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Achieving high efficiency and high power density features of intermediate bus converter (IBC) in data center application is very critical. This paper proposes a nonisolated switched-tank dc–dc converter (STC) to meet the high requirement of IBC. The proposed STC has fixed voltage conversion ratio. Theoretical analysis provides the guideline for designing resonant tank and nonresonant tank as well as selecting proper deadtime for the proposed circuit. With resonant operation feature of the proposed circuit, zero current switching is realized on all switching devices to help the high-efficiency operation of the proposed converter. Through the proposed design methodology in this paper, power loss on switching devices and planar inductors can be minimized. In addition, detailed power loss analysis and breakdown provide hints for further efficiency improvement. Simulation has been performed to validate the operating principle of the proposed STC. A designed 6x STC (450 W nominal/600 W maximum) based on eGaNFETs is demonstrated. With 54 V typical input voltage, the output of the 6x STC is 9 V. The GaN-based prototype achieves a peak efficiency of 98.55%. Also, it achieves 97.18% efficiency and 750 W/in3 power density at 450 W. [ABSTRACT FROM AUTHOR]

This paper presents a study of the losses in the integrated buck–flyback converter (IBFC) used as high-power-factor LED driver. The aim of the study is to investigate the possibilities of increasing the efficiency of the IBFC converter. The procedure of the improvement is done by obtaining the equations of the current through each component in terms of converter parameters. The current is found in an average value or rms value, depending on the type of the parasitic component, whether it is modeled by a parasitic forward voltage source or by a parasitic resistance, respectively. Using these equations and the parasitic model, the losses of each element of the converter are estimated. This paper proposes a technique to increase the efficiency of the IBFC by redesigning the converter parameters. Furthermore, this paper presents a case of study with a step-by-step efficiency enhancement process of an existing driver. The driver is operating under universal input conditions, and 38 V output, supplying an LED luminary of 26.5 W. The new design shows an improvement of the efficiency from 82% in the old design to 89% in the proposed one. Moreover, the new design shows an improvement in the power factor and the THD and a 50% reduction in the output current ripple. Furthermore, a reduction in the number of components has been achieved, as it is found by the analysis that by adjusting the converter parameters, one diode can be removed. Finally, the presented methodology is explained in detail so that it can easily be applied to other dc–dc converters. [ABSTRACT FROM AUTHOR]

The advancement in power electronics has made the use of any number of phases in ac machines possible since with the inverter, any number of phase voltages can be realized as long as the corresponding inverter exists. To supply multiphase drives requires multiphase voltage source inverters (VSIs) whose output voltages depend very much on the methods of generating the pulses to turn on and turn off the inverter devices appropriately. This paper presents an analytical technique for the determination of the expressions for the modulation signals used in the carrier-based sinusoidal and generalized discontinuous pulse width modulation schemes for two-level, five-phase voltage source converters. These expressions can be used for both balanced and unbalanced phase voltages generated by any two-level multiphase inverter, in generating the required reference signals appropriately. An example of a five-phase VSI is presented to illustrate the strategy. Simulation and experimental results are presented in which a close examination shows that both results are similar for the balanced and unbalanced load voltage cases. [ABSTRACT FROM AUTHOR]

This paper investigates the operation of space-vector-based hysteresis current control in the synchronous reference frame (SRF) for grid-connected voltage source converters. The space-vector-based approach allows for the systematic application of zero-voltage vectors and prevents high switching frequencies caused by phase interaction. The average switching frequency can be minimized by always selecting the zero-voltage vector that is closest to the previous switching state. Implementation in the SRF ensures a simple structure based on two three-level hysteresis comparators and a switching table that fits well into the traditional structure of vector-oriented current control. For operation in a grid-connected converter with an LCL filter, the current references to the hysteresis controllers are given by a dc-link voltage controller and an active damping mechanism for suppressing filter oscillations. Results from simulations and laboratory experiments are presented to illustrate the features of the investigated approach compared to traditional phase-current hysteresis controllers. [ABSTRACT FROM AUTHOR]