According to an embodiment, a driving apparatus of a DC brush motor includes: a drive circuit that supplies motor current to a coil of a DC brush motor; and a control circuit configured to: after a predetermined time interval has elapsed since starting-up of the DC brush motor, drop down step-by-step a limit value that sets an upper limit of the motor current; and detect turning into a state where the motor current is limited by the limit value.

According to an embodiment, a driving apparatus of a DC brush motor includes: a drive circuit that supplies motor current to a coil of a DC brush motor; and a control circuit configured to: after a predetermined time interval has elapsed since starting-up of the DC brush motor, drop down step-by-step a limit value that sets an upper limit of the motor current; and detect turning into a state where the motor current is limited by the limit value.

A soft-start circuit which can be applied to a motor controller is provided. The soft-start circuit comprises a controller, a counting unit, a digital-to-analog converter, a current detecting unit, and a comparator. The soft-start circuit uses a plurality of current limit values so as to achieve a maximum output power and prevent damage to a motor coil.

A soft-start circuit which can be applied to a motor controller is provided. The soft-start circuit comprises a controller, a counting unit, a digital-to-analog converter, a current detecting unit, and a comparator. The soft-start circuit uses a plurality of current limit values so as to achieve a maximum output power and prevent damage to a motor coil.

A drive device for an electric motor according to the present invention includes a first relay that turns a power supply line on and off leading from a power supply to an electric motor, a resistor provided on a bypass line that bypasses the first relay, a second relay that turns the bypass line on and off, a relay control circuit that outputs a relay control signal common to the first relay and the second relay, and a delay unit that delays the turn-on timing based on the relay control signal of the first relay later than the turn-on timing based on the relay control signal of the second relay. This configuration makes it possible to add a function for suppressing an inrush current without increasing the number of output connectors of a relay control circuit.

An increase in startup current supplied to a motor is suppressed at an initial stage of starting automatic braking control, while current supply to the motor is performed in a fully energized state after the automatic braking control is started. While output of the motor is increased by controlling the motor in the fully energized state so that a high braking force with high responsiveness is obtained, startup current is prevented from becoming excessive by performing high frequency control only at startup. Thus, decrease in battery voltage is minimized and thus the occurrence of malfunction is minimized in the control systems of various electrical components used in the vehicle.

An electric motor is connected to a voltage source via a drive circuit and, between the drive circuit and the voltage source, the operating switch is arranged for the switching of the supply voltage (U) of the voltage source as the input voltage (U.sub.E) on the drive circuit. Following the switch-out of the electric motor, the input voltage (U.sub.E) on the drive circuit is monitored and a gradient of a rising voltage ramp (dU/dt) of the input voltage (U.sub.E) is determined. The gradient of the rising voltage ramp (dU/dt) of the input voltage (U.sub.E) thus determined is compared with a predefined limiting value and, in the event of an overshoot of the predefined limiting value, the operating switch is detected as closed, and the electric motor is restarted via the drive circuit.

Methods and systems include an actuator 40 adapted to provide drive power and hold power to an external device. A motor 34 provides for driving the external device to a determined position when the motor 34 is energized. A switching circuit is configured to energize the motor 34 with a high voltage to drive the external device to the determined position and energize the motor 34 with a low voltage to hold the external device in the determined position.

A DC/DC converter in which a both-end voltage of each of capacitors can be safely uniformalized while an over current, which is passed through between the capacitors composing the DC/DC converter, is prevented. In a DC/DC converter which includes a plurality of switching elements, a reactor, a low-voltage side capacitor, a high-voltage side capacitor, a charge-discharge capacitor, and a controller which drives and controls the switching elements, the controller performs soft start control in which a duty ratio of at least one of the switching elements is gradually varied from 0% to 100%, and the switching element, in which the soft start control is not performed during the term of the soft start control, is turned off.

A rotary drive system having a voltage source and an electric motor. The motor has a stator with independent phases and a rotor, an inverter designed to connect each phase to the voltage source in order to generate phase currents, and a device for controlling the inverter. The control device includes a unit for determining whether the fundamental frequency of the phase currents is lower than a frequency threshold equal to, at the most, 100 Hz, and a unit for generating a command, configured such that, when the fundamental frequency is determine as being lower than the frequency threshold, the command causes the appearance of a homopolar component in the phase currents.