TECHNICAL FIELD

The technology disclosed herein belongs to a technical field related to a motor controlling device which controls an on-board motor, and an on-board system provided with the motor controlling device.

BACKGROUND OF THE DISCLOSURE

JP2006-044479A discloses a configuration for reducing electromagnetic noise emitted through a steering shaft by lowering the electric potential of the steering shaft toward the ground.

However, it is based on a premise that the steering shaft does not transmit an electrical signal, and, for example, signal wiring which transmits the electrical signal, such as wiring which connects an H-bridge circuit to a motor, cannot be lowered to the ground.

Moreover, in order for the signal wiring which transmits the electrical signal not to be influenced by noise from the outside, it is possible to shield the signal wiring (wire harness). However, the manufacturing cost increases and the weight of a vehicle becomes heavier, and therefore, fuel efficiency may be affected.

SUMMARY OF THE DISCLOSURE

The technology disclosed herein is made in view of the above situation, and one purpose thereof is to reduce an effect of electromagnetic noise by secondary radiation from signal wiring which is unfixable to the ground.

According to one aspect of the present disclosure, a motor controlling device configured to control an on-board motor, is provided. The device includes a drive circuit of H-bridge type comprised of a plurality of first switching elements and configured to drive the on-board motor, and a controlling circuit configured to control the on-board motor by controlling the drive circuit. The controlling circuit carries out an ON control of at least one of the plurality of first switching elements connected to a ground, when not operating the on-board motor.

According to this configuration, output lines of the drive circuit for driving the suspended motor can be lowered to the ground potential (grounded), and therefore, an effect of electromagnetic noise by secondary radiation can be reduced.

Each switching element may be a field-effect transistor (FET).

According to this configuration, the reaction speed of the motor controlling device is improved.

