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This letter addresses the problem of steering a robotic vehicle along a geometric path specified with respect to a reference frame moving in three dimensions, termed the Moving Path Following (MPF) motion control problem. The MPF problem is solved for a large class of robotic vehicles that require a minimum positive forward speed to operate. This restriction poses additional challenges with respect to the control design, and is developed using geometric concepts, wherein the attitude control problem is formulated on the Special Orthogonal group SO(3). To this end, a MPF error model formulation is first derived that allows to exclude the conservative constraints on the initial position of the vehicle with respect to the reference path by enabling the explicit control of the progression of a virtual point moving along the reference path. The task of the MPF control law is then to steer the vehicle towards the moving path and to converge to the virtual point. Stability and convergence guarantees of the resulting closed-loop system are provided using the Input-to-State Stability concept. In particular, we show that the proposed controller is robust to imperfect tracking errors and external disturbances (e.g., autopilot errors and wind gusts). Simulation results are presented to illustrate the efficacy of the proposed MPF control law.

A precise, curvature-based, average modeling technique for switched-capacitor (SC) dc–dc converters is proposed. The generalized modeling technique provides a comprehensive characterization of the converter at steady-state, across the full range of practical operating conditions. An expression for the equivalent output impedance is obtained, which relates the slow- and fast-switching limit impedances to the total output impedance. This expression can be used to accurately compute the output voltage without deriving the converter’s state equations and precisely weighs the contribution of each floating capacitor and parasitic resistance on the output impedance. The modeling technique is applied to a unity-gain SC converter, a multiphase binary converter, and a nonsymmetrical parallel–series converter, and the results are compared with existing steady-state models. The accuracy of the model is validated through simulations and experimental measurements.

Light load efficiency and output voltage regulation of a low- $Q$ LLC resonant converter is a critical problem for wide input voltage and load range applications. Parasitic capacitances such as rectifier diode junction capacitance ( $C_j$ ) degrade the soft switching performance. Compact size, high density, and high transformer turns-ratio requirements for microinverter applications add significant distributed capacitance ( $C_d$ ) of the low-profile transformer, worsening the output regulation and zero-voltage-switching (ZVS) capability at light loads. Wide switching frequency requirement for regulation at light loads, which increases core losses and turn- off switching losses in power MOSFETs, further degrades the power conversion efficiency. The conventional phase-shift modulation causes a high circulating current and loss of ZVS at light loads. Therefore, a hybrid adjustable switching-frequency-duty-cycle modulation technique for improving the light load efficiency is proposed and analyzed for a full-bridge $LLC$ resonant converter. Accurate loss analysis for the proposed modulation scheme, including the effect of parasitic capacitances, is performed using time-domain equations. The proposed methodology precalculates the optimal duty cycle at light load conditions for the required input voltage range such that minimum power losses are incurred. Variation in switching frequency at the preselected duty-cycle value regulates the output voltage. ZVS over a wide range of operating conditions is observed. An experimental prototype for a 20–40 V input, 380-V/300-W output $LLC$ converter is tested for the validation of theoretical analysis.

A comprehensive framework for the analysis and design of multiphase, reconfigurable switched-capacitor (SC) dc–dc converters is presented. A generalized method, utilizing graph theory and network analysis, is first proposed, which enumerates all attainable ideal conversion ratios for a given SC converter structure. From this analysis, the performance limits of multiphase SC converters are expanded, and a reconfigurable, multiphase SC dc–dc converter is proposed. The converter utilizes a programmable and optimized switching configuration that can generate an increased number of attainable ideal conversion ratios for the given number of capacitors and switching states. This property allows the converter to maintain high efficiency across a wide range of operating conditions and achieve very high step-up and step-down conversion ratios. A set of sample switching sequences are provided to generate any attainable ideal conversion ratio, for up to four capacitors, using a minimal number of switching states. An experimental prototype of the converter has been designed and fabricated as an integrated circuit using 0.35- $\mu \text{m}$ CMOS technology to validate the performance.

Three-phase resonant converters are preferred for high power applications as they provide several advantages such as reduced component stress, small filter size requirement, and high power density. The analysis of these converters is generally performed in frequency-domain using a single-phase equivalent circuit which provides approximate results and may lead to the erroneous design of the converter. This paper presents a time-domain modeling technique for the analysis of a low Q three-phase series resonant converter operating under asymmetric pulse width and variable frequency modulation. This method can also be applied to analyze converters with different resonant tank and transformer configurations without compromising accuracy.

Although compact fluorescent lamps (CFLs) have been in the market for a long time, many of them do not achieve the same power factor as the incandescent lamps do, which appears to be a significant problem for the utility with the current widespread use of CFLs for household lightings. A single-stage single-switch electronic ballast with active power factor correction is presented in this study for CFL applications. Unlike other single-switch ballast circuits, the presented integrated dual-boost converter circuit can produce a symmetric bipolar square-wave voltage, thus generating a near-pure high-frequency sinusoidal voltage on the lamp, which is beneficial to the CFL lifetime. Moreover, its soft-switching variant can achieve the ZVZC turn-on and ZV turn-off for the MOSFET to improve the conversion efficiency. Detailed operating principles and circuit analysis of the proposed circuit have been provided in this study. Simulation and experimental results on a prototype of a 15 W CFL validate the theoretical analysis and highlight the merits of the presented work.

