Alenka Hren

RC-RCD clamp circuit for ringing losses reduction in a flyback converter

An RCD clamp circuit is usually used in flyback converters, in order to limit the voltage spikes caused by leakage transformer inductance. Oscillation ringing appears due to the clamp diode, which deteriorates the converters power rate. This brief describes this ringing phenomenon and the use of an RC-RCD clamp circuit for damping the clamp diodes oscillation. This clamp circuit is capable for improving a flyback converters power ratio.

Safe start-up procedures of isolated bi-directional DC-DC converter

This paper presents a safe start-up procedures of an isolated bi-directional DC-DC converter in buck and boost modes. This converter has been developed as a part of multifunctional up to 4 kW power supply system that uses a high voltage (450 V) DC-link. The isolated bi-directional DC-DC converter can charge 28 V batteries and supply auxiliary low voltage DC loads. Additionally, the isolated bidirectional converter can also draw power from the batteries or from trucks engine driven alternator to keep maintain the high voltage DC-link. Modulation strategies, start-up procedures and control of this converter have been validated by using the Matlab SymPowerSystems Toolboxes and finally, they have been also experimentally verified.

An Isolated Single-Phase Rectifier with Power Factor Correction

The paper presents an application example from the large family of the converters with the single-ended switch, or with forward converter. The forward converters with one switch are used for power applications up to 250W. The proposed rectifier construction with one switch and with power-factor correction is derivation from the buck (step down) converter. It also employs the principle of a boost (step up) power-factor-cell. The switching controller is based on that principle as well. The transformer and the output filter are used for galvanic isolation and for the storage of the electric charge. Obtained experimental results for the suggested scheme of 3500W isolated power supply are in good accordance with the simulation results. The comparison of results we have achieved and results reported in the literature confirms the advantage of the proposed rectifier scheme.

PWM algorithm for three-phase three-level AC to DC boost rectifier

This paper considers the connection between switching matrix function and pulse width modulation algorithm with emphasis on the unity power factor correction requirements for three-phase three-level AC to DC converter. Based on the switching matrix converter theory, the switching sequences for PWM of the three-phase three-level AC to DC converter (rectifier) have been developed. Such an approach enables the input displacement factor correction without an input current sensor. The necessary control variable is only the measured displacement angle between the input voltage and the input current.