This paper proposes a 2.4 GHz active mixer without passive inductor for the transceiver system. Taking into account the design requirements of the mixer, a double-balanced down-conversion structure with active inductor and negative resistance is designed. The proposed mixer with 130 nm CMOS technology is designed and simulated using Cadence software at 1.5 V supply voltage. Although we had to compromise conversion gain with linearity, we were able to achieve very high conversion gain with average linearity. Based on the results of post-layout simulations, the conversion gain of 27.57 dB, IIP3 equal to -7.88 dBm, 1-dB compression point equal to -17.34 dBm and IIP2 equal to 44.22 dBm with power consumption of 2.5 mW was obtained for the proposed mixer. The chip size without input and output pads is 95.18 µm × 117.68 µm, which leads to a chip area of 0.0112mm2.

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.

A step-down converter based on buck and buck-boost converters with a loss reduction technique is proposed in this paper. Utilizing non-electrolytic capacitors in the implementation of the proposed converter has resulted in an increase in circuit life and a reduction in weight and volume. This paper compares the proposed converter to other buck converters. To increase the output efficiency of the converter in comparison to other structures, a new method based on determining the working duty-cycles has been employed to reduce the losses of the converter, resulting in an increase in the converter's output efficiency. In order to demonstrate the differences in efficiency between the proposed method and the conventional method, the efficiency of the converter has been calculated using real-world conditions and the output loss results have been compared. In addition, the proposed converter has a common ground with the input source and has a suitable reduction gain. Finally, this converter has been implemented as a PCB and tested with 100 watts of output power.

Reliability consideration is always important among the manufacturers of power modules and converters. Before using of power electronic converters into the related application, it is necessary to predict its reliability over time. In the meanwhile, the power loss and heat generated within the power semiconductors play a key role in the lifespan of the whole system. In this paper, a method for assessing the reliability of a step-down DC-DC converter is employed based on the thermal modeling of power semiconductors. As is evident from the used reliability approach, the junction temperature of power semiconductors – diodes and insulated-gate bipolar transistors (IGBTs) – is the most influential factor on the lifetime of power converters. Therefore, the simultaneous influence of switching frequency and duty cycle is analyzed at the same time as a factor for evaluating reliability. A cut-off of 150° C is considered for the maximum allowable junction temperature for the examined IGBT power module. The results show that a failure can be expected after 46, 000 hours of operation of the considered power converter. Additionally, 3D curves are presented to illustrate the influence of duty cycle and switching frequency on the reliability of circuit’ s components and the overall system. The obtained results confirmed that an increase in switching frequency from 1 kHz to 10 kHz can decrease the circuit’ s lifetime almost 22%.

Variation of frequency and voltage by load changes in a microgrid is a challenge in droop control method. Centralized restoration frequency or voltage in a microgrid requires communication link and therefore affects the advantage of decentralized droop control such as reliability, simplicity and inexpensiveness. This paper proposes a decentralized method that restores the frequency of a microgrid without any communication link and maintains these advantages. The method detects signal changing by wavelet transform (WT) to synchronize distributed energy resource (DER) that interfaced by converter to microgrid. Its operation principle and control method are explained and analyzed. The simulation results are presented to validate the effectiveness of the proposed method.

This paper introduces a new high step-down converter that achieves zero voltage switching in both primary and auxiliary switches without relying on coupled inductors, thus ensuring low ripple in input and output currents. The auxiliary circuit is optimized with the fewest possible components, facilitating zero voltage switching for the main and auxiliary switches and solving the reverse recovery issue of freewheeling diodes through zero current switching conditions. Additionally, this design reduces voltage stress on the switches, allowing the use of MOSFETs with lower drain-source resistance. A key advantage of this converter is that it avoids using coupled inductors, which eliminates issues related to leakage inductance and potential increases in the converter's size and weight. This enhances the converter's efficiency and practicality. The auxiliary circuit design can also be extended to multiple phases, making it adaptable for various applications. The control mechanism is simple because the auxiliary switch operates in complementary with the main switch, simplifying the overall circuit design and integration. The proposed converter's design and operational principles have been validated through PSpice simulations, and a 90W prototype has been constructed. Experimental results demonstrate an impressive 95 percent efficiency at full load.

In this paper, a high step down converter with a synchronous rectifier is presented, so that both the main switch and the rectifier switch operate under soft switching condition. Since the proposed converter gain is much lower than the conventional buck converter, it does not have the problems of these converters such as narrow duty cycle, high voltage stress and high switch current, etc. In the proposed converter, the voltage stress on the switch is reduced, so a switch with lower drain-source resistance (RDS(ON)) can be used and the conduction losses are reduced. On the other hand, because the diodes of the circuit are switched off under zero current switching condition, do not have the problem of reverse recovery. Switching losses of the switches are also greatly reduced due to operating under zero voltage switching conditions. The proposed converter has been thoroughly analyzed and a practical 120 W prototype has been made to prove the correctness of the circuit analysis.

High step-down conversion ratio cannot be achieved by the conventional buck converter. Also, the switch voltage stress is another drawback of the regular buck converter for high input voltages. In this paper, a DC-DC switching converter using interleaved method is proposed based on the buck topology to achieve a high step-down conversion ratio. In the structure of this converter, a coupled inductor is used without need of another auxiliary winding. After presenting key waveforms and analysis of the proposed converter, the conversion ratio curves are offered. Moreover, simulation waveforms of a 240 W converter prototype with the input voltage of 150 V and the output voltage of 24 V are shown to verify the theoretical analysis.

High-frequency power transformers are available in electronic power converters for many applications such as power transmission, renewable energy systems, and power supplies. Magnetic materials production technologies such as ferrite, amorphous, and high-frequency nanocrystals are used to miniaturize transformers and optimize the design. In this paper, the design of a high-frequency transformer based on the finite element method (FEM) is proposed, and a frequency transformer above 5 kV and a power of 100 watts with a ferrite core is designed for use in high voltage charges in pulse power technology. After the calculation step, the three-dimensional model of the transformer with the nonlinear core is created with Maxwell finite element analysis software and then the simulations of the electromagnetic model of the transformer with electronic power converter circuit are implemented with the help of Simplorer software for operating conditions. Also, the efficiency of the transformer, the exact equivalent circuit of the transformer, and the flux distribution in the transformer core are obtained. In addition, transformer samples have been fabricated and tested. The data obtained from the finite element method are compared with the analytical and laboratory methods. The results show that the finite element method seems more accurate compared to the analytical methods. Due to the importance and complexity of designing high-frequency transformers, using this method can provide advantages and simplicity for transformer designers for parameter calculation and optimal design.

In this paper a direct ac-ac converter with low distortion input/output waveforms is investigated. Direct ac-ac converters using self-commutated semiconductor switches, also known as matrix converters, have recently attracted the attention of researchers. However, these converters are still under development due to the problems associated with the commutation of bidirectional switches employed in these converters. In this paper, an ac-ac converter is proposed based on the realization of matrix converters. Absence of bulky and unreliable electrolytic capacitors, low distortion input/output waveforms with independent fundamental frequency and employing two conventional power electronic building blocks are among important advantages of the proposed converter. The PWM patterns of two converters must be synchronized in order to achieve harmonic-free waveforms. This calls for an advanced PWM generation method as compared to conventional PWM strategies. Detailed derivation of the PWM signals based on double space-vector strategy is presented. Simulation results show various aspects of the system operation. The theoretical results are verified using a laboratory prototype. Experimental and simulation results show good agreement.