Patent ID: 6775469
Filing Date: 2004-08-10
Classification: H02P

Abstract:
A method of controlling an electronically commutatable motor including field windings, comprising:selecting a setpoint of one of a rotational speed and an output of the motor; activating the field windings; alternately connecting and disconnecting the field windings from a direct voltage supply in succession, at a commutation frequency, via a semiconductor output stage, using control signals, the control signals being formed as pulse-width modulated signals including rising and falling edges and having an operating value based on the selected setpoint, a current in the field windings increasing with the rising edges of the control signals and decreasing with the falling edges of the control signals, successive control signals overlapping in an overlap region; and clocking at least one of the control signals in the overlap region using pulse width modulation, wherein a pulse width ratio increases in the rising edges of the control signals from a low initial value to the operating value in a number of m steps, the number of m steps being a function of one of the selected setpoint and an actual speed value, wherein the pulse width ratio decreases in the falling edges of the control signals starting from the operating value in a number of n steps before the pulse width ratio drops to a value zero, the number of n steps being a function of one of the selected setpoint and the actual speed value, and wherein selected output ranges of the motor are each assigned a different number of m steps and n steps; and determining values for the number of m steps and the number of n steps based on the actual speed value.