In this paper, a new high step-up Current-fed LLC resonant DC-DC converter with a center-tapped transformer is proposed. By selecting the Switching frequency to be lower than, but near to, the series resonant frequency of the LLC resonant tank, soft-Switching operation of all semiconductors, i.e., Zero voltage Switching (ZVS) turn-on of power MOSFETs and Zero Current Switching (ZCS) turn-off of diodes is achieved. This leads to lower electromagnetic interference (EMI) and lower Switching losses and improves the converter efficiency. An interleaved structure is used at the primary side. Thus, input Current ripple is smaller, and its frequency is twice the Switching frequency. Consequently, a smaller input filter is necessary in practice. The converter with 1.2 kW output power and 760 V regulated output voltage with 80-200 V input voltage variations is simulated. The output voltage is regulated by using asymmetric pulse width modulation (APWM) at 200 kHz Switching frequency. Finally, a 700-W prototype has been implemented and experimental results are also presented to verify the simulation results.

In this paper a new soft Switching Current-fed converter for high voltage high power applications is presented. This converter utilizes parasitic components of high voltage transformers as resonant elements and employs fixed frequency phase shift PWM control to implement soft Switching condition, so the implementation of control circuit is easy and cheap. Every six switches turn on at Zero Current condition (ZCS) and it has high efficiency. The detailed steady state analysis of the converter is presented by computer simulation and analytical method. Finally the experimental results certificate analysis and simulation results of this converter.

A high step-up two-inputs DC-DC converter is presented in this paper. The soft Switching condition is provided for switch in turn on instant, so the converter efficiency is high. Due to the fact that only the capacitor is used to increase the voltage gain and there are no coupled inductors in the converter, the input Current of the converter is continuous. The technique used to increase gain can be used with more stages to achieve higher voltage gain. The converter can also be used as a single input intertwined instead of two inputs, which in this case the input Current ripple is reduced. The voltage stress on the switches is lower than the output voltage, so lower voltage switches can be used, which reduces the converter cost. The proposed converter is completely analyzed and in order to prove the theoretical results, a simulation is performed on the converter at 500 watts. The results of the simulation at full load show an efficiency of about 95. 5%.

The interleaved boost converters are the power circuits that provide high-voltage, high-power with regulated output voltage for renewable energy systems which are generally suffer from low-voltage and unregulated output voltages. The soft Switching methods reduce electromagnetic noises and Switching losses in these converters. In this paper, a ZVT interleaved boost converter with a simple auxiliary circuit is proposed. The proposed converter has a simple structure with low size and cost. In the proposed converter, soft Switching condition is provided without any extra voltage and Current stress on the main switches. The auxiliary circuit comprises two diodes and one auxiliary switch. The leakage inductance of the utilized coupled inductors is used as resonant inductor. The auxiliary switches benefit from significantly reduced voltage stress without requiring floating gate driver. The proposed converter can achieve Zero voltage Switching operation for the main switches and Zero Current Switching for diodes and auxiliary switches, which causes to alleviate the reverse recovery problems of all diodes.

In this paper, a soft Switching buck dc/dc converter applicable for fuel cell has been analyzed and the complete details of designing have been presented. Reduction in Switching losses and the elimination of voltage/Current stresses of the switches are the major advantages of the aforementioned converter. In this converter, the switches are to be ON under Zero voltage and Zero Current conditions, whereas they are to be OFF under Zero voltage condition. This converter can be used in high Switching frequency. In this paper, the principles of the performance, full details of the analyses of conduction modes, and designing approach have been presented. The performance and correct operation of the converter are validated by the experimental and simulation in PSCAD/EMTDC software.

In this paper, a non-isolated three-port Zero voltage Switching bidirectional dc-dc converter without input Current ripple. Some advantages of proposed converter are Zero voltage Switching of main switches, Zero Current Switching of auxiliary switches. By using two active snubbers, it is possible to reduce circulating Current and conduction losses. Free ripple condition of input Currents is obtained by using coupled inductors in any stages that it reduces size of converter. The proposed converter can be used in boost, buck and buck-boost operation mods. If all of low voltage sources are equal or less than high voltage source, it is possible to increase the number of input sources to AWT IMAGEas a kind of AWT IMAGE-port converter. Finally, the Zero voltage and Zero Current Switching of switches and ripple free input Currents of the proposed dc-dc converter is verified thruogh the simulation results in PSCAD/EMTDC software.

In this paper we proposed, a new Zero voltage Switching isolated buck-boost DC-DC converter with active clamp circuit. The active clamp circuit in this converter not only absorbs voltage spikes across the main switch but also provides soft Switching conditions for all switches. All switches are Pulse Width Modulation controlled which simplifies the control implementation. One of the main advantages of this converter is operating at high power levels while soft Switching conditions exist in both buck and boost modes of converter operation. Since this converter can operate over a wide input voltage range, it can be employed in power factor correction. The experimental results obtained from a 150W prototype circuit operating at 100 KHz are presented to confirm the integrity of the proposed circuit.