited by their mechanical properties. In order to achieve a higher switching frequency, more VCBs are switched in parallel to each other. Second, a device is investigated, which consists of mechanically switched capacitors and a mechanically switched reactor. It is connected to a node in the HV system in order to enhance the voltage quality and to avoid a voltage collapse. Since VCBs are mainly available in the medium-voltage range, a transformer is used to connect the mechanically switched device to the HV system. In this paper, it could be shown that the mechanically switched series reactor is able to enhance the damping progress of power oscillations and that the mechanically switched device using VCBs can stabilize the voltage of the node in case of disturbances, such as faults in the power system. Furthermore, the electrical stress on the VCBs has been assessed for different simulation cases with PSCAD. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel family of cascade three-level (TL) ac–ac direct converters based on ac switch cells, which transfer unsteady high ac voltage with distortion into regulated sinusoidal voltage with low total harmonic distortion (THD). The topological family includes buck TL–boost, buck–boost TL, and buck TL–boost TL modes. In order to achieve a reliable TL ac–ac conversion, a double transient voltage feedback control strategy of the output voltage and the voltage across the flying capacitor is introduced in this paper. A 500-VA 220-V \pm10% 50-Hz ac/220-V 50-Hz ac prototype is presented with the experimental results to prove that the converters have four improved advantages simultaneously, including lower voltage across power switches, bidirectional power flow, low THD of output voltage, and higher input power factor. [ABSTRACT FROM AUTHOR]

A family of isolated buck–boost dc/dc converter for wide input-voltage range is proposed in this paper, and the full-bridge (FB) boost converter, being one of the typical topologies, is analyzed. Due to the existence of the resonant inductor (including the leakage inductor), the FB-boost converter can only adopt the two-edge-modulation (TEM) scheme with the FB cell being leading-edge modulated and the boost cell being trailing-edge modulated to minimize the inductor current ripple over the input-voltage range, and a phase-shift-control-scheme-based TEM with the use of the market available controller IC such as UC3895 is proposed, which realizes phase-shifted control for the FB cell to achieve zero-voltage switching. In order to improve the reliability and efficiency of the FB-boost converter, a three-mode dual-frequency control scheme is proposed, in which the FB-boost converter operates in boost, FB-boost and FB modes in low, medium and high input voltage regions, respectively, and for which the expression of the inductor current ripple is derived in this paper. As the input voltage in the FB-boost mode is close to the output voltage, the inductor current ripple in this mode is much smaller than that in the other modes, and the switching frequency of the boost cell in this mode can be lowered to one-(2N+1)th of the preset switching frequency to reduce the switching loss, and hence, to improve the efficiency. A 250–500 V input, 360 V output, and 6 kW rated power prototype is fabricated to verify the effectiveness of the design and control method. The average efficiency over the input-voltage range is 96.5%, and the highest efficiency attained is 97.2%. [ABSTRACT FROM AUTHOR]

This paper presents a single-phase power factor corrector based on a tapped-inductor buck–boost converter. This paper suggests simplified models of the power stage under current-mode control and derives small-signal transfer functions of both the current and voltage control loops. Design rules for implementation of the proposed power factor corrector (PFC) are also suggested. The proposed PFC features low dc bus voltage, arbitrary lower than the peak line voltage. The proposed PFC is suitable for applications in computers and communications, where dc isolation can be provided by the downstream dc/dc converters. Simulation and experimental results are also reported and stand in good agreement with theoretical expectations. [ABSTRACT FROM AUTHOR]

The first single-loop current sensorless control (SLCSC) for single-phase boost-type switching-mode-rectifier (SMR) had been proposed in the prior paper. SLCSC with sinusoidal input voltage possesses good performance, but its performance with distorted input voltage should be improved. In this paper, a modified SLCSC is proposed and implemented in a field-programmable gate array (FPGA)-based system to obtain better performance than SLCSC. Instead of the phase-shift signal in SLCSC, the inductor voltage amplitude signal becomes the output of proportional-plus-integral (PI)-type voltage controller in the modified SLCSC. The provided simulation and experiment results demonstrate the modified SLCSC. [ABSTRACT FROM AUTHOR]

