Electrically powered brake control unit and the electric brake control method

The invention relates to an electrically powered brake system capable of performing a self-diagnosis of elements of the electrically brake system to diagnose a failure before a vehicle is driven. The electrically powered brake system having a parking brake having a conversion mechanism (6) converting a rotary motion of a motor (2) into a linear motion, propelling a piston (7) according to the rotation of a rotor (2A) of the motor (2) by the conversion mechanism, pressing brake pads (3) and (4) against a disc rotor (5) by the piston (7) to generate a braking force, and retaining the braking force by a locking mechanism (10) which has a control unit (20) performing a diagnosis of elements constituting the system during actuation of the parking brake, the control unit (20) performs a diagnosis of a fail safe relay (26) receiving the supply of electric power of the motor (2), and performs diagnoses of a braking force sensor (8), a rotation angle detecting sensor (9) and a current sensor.