Stepper motor driver circuit

A stepper motor driver circuit that controls driving of a stepper motor, comprising:

• a current control circuit that supplies a driving current having a pseudo-sinusoidal waveform that varies stepwise every one period of a reference clock signal to a coil of the stepper motor;
• a comparator that compares an exciting voltage of the coil at a time when the driving current is zero and a threshold and outputs a comparison result signal;
• and
• a logic circuit that outputs a control signal based on the reference clock signal and a command signal input from an outside,
• wherein the current control circuit controls the driving current in response to the control signal, and
• wherein the stepper motor driver circuit generates the driving current having the pseudo-sinusoidal waveform that varies stepwise every one period of a reference clock signal and makes the waveform of the driving current vary in response to a measurement value of the exciting voltage on the coil of the stepper motor at the time when the driving current is zero.