The present work introduces a frequency domain analysis of an improved asymmetrical pulse-width modulation (I-APWM) scheme for dc-dc resonant converters. By adjusting both switching frequency and duty cycle, the improved APWM scheme has been shown to extend zero voltage switching (ZVS) range at light load conditions. However, the existing time-interval analysis proposed by authors results in non-linear transcendental ZVS conditions which are resource intensive to implement on a digital microprocessor. The proposed frequency analysis uses the Fourier series to establish simple analytical solutions that determine both switching frequency and duty cycle for ZVS operation. Necessary ZVS conditions have been established for a dc-dc LLC resonant converter using the derived analytical equations. Theoretical analysis is verified by an experimental prototype of a 300W/400V dc-dc LLC resonant converter operating over an input voltage range of 25-40V.

Light load efficiency and output regulation of LLC resonant converter is a critical problem for wide input voltage and load range applications due to converter’s parasitic capacitances such as rectifier diode junction capacitance (C j ). Compact size, high density and high transformer turns-ratio requirements for micro-inverter applications adds significant distributed capacitance (C d ) of low-profile transformer, worsening output regulation and zero- voltage switching (ZVS) capability at light loads. Magnetic core losses and turn-off switching losses in power MOSFETs further degrade power conversion efficiency at light loads. Therefore, an improved loss analysis for a hybrid modulation technique is proposed for full-bridge LLC resonant converter. The proposed methodology calculates duty cycle offline such that minimum power losses are incurred at different light loading condition. Variation in switching frequency at selected duty cycle value regulates output voltage. Time domain analysis of proposed technique including effects of C d and C j is performed to ensure accurate loss calculation. An experimental prototype for 20-40V input, 380V/300W output LLC converter is tested for validation of theoretical analysis.

This paper analyzes the problem of instability in enhancement-mode gallium nitride (GaN) transistors based half-bridge circuits. The instability may cause sustained oscillation, resulting in overvoltage, excessive electromagnetic interference (EMI), and even device breakdown. GaN devices operate in the saturation region when they conduct reversely during the dead time. Under the influence of parasitic parameters, the GaN-based half-bridge circuit exhibits positive feedback under certain conditions, thus, resulting in sustained oscillation. A small-signal model is proposed to study this positive feedback phenomenon. Like the second-order under-damped system, damping ratio is defined to determine the system's stability. Based on the model, the influence of circuit parameters on instability is investigated and guidelines to suppress the oscillation are given. Reducing the common-source inductance, increasing the gate resistance of the inactive switch or connecting a diode in parallel to the inactive switch are some effective ways to suppress the oscillation. Finally, the analyses are verified by both simulation and experiment.

A precise curvature-based, averaged modelling technique for two-phase switched-capacitor (SC) DC-DC converters is proposed. The generalized technique provides a complete characterization of the converter at steady-state for all operating conditions. From this model, a simple expression for the output impedance is obtained which relates the slow-switching limit and fast-switching limit impedances to the total output impedance. This expression can be used to accurately compute the output voltage without deriving the converter’s state equations. The modeling technique is applied on a 1:1 SC converter topology and compared with existing steady-state models. The accuracy of the model is validated through simulations and experimental measurements.

This paper presents a novel series–parallel current-driven (SPCD) full-bridge dc/dc converter, which is able to process and deliver power efficiently over a wide range of load variations. In order to guarantee reliable operation of high-frequency dc/dc converters, the converter should be able to sustain soft switching for a wide range of operating conditions. The SPCD full-bridge converter, proposed in this paper, is able to offer soft switching for the input power semiconductors and smooth commutations for the output diodes. Also, the particular structure of the proposed converter eliminates the need for extra auxiliary circuits to provide reactive current for soft switching at light loads. The proposed topology can fully eliminate voltage spikes across the output diodes by providing smooth and lossless commutations for the output diodes. Thus, the proposed converter can be an efficient and reliable solution for variety of applications with a high switching frequency and a high output voltage. The SPCD full-bridge converter has the ability to integrate all magnetic components into an integrated transformer in order to achieve a high power density. The integrated transformer is thoroughly analyzed using ANSYS high-frequency structure simulator. Simulation and experimental results confirm the superior performance of the proposed SPCD full-bridge dc/dc converter.

The search for a cost feasible, optimal design of LLC converter for wide input voltage range conditions is inhibited by errors in steady state values of peak gain, tank current, tank voltage, active power etc., due to various approximations in the analysis. This leads to erroneous selection of circuit parameters. The present work provides an exact, approximation free time domain mathematical model of LLC converter operating in transformer secondary current discontinuous mode (DCM) below resonance in boost mode. The proposed approach defines voltage gain as a function of relative switching frequency $\omega$ and t d , which represents the rectifier diode to switch conduction ratio for DCM operation. Existing works have defined voltage gain as an explicit function of quality factor (Q) and $\omega$ . The current approach leads to accurate derivation of converter voltage gain, tank RMS current, tank capacitor voltage, zero voltage switching (ZVS) angle etc. Analytical expressions are validated with simulation studies using PSIM for various inductor ratio values. A final design is verified on an experimental prototype of 320W output LLC converter designed for an input range of 20–40V for solar PV applications.

