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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. Index Terms--High-frequency ac power distribution system, modeling, phasor-domain, pulse phase modulation (PPM), resonant converter, resonant inverter system.

In this paper, a review of switching loss mechanisms for synchronous buck voltage regulators (VRs) is presented. Following the review, a new simple and accurate analytical switching loss model is proposed for synchronous buck VRs. The model includes the impact of common source inductance and switch parasitic inductances on switching loss. The proposed model uses simple equations to calculate the rise and fall times and piecewise linear approximations of the high-side MOSFET voltage and current waveforms to allow quick and accurate calculation of switching loss in a synchronous buck VR. A simulation program with integrated circuit emphasis (Spice) simulations are used to demonstrate the accuracy of the voltage source driver model operating in a 1-MHz synchronous buck VR at 12-V input, 1.3-V output. Switching loss was estimated with the proposed model and compared to Spice measurements. Experimental results are presented to demonstrate the accuracy of the proposed model. Index Terms--DC-DC power conversion, modeling, MOSFETs.

This paper proposes a new current-source gate drive circuit for a synchronous buck converter. The proposed driver can drive two MOSFETs independently with different drive currents for optimal design. For the control MOSFET, the optimal design involves a tradeoff between switching loss reduction and drive circuit loss; while for the synchronous-rectifier MOSFET, the optimal design involves a tradeoff between body diode conduction loss and drive circuit loss. Furthermore, the new drive circuit can achieve: 1) significant switching loss reduction; 2) gate energy recovery and high gate drive voltage to reduce [R.sub.DS(ON)] conduction losses; 3) reduced conduction loss and reverse recovery loss of the body diode; and 4) zero-voltage switching of all the drive switches. The improved driver using integrated inductors is presented with multiphase buck voltage regulators (VRs) to reduce the number of magnetic cores and the core loss. The experimental results prove that a significant efficiency improvement has been achieved. At 1.5-V output, the new driver improves the efficiency from 84% using a conventional driver to 87.3% at 20 A, and at 30 A, from 79.4% to 82.8%. Overall, the new driver approach is attractive from the standpoints of both performance and cost-effectiveness. Index Terms--Current-source gate driver, microprocessor, power MOSFET, resonant gate driver, voltage regulator (VR).

In this paper, the advantages of a new resonant driver are verified thoroughly by the analytical analysis, simulation and experimental results. A new accurate analytical loss model of the power metal oxide semiconductor field effect transistor driven by a current-source resonant gate driver is developed. Closed-formed analytical equations are derived to investigate the switching characteristics due to the parasitic inductance. The modeling and simulation results prove that compared to a voltage driver, a current-source resonant driver significantly reduces the propagation impact of the common source inductance during the switching transition at high (> 1 MHz) switching frequency, which leads to a significant reduction of the switching transition time and the switching loss. Based on the proposed loss model, a general method to optimize the new resonant driver is proposed and employed in the development of a 12 V synchronous buck voltage regulator (VR) prototype at 1 MHz switching frequency. The level-shift circuit and digital implementation of complex programmable logic device (CPLD) are also presented. The analytical modeling matches the simulation results and experimental results well. Through the optimal design, a significant efficiency improvement is achieved. At 1.5 V output, the resonant driver improves the VR efficiency from 82.7% using a conventional driver to 86.6% at 20 A, and from 76.9% using a conventional driver to 83.6% at 30 A. More importantly, compared with other state of the art VR approaches, the new resonant driver is promising from the standpoints of both performance and cost-effectiveness. Index Terms--Resonant gate driver, switching loss model, voltage regulator (VR).

In this paper, a new current source gate drive circuit is proposed for power MOSFETs. The proposed circuit achieves quick turn on and turn off transition times to reduce switching loss and conduction loss in power MOSFETs. In addition, it can recover a portion of the C[V.sup.2] gate energy normally dissipated in a conventional driver. The circuit consists of four controlled switches and a small inductor (typically 100 nH or less). The current through the inductor is discontinuous in order to minimize circulating current conduction loss. This also allows the driver to operate effectively over a wide range of duty cycles with constant peak current--a significant advantage for many applications since turn on and turn off times do not vary with the operating point. Experimental results are presented for the proposed driver operating in a boost converter at 1 MHz, 5 V input, 10 V/5 A output. At 5 V gate drive, a 2.9% efficiency improvement is achieved representing a loss savings of 24.8% in comparison to a conventional driver. Index Terms--Metal oxide semiconductor field effect transistor (MOSFET), root mean square (RMS), zero voltage switching (ZVS).

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 H[infinity] 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). Index Terms--Full bridge, high frequency, one-cycle control, phase-shift modulation, resonant inverter, robust control.