In many modern energy conversion systems, a dc voltage, which is provided from a sustainable energy source or energy storage device, must be boosted and converted to an ac voltage with a fixed amplitude and frequency. In this paper, a switching pattern based on the concept of the conventional space-vector pulsewidth-modulated (SVPWM) technique is developed for single-stage, three-phase boost-inverters using the topology of current-source inverters. The six main switching states, and two zeros, with three switches conducting at any given instant in conventional SVPWM techniques are modified herein into three-charging states and six discharging states with only two switches conducting at any given instant. The charging states are necessary in order to boost the dc input voltage. The developed switching pattern was experimentally verified through a laboratory-scaled three-phase 500-W boost inverter and the results are presented in this paper. [ABSTRACT FROM AUTHOR]

The conventional current-source inverter has two major problems: unidirectional power flow and voltage boost operation, which make it impossible to be used in many applications, such as hybrid electric vehicles and general-purpose variable-speed motor drives. Z-source inverters (ZSIs) can solve both problems. Quasi-ZSIs (qZSIs) were recently proposed as an important improvement to traditional ZSIs. Besides the advantages inherited from ZSIs, qZSIs also have several of their own merits. This paper presents a comprehensive study on the new features of current-fed qZSI, including the advantageous buck–boost function, improved reliability, reduced passive component ratings, and unique regeneration capability. The current-fed qZSIs are bidirectional with an additional diode, unlike the voltage-fed ZSI that needs a switch to achieve bidirectional power flow. A modified space vector pulse-width-modulation method is proposed, and the available operating regions for motoring and regeneration operation are analyzed in this paper. Since the current-fed qZSI has the same operation as the current-fed ZSI, many results of this paper are also applicable to the current-fed ZSI. A reverse-blocking insulated-gate bipolar-transistor-based current-fed qZSI prototype was developed in the laboratory. Simulation and experimental results are shown to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper presents a novel closed-loop current-control strategy for a hybrid 12-pulse rectifier that uses a two-switch boost stage for output-voltage regulation. Unlike previous attempts to mitigate input-current distortion, e.g., by modulating the rectifier output voltage with open-loop control, this new closed-loop current-control scheme directly controls the line-interphase-transformer input voltage and/or impresses sinusoidal input currents. In this paper, the control strategy is explained and the modulation functions for each (\pi /6)-wide mains voltage sector are derived. The hardware implementation is described, and experimental results demonstrate that the control strategy ensures a high-quality input current for ideal as well as for distorted/unbalanced mains. [ABSTRACT FROM PUBLISHER]

This paper presents design and implementation of a 5-kW single-phase bidirectional inverter with wide inductance variation. For dc-microgrid applications, the bidirectional inverter has to fulfill grid connection and rectification with power factor correction to regulate the dc bus to a certain range of voltages. In the inverter operation, inductor current can vary from 0 to 32 A in one line cycle. This will result in wide inductance variation, around seven times for an inductor constructed with a molybdenum permalloy powder core, and thus, high current ripple and fluctuation. In this paper, we take into account this variation while designing controller and selecting key components to ensure inverter normal operation. Additionally, to adopt a cost-effective microcontroller for the inverter, the sensitivities of the control to various parameters are investigated and presented in this paper. Experimental results measured from a 5-kW single-phase prototype have verified the feasibility of the designed inverter. [ABSTRACT FROM PUBLISHER]

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]

This paper presents a new dual-switch control structure for an ac/dc noninverting cascaded buck–boost power factor correction converter. The proposed converter operates at a discontinuous capacitor voltage mode providing an inherent high-power factor and a zero voltage turn-off switching. Additionally, the proposed control structure enables for a nondistorted sinusoidal current for a wide range of output voltage levels. Unlike the conventional methods, a mode detector is not required and consequently there is no hard transition between buck and boost modes. Although both converter switches are controlled, only one feedback control loop is required to obtain the desired power flow at a unity power factor. The principle of operation, theoretical analysis, simulation, and experimental results of a 1.6-kW prototype grid-connected converter are presented. The results confirmed the validity of the proposed system under various operating conditions. [ABSTRACT FROM PUBLISHER]

