Method of controlling a line-feed stepping motor in a printer and a driver circuit therefor

DETAILED DESCRIPTION An object of this invention is to solve this problem in the prior art by providing a method of controlling the line-feed motor so that step-out does not occur even if load fluctuations occur while the printer is spacing and printing.
Another object of the invention is to provide a drive circuit used for implementing the above method.
The invention provides an improvement in a method of controlling a line-feed stepping motor in which the line-feed motor is controlled by a driver circuit so as to generate a rotational torque for performing the line-feed operation and a holding torque for preventing unwanted motion of the printing medium.
According to the invention, to solve the problem of the prior art described above, the driver circuit is configured to generate a first holding torque of a magnitude permitting the operator to feed the printing medium manually, and a second holding torque larger than the first holding torque.
The first holding torque is generated when the printer is in the ready state.
The second holding torque is generated while the printer is printing.
This invention overcomes large load fluctuations on the printing medium caused by friction and other factors by generating two holding torques, a first holding torque and a stronger second holding torque, and applying the second holding torque during the printing operation.
This method of control can effectively prevent step-out, thus solving the above problem of the prior art.