This paper presents a new power converter topology generated by the integration of the asymmetrical ZVS-PWM dcdc converter with a switched-capacitor ladder-type commutation cell. Circuit operation and theoretical analysis with emphasis on the soft-commutation process are included in the paper. The main advantage of the proposed converter with respect to the conventional asymmetrical half-bridge dc-dc converter is the reduction of the voltage stress across the power switches to the half of the input dc bus voltage, enabling the utilization of lower voltage rating components. Experiments conducted on a laboratory prototype with 1.4 kW power-rating, 800 V input voltage, 48 V output voltage and 100 kHz switching frequency are included, to verify the theoretical analysis and the design methodology. The maximum efficiency of the experimental nonoptimized prototype was 93.6%. Index Terms - Asymmetrical dc-dc converter, pulse-widthmodulation, switched-capacitor, zero voltage switching.

This paper provides contributions to the study of weakly nonlinear electrical circuit oscillators. A method is introduced for the determination of the stable limit cycle and the dynamics of a family of oscillators, employed in the analysis of a nonlinear oscillator similar to the van der Pol circuit. The circuit studied includes the power dissipated in the inductor resistance and in a load resistor connected in parallel with the capacitor, along with a more generic nonlinear damping system.  It is demonstrated that the system has a stable limit cycle which is dependent on the internal power losses. The results of the theoretical analysis are verified with the use of computer simulation.

A design oriented analysis of the RCD-type voltage clamp circuit, used to protect the active power semiconductor of the forward converter with demagnetizing winding. The operation of the circuit is described and analysis aimed at the dimensioning of the parameters is presented. The results are validated with the use of numerical examples and computer simulation, and are appropriate for the dimensioning and optimization of the circuit parameters.

The behavior of a circuit formed by two inductors magnetically decoupled from each other, with identical inductances or not, associated in parallel with a resistor, is studied in this article. It is shown that when the inductances of the inductors are identical, half of the initial energy is dissipated in the resistor, regardless of its value. For unequal inductances, the energy lost depends on the ratio between the values of the inductances, which can be greater or less than half of the initial energy. It is also shown that, regardless of the circuit parameters, whatever they may be, the algebraic sum of the magnetic fluxes of the two inductors is constant and equal to its initial value, not varying over time along the energy transfer process between the inductors.

An analysis of the transient behavior of DC networks consisting of voltage sources, capacitors, and series loss-free resistors (SLFRs) is presented. The realization of an SLFR was achieved by means of a topological variation of the positive output-voltage buck-boost converter operated in discontinuous-conduction mode (DCM). It is demonstrated that even simple RC circuits containing SLFRs exhibit behavior that is described by Abel nonlinear differential equations, which do not have an exact analytical solution. Some possible applications of the SLFRs in power electronics, DC microgrids and renewable energy power systems, include loss-free charge and discharge of capacitor banks, voltage equalization of capacitors, and loss-free voltage clamping circuits. The concept of the SLFR can also be applied for voltage control in DC microgrids, employing the droop voltage technique, equalization of power and current in voltage sources associated in parallel (including batteries and DC-DC converters), and also input and output voltage natural balance in input-series output-series (ISOS) association of DC converters. The theoretical analysis results are validated via numerical examples and computer simulation.

A study of the phase synchronization transient of three identical linear LC oscillators, coupled through identical resistors is presented. Exact equations that represent, as a function of time, the evolution of the phase angles between the oscillators, from the initial condition until the synchronization are provided.

This paper studies a high step-up DC-DC converter, derived from the DC-DC voltage-fed push-pull converter, which main features are magnetic and electric symmetry of the internal transformer, transfer to the load of the energy trapped in the leakage inductances, natural clamping of the voltages across the power switches and independent of the duty cycle, voltage across the active switches five times lower than the load voltage, high efficiency, and high power density. Operation stages, main waveforms, and design-oriented analysis and equations are included. A 1-kW, 50-V DC input, 500-V DC output prototype, operating at 40 kHz, was designed, fabricated, and tested in the laboratory, with a measured efficiency of 95% at rated power. The studied converter is suitable for renewable and vehicle electric power conversion systems.

An AC-AC converter with high-frequency link employing LLC resonant converter operating in the vicinity of the resonance frequency is studied, in which the output stage is unique and formed by a high-frequency AC-AC converter employing four quadrant switches. The topology, its operation and the modulation strategy are presented. The high-frequency stage switches located on the primary side of the transformer operate with soft switching of the ZVS type, while the four quadrant switches that form the output stage operate with soft switching of the ZCS type. Experimental data on a 1.5 kW experimental prototype that was designed, built and tested in the laboratory, with 220 VRMS input, 220 VRMS output and 40 kHz switching frequency are given in the paper. The studied converter can be considered a candidate for the building block of medium voltage solid-state transformers (SST) for power distribution systems.

This paper presents a generic algebraic proof of a recently published theorem [4], on the power conservative equivalent circuit for linear DC networks formed by time-invariant resistors and independent voltage and current sources. As the cited publication states, the internal losses of any network have two components: one variable and dependent on the internal resistances of the actual circuit and the power transferred to the pair of accessible terminals; and the other constant and dependent only on the internal voltage and current sources and the resistances of the actual network. It is also noted that the traditional Thévenin and Norton equivalent circuits are particular cases of the proposed equivalent circuit.

The superposition theorem, a particular case of the superposition principle, states that in a linear circuit with several voltage and current sources, the current and voltage for any element of the circuit is the algebraic sum of the currents and voltages produced by each source acting independently. The superposition theorem is not applicable to power, because it is a non-linear quantity. Therefore, the total power dissipated in a resistor must be calculated using the total current through (or the total voltage across) it. The theorem proposed and proved in this paper states that in a linear DC network consisting of resistors and independent voltage and current sources, the total power dissipated in the resistors of the network is the sum of the power supplied simultaneously by the voltage sources with the current sources replaced by open circuit, and the power supplied simultaneously by the current sources when the voltage sources are replaced by short-circuit. This means that the power is superimposed. The theorem can be used to simplify the power analysis of DC networks. The analysis results are validated via numerical examples.

A bidirectional isolated DC-DC converter with high efficiency and static gain, formed by the combination of a FBZVS-PWM and a current fed push-pull converter is presented in this paper. These features are accomplished through a partial regeneration of the energy stored in the transformer's leakage inductance with an active clamping voltage circuit performed by a buck converter. Normally, current-fed push-pull converters have an energy loss in passive snubber circuits. The converter description, operation principles, waveforms, modeling, design and the experimental results of a 2000 Watts prototype are presented. The proposed converter can be implemented in high power applications that require bidirectional power flow and galvanic isolation, such as DC microgrids and electric vehicle battery chargers.

This paper introduces a new equivalent circuit for linear direct current networks consisting of independent voltage and current sources, and resistors, which represents all the power dissipated internally in the resistors. It is demonstrated that the internal losses of any network have two components. One is variable and dependent on the internal resistances of the actual circuit and the power transferred to the pair of accessible terminals. The other is constant and dependent only on the internal voltage and current sources and the resistances of the actual network. It is also demonstrated theoretically and validated by numerical simulation that the traditional Thevenin and Norton equivalent circuits are particular cases of the proposed equivalent circuit in this paper. The proposed equivalent circuit can be used to analyze power and efficiencies of the actual network.