Patent ID: 8796967
Filing Date: 2014-08-05
Classification: H02P

Abstract:
1. A motor drive device for controlling rotational operation of a motor by using a pulse-width modulated PWM signal, the device comprising: a drive controller for generating a driving signal to drive the motor; a duty calculator for calculating a duty command value corresponding to the driving signal; a duty limiter for limiting the duty command value to a value according to a limit value; a PWM signal generator for generating the PWM signal of a duty factor corresponding to an output value of the duty limiter; a drive output unit for generating an energizing signal corresponding to the PWM signal, and energizing a winding of the motor with the energizing signal; a current flow monitor for monitoring a current value that flows through the winding, and determining the current value as being an overcurrent when the current value exceeds a predetermined threshold value; and a limit value generator for generating the limit value, wherein the limit value generator updates the limit value at predetermined time intervals and for a value corresponding to a difference between the threshold value and the current value at a time, in order to decrease the current value during a period in which the overcurrent is determined.