Design of a buck converter with zero-current turn-off MCT

The buck converter is a class of commonly used power electronics apparatus. During the last decade many new buck converters have been introduced. Today the following classification can be made: converters with hard switching device, resonant converters and quasi-resonant converters. The main optimization goals are: high efficiency, small volume and weight, simple control circuit, and low price. Not all of these goals are satisfied by all of these classes. Choice of topology is mostly a compromise. Hard switching converters are described by high switching losses, high EMI emission caused by du/dt i di/dt, and the need for turn-on and -off networks. Resonant and quasi-resonant converters are known for reduced switching losses, however, especially for quasi-resonant converters, increased conduction losses and complicated control circuits reduce their practical applications. A wide group of buck converter applications is in PVD (physical vapor deposition) supply apparatus. They can be described by the following output power values: current in kA range and relatively low voltages. Efficiency is a very important key, depending mostly on the choice of the semiconductor switch and topology. The authors present a buck converter based on MCT and additional commutating circuit by turn-off designed as a PVD supply converter