Patent ID: 8564230
Filing Date: 2013-10-22
Classification: H02P

Abstract:
1. A method for sensor-free motor load or load angle detection in a stepper motor that is controlled with ON and FD (fast decay) phases during chopper operation, comprising calculating during a decreasing amount of a current (I(t)) that flows through at least one of the coils of the motor, a load sum (Ls) in the form of the product of the supply voltage of the motor and the temporal integral of (tON*I(t)−tFD*I(t))dt, wherein tON is the temporal duration of the ON phases and tFD is the temporal duration of the FD phases, and wherein the load angle is assumed to be approximately 90° and, respectively, the motor load is assumed to be at a maximum when the load sum (Ls) is at least essentially zero.