Voltage balancers have been extensively employed in hybrid microgrids in order to maintain the feeder DC voltage. The closed-loop control system needs the voltage across the output capacitor and the current through the output inductor to be measured. In this paper, a current sensorless control scheme is proposed for controlling the voltage balancer. First, the state-space equations of the system are derived. Then, using the derived equations, the state variables of the system are estimated using an observer. The proposed observer eliminates the need for the current sensor required in the closed-loop control system. Simulation results and experimental results verify the feasibility of the proposed sensorless control technique.

A variable-gain, multiphase switched-capacitor DC-DC converter is proposed and implemented as an integrated circuit. The converter utilizes an optimized switching configuration that maximizes the number of attainable ideal conversion ratios for the given number of capacitors, according to the generalized Fibonacci number. This property allows the converter to maintain high efficiency across a wide range of operating conditions. A set of sample switching sequences are provided to generate any attainable ideal conversion ratio, for up to four capacitors. An experimental prototype of the converter is designed and fabricated using $0.35 \ \mathbf{\mu} \mathbf{m}$ CMOS technology to validate the performance.

A novel high gain current-driven DC-DC converter topology is proposed in this paper. This circuit is aimed for applications which require wide input and output voltage ranges, such as PV micro-inverters, electric vehicle battery chargers etc. As compared to the resonant converters, the size of inductor can be reduced by an order of magnitude and resonant capacitors eliminated, by the use of current-driven topology. These advantages result in increased power density and higher power conversion efficiency of the converter. A major limitation of the current-driven topology is that it can provide a maximum gain of just over unity. Further, this value of maximum gain also depends on the parasitic capacitances of the converter components. These issues make the converter operation more susceptible to component parasitics (such as the transformer inter-turn capacitance), resulting in degraded converter performance. The high-gain current-driven topology, presented in this paper overcomes the disadvantages of the conventional current-driven converter topology, by the introduction of a parallel capacitor at the high voltage side of the transformer winding. Introduction of parallel capacitor provides a two-fold advantage to the conventional current-driven topology. First it makes the effect of parasitic capacitor small so that the control system is not much sensitive to it, and it provides a high gain due to pre-charging of the network inductances at the beginning of each switching cycle. Simulation and experimental results validate the viability of proposed converter topology for applications requiring wide range of input and output voltages.

In recent years, wireless power transfer technology has come to limelight because of its possibility of providing viable solutions to the challenges encountered by electronic device consumers when using traditional methods of charging batteries. This paper presents a multiple receiver wireless power transfer system for charging mobile phone batteries. The circuit consists of a transmitter and two receiver systems. A mathematical analysis of the circuit is carried out and simulated to understand its behavior with variation in coupling coefficient and load. In order to charge mobile phones without an extra communication module over a wide range of coupling coefficients, a variable frequency control algorithm is used. The transmitter circuit uses the algorithm to track the maximum input power of the system. The output voltage of the receiver circuit is controlled to meet the power requirement of the load as coupling coefficient varies by using a switch capacitor modeled as two back to back connected MOSFETs with their drain-to-source capacitance. The proposed converter circuit topology is simulated and the results are presented. The circuit operates over a wide range of coupling coefficient and the power requirement of the mobile phones are met without using an extra communication module. The resonance frequency of the circuit is 5.7MHZ and it is design to deliver 10W (5V, 2A) each to two mobile phones.

Energy-efficient residential lighting such as household light-emitting diode (LED) lamps with ac input require an ac/dc converter (or driver) with large output capacitance to minimize the low frequency LED current ripple. The energy storage capacitor used in the conventional ac/dc LED driver is usually an electrolytic capacitor due to its low cost and high energy density. However, the average lifetime of an electrolytic capacitor is at least 2–3 times less than that of an LED device. Hence, the potential lifetime of the LED lamp is significantly affected by the presence of the electrolytic capacitor in the driver circuit. In this paper, two novel isolated single-switch ac/dc high power factor LED drivers without using any electrolytic capacitors are proposed. In the proposed circuits, the energy storage capacitor is moved to the rectifier side, with a three-winding transformer used to provide isolation; input power factor correction as well as to store and provide the required energy to the output. As a result, the energy storage capacitance is significantly reduced, which allows film capacitor to be used to replace the conventionally used electrolytic capacitors. The circuit’s operating principles and its characteristics are described in this paper. Simulation and experimental results are given on a 120 $\text{V}_{\rm rms}$ , 12 W prototype to confirm that a power factor of at least 0.96 is achieved.

This paper presents a description and analysis of a full-bridge converter with a novel passive and robust auxiliary circuit for zero-voltage-switching (ZVS) operation. A generalized time-domain state-space analysis is provided to describe the steady-state behavior of the auxiliary circuit. Complete comparison between the well-known single-inductor auxiliary circuit, and the proposed one is presented. For a similar peak current in the auxiliary branch, needed for ZVS, a minimum of 20% reduction in rms current is achieved to decrease the conduction losses in the power switches and in the auxiliary circuit. Also, 65% reduction in switching frequency variation is obtained. This narrower frequency range reduces the need for very high-frequency operation and the associated gate driver losses as well as the difficulty of electromagnetic interference (EMI) filter design. All the theoretical results are experimentally verified.

