Input current shaping in BLDC motor drives using a new converter topology

A new converter topology is proposed for driving a permanent magnet brushless DC (BLDC) motor with unipolar currents. It is based on a single-ended primary inductance converter (SEPIC) operating in the discontinuous conduction mode. In this operation mode, it approximates a voltage follower and the line current follows the line voltage waveform to a certain extent. The reduction in low-order harmonics and improved displacement power factor is achieved without the use of any voltage or current sensors. The simplicity and reduced parts count of the proposed topology make it an attractive low-cost choice for many variable speed drive applications.