PURPOSE: To prevent return to a rectification circuit at a power supply side by looping current within a switching circuit by continuously keeping on a switching element which was at ON timing before switching for a specific period after switching two-phase conduction and intermittently turning on the switching element which newly becomes ON timing.

CONSTITUTION: A three-phase AC power supply is connected to a stator with three-phase coil windings LU, LV, and LW of star-type connection via a rectification circuit, the rotary reference position of a rotor with a permanent magnet is detected, and commutation is repeated with a delay of an electrical angle of 30 degrees, thus rotating the rotor, where a conduction mode corresponding to a specific period (an electrical angle of 20 degrees) after the commutation of two-phase conduction is provided at the prestage of the conduction mode of an original control pattern. Then, transistor TV+ intermittent ON and transistor TW- continuous ON are enabled for a specific period when commutating from the conduction mode of. for example, transistor TU+ intermittent ON and transistor TW- continuous ON, thus shifting to the conduction mode of transistor TV+ continuous ON and transistor TW- intermittent ON.