The use of multiple heterogeneous, low-cost, small Unmanned Aerial Vehicles (UAVs) as a tool in several application domains is becoming increasingly important. One critical aspect to enable the use of such vehicles is the coordination/planning system, whose task complexity increases with the number of vehicles and the communications constraints that arise due to their small size and large distances. In this work, we propose a control architecture for a platoon of relay UAVs that are independent of the coordination system. The platoon task consists in interconnecting the communication link between the possibly mobile command station and a UAV in a mission. The relays are actively driven to deploy, create a network and maintain a desired Quality-of-Service (QoS) level, defined in this paper. We present an architecture that is composed by a waypoint generator based on the network QoS and a Time Coordinated Path Following (TCPF) controller with a method to reduce the frequency of information exchange between the relay UAVs, through the use of a self-triggered control strategy. Exploiting this architecture, it is possible to plan a mission operation for a UAV without the need of considering vehicle-to-command-station communication constraints that will be satisfied by the introduction of the relay-UAVs platoon. Simulation results are provided to illustrate the efficacy of the developed strategy. The self-triggered approach results in significant reduction of information exchange between the relay UAVs, while maintaining the user desired network QoS.

In this paper, a fully ZVT auxiliary cell for boost type resonant converters is proposed to achieve soft switching in ON-OFF control mode. In conventional ON-OFF methods, transient and switching losses at the beginning and end of each power pulse decrease the overall efficiency of the system at high modulation frequencies. This ZVT cell offers zero voltage switching without imposing extra resonant current. This structure can be implemented in most boost type resonant converters such as class E, ϕ 2 and quasi-resonant DC-DC converters. The fully ZVS operation, the absence of inductive components, and low voltage and current stress are main advantages of this cell. Thus, the ON-OFF control can be implemented at higher modulation frequencies without any significant drop in the efficiency. Simple structure and timing are other advantages of the proposed cell, which makes it useful for solar applications. The operation of the proposed auxiliary cell is analyzed in individual intervals. To verify the mathematical analysis, the proposed cell is implemented in a 3 MHz quasi-resonant boost converter. A maximum efficiency of 95.8% is obtained at 385 watts output and the efficiency drops about two percent at 80 watts at 500 kHz modulation frequency.

Multilevel inverters as the best existing solution for high power/ medium voltage applications have been utilized to incorporate renewable energy sources into electric grid. Solar energy, and fuel-cells as two major sources of power can only provide unidirectional power flow. However, utilizing cascaded H-bridge inverters or other inverters with trinary voltage ratios at the input DC links might cause regeneration phenomenon which results in bidirectional power flow. This paper provides a solution to prevent regenerative current from DC link of multilevel inverters using predictive current control. The controller can simultaneously control the DC-link capacitor voltages and the AC side current by regulating the DC link current. Simulations and experiments have been carried out to prove the validity and performance operation of the proposed method.

This paper presents a boost switched-capacitor nine-level single-phase inverter, which utilizes flying capacitors and an H-bridge. Besides the boosting ability, the inverter is capable of producing redundant switching states that are used as a degree of freedom in controlling the voltage of DC link capacitor. A comprehensive study of the theoretical aspects of the proposed structure and its practical considerations have been conducted. The performance of the inverter has been evaluated using simulation and experimental results.

With the global concerns on the issue of how to conserve the limited energy resources, compact fluorescent lamps (CFLs) have been forced in a lot of countries to replace the power-hungry incandescent lamps to reduce the energy cost. However, conventional passive power factor corrected electronic ballasts used in CFLs suffer two major drawbacks: 1) they are unable to achieve close-to-unity power factor and 2) they are unable to provide the same amount of light intensity under fluctuating line voltage. This paper proposed a simple lamp power regulation method for a very high-power factor single-switch electronic ballast, which allows the electronic ballast to maintain almost constant lamp power at its full-power condition for a wide range of the input voltage by controlling the dc-link voltage of the ballast power circuit through duty ratio control. When a TRIAC phase-cut dimmer is used to dim the CFL, the dc-link voltage regulation control loop is deactivated; so that the lamp power decreases accordingly during dimming. The analysis and operating principles of the controller are discussed in this paper. MATLAB, PSIM simulation, and experimental results are provided to highlight the merits of the proposed work.

Although compact fluorescent lamps (CFLs) have been on the market for a long time, many of them do not achieve the same power factor as the incandescent lamps do, which presents a significant problem for the utility with the current widespread use of CFLs for household lightings. A simple single-switch electronic ballast with passive valley-fill power factor correction is proposed in this paper for CFL application. The proposed single-switch ballast circuit is able to achieve zero current switching to maximize the circuit efficiency. A simple feedback circuit with duty ratio control is also proposed to improve the high lamp current crest factor caused by the valley-fill circuit. Detailed descriptions and analysis of the circuit operating principles are provided in this paper. Simulation and experimental results are given on a 13-W CFL tube from Osram Sylvania to highlight the merits of the proposed work.

