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In the technical literature the interconnection of switching converters to increase power handling capabilities on dc applications has been widely reported. This study presents a family of switching step-down dc–dc converters based on the principle of reduced redundant power processing (R2P2). This states that the power transfer from input port to output port on interconnected converters can be reduced, if a non-cascading connection is used. As shown in this study, the principle R2P2 is useful for developing new converters. The resulting converters are formed by a pair of L–C networks and a pair of active switches, also they have wide conversion ratios and quadratic dependence with respect to the duty ratio. In this study, the voltage conversion ratios and steady-state operating conditions are derived for the proposed converters, which are verified by experimental results.

A high-voltage gain two-switch quasi-Z-source isolated DC/DC converter has been presented in this study. It consists of a quasi-Z-source network at its input, a push–pull square-wave inverter at its middle, and a voltage-doubler rectifier at its output. When coordinated appropriately, the new converter uses less switches, a smaller common duty cycle and less turns for the transformer when compared with existing topologies. Its size and weight are therefore smaller, whereas its efficiency is higher. It is therefore well-suited for applications, where a wide range of voltage gain is required like renewable energy systems, DC power supplies found in telecom, aerospace and electric vehicles. To demonstrate the performance of the proposed converter, a 400 V, 500 W prototype has been implemented in the laboratory. Efficiency of the prototype measured is found to vary from 89.0 to 97.4% when its input voltage changes from 44 to 82 V at full load.

Compared with a pulse-width modulated voltage-mode controlled switching converter, a constant on-time (COT) controlled switching converter has extensive industry application due to its fast transient response. However, the conventional COT controlled switching converter has poor output-regulation accuracy. A new control method that provides both fast transient response and high output-regulation accuracy for switching converters, called dual COT control, is proposed. The analysis results are verified by circuit simulation.

In this study, the authors focused on developing a bidirectional power converter for a stand-alone photovoltaic power generation system when a lithium-ion battery is used to regulate the power supply. Also, a small-scale air-conditioner was provided as the load for the bidirectional power converter developed to examine the efficiency of the converter. The overall framework of the proposed system comprised a maximum power point tracking controller, bidirectional buck–boost soft-switching converter, lithium-ion battery and small-scale air-conditioner. By attaching a resonant branch to a general bidirectional buck–boost converter and applying a simple switching signal control, soft switching was achieved, thereby increasing the power conversion efficiency of the photovoltaic power generation system. Some measurement results are made to verify the feasibility of the developed bidirectional dc–dc soft-switching converter for stand-alone photovoltaic power generation systems.

It is 18 years since the V2 control was proposed in 1996. Many publications have shown that the V2 controlled switching converter exhibits an ultra-fast load transient response. Recently, it has been reported that the conventional V2 control is inherently a peak V2 control, based on which V2 control can be classified as peak V2 and valley V2 controls. However, till now the switching converter with V2 control is almost a buck converter. This leads to the investigation of whether the V2 control can be applied to a boost converter.

A typical fuel-cell stack produces a low DC voltage with wide variations; therefore a DC–DC switching converter is required to step up and regulate the output voltage. In this work, a model based on electrical variables is developed for a fuel-cell stack. This model is later combined with the model of a high step-up voltage converter to obtain a combined model that incorporates the behaviour of fuel-cell stack. The resulting model is then used to design an average-current mode controller for a switching regulator. To test the proposed regulator, a power module with polymer electrolyte membrane fuel cells is used as an input source. This module delivers an output voltage between 26 and 42 V depending on the current being drawn. Experimental results exhibit the robustness of the switching regulator to step changes in the output load and the output voltage of the fuel-cell stack.

An interleaved series resonant converter with fixed frequency pulse-width modulation (PWM) is presented to achieve load current sharing, ripple current cancelation, zero-voltage switching (ZVS) for power switches and zero-current switching (ZCS) for rectifier diodes. Two three-level DC converters with clamped diodes and flying capacitor are adopted to share load current. The voltage stress of power switches is clamped at one-half of DC bus voltage. The interleaved PWM scheme is used to control two converters in order to reduce the output current ripple and size of output capacitor. The series resonant tank in three-level PWM converter is adopted to realise ZVS turn-on for all power switches andZCS for rectifier diodes. Thus, the switching losses of active switches are reduced and the reverse recovery losses of rectifier diodes are eliminated. The fixed frequency PWM operation is adopted to regulate output voltage, so that the drawback of a wide range of switching frequency in the conventional series resonant converters is overcome. Finally, experiments based on a scale-down prototype are provided to verify the effectiveness of the proposed converter.

A compact and highly efficient unidirectional DC–DC converter is required as a battery charger for electrical vehicles, which will rapidly become widespread in the near future. The single active bridge (SAB) converter is proposed as a simple and high-frequency isolated unidirectional converter, which is comprised of an active H-bridge converter in the primary side, an isolated high frequency transformer, and a rectifying secondary diode bridge output circuit. This paper presents a novel, unidirectional, high-frequency isolated DC–DC converter called a Secondary Resonant Single Active Bridge (SR–SAB) DC–DC converter. The circuit topology of the SR–SAB converter is a resonant capacitor connected to each diode in parallel in order to construct the series resonant circuit in the secondary circuit. As a result, the SR–SAB converter achieves a higher total power factor at the high frequency transformer and a unity voltage conversion ratio under the unity transformer turns ratio. Small and nonsignificant overshoot values of current and voltage waveforms are observed. Soft-switching commutations of the primary H-bridge circuit and the soft recovery of secondary diode bridge are achieved. The operating philosophy and design method of the proposed converter are presented. Output power control using transformer frequency variation is proposed. The effectiveness of the SR–SAB converter was verified by experiments using a 1 kW, 48 VDC, and 20 kHz laboratory prototype.

This study presents a new isolated DC/DC converter of full-bridge to connect a fuel cell to DC bus in a hybrid distribution generation system. This converter consists of a high-frequency transformer and a voltage booster circuit. The circuit has been designed and each isolated-gate bipolar transistor (IGBT) presents soft-switching during the whole power range of the converter. The switching losses of the IGBTs, the reverse-recovery losses of all of the diodes, and the core losses have almost been eliminated. To improve the efficiency, transformer cores and inductors have been built with material nanocrystalline. The efficiency is improved if this is compared with that of a conventional zero-voltage switching converter. Also, this converter can obtain a high-voltage gain and medium and high DC power can be converted. The analysis and switching techniques have been reported. Finally, to verify the principle of operation, a laboratory prototype of 2 kW has been performed.

Forward converter is popular for isolated switching power supply. Generally, power switching converters are the sources of electromagnetic interference (EMI) because of their high transient voltage and current. In this study, reduction of conducted EMI in the single-switch forward converter is examined using a symmetric topology. At this end, the forward converter topology is modified to achieve a symmetric topology. EMI model of the conventional forward converter and symmetric forward converter are derived taking into account the main parasitic of components and printed circuit tracks. Accuracy of the predicted EMI is verified by the measured EMI for two converters. In addition to the symmetric approach evaluation from the EMI viewpoint, the effect of this approach on the output voltage noise is examined. Finally, the combination of a passive EMI filtering with the symmetric method is utilised for EMC compliance.