Electronic Thesis and Dissertation Repository

Thesis Format



Master of Engineering Science


Electrical and Computer Engineering


Moschopoulos, Gerry


Low power AC-DC power conversion is typically done with a two-stage converter that consists of an AC-DC front-end boost converter that also performs input power factor correction and an isolated DC-DC back-end converter that is either a flyback or a forward converter. In applications where cost is an overriding factor, single-stage AC-DC converters that use a single power converter to simultaneously perform input power factor correction and AC-DC conversion can be used. In applications where output filtering and hold-up time are important considerations, single-stage AC-DC converters are implemented with a DC bus capacitor.

The main objective of this thesis is to investigate the interleaved operation of a single-stage stacked AC-DC flyback converter that has less cost, size, and component stress than interleaved two-stage converters and interleaved non-stacked single-stage AC-DC converters. In this thesis, the steady-state operation of a stacked converter with interleaving is explained and analyzed in detail by using a computer program that is based on the principle of energy equilibrium. The results of the analysis, which are a set of equations related to key component stresses and losses and a set of graphs of steady-state characteristic curves is then used to select component values using an iterative design procedure. The performance of the stacked converter with interleaving is confirmed with results obtained by PSIM simulation as is the accuracy of the analysis. The thesis concludes with a summary of the thesis contents, conclusions, contributions, and suggestions for future work.

Summary for Lay Audience

Power electronics is very closely related to daily life and can be found in many applications, such as in mobile phones, personal computers, and hybrid vehicles. It is the field of electrical engineering that involves the use of semiconductor devices (i.e. switches, diodes, etc.) and other passive elements to convert electrical power from one form to another. The main objective in most applications where power converters are required is to implement converters with as little size, weight, cost, and power losses as possible and with the best performance possible.

Power Converter is a device which can convert power from one condition to another condition to meet the requirement of electric power consuming applications. The AC-DC converter can convert the AC power from the power grid to the DC power which can be used by the electrical devices, such as computer, cell phone and other devices. In this research, an investigation of the interleaved stacked AC-DC flyback converter has been done step by step. Flyback converter is one of the basic converters with a transformer, it can adjust the output voltage by using different control signals. The proposed converter is put one flyback converter over another one, which is called stacked structure, to reduce the voltage stress on the components, to shrink the size and the cost of the whole design. The investigation is focused on the new operation mode with interleaved operation. To achieve the interleaved operation, there is some test and analysis have to be done with equations and simulation software. The interleaved operation makes the input current ripple smaller, and increase the total power factor of the converter, which can increase efficiency as well.