This paper presents a novel zero-voltage switching (ZVS) approach to a grid-connected single-stage flyback inverter. The soft-switching of the primary switch is achieved by allowing negative current from the grid side through bidirectional switches placed on the secondary side of the transformer. Basically, the negative current discharges the metal-oxide-semiconductor field-effect transistor's output capacitor, thereby allowing turn on of the primary switch under zero voltage. To optimize the amount of reactive current required to achieve ZVS, a variable-frequency control scheme is implemented over the line cycle. In addition, the bidirectional switches on the secondary side of the transformer have ZVS during the turn- on times. Therefore, the switching losses of the bidirectional switches are negligible. A 250-W prototype has been implemented to validate the proposed scheme. Experimental results confirm the feasibility and superior performance of the converter compared with the conventional flyback inverter.

Presently, there is an immense impetus in the automotive industry to develop plug-in electric vehicles (PIEVs) to reverse the ever increasing green house gas emissions from fossil fuels and depleting fossil fuel resources. High-frequency ac-dc converters with an isolated output are one of the essential building blocks for transferring power from utility mains to the traction battery packs which store energy for propelling the EV. Generally, the ac/dc converters used in EVs include a PFC stage at the input side and an isolated dc/dc converter at the battery side. Due to the switching nature of the converter, electromagnetic compatibility (EMC) of these converters is an essential requirement, to ensure not only its own operation but also the safe and secure operation of surrounding electrical equipment. EVs possess a lot of sophisticated electronic circuits in the vicinity of the battery charging power converters. Thus, strict EMC standards of the on-board power converters must be met according to the CISPR 12 or SAEJ551/5 relevant EMC standards. Conventional passive filters used for EMI mitigation in power converters, comes at the expense of cost, size and weight, power losses, and printed circuit board real estate. In this paper, an electromagnetic interference (EMI) filter embedded into the main high-frequency planar transformer used in the dc/dc converter is proposed as a very cost-effective and efficient solution for EVs. The proposed structure is able to significantly suppress the common-mode (CM) EMI noise generated in the dc/dc converter. Experimental results have been obtained from a 3-kW prototype in order to prove the feasibility and performance of the proposed EMI filter. The results show that the proposed embedded EMI filter can effectively suppress the CM noise particularly for high switching frequency power converters. The proposed structure can be a very simple and cost-effective EMI filtering solution for future PIEVs.

This paper presents a novel control approach for a current-driven full-bridge dc/dc converter, which is able to significantly improve the converter performance over a very wide range of operating conditions. The proposed control approach is based on the self-sustained oscillating control (SSOC) scheme, in order to adaptively change the phase shift and the switching frequency of the converter for different operating points. In this control technique, the timing signal is produced based on the transformer primary current, which is a feedback to the control system to determine the switching instants of the power MOSFETs. Therefore, the control system automatically tunes the control variables for different operating conditions. The comprehensive mathematical analysis of the proposed SSOC scheme is presented in detail. The mathematical analysis is based on the geometric viewpoint of the control system, which provides a very good insight into designing the control system. Experimental results provided from a 3 kW prototype confirm the feasibility of the proposed scheme and prove the superiority of the performance compared to the conventional phase-shift control approach.

An isolated, single-stage bidirectional AC-DC converter for electric vehicle battery charger is proposed. The topology utilizes two half-bridge circuits and a series resonant LC circuit in between. The proposed topology uses only six switches. Low component count in the circuit results in lower cost and volume. Control methods using variable phase-shift and duty-cycles of the half-bridge circuits are proposed. They transfer the desired power and obtain ZVS for all the switching instants while minimizing the RMS current through the resonant circuit and switches. ZVS operation of the circuit enables the switching frequency to increase, without increasing the switching losses. This will result in smaller reactive components and transformer. The proposed controllers also obtains the best performance out of the circuit. Simulation results with PSIM and experimental results to verify the theory have been done.

An isolated single-stage bi-directional AC-DC converter with no electrolytic capacitor for electric vehicle battery charger application is proposed. The topology utilizes a single-stage series resonant dual Half-bridge AC-DC converter to transfer the power and an active-shunt filter on the DC-side to absorb the 100/120Hz current ripple and prevent it from going to the battery. Diverting the low frequency ripple to the active filter prevents extra heat production in the battery and increases of the lifespan of the battery. Also film capacitors, instead of electrolytic capacitors with a lower lifetime, can be used on the DC-side filter. The reliability of the system is increased by not using an electrolytic capacitor in the circuit. To control the circuit for a wide range of power and power angle under soft switching, a four-part controller is proposed. The controller obtains ZVS for all the active switches while it optimizes the performance of the system in terms of conduction losses. ZVS operation of the circuit, enables the switching frequency to increase without increasing the switching losses. Increased switching frequency will result in smaller reactive components and smaller transformer size. The proposed controller obtains the best performance from the circuit. Simulation results with PSIM and experimental results to verify the theory have been carried out.

In this paper, a generalized analysis for the auxiliary network in a modified series-resonant asymmetrical pulse-width-modulated (APWM) converter is performed to produce a design procedure that ensures that zero voltage switching (ZVS) is achieved for any series-resonant APWM converter design. New equations that correctly predict the magnitude of auxiliary current are obtained by accounting for the trapezoidal nature of the waveforms associated with high-frequency operation, and the dead time between the switches in the half-bridge. A design example of a 48-V/1.2-V, 25-A converter operating at 1 MHz is chosen to highlight the validity of the proposed design and that superior results can be achieved if the resonant tank is designed in tandem with the auxiliary network. Experimental results verify that ZVS is achieved, and that the proposed design reduces the auxiliary inductor by close to a factor of 3.

