The paper deals with modelling and design of HF 200 kHz (and more) low-power transformers with determinated leakage induct-ances for both hard- and soft-switching applications. The first group features by small value of the leakage inductance contrary to sec-ond one demanding that value substantially higher. The further aims of the design are minimized weights and dimensions of the trans-formers. Results of numerical simulations and experimental verifications of designed transformers operated in converter circuits are given at the end of the paper. Ill. 13, bibl. 5, tabl. 2 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.110.4.276

Many electric circuits feature some type of nonlinearity of their used devices. Non-linear resistors or inductors could be typical examples. Also, all semiconductor devices are in their nature non-linear ones. From the point of view of the circuit solution they are presented non-linear static and dynamical system described by differential equations. Particularly, in steady state, it could be system of non-linear algebraic equations.

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the paper deals with research of the ways of efficiency increase of proposed hard switching full bridge converter which is suited for electroplating. The main circuit is designed as standard full bridge converter with IGBT transistors, whose switching frequency is 17 kHz. Main attention of optimization of power stage is focused on configuration of output, secondary side rectifier, which is designed in double center tapped configuration providing therefore current doubling of output current. Various types have been investigated, including diode Schottky rectifier, synchronous MOSFET rectifier together with additional auxiliary and snubber circuits and its combinations. Each solution has been experimentally verified for various and most probable operating conditions of proposed converter, whereby results have been consequently compared. Several results show, that efficiency is able to be increased when proper optimization steps are being utilized.

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