Patent ID: 7176646

Claim:
An electric power steering apparatus installed in a vehicle having a primary power source that generates primary voltage, wherein the vehicle has a steering system and an in-vehicle network for communicating information, the electric power steering apparatus comprising: a steering force assisting device that supplies assisting force for assisting steering operation to the steering system, wherein the assisting device has a steering motor serving as a driving source of the assisting force; a transformer section that transforms the primary voltage and outputs secondary voltage; and a control section that controls the steering force assisting device by supplying driving electricity based on the secondary voltage to the steering motor, wherein the control section inputs a first signal indicating a state of electricity supply of the primary power source through the in-vehicle network, wherein the control section supplies driving electricity to the steering motor based on the first signal, wherein the transformer section outputs a second signal indicating a state of electricity supply of the transformer section, and wherein, when the input of the first signal is disrupted, the control section limits the driving electricity supplied to the steering motor based on at least one of a value of the secondary voltage and the electricity supply state of the transformer section indicated by the second signal.