Semiactive quadrupler rectifiers (SAQRs) are proposed in this paper to serve as the secondary rectification circuits, which make the secondary-side voltages to be controllable and help reduce current stress and conduction losses. An interleaved isolated boost converter is developed based on the proposed SAQRs. By utilizing the pulse-width modulation (PWM) plus phase-shift (PPS) control strategy, the primary- and secondary-side voltages are well matched to reduce the current values and circulating conduction losses. With the proposed SAQRs, the voltage gain is extended and the voltage stresses on power devices and passive components used in rectification circuits are reduced to the half of the high output voltage. Hence, the efficiency is improved by using a transformer with a smaller turns ratio and reduced parasitic parameters, and by employing low-voltage rating devices with better switching and conduction performance. With optimal design, lower voltage, and current stresses on the primary-side switches, minimized input current ripple can be realized. Moreover, the zero-voltage turn on switching of the active switches and the zero-current turn off switching of the diodes can be achieved over a wide load and voltage range by the proposed SAQR-based converter and the control strategy. Meanwhile, the higher voltage gain, the lower voltage, and the current stresses on power devices can be obtained with the proposed SAQR-based converter compared with passive quadrupler rectifier-based converter. The feasibility and effectiveness of the proposed SAQRs and the derived converter are verified by a 380-V output prototype. [ABSTRACT FROM PUBLISHER]

This paper presents a model predictive voltage control (MPVC) method for the single-inductor multiple-output (SIMO) dc–dc converter. The proposed MPVC method is able to solve the cross-regulation problem, which is a critical issue in SIMO dc–dc converters. The design of the proposed method including augmented state-space model, cost function, enumerated algorithm, and constraints for the SIMO dc–dc converter is discussed. Simulation for the influences of predict horizon NP, control horizon NC, and Lagrange multiplier $\lambda$ on the voltage ripple is conducted to guide the control parameters’ setting for hardware implementation. Steady-state operation and dynamic performance of the proposed MPVC method are conducted in simulation and experiment based on the single-inductor dual-output (SIDO) buck converter to verify the proposed MPVC method. In addition, the comparison between the proposed method and state-of-art methods for the SIMO dc–dc converters is presented. Simulation and experimental results demonstrate that the MPVC method guarantees low cross regulation for the SIMO dc–dc converter in continuous-conduction mode (CCM) and has a fast response speed to variations in load and reference. [ABSTRACT FROM PUBLISHER]

Compared with constant duty cycle-controlled discontinuous conduction mode (DCM) boost power factor (PF) correction (PFC) converter, constant duty cycle-controlled quadratic DCM–DCM boost PFC converter features with much lower second-order line frequency output voltage ripple, and however, it suffers from low PF. To increase PF of quadratic DCM–DCM boost PFC converter, a variable duty cycle control technique for quadratic DCM–DCM boost PFC converter is presented in this paper. An approximation equivalent for the variable duty cycle is employed to simplify the implementation circuit. The corresponding expressions of PF and output voltage ripple are analyzed. For input voltage range of 100–240 Vac, quadratic DCM–DCM boost PFC converter with variable duty cycle control benefits with very high PF, and tradeoff between PF and output voltage ripple of this converter is analyzed. Experimental results from 100-W prototypes are given to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

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]

