Patent ID: 7369378

Claim:
An electric motor driving apparatus, comprising: a power-supplying line, one end of said power-supplying line to be connected to a direct-current power supply; an electric motor connected to the other end of said power-supplying line to receive a supply of power via said power-supplying line from said direct-current power supply; a switching device inserted in said power-supplying line; a flywheel diode connected with said electric motor in parallel; a PWM signal generator for outputting PWM signals to said switching device to control operation of said electric motor; said switching device adapted for receiving said PWM signals and carrying out a switching operation according to the PWM signals upon receiving the PWM signals; a first circuit including a first capacitor coupled with a common resistor provided in said power-supplying line, thereby establishing a surge protective circuit comprising the first capacitor and the common resistor, being adapted for protecting said switching device from surge voltage generated during operation of said electric motor; a second circuit including a second capacitor coupled with the common resistor provided in said power-supplying line, thereby establishing a noise filter circuit comprising the second capacitor and the common resistor, being adapted for absorbing noise generated during operation of said switching device; and a connection point provided in the power-supplying line and connecting one end of the first capacitor and one end of the second capacitor mutually, and connected with one end of the common resistor, wherein the switching device comprises a drain, a source, and a gate for switching an electrical connection between the drain and the source of the switching device; the electric motor comprises first and second terminals, said first terminal is connected with the drain of the switching device and said second terminal is connected with a positive pole of the direct-current power supply; an other end of the first capacitor opposite of said one end of the first capacitor connected with the connection point is connected to said second terminal of the electric motor; said one end of the second capacitor and said one end of the common resistor are connected mutually with the connection point, and an other end of the second capacitor opposite of said one end of the second capacitor is connected with the gate of the switching device; and an other end of the common resistor opposite of said one end of the common resistor connected with the connection point is connected with the drain of the switching device.