Patent ID: 7023157

Claim:
A stepping motor drive device comprising: a supply current measurement unit operable to measure a supply current supplied to a coil of a stepping motor; a reference signal generation unit operable to generate a reference signal whose signal level changes continuously over time and which represents a limit value for the supply current; a chopper unit operable to pass the supply current in a conducting state through thereof 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 the limit value, 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 in 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 value is decreasing, the synchronous rectification control unit from bringing the synchronous rectification unit into the conducting state.