Patent ID: 7129671

Claim:
A stepping motor drive device comprising: a supply current measurement unit operable to measure a supply current to a coil of a stepping motor; a chopper unit operable to pass the supply current in a conducting state and stop the supply current in a non-conducting state; a PWM control unit operable to (i) bring the chopper unit into the conducting state in a predetermined cycle, and (ii) when in each cycle the measured supply current exceeds a limit indicator, to which the supply current is to be controlled and which is represented by a predetermined reference signal whose signal level changes over time, bring the chopper unit into the non-conducting state; a synchronous rectification unit operable to form, in a conducting state, a closed circuit together with the coil; a synchronous rectification control unit operable to bring, during a time period when the chopper unit is in the non-conducting state, the synchronous rectification unit into the conducting state so as to make a regenerative current from the coil circulate around the closed circuit; and a synchronous rectification prohibition unit operable to prohibit, for at least a portion of a time period during which the limit indicator is decreasing, the synchronous rectification control unit from bringing the synchronous rectification unit into the conducting state.