The design of a resonant inverter for high-frequency ac (HFAC) power distribution systems is complicated by the following three factors: 1) A number of electronic loads located in different locations are connected to the resonant inverter, the impedance, and the power factor of the equivalent load of which varies over a wider range than a system with a certain load; 2) the resonant inverter is subject to an input-line voltage varying over a wide range; and 3) the characteristics of the resonant inverter depend on the load impedance. It is mandatory to operate the inverter with zero-voltage switching under various load conditions of different power factors and over wide input variations. It is further desirable that multiple resonant inverters can be paralleled with simple current-sharing control (CSC). A phase-shift-modulation (PSM)-controlled full-bridge series-parallel resonant inverter is proposed for the HFAC power distribution architectures. A new PSM method is proposed with which the phase angle of the inverter output voltage is independent of the modulation signal of the phase-shift modulator. Such a feature allows multiple resonant inverters to operate in parallel with a magnitude CSC. The resonant inverter is analyzed with a general nonresistive load model, and the design curves are developed. A prototype resonant inverter system is designed and implemented with an operation frequency of 1 MHz, a rated output power of 150 W, and a sinusoidal output voltage of 1-MHz 28-V rms. The proposed resonant inverter has the advantages of high efficiency over wide input/output line variations, high waveform quality of the output voltage, and phase-angle independence of the voltage-feedback/feed-forward control and CSC. Index Terms--Full bridge, phase-shift modulation (PSM), power distribution architecture, resonant inverter, soft switching.

A high-efficiency two-stage resonant inverter with effective control of both the magnitude and phase angle of the output voltage was proposed in this paper for high-frequency ac (HFAC) power-distribution applications, where a number of resonant inverters need to be paralleled. In order to parallel multiple resonant inverters of the same operation frequency, each inverter module needs independent control of the phase angle and magnitude of the output voltage. It is also desirable that the output voltage has very low total harmonics distortion, as well as high efficiency over wide input and load ranges. The proposed resonant inverter consists of two stages. The first stage is a two-switch dc/dc converter with zero-voltage transition, and the second stage is a half-bridge resonant dc/ac inverter with fixed duty ratio. A series-parallel resonant tank is used to achieve high waveform quality of the output voltage. The magnitude of the output voltage is regulated through the duty-ratio control of the first stage with pulsewidth modulation. The phase angle of the output voltage is regulated through a pulse-phase-modulation control of the second stage. The proposed resonant inverter has the advantages of better waveform quality, wide range of input and load variations for soft-switching, and independent control of the phase angle and magnitude of the output voltage, making it an attractive candidate for applications where a number of resonant inverters need to be placed in parallel to the HFAC bus and a number of distributed loads are connected to the HFAC bus. The performance is verified with both simulation and experiments. Index Terms--High-frequency ac (HFAC), power-distribution architecture, pulse-phase modulation (PPM), pulsewidth modulation (PWM), resonant inverter, zero-voltage switching (ZVS).

The control issue of multiple inverter modules operated in parallel is investigated for high-frequency alternative current (HFAC) power distribution architectures, where multiple high-frequency resonant inverters are connected in parallel to the high-frequency high-voltage low-current (HVLC) ac bus, to feed a number of point-of-use power supplies. The circulating current in the multiple inverter system is analyzed first. A novel control scheme is proposed based on the active and reactive current decomposition concept. In the proposed control, there are two loops: 1) the current sharing control loop and 2) the voltage feedback control loop. For the current sharing loop, the active current and reactive current are controlled separately. It is shown that the minimization of the circulating current can be achieved if both the active current and reactive current of the equivalent load are evenly distributed among activated inverter modules. This control method is superior to the scalar control where only the magnitudes of the currents are controlled. Performance is verified with both simulations and experiments on a prototype HFAC power distribution system where two two-stage resonant inverter modules of 500 kHz and 100 W are connected in parallel through small connection inductors to the 500-kHz 28-V rms HFAC bus. Index Terms--Circulating current minimization, current decomposition, current sharing, high-frequency ac (HFAC) power distribution system, resonant inverter.

This paper proposes a novel design procedure of proportional and integral (PI)-like fuzzy logic controller (FLC) for dc--dc converters that integrates linear control techniques with fuzzy logic. The design procedure allows the small signal model of the converter and linear control design techniques to be used in the initial stages of FLC design. This simplifies the small signal design and the stability assessment of the FLC. By exploiting the fuzzy logic structure of the controller, heuristic knowledge is incorporated in the design, which results in a nonlinear controller with improved performance over linear PI controllers. Index Terms--Digital control, digital pulsewidth modulation (DPWM), dynamic response, fuzzy logic control (FLC), pulsewidth modulation (PWM), switching converter.

A new soft-switching technique for buck, boost, and buck-boost converters using coupled inductors is proposed in this paper. The principles of operation of these converters are analyzed in detail. An additional winding is added on the same core of the main inductor for the purpose of commutation. By using hysteresis current control, zero-voltage switching conditions are ensured over a wide load range. The main inductor current is kept in continuous conduction mode with small ripple, which allows high output power and small filter parameters. Also, the switching frequency can be kept constant when the load changes. Prototypes of buck, boost, and buck-boost converters have been built to verify the proposed concept. The experimental results are presented and they verify the analysis. Index Terms--Coupled inductor, hysteresis current control, zero-voltage switched pulsewidth-modulation (ZVS PWM) converters.