A systematic method for deriving soft-switching three-port converters (TPCs), which can interface multiple energy, is proposed in this paper. Novel full-bridge (FB) TPCs featuring single-stage power conversion, reduced conduction loss, and low-voltage stress are derived. Two nonisolated bidirectional power ports and one isolated unidirectional load port are provided by integrating an interleaved bidirectional Buck/Boost converter and a bridgeless Boost rectifier via a high-frequency transformer. The switching bridges on the primary side are shared; hence, the number of active switches is reduced. Primary-side pulse width modulation and secondary-side phase shift control strategy are employed to provide two control freedoms. Voltage and power regulations over two of the three power ports are achieved. Furthermore, the current/voltage ripples on the primary-side power ports are reduced due to the interleaving operation. Zero-voltage switching and zero-current switching are realized for the active switches and diodes, respectively. A typical FB-TPC with voltage-doubler rectifier developed by the proposed method is analyzed in detail. Operation principles, control strategy, and characteristics of the FB-TPC are presented. Experiments have been carried out to demonstrate the feasibility and effectiveness of the proposed topology derivation method. [ABSTRACT FROM AUTHOR]

This paper introduces a novel power management architecture (PMA) and its on-chip implementation, designed for battery-powered portable applications. Compared to the conventional two-stage PMA, consisting of a front-end inductive converter followed by a set of point-of-load buck converters, the presented PMA has drastically improved power density. The new architecture, named multioutput switched-capacitor convertor–differential-input buck (MSC–DB) convertor, is based on a novel hybrid converter topology that combines a fixed ratio MSC and a set of DB converters, to achieve low volume and high power processing efficiency. The front-end switched-capacitor stage has a higher power density than the conventionally used inductive converters. The downstream DB converters enable tight output voltage regulation, and allow for up to four times reduction of output filter inductors without the need for increasing switching frequency, hence limiting switching losses and improving the efficiency of the system. Furthermore, the new PMA is able to balance the state-of-charge of the input battery cells, a feature not existing in conventional systems. The PMA architecture is implemented both as a discrete prototype and as an application-specific integrated circuit (IC) module. The on-chip implemented architecture is fabricated in a standard 0.13-μm CMOS process and operates at 9.3-MHz switching frequency. Experimental comparisons with a conventional two-cell battery input architecture, providing 15 W of total power in three different voltage outputs, demonstrate up to two times reduction in the inductances of the downstream converter stages and more than two times reduction in losses, equivalent to the improvement of the power processing efficiency of a 12%. Moreover, the fabricated IC module is copackaged with low-profile thin-film inductors to demonstrate the effectiveness of the introduced architecture in reducing the volume of PMAs for portable applications. [ABSTRACT FROM AUTHOR]

Parabolic current control is an attractive current control method with fast transient response and constant switching frequency. Due to the good dynamics of the parabolic current control, it can be employed in voltage source inverters to improve the system performance such as minimizing the distortion of current waveforms or voltage waveforms. To implement the parabolic current control, a current sensor is required, associated with the current conditioning circuit and parabolic carrier generators. Since the parabolic current control is based on the real-time information of the inductor current, any phase delay or propagation delay of the sensor itself and the conditioning circuitry, or limited resolution of parabolic carrier generators, could impact the current control performance. Since the parabolic current control compares analog signals to generate the required control signals, noise from the control board impacts the control precision as well. This paper will explore solutions to these problems. First, the inductor current of the voltage source inverter is analyzed and the parabolic current control strategy is studied, then a sensorless parabolic current control method is proposed. The new sensorless parabolic control method utilizes a current emulator to rebuild the inductor current on a microcontroller. To avoid a dc offset on the ac-side output voltage caused by the current emulator, an additional control loop in the current emulator is added. The effectiveness of the proposed methods is experimentally verified by the use of an H-bridge voltage source inverter. [ABSTRACT FROM AUTHOR]

This paper proposes a power-factor-corrected canonical switching cell (CSC) converter-based switched-mode power supply for arc-welding applications. In the proposed arc-welding power supply (AWPS), CSC converter operating in discontinuous inductor current mode (DICM) is used to attain inherent power factor correction. The DICM operation substantially reduces the complexity of the control and effectively regulates the dc-link voltage. At the back end, a pulsewidth-modulated (PWM) isolated full bridge dc–dc converter is used to provide a high-frequency isolation, which is mandatory for the arc-welding process. A dual-loop control scheme is utilized to incorporate overcurrent protection and to regulate dc voltage at the output making it suitable for arc-welding applications. Test results are presented to confirm the viability of the proposed AWPS. The performance of the proposed AWPS is evaluated on the basis of total harmonic distortion (THD) of the supply current, power factor, dynamic response, and voltage regulation to prove its effectiveness. [ABSTRACT FROM PUBLISHER]

