Patent ID: 7040450

Claim:
A power-assisted steering system for applying an auxiliary steering force to a steering mechanism of a vehicle by driving an electric motor based on a target value determined in accordance with an operation by an operation unit for steering the vehicle, the power-assisted steering system comprising: a PWM type driving circuit that includes a switching element pair having a first switching element disposed on a power supply line side and a second switching element disposed on a grounded line side and connected to each other in series, adapted to supply current to the electric motor from a connecting point between the first switching element and the second switching element; a current detector that detects current flowing to one of the first switching element and the second switching element; a correcting unit that corrects a first detected value of the current detected by the current detector when the one of the first and second switching elements is in an ON state based on a second detected value of current detected by the current detector when the one of the first and second switching elements is in an OFF state, and outputs the corrected detected value; and a controller that controls the driving of the electric motor by switching on and off the first switching element and the second switching element based on the target value and the corrected detected value.