Patent ID: 7586277

Claim:
An electric power steering device for controlling the output of a motor that applies an auxiliary steering force to a steering mechanism from a current reference value calculated based on at least a steering torque signal generated in a steering shaft, said device comprising: a duty ratio calculator for calculating a duty ratio D 1 and a duty ratio D 2 determined by a motor terminal voltage based on said current reference value; and a motor drive circuit including a motor connected across the output terminals and a power supply connected across the input terminals of an H bridge circuit made up of a first arm and a second arm each containing a pair of semiconductor devices connected in series, a PWM signal for a duty ratio D 1 driving said semiconductor device in the upper stage of said first arm, and a PWM signal for a duty ratio D 2 driving said semiconductor device in the lower stage of said second arm of said H bridge circuit, wherein said duty ratio calculator calculates said duty ratio D 1 and said duty ratio D 2 having a continuous characteristics between the motor current and a duty ratio D from said current reference value based on a specified calculation formula.