Improving Input Current Waveforms in a Switching Mode Rectifier with a High Frequency Transformer

Abstract

In recent years, switching mode rectifiers (SMRs) which are composed of a capacitor input type rectifier and a DC-DC converter have been used to supply DC power to various electronic systems. Despite their desirable features such as small-size, light-weight, and high-efficiency, there is a disadvantage in that their input current waveforms include many harmonic components, which could severely influence other systems that AC power lines in common with the SMR. Conventional method to improve the waveforms uses bidirectional switch modules or three full bridge conversion circuits. However, this method cannot decrease the size, because the number of the switching devices increase.
To solve this problem, a novel SMR with a high frequency transformer has been studied. In it, input 3-phase AC voltage is directly converted into high frequency AC, then rectified. Futhermore, low order harmonics in the input current waveforms can be eliminated by controlling the conduction intervals of switches, proportional to the instantaneous input line to line voltage.
This paper describes the configuration of the novel SMR and its operating principle for obtaining sinusoidal input current waveforms as well as discusses the distortion factor characteristics of the input current waveforms.