The aim of this thesis is to design a step-up DC/AC converter, an inverter from 12 V to 120 Vrms, with a sinus output signal. The converter should deliver a continuous performance of 300 W and a double peak power output of 600 W. The supposed usage of this inverter would be as a back-up power source for the circulatory pump of the central heating in the case of power outage. The inverter is consisting of a T-type power section.

The master thesis deals with design of a switched DC power supply with output parameters of 30 V 60 A. The power supply uses the connection of two single switch forward converters with opposite phase. The topology was chosen based on a comparison of specific schematics in the first part. The body of the thesis is covered in chapter which deals with design and analysis of power circuits of the converter. The chapter describes detailed design of pulse transformers, dimensioning of semiconductors and cooling system of the converter. For lower power losses, the system of synchronous rectifying is chosen at the output of the circuit. The regulation of the output is based on cascade structure with a superior voltage and dependent current loop. Appropriate over current protection is provided by sensing the output current and using current transformers for primary current measure.

Among PWM power conversion topologies, the single-switch forward topology is the one that has been most widely used for decades. Its popularity has been based on many factors, including its low cost, circuit simplicity and high efficiency. However, several issues need to be addressed when using the forward converter such as the core reset, the voltage spikes caused by the transformer leakage inductance, and the pulsating input current waveform. The transformer is driven in a unidirectional fashion in the forward converter; a tertiary forward converter (TFC) is an example of this. Therefore, the third winding and reset diode must be provided with an adequate period of reset time so that the flux can be fully reset by the end of each switching cycle to prevent core saturation. Also, due to the utilization of a transformer, leakage inductances cannot be avoided. The energy stored in the leakage inductance during current ramp-up is not transferred to the load, and is not recovered during its discharge phase. As a result, the VDS waveform has a voltage spike and undesirable high-frequency oscillation. Therefore, a higher voltage-rating switch should be used to reduce the risk of high-voltage breakdown. Although a switch with amply high voltage ratings is available, it would tend to have a higher on-resistance, RDS(ON), resulting in increased conduction losses. Moreover, selection of a switch with higher voltage ratings than necessary may needlessly increase the cost of the design. Usually an additional circuit such as a snubber circuit or a clamp circuit or the soft-switching technique is used to absorb these voltage spikes. Consequently, the leakage inductance is intentionally minimized in the PWM power conversion technique so that it will not degrade the circuit performance. In contrast, the leakage inductance of the transformer may enhance rather than detract from circuit performance with a resonant power conversion technique. To date, however, no single-switch forward converter has been claimed to be able to enhance the converter performance with the PWM power conversion technique by utilizing the leakage inductance. Therefore, research on the utilization of the transformer leakage inductance in the PWM forward converter is needed. Two techniques, input current ripple reduction and an embedded filter, are proposed to enhance the performance of forward converter using the PWM technique. By inserting a capacitor between two primary windings of the TFC, an input current ripple reduction technique is proposed and a forward converter with ripple reduction (FRR) is presented in this research work. Because the voltage of the capacitor is clamped to input voltage, the capacitor becomes a second voltage source to share part of the load current. As a result, the input current ripple is reduced. Moreover, the capacitor voltage is clamped both at the static and dynamic states; thus the excessive voltage stress on the main switch S1 of the FAC during low-line to high-line step transient is eliminated. Furthermore, without an external LC filter, the EMI noise levels can be further reduced as a result of the embedded notch filter formed by the transformer leakage inductance and clamp capacitor if the notch frequency is designed to be the same as the switching frequency. With the help of the clamp capacitor, therefore, the leakage inductance can enhance rather than detract from the converter performance. The input current ripple can be reduced further by employing the proposed techniques. Two sets of the clamp capacitors and the leakage inductances are utilized, and the current ripple can even be cancelled if the condition is met. Consequently, the input current becomes a non-pulsating waveform and a forward converter with ripple cancellation (FRC) is presented. Moreover, without an external LC filter, the EMI noise levels can be further attenuated as a result of the embedded low-pass filter formed by the transformer leakage inductances and clamp capacitors. Again, the leakage inductance can enhance the converter performance just as the resonant converter does. In addition to providing the analysis and design procedure, this work verifies the performance of the presented converters, the FRR and the FRC, by the experimental results. By employing the proposed techniques, eight new topologies have been extended for different power conversion applications. Each member of the FRR and the FRC families is able to enhance the converter performance, in ways such as the elimination of the voltage spikes on the main switch without a snubber circuit and the improvement of the EMI performance with small filter components. Consequently, the cost can be reduced and the space of the converter can be saved. / Ph. D.