For interleaved boost-type converters, both functions of voltage regulation and current balance are important. In this paper, the decoupled current-balancing control (DCBC) with two parallel loops is proposed. At first, the small-signal transfer functions of the voltage-regulation loop and the current balancing loop to the controller output are derived. The results show that the voltage-regulation loop and the proposed current-balancing loop are nominally decoupled. That is, two PI-type controllers can be designed independently and included to implement the proposed DCBC. Additionally, the single-sensor sampling-current strategy is proposed to obtain two average inductor currents by sensing only the sum of diode currents. All the controllers are implemented in field-programmable gate array (FPGA). The provided simulation and experimental results demonstrate the proposed DCBC. [ABSTRACT FROM PUBLISHER]

It is known that the ripple-based control of a switching dc–dc converter benefits from a faster transient response than a conventional pulse width modulation (PWM) control switching dc–dc converter. However, ripple-based control switching dc–dc converters may suffer from fast-scale oscillation. In order to achieve fast transient response and ensure the stable operation of a switching dc–dc converter over a wide load range, based on a conventional pulse train (PT) control technique, a peak capacitor current PT (PCC-PT) control technique is proposed in this paper. With a buck converter as an example, the operating modes, steady-state performance, and transient respond performance of a PCC-PT controlled buck converter are presented and assessed. To eliminate fast-scale oscillation, circuit and control parameter design considerations are given. An accurate discrete iteration model of a PCC-PT controlled buck converter is established, based on which the effects of circuit parameters on the stability of the converter operating in a discontinuous current mode (DCM), mixed DCM-continuous conduction mode (CCM), and CCM are studied. Simulation and experimental results are presented to verify the analysis results. [ABSTRACT FROM PUBLISHER]

In this paper, a novel grid-connected high step-up inverter is proposed. The topology is composed of two stages. The first stage is a single-switch high step-up dc–dc converter with bipolar outputs, and the second stage is a conventional half-bridge dc–ac grid-connected inverter. Negative grounding of the photovoltaic (PV) module has resulted in elimination of unwanted ground leakage currents in the PV system. Simple structure, employing few semiconductor switches, simple control, and high efficiency are the features of the proposed topology. Theoretical analysis and principal operation of the circuit are discussed. An experimental prototype is implemented to verify the performance of the proposed inverter. The experimental results confirm the aforementioned features and the theoretical analysis of the converter operation. [ABSTRACT FROM PUBLISHER]

A three-phase single-switch discontinuous conduction mode (DCM) boost power factor correction (PFC) converter features zero-current turn on for the switch, no reverse recovery in the diode, a constant-switching-frequency operation, a simple control, and a low cost, which are suitable for low-to-medium-power and cost-sensitive applications. Due to the DCM, the energy transfer does not cover the whole switching cycle, the rms and peak values of the inductor current are large, and those of the switch and the diode are also large. This increases not only the current stress of the power components but also the conduction and switching turn-off losses, which lower the efficiency of the converter. An optimum utilization control of switching cycles is proposed in this paper to increase the critical boost inductance. The rms and peak current values of the main power components are reduced, and the conduction and switching turn-off losses are therefore decreased, leading to higher efficiency. The proposed method also slightly achieves an output voltage ripple reduction, and the input current harmonics comply with the standard of the International Electrotechnical Commission 61000-3-2 Class A. [ABSTRACT FROM AUTHOR]

