Abstract: An electric power steering apparatus that protects Zener diodes without impairing steering performances by time-integrating a loss power of the Zener diodes for protecting FETs and gradually limiting a duty ratio with an increase in an integrating loss. The apparatus includes a loss power calculating section that calculates a loss power when a difference between an ignition voltage and an inverter applying voltage is equal to or more than a predetermined voltage; an integrating loss calculating section to calculate an integrating loss of the loss power; a permissible loss calculating section to calculate a permissible loss based on a temperature; a minimum value selecting section to select a minimum value of a loss difference of the permissible loss and the integrating loss; and a limit value calculating section to calculate a limit value of the PWM-signal based on the minimum value of the loss difference and the permissible loss.

Abstract: An electric power steering apparatus that protects Zener diodes without impairing steering performances by time-integrating a loss power of the Zener diodes for protecting FETs and gradually limiting a duty ratio with an increase in an integrating loss. The apparatus includes a loss power calculating section that calculates a loss power when a difference between an ignition voltage and an inverter applying voltage is equal to or more than a predetermined voltage; an integrating loss calculating section to calculate an integrating loss of the loss power; a permissible loss calculating section to calculate a permissible loss based on a temperature; a minimum value selecting section to select a minimum value of a loss difference of the permissible loss and the integrating loss; and a limit value calculating section to calculate a limit value of the PWM-signal based on the minimum value of the loss difference and the permissible loss.

Abstract: An electric power steering device which has, on the outer surface of its gear box, the circuit modules of a control device such as a power module, a frame module, and a control module, and which is easily mountable on a vehicle and less affected by heating. The upper half of the gear box (11) is formed in a rectangular parallelepiped box (11b) in which a reduction gear mechanism is assembled. The first flat face (11b1) of the gear box (11) on the outside of the axis of the center shaft of an electric motor (12) as viewed from a worm gear meshing point is formed as a mounting face for the power module (PM), and the second flat face (11b2) of the gear box crossing the first flat face is formed as a mounting face for circuit parts forming the frame module (FM) and the control module (CM).