This thesis deals with the peripheral design, construction design and implementation welder DC arc. The concept of welder is based on the use of two single action forward converter working-pull. Converters operate at a frequency of 60 kHz. Output current can be adjusted in the range from 0 to 140 A. After switching function the welder can operate as a battery charger. Charging current can be adjusted in the range of 0-70 A. The device is powered from a single phase supply 230 V.

This diploma thesis deals with design and comparison of selected DC/DC converters, where the better of them is practically realized. The first part of the diploma thesis is focused on the general analysis of DC/DC power converters. The following part is theoretical analysis focused on the first selected topology – step-up converter. The second analysed topology is forward converter with full bridge on the primary side. The theoretical analysis also includes a description of synchronous rectifier, the differences between hard and soft switching, and the types of secondary rectifiers. Another part specializes in the detailed calculation of main components of selected converters and their subsequent power dimensioning. Both designed topologies are compared according to the required aspects. The selected better topology is supplemented by the design of control circuits and an auxiliary power supply. Practical realization of converter and commissioning follows. The diploma thesis ends with verification measurements on the realized converter and their subsequent analysis.

No description available.

In this thesis / analysis, design and implementation of a DC-DC converter with active clamp forward topology is presented. The main objective of this thesis is generating a rectified sinusoidal voltage at the output of the converter. This is accomplished by changing the reference signal of the converter. The converter output is applied to an inverter circuit in order to obtain sinusoidal waveform. The zero crossing points of the converter is detected and the inverter drive signals are generated in order to obtain sinusoidal waveform from the output of the converter. Next, the operation of the DC-DC converter and sinusoidal output inverter coupled performance is investigated with resistive and inductive loads to find out how the proposed topology performs. The design is implemented with an experimental set-up and steady state and dynamic performance of the designed power supply is tested. Finally an evaluation of how better performance can be obtained from this kind of arrangement to obtain a sinusoidal output inverted is thoroughly discussed

Goal of this semestral thesis is to design power converter which is to be used for measurement. The converter consists of two forward converters in push-pull topology. The converter is to behave as a constant current source with maximum open-circuit voltage of 1000V. Maximum current is 5A. The current range is split into three sub-ranges, to meet the strict requirements on ripple current. The range of currents is 0-5A. The operating frequency of converter is 34KHz. The converter will be charged using two portable electric generators with output voltage 230V.

This thesis presents an active clamp forward converter for use in the Energy Harvesting From Exercise Machines project. Ideally, this converter will find use as the centerpiece in a process that links elliptical trainers to the California grid. This active clamp forward converter boasts a 14V-60V input voltage range and 150W power rating, which closely match the output voltage and power levels from the elliptical trainer. The isolated topology outputs 51V, higher than previous, non-isolated attempts, which allows the elliptical trainers to interact with a central grid-tied inverter instead of many small ones. The final converter operated at greater than 86% efficiency over most of the elliptical trainer’s input range, and produced very little noise, making it a solid choice for this implementation.

The diploma thesis is describing how forward converter works. The diploma thesis presents the function of forward converter with demagnetizing winding and presents the function of two-switched forward converter. The diploma thesis descibes the behaviour of continuous current mode and discontinuous current mode. The diploma thesis explains the reasons for implementation feedback and presents the basic types of compensations. The project deals with AC analysis of two-switched forward converter with continuous peak current mode control. The Analog prototyping metod is used for digital control design. The function of the converter was tested in laboratory. The laboratory results have been compared with the theoretical and the simulation results.