Carrier-based pulsewidth-modulation (CBPWM) techniques are popular due to their simplicity, and have been widely researched for various three-phase inverter configurations. In this paper, two CBPWM techniques are proposed to reduce the common-mode (CM) voltage generated by the five-phase inverter. The five-phase inverters have more flexibility in reducing the CM voltage than their three-phase counterparts because they have more phase legs, hence finer control over the star-point voltage of the load. Two methods are proposed for the conventional two-level five-phase inverter to reduce the CM voltage; one utilizing adjacent modulating waveforms and the other utilizing nonadjacent modulating waveforms. The coupled inductor inverter (CII) uses coupled inductors to generate multilevel outputs. As the volt-second balance must be maintained across each coupled inductor, direct application of the proposed methods on the CII inverter will result in overcurrents in the coupled inductors. Hence, the proposed methods are further improved to ensure the volt-second integral over each switching period is zero. Moreover, the two proposed methods are designed to reduce switching events and prevent unexpected states occurring during the switching transitions. The performance and the switching strategy of both methods are verified by both simulations and experiments on a prototype of five-phase CII. [ABSTRACT FROM AUTHOR]

For discontinuous conduction mode (DCM) dc–dc converters with digital sensorless current mode (DSCM) control, an observed current error occurs, owing to a low-accuracy current observer. Moreover, a reference current error occurs due to a low-accuracy current controller or a finite dc gain of current loop. Conventionally, the observed current is compensated to increase current regulation accuracy, whereas the reference current error is neglected. However, for charge balance principle (CBP)-based DSCM (CBP-DSCM) control, this paper proves that the reference current should be compensated in a same quantity to that of observed current. Otherwise, single or unequal compensation leads to output voltage steady-state error. For this reason, a dual current error compensation strategy for CBP-DSCM control is proposed. It compensates the errors in a same quantity through a current error observer, which considers parasitics and calculates the current errors without approximation. To verify the proposed strategy, small-signal models with parasitics for both the converter and the controller are constructed by differential functions of key variables. Furthermore, converter stability is analyzed at typical operation condition, while the stability at various operation conditions is verified through robustness analysis. Finally, simulations and experimental results verify the analysis and the improved transient response of the converter. [ABSTRACT FROM AUTHOR]

This paper introduces the application of a switched-diode-capacitor voltage accumulator (SDCVA) on conventional boost converter. This study aims to obtain two different kinds of multi-input step-up converters with high voltage gains, low component stresses, low ripples, simple control, and high conversion efficiencies: one is based on the parallel SDCVA and the other based on the serial SDCVA. The double-input step-up converter based on the parallel SDCVA and the double-input step-up converter based on the serial SDCVA are, respectively, taken as an example to do theoretical analysis, including operating principles and performance analyses when they work individually and simultaneously. The two proposed converters are implemented with a voltage closed-loop control at the switching frequency of 30 kHz. Experimental results obtained from the implemented prototypes are provided to validate the feasibility and effectiveness of the proposed converters. [ABSTRACT FROM AUTHOR]

In this paper, a high step-down bidirectional converter, utilizing one coupled inductor and two energy-transferring capacitors, is presented. In the step-down mode, the capacitor is connected between input voltage and coupled inductor, which plays a role to step down the input voltage. Therefore, the corresponding voltage conversion ratio is much lower than that of the traditional buck converter and also can be lower than that of the tapped-inductor buck converter. Moreover, the output voltage varies with the duty cycle linearly, making control easier. In the step-up mode, one capacitor is first charged by the coupled inductor, and then releases the energy along with the coupled inductor and the other capacitor connected in series. Therefore, a higher voltage gain can be obtained. Furthermore, the leakage inductance energy can be recycled. Therefore, the switching losses can be reduced and the efficiency can be improved. In this study, the operating principles and experimental results are provided to verify the effectiveness and performance of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, it is shown that in the three-phase six-switch boost power factor correction rectifier with average-current control with mismatched input-voltage and input-current sensing gains as well as offset errors in input-voltage and input-current sensing, the current controller with proportional (P) compensation exhibits lower total harmonic distortion (THD) and higher power factor compared with that of proportional and integral compensation. It is also shown that P compensation with input-voltage feedforward is effective in improving output-voltage transient response with respect to input-voltage changes only if duty-cycle feedforward is also implemented. Finally, it is shown that zero-sequence-signal injection, in addition to enabling the output-voltage regulation in a wider input-voltage range, also improves the THD of the input currents. [ABSTRACT FROM AUTHOR]

