In this paper, the power factor correction system consisted of: bridge converter, parallel resonant circuit, high frequency transformer, diode rectifier and LFCF filter is presented. This system is controlled by a pulse density modulation method and the principle of its operation is based on the boost technique. The modeling approach is illustrated by an example using AC/HF/DC converter. Verification of the derived model is provided, which demonstrated the validity of the proposed approach.

In the paper an improved method of calculation of the inductance and capacitances in the ?1 circuit for Class A, AB, B, and C resonant power amplifiers is presented. This method is based on an assumption that the quality factor of the inductor is inite and the capacitors are lossless. The input parameters for calculations are the amplifier load resistance, the transistor load resistance, the quality factor of the inductor, the loaded quality factor of the designed circuit, and the operating frequency. The presented method allows reducing the required regulation range of ?1 circuits elements In built resonant amplifiers as compared to the traditional calculation methods assuming lossless capacitors and inductor. This advantage is important, in particular, for long- and medium-wave transistor power amplifiers, where capacitances in ?1 circuits are high comparing to typical trimming capacitors.

In this paper the problem of resistance measurement of ultrathin conductive lines on dielectric substrates dedicated for printing electronic industry is discussed. The measured line is transformed in a non-invasive way into a resonance circuit. By using a magnetic coupling between the source line and the tested line, the resistance measurement can be performed non-invasively, i:e. without a mechanical contact. The proposed contactless resistance measurement method is based on the resonance quality factor estimation and it is an example of the inverse problem in metrology.