This paper presents a novel, yet simple zero-voltage switching (ZVS) interleaved boost power factor correction (PFC) ac/dc converter used to charge the traction battery of an electric vehicle from the utility mains. The proposed opology consists of a passive auxiliary circuit, placed between two phases of the interleaved front-end boost PFC converter, which provides enough current to charge and discharge the MOSFETs' output capacitors during turn-ON times. Therefore, the MOSFETs are turned ON at zero voltage. The proposed converter maintains ZVS for the universal input voltage (85 to 265 Vrms), which includes a very wide range of duty ratios (0.07-1). In addition, the control system optimizes the amount of reactive current required to guarantee ZVS during the line cycle for different load conditions. This optimization is crucial in this application since the converter may work at very light loads for a long period of time. Experimental results from a 3 kW ac/dc converter are presented in the paper to evaluate the performance of the proposed converter. The results show a considerable increase in efficiency and superior performance of the proposed converter compared to the conventional hard-switched interleaved boost PFC converter.

A multiblock soft-switched bidirectional ac-ac converter using an active snubber is proposed in this paper. The snubber provides zero-voltage switching (ZVS) for the main switches of the entire power converter blocks in the entire input voltages and polarities. To achieve ZVS operation, the snubber block extracts the energy of the main switch drain-source capacitors and delivers it to the high-voltage side. Moreover, the snubber switches have zero-current switching (ZCS) turn-on and ZVS turn-off transitions. The performance of the proposed converter system is evaluated on a prototype including two converter blocks of 500 W working at 150 kHz with an input-voltage range of 110 V (-30% to +20%) and output of 175 V. Experimental results confirm that the proposed snubber improves the efficiency by 3% (4%) at half (full) load power for the entire input-voltage range.

A novel single-stage single-switch electronic ballast topology with a unity power factor is presented in this paper. The proposed circuit consists of an integrated buck-boost stage that operates in the discontinuous conduction mode to provide a high power factor and a single-switch current-fed resonant inverter to stabilize the lamp current. The proposed topology presents a low cost and compact electronic ballast design method. The detailed descriptions of the circuit's operating principles are provided in this paper. The design equations and mathematical analysis regarding the proposed circuit are discussed in this paper. The proposed ballast has been tested with an 18-W compact fluorescent lamp, and the experimental results confirmed that a very high power factor of 0.995 and an efficiency of 83.4% have been achieved.

A very high power factor electronic ballast that uses a single switch in the power circuit is proposed in this paper for compact fluorescent lamps (CFLs). The proposed power circuit is designed by integrating a SEPIC power factor corrector with a novel single-switch current-fed resonant inverter. The advantage of this single-switch electronic ballast is that it greatly simplifies the gate-drive circuit design due to the elimination of isolation devices that are otherwise required in the conventional half-bridge totem pole configuration. This topology features a reduction of at least two switches in the power stage compared to conventional two-stage approach for high-power-factor electronic ballasts. In addition, the proposed circuit is also able to achieve close-to-unity power factor by operating the integrated SEPIC power factor corrector in discontinuous conduction mode. The conduction loss of the switch in the proposed circuit is also significantly reduced compared to the conventional class-E single-switch resonant inverter. Experimental results are provided to justify all the theoretical analysis and highlight the features of the proposed circuit on a 13-W CFL.

A digital adaptive voltage positioning (digital AVP) technique with fast transient response for voltage regulators (VRs) is proposed in this paper. The proposed digital control architecture operates with fixed-frequency peak current mode control. Two digital-to-analog converters (DACs) are used instead of analog-to-digital converters (ADCs), thus significantly reducing system complexity. The control law is straightforward and no compensator is involved in the control loop, which greatly reduces the computation delay. Both the voltage and current references are changed dynamically at DAC clock frequency to achieve fast transient response. Furthermore, dynamic reference step adjustment method is employed to reduce the high-speed requirement on reference updating clock without compromising steady-state performance. Nonlinear control, including operation state recognition, multimode operation, decision-making and multiturn-on/turn-off control schemes, is used to minimize the transient-assertion-to-action delay and maximize the inductor current slew rate. Steady-state analysis was performed to demonstrate the digital controller operation. Finally, a two-phase 12- to 1-V, 40-A, 250-kHz synchronous buck converter with the proposed digital controller was designed to verify the theoretical analysis by simulation and experimental results.

The circuit modeling and analysis of resonant inverters is complex because the state variables such as inductor currents and capacitor voltages are AC dominant. The phasor dynamic modeling method maps the periodical time-varying state variables into stationary frame for each harmonic of interest. Correspondingly, the circuit is decomposed into two DC subcircuits, the state variables of which are the time-varying Fourier coefficients of the original AC variables. A small-signal model can be derived by applying small perturbation and linearization to the Fourier coefficients. A phasor-domain modeling method is used to investigate the resonant inverters in high-frequency AC power distribution systems. A resonant inverter system with five energy storage elements is modeled and simulated, and compared with switch simulation for both steady state and transients. The phasor model simulation matches the switch model simulation in both steady state and transients, but takes much less computing time. In addition, this model closely relates to the power converter topology in time domain, and therefore, keeps the physical meaning of the state variables. It can be used for high accuracy of modeling, simulation, and circuit analysis and control design. It can be extended to a higher order of resonant topologies including parasitic components. A high-frequency AC system with two pulse-phase-modulation-controlled resonant inverters is modeled and simulated, and the current distribution control is investigated with the phasor model. The model simulation is compared with switch-level simulation and experimental results.

