Controller for energization of a stepper motor

Abstract

The present invention provides an N phase/N+1 phase energization type stepper motor controller for alternately energizing an N number and an N+1 number of phases where N is an integer equal to or greater than one. The controller detects which phase(s) is(are) energized at a time when the stepper motor is paused, and sets a starting pulse width for N phase energization to be made shorter than that of N+1 phase energization, in response to the detected results. When the initial energization in starting is N+1 phase, a driving pulse having a width which is longer than that N phase for energization is outputted. The N+1 phase energization has stronger magnetism for rotating a rotor than N phase energization, thereby increasing the rotational speed for starting. When the initial energization is N phase, a driving pulse having a width which is shorter than that for N+1 phase energization is outputted. Thus the magnetism is made stronger so that the starting rotational speed is increased when performing either N+1 phase energization or N phase energization. The period for executing N phase energization is made shorter than that for N+1 phase energization, and the ratio of periods for N phase and N+1 phase energization is kept constant. By shortening the period for N phase energization and extending the period for N+1 phase energization, smooth and constant rotation is obtained.