Sharif Digital Repository

A three-phase dual active bridge (DAB) topology has been widely applied in high power DC-DC conversion due to its advantages such as bidirectional power transfer, inherent soft switching capability and small filter size. In order to reach the high power density, the volume of the converter must be decreased. The basic idea to reduce the component size is to increase the switching frequency which causes the higher switching loss and reduces the efficiency of the converter. In this paper, the power losses of the three-phase DAB dc/dc converter are formulated and the variation of the efficiency as a function of switching frequency is investigated. In this analysis, the switching loss of the... 

Today's technology is going to be switched to power electronics equipment due to their wide applications in industries. Their development is too fast since the electronic and microprocessor technology promoted together, which play a significant role in this issue. In this paper, a novel boost converter with an h-bridge auxiliary LCC resonant circuit which provides soft switching technique to the converter is introduced. Then different modes of its operation are investigated and key parameters of the converter are extracted. Finally, simulation analyses are carried out to validate each mode's equation. In this study, the proposed structure of auxiliary circuit permits converter to work in... 

In this paper, the Line-Modulated Fixed Off-Time method is used as the current control strategy for a Power Factor Corrector (PFC) pre-regulator. A zero voltage switching PWM (ZVS-PWM) auxiliary circuit is configured to perform ZVS in the switches. Soft commutation of the main switch is achieved without additional current stress. A significant reduction in the total conduction loss is achieved, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path .The proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode... 

LLC resonant converter has been widely used in dcdc converters. In this paper, optimum dead-time and maximum switching frequency of a wide-adjustable-range LLC resonant converter are investigated for realizing the zero voltage switching (ZVS) operation even under the worst-case conditions. Analyses demonstrate that these parameters depend on the converter inductance ratio and ratio of the converter resonant capacitor and the effective capacitance appeared in parallel with the drainsources of the power MOSFETs. The necessary dead time for realizing the ZVS operation can be minimized by choosing the normalized maximum switching frequency, properly. Using the dead-time optimum value, soft... 

LLC resonant converter with significant resonant inductance is proposed for designing an adjustable wide-range regulated voltage source. Large resonant inductance increases output voltage adjustment range and conversion efficiency, particularly at light loads. Soft switching is achieved for all power devices under all operating conditions by choosing the dead time and maximum switching frequency properly and operating in the converter's inductive region. Using a power-factor-correction (PFC) converter reduces the resonant converter's output voltage dependence to the variations of the main ac input voltage. Thus, the compensation of the load variations and the wide-range adjustment of the... 

Power density is an influential factor in 400 volt telecom energy distribution systems. In addition, systems are desired to reach an acceptable efficiency while they take advantage of a galvanic isolation. This paper presents a new architecture that is based on push pull topology and its power switches perform ZVS in both their turn on and turn off conditions. Besides, the presented topology uses an interleaving technique that has made it desirable for high power applications. Power loss for the presented topology is calculated and compared to conventional topologies. Finally, by considering the efficiency and power density of the presented topology, it is concluded why this topology is... 

In this paper, a new zero-voltage-switching, high power-factor, bridgeless rectifier is introduced. In this topology, an auxiliary circuit provides soft switching for all of the power semiconductor devices. Thus the switching losses are reduced and the highest efficiency can be achieved. The proposed converter has been analyzed and a design procedure has been introduced. The control circuit for the converter has also been developed. Based on the given approach, a 250 W, 400 Vdc prototype converters has been designed at 100 kHz for universal input voltage (90-264 Vrms) applications. A maximum efficiency of 94.6% and a power factor correction over 0.99 has been achieved. The simulation and... 

LLC resonant converter is one of the most suitable circuit topologies that have been introduced for designing constant output voltage switched-mode power supplies. In this paper, a design procedure is introduced for using this converter as a wide output range voltage source. Unlike constant output voltage applications which need small converter inductance ratio and narrow switching frequency variations, for wide output range applications, large values of these parameters are needed simultaneously and should be optimized. Instead of minimizing the components stresses, leading to a great value of the inductance ratio, proper choice of the converter parameters resulting in a smaller inductance... 

This paper proposes a design technique for the implementation of a class-EM power amplifier (PA). Class- EM mode of operation has been proposed as an improved version of class-E in terms of efficiency and power gain, provided that the current fall time of switch is an appreciable portion of a period; the frequency of operation is high enough that the switching time of transistor can no longer be considered instantaneous. A novel approach for harmonic injection required for class-EM operation is proposed, followed by the system of equations and the design methodology governing the proposed circuit. As a proof of concept and verification of the proposed design method, a class-EM PA is designed... 