This paper proposes a novel 3 $\phi$ stand-alone solar photovoltaic (PV) system configuration that uses high-gain high-efficiency $(\approx\! 96\%)$ dc–dc converters both in the forward power stage and the bidirectional battery interface. The high-voltage-gain converters enable the use of low-voltage PV and battery sources. This results in minimization of partial shading and parasitic capacitance effects on the PV source. Series connection of a large number of battery modules is obviated, preventing the overcharging and deep discharging issues that reduce the battery life. In addition, the proposed configuration facilitates “required power tracking (RPT)” of the PV source as per the load requirements, eliminating the use of expensive and “difficult to manage” dump loads. High-performance inverter operation is achieved through $abc$ to $dq$ reference frame transformation, which helps in generating precise information about the load's active power component for RPT, regulation of ac output voltage, and minimization of control complexity. Inverter output voltage is regulated by controlling the modulation index of sinusoidal pulsewidth modulation, resulting in a stable and reliable system operation. The active power demand is controlled by regulating the dc link voltage. All the analytical, simulation, and experimental results of this work are presented. [ABSTRACT FROM PUBLISHER]

This paper presents high step-up dc-to-dc converter for low voltage sources such as solar photovoltaics, fuel cells, and battery banks. To achieve high voltage gain without large duty cycle operation, combination of coupled inductor and switched capacitor voltage doubler cells are used. By incorporating active clamp circuit, voltage spike due to the leakage inductance of the coupled inductor is alleviated and zero-voltage switching turn on of the main and auxiliary switch is obtained. Due to the use of MOSFETs of low voltage rating and soft turn on of the switches, conduction loss and switching losses are reduced. This improves the efficiency and power density of the converter. The proposed converter can achieve high voltage gain with reduced voltage stress on MOSFET switches and output diodes. Design and analysis of the proposed converter is carried out, and finally, a 500-W experimental prototype is built to verify theoretical analysis. [ABSTRACT FROM PUBLISHER]

In this paper, the two-input buck converter is proposed as the dc/dc stage for photovoltaic (PV) cascaded converters. This converter is attractive for this application because it is cost effective and reliable and can achieve dual maximum power point tracking (MPPT) with only one power transistor. However, due to the simplified and integrated structure, the nonlinear characteristics of the converter and the two PV arrays complicate the control. By means of a small-signal modeling, the control theme of the two PV voltages is formulated, and the effect of the nonlinearities is presented. It is shown that, while fast voltage dynamics are achieved for the first input, the second-input voltage response depends on the second-stage converter control. Simulation and experimental results are reported to validate the theoretical analysis, showing the dual MPPT capability. [ABSTRACT FROM PUBLISHER]

The three-level boost power factor correction (PFC) converter has advantages of lower inductor current ripple and lower switch withstanding voltage compared with the boost PFC converter. Interleaved pulsewidth modulation had been used in the multiphase boost PFC converter. In the literature, interleaved current sensorless control (ICSC) for the multiphase boost PFC converters had been proposed. In this paper, the behavior of the three-level boost PFC converter is first analyzed. The results show that three-level converter has the same average equation as the interleaved boost PFC converter. Then, ICSC is modified for the three-level boost PFC converter with considering the voltage imbalance and the zero-crossing current distortion. The proposed modified ICSC (MICSC) is implemented in a field-programmable gate array board. Simulation results and experimental results are also provided to validate the proposed MICSC. [ABSTRACT FROM PUBLISHER]