This paper presents a simple voltage balancing scheme for m-level diode-clamped multilevel converters (DCMC). This paper first introduces a novel and simple current flow model for general m -level DCMCs. The superiority of the proposed model is its independence from the modulation scheme and its simplicity. It also provides a new perspective for voltage sharing accessibility among the dc link capacitors. The proposed current flow model, a cost function, and a space vector modulation (SVM) switching strategy are then used to balance the capacitors' voltages of the DCMCs in a very simple and optimized manner. Such a voltage balancing scheme was not developed for converters of five levels or greater due to the complexity of the converter and its modeling approaches. To validate the feasibility of the proposed voltage balancing scheme, this paper presents analytical and simulation results obtained from a five-level DCMC. In particular, this paper introduces a stability region within which the voltage balancing strategy converges. The impact of the cost function on the stability margins and converter performance is examined and discussed by means of comparison with different cost functions, and it is shown that the proposed cost function will improve the stability margins. The performance of the strategy for unbalanced and polluted loads shows that, unexpectedly, in some specific cases output current harmonics will improve the stability margin.

In this paper, a modified valley fill (VF) circuit is employed to combine with a current-fed resonant inverter as a passive high power factor (PF) electronic ballast. A conventional VF circuit limits the line current to conduct when the conduction angles are: 30deg les omegat les 150deg and 210deg les omegat les 330deg during the line period, which results in high total harmonic distortion (THD). The modified VF circuit has the following advantage: When the capacitors are connected in parallel, the voltage across the capacitors is one-third of the peak voltage, which allows the conduction angle of the line current to be further extended to 19.5deg les omegat les 160.5deg and 199.5deg les omegat les 340.5deg, so that a lower THD can be achieved. The high lamp crest factor (CF) problem generated by the high ripple voltage from the modified VF circuit is improved in the proposed ballast as variable frequency control is employed to continuously regulate the lamp current. An experimental prototype is then built in the laboratory to verify the feasibility of the proposed work for a 26-W compact fluorescent lamp. The final results confirm that a PF of 0.986 and a lamp CF of 1.49 are achieved with the proposed circuit, whereas a PF of 0.96 is achieved with the conventional VF ballast.

Resonant inverters are connected to a high-frequency AC (HFAC) bus, where power is delivered to different locations for points-of-use power management. Such a power distribution system subjects to more perturbations and load uncertainties than inverters operating with single load. A novel voltage control method is proposed in this paper for a high-frequency full-bridge resonant inverter with series-parallel resonant tank. A modified one-cycle controlled phase-shift modulation is proposed to effectively compensate the input line variations. The uncertainty model of the high frequency resonant inverter is developed and analyzed with the resonant circuit component tolerance, input line and load variations taken into design considerations. The voltage feedback controller is designed based on the Hinfin robust control theory and is implemented with analog discrete devices. The proposed control scheme has the advantages of fast response for both input line and load perturbations. It also ensures a wide range of system stability and guarantees robustness of the power converter. Both simulations and experimental results are provided to verify with the theoretical analysis through an experimental prototype of a full-bridge resonant inverter with an output power of 150-W operating at 1 MHz and an output voltage of 28 V (rms).

An accurate modeling of the series-parallel resonant converter operating in self-sustained oscillation mode including the overlap effects of the output rectifying stage due to the leakage inductance of the transformer is presented. This paper presents a systematic procedure to study the aforementioned effects on the converter dynamic and steady-state performance. Such information is critical in designing isolated high-frequency resonance-based voltage-regulator modules for powering future subvoltage very large scale integration circuits such as microprocessors. The extended describing function technique is used to extract the steady-state characteristics in order to get an optimum converter design. Averaging state-space techniques are employed to derive a small-signal model that can describe the converter dynamics accurately. Analytical and simulation results are given. Finally, a 1-kW experimental prototype is built to verify the validity of the proposed work

With the growth of telecommunication systems in remote areas, demand of wind solar hybrid systems is demanding in this industry. In this paper a 3 MHz DC-DC converter for standalone wind/solar application is proposed. The proposed converter is able to operate at a high frequency and to function in a wide range of input voltage. These specs make the system ideal for wind/solar energy systems. All MOSFETs and diodes in this converter are switched under soft switching condition. In addition, using finite inductors in the input of the converter makes it suitable for bang-bang control to keep the high efficiency at low loads. Experimental results are in agreement with simulations and analysis.

In this paper a novel structure of a zero- voltage transition PWM boost converter is proposed. The main switch and diode of the converter are turned on and off under zero voltage transition. In addition the auxiliary switch and both diodes operate in ZCT condition. The auxiliary circuit consists of a transformer, a snubber capacitor and two diodes. Without imposing much current stress, the switching loss reduces significantly. So a higher efficiency converter is achieved. The simple structure and a wide range of operating current are the advantages of the proposed converter, which make it useful for solar battery chargers etc. The operation principles of the proposed converter are explained and analyzed. Experimental results of a 1 kW and 250 V output at 200 kHz prototype verify the theoretical conclusions.

