A single to three-phase converter for home appliances featuring four switches and an active power factor control

Three switch, unipolar power converters have been presented in the past with the aim to reduce cost and circuital complexity of induction motor drives for low power applications in household appliances or in the automotive field. However, such topologies to be of practical use, require an extra switch to control the voltage of the dump capacitor or special winding arrangements. Moreover, they generally require closed loop current and speed control. In the present paper a new converter topology is presented, aimed to equip household appliances, where the additional switch required to control the dump capacitor voltage is also exploited to improve the input power factor. Therefore, the presented topology is equivalent, from the point of view of the amount of power switches, to a true three switch unipolar converter with an active power factor control input stage. In addition, a simple constant V/f speed regulation is introduced thus avoiding expensive current and speed sensors. Finally, the proposed converter topology featuring only switches of the low side type, makes noticeably simpler the design of driver circuits and opens the perspective for a full integration of the converter power stage on a single chip, exploiting smart power technologies.