Sharif Digital Repository

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... 

Widespread use of sensitive loads in industries has required the need for high efficiency voltage regulators in order to provide continuous and fast dynamic adjustable AC voltage. This paper introduces a new control strategy to improve the response time and performance of a double stage switch mode regulator. The proposed strategy responds to input voltage variations quickly and improves the efficiency and performance of the circuit. Results of some simulations are presented and analyzed. Experimental tests on a laboratory prototype verify the excellent performance of the proposed system  

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... 

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... 

Plug-in hybrid electric vehicles draw electricity from the electrical grid and store energy in their batteries. To increase charge availability for plug-in hybrid electric vehicles, on-board chargers can be used, which should be small in size and lightweight. In this article, an on-board bidirectional soft-switched battery charger is proposed that utilizes a phase-shift-controlled dual-bridge series resonant converter with isolation. The bidirectional characteristic of proposed charger makes it suitable for vehicle-to-grid operation (i.e., injecting power from the vehicle to the grid) in smart grids. A switching control scheme is also proposed to provide soft-switching operation for all... 

Conventional back-to-back converters with input power factor correction are still the best solution for motor drive applications which are usually subjected to considerable load changes during their operation. Since converter components, especially input-side inductances are designed for nominal power rating, the rated input power factor and input current distortion aren't achievable in light loads. In this paper a control method is proposed to improve the input current distortion and input power factor in light loads. This is achieved by increasing the switching frequency according to the reduction in load. Since conduction and switching losses decrease in light loads, the overall losses by... 

One of the major limitations of the multilevel converters is the voltage unbalance between different levels. The techniques to balance the voltage between the different levels normally involve voltage clamping or capacitor charge and discharge control. However, traditional Flying Capacitor Converter (FCC) may be quite limited by the voltage unbalance of flying-capacitors that is the most serious problem. This paper describes operating principles of a new softswitching seven-level converter topology based on FCC for self-voltage stabilization and balancing. By adding power electronic devices to the traditional FCC topology, the proposed topology regulates the DC bus voltage and balances the... 

This paper proposes a novel FPGA-based matrix-inversion technique that is specifically tailored and optimized for real-time electromagnetic transients simulation of power electronic converters with high switching frequency. This is the first reported solution that is capable of solving the real-time equations related to using ideal switch model and the associated circuitry in very small time-steps (e.g., an average of 36 ns in a three-phase back-to-back converter case study), without requiring large amount of memory, being limited to small number of switches, adding parasitic elements, or depending on a priori knowledge of the circuit operation or switching strategy. The accuracy of the... 

A high energy-efficiency and low-area switching method is proposed for the successive approximation register analog-to-digital converters. In the proposed scheme, the threshold voltage for comparison is derived from the charge sharing technique and using a voltage source connected to the bottom plates of the digital-to-analogue converter (DAC) capacitors. The switching method achieves an average DAC switching energy and DAC area reduction of 99.15% and 84.27%, respectively, with respect to the conventional method. The differential nonlinearity and integral nonlinearity of the proposed scheme are 0.1288 LSB and 0.1207 LSB, respectively. In addition, in the proposed method, the number of DAC... 

This article describes the development of an 18 kV, 30 kW power supply for a pulsed current load with the maximum current of 20 A and a di/dt equal to 100 A/μs. The achieved output ripple is less than 0.01%. In such a high level of precision, the most important issues are considerable difference between the instantaneous and average output powers, as well as insufficient reaction speed of the converter to the fast load change. Very low level of the voltage feedback and its sensitivity to the noise. The first issue necessitates a notable overdesign of the converter switches if the output voltage precision is dedicated to the converter. The second issue raises the problems relevant to... 

This paper is a summary and in-depth evaluation of some popular models for power electronic converters. Proper examples are given to support the evaluation with a complete comparison between the actual and simulated results. The paper presents the effort behind the design and analysis of DC-DC Converters and discuses their features. Some advantages and disadvantages of the studied models and the complicities of the nonlinear structure of the switching function of the converters are explained here. The paper offers some useful criteria for future selection and development on different DC-DC Converters. © 2006 IEEE  

A high energy-efficiency and low-area switching method is proposed for the successive approximation register analog-to-digital converters. In the proposed scheme, the threshold voltage for comparison is derived from the charge sharing technique and using a voltage source connected to the bottom plates of the digital-to-analogue converter (DAC) capacitors. The switching method achieves an average DAC switching energy and DAC area reduction of 99.15% and 84.27%, respectively, with respect to the conventional method. The differential nonlinearity and integral nonlinearity of the proposed scheme are 0.1288 LSB and 0.1207 LSB, respectively. In addition, in the proposed method, the number of DAC... 

The method for modeling switching converters plays a key role in real-time simulators. Associate discrete circuit (ADC) modeling technique is a commonly used method for modeling the switching converter. However, the optimal selection of the ADC-based switch model parameters has great importance in the accuracy of the real-time simulator. In this paper, the design of a real-time simulator for a switching power converter has been done, in which a novel method for detecting optimum values of the switch model parameters has been expressed. Particle swarm optimization (PSO) algorithm is used to find these optimum values using state-space analysis of the modeled circuit in the z-domain. The... 

This paper offers a new EF-class converter for dynamic wireless power transfer application. The proposed high-frequency converter employs a floating-frequency switching algorithm to control the converter in a continuous frequency range, eliminate the requirement to any additional operational data from the secondary (receiver) side, accelerate the load impedance match while moving, maximize the transferred power rate, reduce charging interval and compensate power transfer tolerances. Moreover, an optimized super elliptical shape coil is designed to cope with lateral misalignment, enhance coil coupling, and increase efficiency. In the proposed converter, (i) soft switching is implemented to...