Drive control method for stepping motor

A drive control apparatus for a stepping motor provided with two exciting coils, comprising:

• a driving circuit for outputting current signals to the respective exciting coils to drive the stepping motor;
• and
• a controller for outputting a control signal to the driving circuit to set up a 1-2 phase driving mode in which a one-phase excitation and a first two-phase excitation of the exciting coils are alternately performed, when the stepping motor is in a constant-speed state, and to set up a W1-2 phase driving mode in which the one-phase excitation and a second two-phase excitation of exciting coils are alternately performed, when the stepping motor is in acceleration and deceleration states,
• wherein the one-phase excitation is an excitation aspect in which one exciting coil is excited by the current signal having a maximum absolute value thereof, and no current signal is supplied to the other excitation coil;
• wherein the first two-phase excitation is an excitation aspect in which two exciting coils are excited by the current signals, each having the maximum absolute value thereof;
• and
• wherein the second two-phase excitation is an excitation aspect in which two exciting coils are excited by the current signals such that a sum of the absolute values of the respective current signals is a constant value which is smaller than a sum of the absolute values of the respective current signals in the first two-phase excitation.