This paper presents a peak-current mode self-sustained oscillating control (SSOC) technique for a Dual-Active Bridge (DAB) DC/DC converter. The proposed control approach is able to significantly improve the performance of the bi-directional DAB DC/DC converter over a very wide range of operating conditions. Basically, the proposed PCM-SSOC scheme adaptively regulates the respective phase-shifts for each bridge, as well as the switching frequency of the converter for different operating conditions in order to achieve an optimal performance. In this control technique, the timing signal is produced based on the transformer primary current, which is a feedback to the control system to determine the switching instants of the power MOSFETs. Therefore, the control system automatically tunes the control variables for different operating conditions. Comprehensive mathematical analysis based on the geometric viewpoint of the control system of the proposed PCM-SSOC scheme is presented, which provides a very good insight into designing the control system. Experimental results provided from an experimental prototype confirm the superiority of the converter performance compared to the conventional fixed-frequency phase-shift control approach.

In this paper, the feedforward and feedback control loops are designed for the asymmetrical pulsewidth-modulated (APWM) resonant inverter to achieve fast transient response for the application in high frequency ac power distribution systems. In the proposed control scheme, the modulated integral control acts as a feedforward loop and provides pre-regulation for the feedback loop. As a result, the APWM resonant inverter has fast transient response against the line and load variation. Simulation and experimental results are presented to prove the dynamic performance of the APWM resonant inverter

Single-phase single-stage power-factor-corrected converter topologies are reviewed in this paper. The topologies discussed in the paper are related to ac-dc and ac-ac converters that are classified on the basis of the frequency of the input ac source, the presence of a dc-link capacitor, and the type of control used (resonant or pulsewidth modulation). The general operating principles and strengths and weaknesses of the converters, which the authors have investigated over the last decade, are discussed in detail, and their suitability in practical applications is stated. Considering practical design constraints, it is possible to effectively employ many single-stage converter topologies in a wide range of applications.

A modified asymmetrical pulse-width-modulated resonant dc/dc converter employing an auxiliary circuit will be proposed in this paper. The auxiliary circuit consists of a network of two capacitors and an inductor. The aim of this network is to produce zero-voltage-switching (ZVS) over a wide input voltage range, while reducing the voltage stress on the resonant component. A detailed analysis and performance characteristics are presented. Experimental results for a 5 V, 35 W converter show an efficiency of 83% at a constant operating frequency of 500 kHz. Using metal oxide semiconductor field effect transistors (MOSFETs) as synchronous rectifiers can further reduce power losses and improve the efficiency to be greater than 90%.

This paper presents a zero-voltage-transition (ZVT) boost converter using a soft switching auxiliary circuit for power factor correction (PFC) applications. The improvement over existing topologies lies in the positioning of the auxiliary circuit capacitors and the subsequent reduction in the resonant current and therefore the conduction losses as compared to other similar topologies. The proposed converter operates in two modes - Mode 1 and Mode 2. It is shown in the paper that the converter should be designed using the constraints obtained in Mode 1 to achieve low-loss switching. The converter is analyzed and characteristic curves presented which are then used in a detailed design example. Experimental results from a 250 W, 127 V input laboratory prototype switching at 100 kHz verify the design process and highlight the advantages of the proposed topology. The proposed converter is suitable for single-phase, two stage power factor correction circuits with universal input voltage range and power levels up to 3 kW.

This paper presents a forward converter topology that employs a small resonant auxiliary circuit. The advantages of the proposed topology include soft switching in both the main and auxiliary switches, recovery of the leakage inductance energy, simplified power transformer achieving self-reset without using the conventional reset winding, simple gate drive and control circuit, etc. Steady-state analysis is performed herein, and a design procedure is presented for general applications. A 35-75-Vdc to 5 Vdc 100-W prototype converter switched at a frequency of 200 kHz is built to verify the design, and 90% overall efficiency has been obtained experimentally at full load.

This paper presents a single high-frequency transformer full isolated uninterruptible power supply based on series-parallel resonant converters for powering hybrid fiber-coaxial (HFC) networks. The proposed UPS provides galvanic isolation for the load and the battery, and operates with high input power factor while producing a trapezoidal output voltage waveform either at 60 Hz or at 1 Hz. Small size and light weight are achieved without penalizing the overall efficiency by operating at high frequency and by ensuring zero voltage switching (ZVS) under the different operating conditions. In addition, it is demonstrated that by using capacitive output DC bus filter it is possible to reduce the current stresses during the backup mode by the appropriate selection of the transformer turns ratio. A design procedure for the selection of the key resonant circuit parameters is developed and exemplified. Experimental results obtained from a laboratory prototype demonstrate the overall performance of the system.

Four distinct uninterruptible power supply topologies are presented here for powering hybrid fiber/coaxial (HFC) networks. Topologies based on a low frequency isolation transformer are found to have better efficiency than the topologies with high frequency transformer. However, the latter topologies have much better performance in terms of transient response, quality of the output voltage, input power factor, total harmonic distortion of the input current, size and weight. The series-parallel resonant based UPS topology is found to have best overall performance for the emerging HFC applications.