A method and circuit arrangement for sensorless determination of the rotor position of a brushless dc motor

摘要

It is a method and a circuit arrangement is proposed for sensorless determination of the rotor position, as well as for the operation of a brushless dc motor (10) with a preferably a permanently magnetically excited rotor (12) and with a preferably three-phase, in a star armature winding (14) as well as with a control unit (26) for a semiconductor device (24) for the purpose of connecting the windings of the dc motors (10) to a dc network (16, 18) as a function of the rotor position. According to the invention, the control unit (26) a from the phases sums current (i) of the motor (10) is fed to a trigger signal (58) for fixing the points in time for the detection of reference values of the voltages induced in the individual phases (u_i) as a time criterion for the generation of the commutation signals of the semiconductor switching unit (24). In this case, the from the difference in each case of a phase voltage (u_x) and the star point voltage (u_s) output signal formed of a summer (34, 36, 38) in a subsequent comparator (40, 42, 44) with a voltage value for the internal resistance (r) of the phase by a predetermined phase current (i_ref) compared and voltage drop produced from this, the induced voltages (u_ix) and the zero transitions are determined.