Methods for controlling a voltage present at an electric fan during a startup of the fan are disclosed herein. The fan serves to generate a flow of air for cooling a device. The method includes applying an output voltage of a power supply, which serves to supply voltage to the device, to the fan; and switching on and switching off the output voltage of the power supply applied to the fan by a switch pulse-width-modulated-controlled by a control unit so that the Root Mean Square value of the current flowing through the fan is less than a startup current of the fan.

Methods for controlling a voltage present at an electric fan during a startup of the fan are disclosed herein. The fan serves to generate a flow of air for cooling a device. The method includes applying an output voltage of a power supply, which serves to supply voltage to the device, to the fan; and switching on and switching off the output voltage of the power supply applied to the fan by a switch pulse-width-modulated-controlled by a control unit so that the Root Mean Square value of the current flowing through the fan is less than a startup current of the fan.

According to one embodiment, there is provided a control device including a detecting circuit, a control circuit and a drive circuit. The detecting circuit detects changes in a current flowing between a node and a smoothing circuit, the node being to which a DC brush motor, a power supply circuit and the smoothing circuit can be electrically connected via respective different lines. The control circuit generates a control signal to control rotation speed of the DC brush motor according to the detected changes in the current. The drive circuit drives the DC brush motor according to the control signal.

According to one embodiment, there is provided a control device including a detecting circuit, a control circuit and a drive circuit. The detecting circuit detects changes in a current flowing between a node and a smoothing circuit, the node being to which a DC brush motor, a power supply circuit and the smoothing circuit can be electrically connected via respective different lines. The control circuit generates a control signal to control rotation speed of the DC brush motor according to the detected changes in the current. The drive circuit drives the DC brush motor according to the control signal.

Disclosed is a motor driving device for driving a motor having coil sets that includes energization systems each including a drive circuit, the drive circuits being one-to-one connected to the coil sets; first semiconductor switches disposed in the energization systems in a one-to-one correspondence, each first semiconductor switch lying between a power supply and the corresponding one of the drive circuits; and a second semiconductor switch which connects the power supply and each of the first semiconductor switches in series. Each of the first semiconductor switches includes a parasitic diode of which a forward direction is from the corresponding drive circuit to the second semiconductor switch, and the second semiconductor switch includes a parasitic diode of which a forward direction is from the power supply to the first semiconductor switches.

Disclosed is a motor driving device for driving a motor having coil sets that includes energization systems each including a drive circuit, the drive circuits being one-to-one connected to the coil sets; first semiconductor switches disposed in the energization systems in a one-to-one correspondence, each first semiconductor switch lying between a power supply and the corresponding one of the drive circuits; and a second semiconductor switch which connects the power supply and each of the first semiconductor switches in series. Each of the first semiconductor switches includes a parasitic diode of which a forward direction is from the corresponding drive circuit to the second semiconductor switch, and the second semiconductor switch includes a parasitic diode of which a forward direction is from the power supply to the first semiconductor switches.

Methods for controlling a voltage present at an electric fan during a startup of the fan are disclosed herein. The fan serves to generate a flow of air for cooling a device. The method includes applying an output voltage of a power supply, which serves to supply voltage to the device, to the fan; and switching on and switching off the output voltage of the power supply applied to the fan by a switch pulse-width-modulated-controlled by a control unit so that the Root Mean Square value of the current flowing through the fan is less than a startup current of the fan.

Disclosed is a motor driving device for driving a motor having coil sets that includes energization systems each including a drive circuit, the drive circuits being one-to-one connected to the coil sets; first semiconductor switches disposed in the energization systems in a one-to-one correspondence, each first semiconductor switch lying between a power supply and the corresponding one of the drive circuits; and a second semiconductor switch which connects the power supply and each of the first semiconductor switches in series. Each of the first semiconductor switches includes a parasitic diode of which a forward direction is from the corresponding drive circuit to the second semiconductor switch, and the second semiconductor switch includes a parasitic diode of which a forward direction is from the power supply to the first semiconductor switches.

Disclosed is a motor driving device for driving a motor having coil sets that includes energization systems each including a drive circuit, the drive circuits being one-to-one connected to the coil sets; first semiconductor switches disposed in the energization systems in a one-to-one correspondence, each first semiconductor switch lying between a power supply and the corresponding one of the drive circuits; and a second semiconductor switch which connects the power supply and each of the first semiconductor switches in series. Each of the first semiconductor switches includes a parasitic diode of which a forward direction is from the corresponding drive circuit to the second semiconductor switch, and the second semiconductor switch includes a parasitic diode of which a forward direction is from the power supply to the first semiconductor switches.

The present invention relates to a multi-set switched DC electric machine having conduction ring and brush and having its rotary part of electric machine being installed with an auxiliary excitation winding set, which is served to be driven by the DC power source or by the DC power source rectified from the AC power source, for being connected in series with a magnetic field winding set of electric machine of another electric machine through the auxiliary excitation winding set installed on the rotary part of electric machine, such that the excitation can be variable through altering the current of the magnetic field winding set of electric machine of the another electric machine thereby changing the operational characteristic of the electric machine.