A digitally controlled switch mode power supply

High power telecommunication power supply systems consist of a 3-phase switch mode rectifier followed by a DC-DC converter to supply loads at -48V DC. These rectifiers draw significant harmonic currents from the utility, resulting in poor input power factor with high total harmonic distortion (THD). In this paper, a digitally controlled 3-phase switch mode power supply based on a matrix converter is proposed for telecommunication applications. In the proposed approach, the matrix converter directly converts the low frequency (50/60Hz, 3-phase) input to a high frequency (10/20 kHz, 1-phase) AC output without a dc-link. The output of the matrix converter is then processed via a high frequency isolation transformer to produce -48V DC. Digital control of the system ensures that the output voltage is regulated and the input currents are of high quality under varying load conditions. Due to the absence of dc-link electrolytic capacitors, power density of the proposed rectifier is expected to be higher. Analysis, design example and experimental results are presented from a 3-phase 208V, 1.5kW laboratory prototype converter.