Sharif Digital Repository

High frequency transformer is an important component in lots of modern power electronic circuits. In order to analyze the behavior of these transformers, equivalent circuit models containing parasitic elements have been proposed. But most of them are complicated and not appropriate to use in processes in which high speed analysis is crucial. In this paper, a second-order simplified model for high frequency transformers is obtained. Besides, the frequency ranges in which the proposed model has enough precision, are calculated and examined. To validate the simplified circuit model, some simulations are carried out. During the simulation, the effects of transformer equivalent circuit parameters... 

In high-voltage applications, due to the use of high-ratio step-up transformers, the value of parasitic capacitance of these transformers is large compared to the low-voltage transformers. Moreover In these applications it is prefered to use single-capacitor filters instead of filters with inductors. In this paper a simple electrical model for two-winding high frequency transformer considering all of the parasitic elements is presented. This model is used in a full-bridge based dc-dc converter with capacitive output filter controlled by phase-shifted method. The operation of this converter in DCM is analysed and its analytical relations in different time intervals is derived and confirmed by... 

Stray capacitance of transformer winding is an important parasitic element influencing the behavior of the switching power converters, especially for high-voltage transformers. There are various methods for calculating the stray capacitance in transformers and inductors with ordered windings. However, an ordered winding is less likely with an increased number of turns and layers. In this paper, it is shown that a slight disorderliness in winding leads to a considerable difference between the value of winding stray capacitance of the former ordered winding and its slightly disordered scheme. Therefore, regular methods for calculating the stray capacitance have significant errors in a... 

Microwave power modules are the result of integration of vacuum tubes and their respective power supplies. In these modules, volume and weight are very important factors because the modules are used in many portable applications. There are many parameters that they affect the volume and weight of the microwave power module. High voltage issues are one of these factors because the required voltages of vacuum tubes are high voltage. Thermal management relates to the module volume directly. In high-voltage high-frequency converters as power supplies of vacuum tubes, parasitic elements of the transformer are dominant. Tuning the transformer parameters leads to variation in the volume of the... 

This paper investigates a predictive control strategy for a single-phase PFC rectifier exploiting the Sheppard-Taylor converter. By using this converter, the detuning problem occurring in conventional PFC rectifiers, especially at low input voltages, is avoided. This paper addresses a predictive method for designing the current controller of the Sheppard-Taylor PFC converter. The control law is derived for an ideal circuit as well as a more accurate model of the converter including parasitic elements. Input voltage feed-forward compensation provides sinusoidal input current and a desired output voltage even if the input voltage is distorted. To investigate the dynamic performance of the PFC... 

This paper presents an input/output feedback linearization control strategy for the three-level three-phase neutral-point-clamped rectifier using it's dual Lagrangian modeling, which is obtained based on the superposition law, the load current and The Euler-Lagrange description of the rectifier. The load current can be given in two forms: 1. the load current involving the current of capacitor C1 and 2. The load current involving the current of capacitor C2 Applying the obtained load current to the Euler-Lagrange parameters of the rectifier, two nonlinear models of the system are derived. Also two the power-balance equations between the input and output sides are obtained by considering the... 

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...