Patent ID: 9654040
Date: 2017-05-16
CPC Classifications: B41J,H02P

Claim:
1. A drive circuit of a stepping motor comprising: a drive unit configured to switch a level of an excitation current to the stepping motor based on an phase signal; a target voltage generating unit configured to generate a target voltage for determining a target value of the excitation current, when the excitation current flowing into the stepping motor is maintained at the same level; a current controller configured to control the excitation current so as to maintain a value of the excitation current at the target value based on the target voltage; an oscillation circuit configured to generate an oscillation signal which has an oscillation cycle shorter than a switching cycle of the level of the excitation current; a logic controller configured to turn the drive unit on and off based on the oscillation signal and an output reversal of a comparing unit within a first period in which the excitation current flowing into the stepping motor is to be maintained at the same level, the comparing unit being configured to reverse its output based on a comparison between a signal varying in accordance with turning the drive unit on and off by the logic controller and the target voltage; and an abnormality detecting unit configured to detect a state, where the output reversal of the comparing unit does not occur within a predetermined period that is shorter than the first period, as an abnormal state.