Driving circuit for stepping motor, method of driving stepping motor, and electronic device using the same

A driving circuit for a stepping motor, comprising:

• a counter electromotive force detection circuit configured to detect a counter electromotive force generated in a coil;
• a current value setting circuit configured to generate a current set value based on the counter electromotive force;
• a constant current chopper circuit configured to generate a pulse-modulated signal which is pulse-modulated so that a detected value of a coil current flowing through the coil approaches a target amount based on the current set value;
• and
• a logic circuit configured to control a bridge circuit connected to the coil according to the pulse-modulated signal,
• wherein the driving circuit is configured to output the detected value of the coil current to outside or to access the detected value of the coil current from the outside, and
• wherein the constant current chopper circuit includes:
• a comparator configured to compare the detected value of the coil current with a threshold value based on the current set value;
• an oscillator configured to oscillate at a predetermined frequency;
• and
• a flip-flop configured to output the pulse-modulated signal which transitions to an OFF level in response to an output of the comparator and transitions to an ON level in response to an output of the oscillator.

A method of driving a stepping motor, comprising:

• detecting a counter electromotive force generated in a coil;
• generating a current set value based on the counter electromotive force;
• generating a pulse-modulated signal which is pulse-modulated so that a detected value of a coil current flowing through the coil approaches a target amount based on the current set value;
• controlling a bridge circuit connected to the coil of the stepping motor according to the pulse-modulated signal;
• and
• supplying the current set value to a host controller,
• wherein the generating the pulse-modulated signal includes:
• comparing, by a comparator, the detected value of the coil current with a threshold value based on the current set value;
• and
• outputting, by a flip-flop, the pulse-modulated signal which transitions to an OFF level in response to an output of the comparator and transitions to an ON level in response to an output of an oscillator that is configured to oscillate at a predetermined frequency.

A method of driving a stepping motor, comprising:

• detecting a counter electromotive force generated in a coil;
• generating a current set value based on the counter electromotive force;
• generating a pulse-modulated signal which is pulse-modulated so that a detected value of a coil current flowing through the coil approaches a target amount based on the current set value;
• controlling a bridge circuit connected to the coil of the stepping motor according to the pulse-modulated signal;
• and
• supplying the detected value of the coil current to a host controller,
• wherein the generating the pulse-modulated signal includes:
• comparing, by a comparator, the detected value of the coil current with a threshold value based on the current set value;
• and
• outputting, by a flip-flop, the pulse-modulated signal which transitions to an OFF level in response to an output of the comparator and transitions to an ON level in response to an output of an oscillator that is configured to oscillate at a predetermined frequency.