The discontinuous current mode boost power factor (PF) correction converter features a zero-current turn-on for the switch, no reverse recovery in diode, and constant frequency operations. However, when the duty cycle is constant in a line cycle, the input current contains rich third harmonic which has a phase difference of π with respect to the fundamental component. The harmonic results in not only a lower PF but also larger peak and RMS current values of the main power components, which lead to a higher conduction and switching turn-off loss. In this paper, a variable duty cycle control scheme is proposed to make the input current contain only third harmonic which is in phase with fundamental component, while remaining the same PF at a certain input voltage as that of constant duty cycle control. A method of fitting the duty cycle is further proposed for simplifying the circuit implementation. The efficiency is improved as the critical inductance increases and the peak and RMS current values consequently decrease. The proposed method also achieves an output voltage ripple or the output storage capacitance reduction. The experimental results from a prototype of 120 W are given to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Multiple-output Switched Mode Power Supplies (SMPSs) for personal computers (PCs) normally depict extremely bad power quality indices at the utility interface such as total harmonic distortion of the input current being more than 80%, power factor being lower than 0.5 and output voltage regulation being very poor. They violate the limits of harmonic emissions set by international power quality standards. In this paper, a nonisolated power factor corrected (PFC) converter is being proposed to be used at the front end to improve the power quality of an SMPS for a PC. The front-end converter is able to reduce the 100-Hz ripple in its output that is being fed to the second stage isolated converter. The performance of the front-end Zeta converter is evaluated in three different operating conditions to select the best operating condition for the proposed SMPS system. The performance of the proposed SMPS is simulated and a laboratory prototype is developed to validate its performance. Test results are found to be in line with the simulated performance under varying input voltages and loading conditions and all the results demonstrate its enhanced performance. [ABSTRACT FROM PUBLISHER]

A modeling approach is presented that calculates an accurate open-loop transfer characteristic for a boost converter that employ peak current-mode control (PCMC). Many techniques exist for modeling a PCMC-based boost converter; however, all these techniques focus on purely resistive loads and are not always accurate for a purely capacitive load. In this paper, a new modeling technique is presented, which is simple and gives accurate results for both capacitive and resistive loads. Furthermore, the useful expressions for dc gain and pole locations of a boost converter operating in continuous-conduction mode with PCMC are derived and compare well to simulations and measurements. [ABSTRACT FROM AUTHOR]

Recently, the various types of the half-bridge (HB) converters with the output inductor have been developed, and they exhibit a good performance in medium power applications such as the server power supplies and personal computer power supplies requiring high output current. However, they have common problems such as the primary and secondary switch turn-off losses and snubber loss in the secondary side caused by the output inductor, which degrades light load efficiency. To relieve these limitations of the conventional HB converters, a new HB converter, which employs one additional switch and capacitor in the secondary side, is proposed for a high efficiency under light load conditions in this paper. Since the proposed converter operates like the HB LLC converter with below operation by turning on additional switch under light load conditions, the switch turn-off losses and snubber loss can be minimized, and the zero-voltage switching (ZVS) capability can be improved. Consequently, the proposed converter can achieve a high efficiency under light load conditions. To confirm the operation, features, and validity of the proposed converter, a 330–400 V input and 12 V/300 W output laboratory prototype is built and tested. [ABSTRACT FROM AUTHOR]

This paper introduces the adaptive slope compensation method into the digital clamping current control at various input voltages to improve the power factor (PF) and the total harmonic distortion (THD) of the universal input. The controller conducts a phase-management mechanism for various input voltages and load conditions to raise the circuit conversion efficiency. The optimal switching timing for one- and two-phase operations can be determined from the power loss distribution. A digital signal processor chip TMS320F28035 is used to implement the digital platform. A 300-W laboratory prototype with a universal line voltage 80-V dc output voltage is designed and tested to verify the feasibility. The values of efficiency from light load (10% of rated power) to full load at 115- and 230-V inputs are greater than 95%. PF values from medium to full load are greater than 0.94. Input current harmonics also meet the norm of IEC 61000-3-2 Class D. [ABSTRACT FROM PUBLISHER]