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Abstract: In this paper, a new wide conversion ratio step-up and step-down converter is presented. The proposed converter is derived from the conventional Single Ended Primary Inductor Converter (SEPIC) topology and it is integrated with a capacitor–diode voltage multiplier, which offers a simple structure, reduced electromagnetic interference (EMI), and reduced semiconductors' voltage stresses. Other advantages include: continuous input and output current, extended step-up and step-down voltage conversion ratio without extreme low or high duty-cycle, simple control circuitry, and near-zero input and output ripple currents compared to other converter topologies. The low charging/discharging current ripple and wide gain features result in a longer life-span and lower cost of the energy storage battery system. In addition, the “near-zero” ripple capability improves the fuel cell durability. Theoretical analysis results obtained with the proposed structure are compared with other bi-direction converter topologies. Simulation and experimental results are presented to verify the performance of the proposed bi-directional converter. [Copyright &y& Elsevier]

Abstract: To raise the utilization ratio of lithium-ion battery in portable devices, a novel green-switch controller IC is proposed to constitute a 4-switch cascade buck–boost prototype, which is capable of outputting non-inverting step down and step up voltages. According to the relations between the input and output voltages through duty ratio, a finite state machine automatically determines the work method of converter namely buck method, boost method or transition method by combining peak and valley current programmed mode so as to improve the line regulation over the entire input voltage range. A three-phase seamless transition method is introduced into the controller. Its additional advantage is to lower output ripples. Furthermore, a special burst mode is added to reduce the power consumption during light-load operation. An elaborately designed circuitry and rigorous stability analysis further improves the seamless performance. The controller IC is designed and fabricated in 1.5μm BCD (Bipolar-CMOS-DMOS) technology with an area of 8.75mm2 and applied to a 2.7V–4.2V/3.3V, maximum output power 1.65W buck–boost converter. It features over 90% conversion efficiency during normal application and still remains over 80% under standby mode. The experimental results show that all functional and performance targets are successfully achieved as expected. [Copyright &y& Elsevier]

Abstract: Switching power converters are extensively used in powering various electronics loads and processes. The proper functioning of those processes may be vital for the every day life of the society. Therefore, the reliable operation of the switched-mode converters is of prime importance and the functioning has to be verified reliably both during the design phase and in the production. It has been shown lately that the main deficiencies in the verification process are related to the dynamics of the converter which can be characterized with a certain set of transfer functions. This paper investigates the frequency response measurement methods by means of which the transfer functions can be identified fast and accurately being economically feasible to apply also in the production phase. Multi-period maximum length pseudo random binary sequence (m.l.b.s.) is used as the excitation signal and the transfer functions are identified from the measurement data with circular cross-correlation method. The measurement uncertainty is computed by means of fuzzy density approach yielding a certain confidence band around the measured nominal response. The proposed methods are verified both by simulations and experimental data from high-frequency switched-mode converters. [Copyright &y& Elsevier]

This work applies unequal duty cycle to switched-capacitor (SC) dc-dc converters to improve its output ripple as well as the power conversion efficiency. By adjusting the duty cycle, the capacitor charge and discharge states are reasonably balanced. Therefore, we effectively reduce the output ripple and the charge redistribution loss, improving the efficiency. A SC converter verifies this scheme with voltage conversion ratios (VCRs) of 1/4 and 1/3, in a 65 ​nm CMOS low-power process. Operating with a switching frequency of 33 ​MHz, an input voltage of 2.4 ​V, an output range of 0.5–25 ​mA, and a VCR of 1/4, the peak efficiency increases by 1.0% and the output ripple drops by 43.6%, when compared with the equal duty cycle mode. With the input voltage equal to 1.8 ​V and the VCR ​= ​1/3, the peak efficiency increases by 0.7% and the output ripple reduces by 48.0%, compared to the equal duty cycle mode. [ABSTRACT FROM AUTHOR]

• This paper proposes topologies A,B and C of acdc buck–boost converters for MV applications, with 'A' and 'C' have been identified as promising. • Topologies 'A' and 'C' facilitate scalability to higher and lower MV applications, with 'C' uses a novel parallel charging of inductors. • The theoretical principles that underpin the operation of the proposed topologies are established and verified using simulations and experiments. This paper proposes three topologies of single-stage three-phase ac–dc buck–boost converters suitable for medium-voltage and high-power wind energy conversion systems (WECS). The proposed converters draw sinusoidal input currents with nearly unity power factor from wind generators over wide range of ac voltages and frequencies. The proposed converters reduce the voltage and current stresses on the self-commutated switching device compared to existing solutions; thus, promising for new generation of relatively cheap WECSs. The proposed converters operate in Discontinuous Condition Mode (DCM), with their ac terminals connected to three-phase generator with open ended windings, or to ac supply using three single-phase transformers with isolated windings at converter side. The validity of the proposed converters and its detailed theoretical analysis and discussions are confirmed using PSCAD/EMTDC simulations, and further corroborated by experimentations, considering different operating conditions. [ABSTRACT FROM AUTHOR]