Abstract: An electric power steering device includes: a fail-safe power relay (9a) and a motor relay (10a) for interrupting power supply to an electric-motor driving unit for driving an electric motor for applying an assist torque for steering performed by a driver; and a relay driving circuit (8a) including a switch (13a) connected in parallel to drive coils of the relays (9a and 10a) and a diode (16a). A target value of a relay-contact energizing current is lowered and the relays (9a and 10a) are gradually interrupted while an amount of current corresponding to a back surge generated when the relays are turned OFF is caused to flow back to the diode (16a) of the relay driving circuit (8a) in a normal relay-OFF operation, whereas the relays (9a and 10a) are quickly interrupted without operating the relay driving circuit (8a) in case of detection of an abnormality.

Abstract: An electric power steering device includes: a fail-safe power relay (9a) and a motor relay (10a) for interrupting power supply to an electric-motor driving unit for driving an electric motor for applying an assist torque for steering performed by a driver; and a relay driving circuit (8a) including a switch (13a) connected in parallel to drive coils of the relays (9a and 10a) and a diode (16a). A target value of a relay-contact energizing current is lowered and the relays (9a and 10a) are gradually interrupted while an amount of current corresponding to a back surge generated when the relays are turned OFF is caused to flow back to the diode (16a) of the relay driving circuit (8a) in a normal relay-OFF operation, whereas the relays (9a and 10a) are quickly interrupted without operating the relay driving circuit (8a) in case of detection of an abnormality.