Simplified equations are used for the analysis of a dual active bridge converter leading to a conservative estimation of the zero voltage switching (ZVS) region. The ZVS is directly affected by the inserted deadband in each leg of the converter. In this paper the impact of the ZVS capacitor and deadband on soft switching region for this converter is analyzed. Also, the sufficient constraints for ZVS condition in the input and output bridges are determined by analyzing the circuit behavior during the bridges deadband. Simulation results of a 700V-350V, 50-kW DC-DC converter validate the analysis. © 2017 IEEE  

A three-phase dual active bridge (DAB) topology has been widely applied in high power DC-DC conversion due to its advantages such as bidirectional power transfer, inherent soft switching capability and small filter size. In this paper, the three-phase DAB dc/dc converter is analyzed during its deadband. Moreover, the influence of the zero-voltage-switching (ZVS) capacitor and deadband on ZVS region are investigated by utilizing an accurate circuit analysis during the deadband. The theoretical results are verified in simulation and in a50 kW experimental setup. © 2017 IEEE  

This paper presents an analytical model to design a class-E power amplifier under only zero-voltage-switching (ZVS) term with the MOSFET nonlinear drain-source shunt parasitic capacitance that is named as the subnominal operation. The presented analysis is performed under any grading coefficient m of MOSFET body junction diode and any duty ratio D. The grading coefficient m along with the switching duty ratio D are implemented as tuning variables to satisfy design specifications and ZVS term simultaneously. The restriction of selecting the value of m and D for the subnominal operation has a major effect on simultaneously satisfying of load-resistance, operating frequency, and junction... 

Multi-port converters (MPC), used in multi-input/multi-output power electronic systems have low cost, low weight and low mass integrated control system. Besides these converters offer bidirectional and isolated ports, which are inevitable in some applications. Three-Port Half Bridge Converters (TPHBC) are the ones which have the lowest component count. But these converters suffer from a low Zero Voltage Switching (ZVS) range that is lost in medium to low load powers. Low ZVS range cause low efficiency, especially in low output powers. In this paper a modified Pulse Width Modulation (PWM) technique is introduced to increase the ZVS range of main switches which results higher efficiency and... 

Boost converter operating in critical conduction mode is widely used in low-power power factor corrector because of its simplicity and low switching losses. The switching loss due to parasitic capacitor discharge at the on-time instant can also be reduced by a valley switching technique. In this paper, we introduce a new driver topology for the high-side switch in a synchronous boost converter operating in the critical conduction mode to obtain full zero-voltage switching. Using the proposed high-side driver topology, the conventional control circuit is sufficient to control the low-side switch, and no additional control circuit is required to adjust the timing of the switches. Finally, the... 

LLC resonant converter has been used widely as dc-dc converter for achieving constant dc voltage. In this paper, an LLC resonant converter, by adding an inductance to its conventional topology and considering the rectifying stage stray inductances, is proposed for an adjustable wide range regulated current source (20-200 A dc) for using as ion implanter's filament power supply. The additional inductor increases output current adjustment range and efficiency, especially at light loads. Transformer's leakage inductances and rectifying stage stray inductances have been considered. Because of these inductances, the rectifier stage always works in continuous conduction mode, and its conduction... 

In this paper, the FHA and a simple TDA approaches have been used to derive the normalized maximum switching frequency of wide adjustable range LLC resonant converter for realizing the ZVS operation even under the worst-case conditions. By accounting the resonant current higher harmonics, more accurate expressions are derived. These analyses demonstrate that the normalized maximum switching frequency depends on the dead-time and the converter inductance ratio. It also depends on the ratio of the converter resonant capacitor and the effective capacitance appeared in parallel with the power MOSFETs drain-sources. The simulated and experimental results are in good agreement with the derived... 

LLC-LC resonant converter is a suitable circuit topology to design switched-mode power supplies for wide-output-voltage and wide-output-load applications. In this paper, a design procedure is introduced to optimize this converter. Unlike soft switching techniques for pulse width modulated converters, which usually apply an active auxiliary circuit to reduce switching losses and EMI, in the proposed converter, not only such circuits are not used, but also all of the parasitic elements are merged to the converters main components. Zero-voltage switching (ZVS) operation is realized for all power devices under all operating conditions. Thus, this converter is a suitable choice for...