This paper presents a novel power factor correction technique for single-phase boost type ac-to-dc converters in continuous conduction mode. Instead of using the inductor current or switching device current, in this paper, the diode current in the boost converter is used to formulate the duty ratio of the switch in a special way which makes the input current sinusoidal and in phase with the input voltage. To improve the dynamic performance and minimize the input current harmonic components, a new double-injection compensation method is employed in the voltage feedback loop. The power factor corrector has the following advantages: 1) operation with constant switching frequency; 2) elimination of input voltage sensing, error amplifier in the current loop and multiplier in the output voltage feedback loop; 3) minimal total harmonic distortion in the input current; 4) fast dynamic response of the output voltage loop 5) simple implementation of the control circuit. The principles of operation of the proposed control scheme are explained. Simulation and experimental results are presented to verify the feasibility of the control strategy. Index Terms--Double injection compensation, power factor correction, pulse width modulation, switch-mode rectifier.

A switch-mode dc-to-ac inverter based on a dc-to-dc converter topology using a novel nonlinear robust control to generate a sinusoidal output waveform is presented. The control scheme is based on simultaneous feedback of the output voltage and feedforward of the input voltage and inductor voltage. As a result, the output voltage remains dynamically unchanged when there are large disturbances in input voltage or load current. The nature of the control law is explained. Computer simulation results show the robustness and fast dynamical response of the control system. The experimental results are presented to verify the analysis and demonstrate the feasibility of the control strategy. Index Terms - Control techniques, dc-ac power conversion, dynamic response, pulsewidth modulated inverters.

The Class-E dc-dc converters with half-wave and full-wave controlled current rectifier are proposed. Zero voltage switching for all the switches can be maintained from full load to no load. The switching frequency is constant. When the load current changes from maximum to zero, the output voltage can be kept constant by regulating the conducting angle of the rectifier switch. The operation of the new converters is analyzed and the zero voltage switching characteristic has been demonstrated. The current gain of the circuit versus the conducting angle has been presented.

Large-signal dynamic models for hysteretic current-programmed buck, boost, and buck-boost converters are proposed. The model is expressed by a single differential equation. The small-signal transfer functions of these three converters are also derived, based on the large-signal model. The analysis shows that under the hysteretic current-programmed control, the output voltage of the buck converter is independent of the supply voltage, and there is a right-half plane (RHP) zero in the control-to-output transfer function of boost and buck-boost converters. An experimental prototype is breadboarded to verify the analysis.

The mechanism of zero current switching and zero voltage switching is analyzed. The concept of Source Reactance Lossless Switch (SRLS) is proposed. The switch can be implemented in SRLS voltage rectifier and SRLS current rectifier. Using SRLS technique, several dc-to-dc resonant converters with constant switching frequency control are proposed, in which zero current switching and/or zero voltage switching can be maintained from full load to no load. Steady-state analysis is presented for two basic topologies, Parallel-SRLS resonant converter and Series-SRLS resonant converter. Experimental results are presented to verify the analysis.

This paper presents a suitable control law and a novel method for the implementation of the sliding mode speed control (SLMSC) of a variable speed drive system. The analysis and results presented demonstrate that considerable simplification of design and circuit complexity can be achieved for SLMSC by employing the system states which are accessible or measurable. Both experimental and simulation results are presented to illustrate the potential of the proposed method.

The control strategy of the dc-to-dc switching converters is studied to obtain the switching regulators with zero-voltage regulation. A novel control strategy, the Function Control, is presented for the dc-to-dc switching converters to achieve this objective. The control law and the corresponding feedbacks are derived directly from the equations governing the switching converters. With the Function Control strategy presented in the paper, the switching regulators become robust, i.e., the output is independent of the disturbances from either the supply voltage or the load and exhibits other desirable advantages. The strategy is applicable to all the four basic PWM converters, i.e., Buck, Boost, Buck-Boost, and Cuk. The analysis is confirmed by experiments and computer simulations.

The switch-mode dc-to-ac inverter using dc-to-dc converter configuration has many advantages over the traditional bridge-type inverter. The previously presented circuit with nonlinear robust control works only for resistive load and its output voltage has considerable distortion near the zero-crossing point. A novel bidirectional circuit with nonlinear robust control is proposed in this paper to overcome those drawbacks. This inverter can dynamically stabilize the output voltage, i.e., the output voltage of the inverter remains dynamically unchanged when subjected to large disturbances in the input voltage or output load. The stability analysis is presented. The closed-loop control system under P control, PI control, PD control, and PID control of the voltage loop for different types of loads are investigated. The results show that the PD control is the best choice. The performance of the circuit is also studied. Computer simulation and experimental results are provided. Index Terms--Control techniques, dc-ac power conversion, dynamic response, pulse width modulation inverters.