Kenichiro Fujiwara

A loss-less passive snubber for soft-switching boost-type converters

A novel loss-less passive snubber is proposed for the soft-switching boost-type converters. The proposed snubber does not use any auxiliary switches, but uses two snubber capacitors which are charged in parallel and discharged in series automatically. The discharged energy is recovered effectively (more than 95% recovery) into the output capacitor. Thus the snubber provides zero-voltage switching for the converter main switch reducing the turn-off losses and improves the converter efficiency. The experimental results of a 20 kHz DC-DC boost converter and a single-phase AC-DC boost rectifier with the new snubber are presented.

A power factor compensator using a force-commutated cycloconverter

A power-factor compensator using a force-commutated cycloconverter (FCC) is proposed that keeps the displacement factor of the AC system at unity regardless of the load power factor. No energy storage elements or feedback controls are required. An FCC with half of the load capacity can provide fast and complete compensation of the reactive power in the load. An extension of the basic concept results in a power-factor compensator with output-voltage control that retains most of the merits of the original system and extends the areas of application.<<ETX>>

Improvement of current waveform for 200 V input single-phase rectifiers using modified voltage-doubler circuit

To improve the current waveform of rectifiers, we propose a new operating principle for the voltage-doubler rectifiers with 200 V utility voltage. For the limited input range, 0.3 kW/spl sim/1.6 kW, the conventional diode voltage-doubler rectifier can be designed such that the input current satisfies the harmonic guidelines. A high power factor of 97% and efficiency of 98% are experimentally obtained. The proposed method seems to be very attractive for an air conditioner DC source using inexpensive and reliable components.