Patent ID: 7423520

Claim:
A noise suppressing circuit comprising: a common mode noise suppressing means for suppressing common mode noise propagating through a first conductor line and a second conductor line with identical phases; and a normal mode noise suppressing means for suppressing normal mode noise transmitted through the first and second conductor lines and creating a potential difference between the conductor lines, wherein: the common mode noise suppressing means comprises a first detection/injection section and a second detection/injection section that are connected to the first and second conductor lines at different points and connected to each other through a path different from the first and second conductor lines, and that each perform detection of a signal corresponding to common mode noise or injection of an injection signal for suppressing common mode noise; when the first detection/injection section performs the detection of the signal corresponding to the common mode noise, the second detection/injection section injects to the first and second conductor lines the injection signal generated based on the signal detected; when the second detection/injection section performs the detection of the signal corresponding to the common mode noise, the first detection/injection section injects to the first and second conductor lines the injection signal generated based on the signal detected; at least one of the first and second detection/injection sections incorporates two windings inserted to the first and second conductor lines and coupled to each other so as to produce a leakage inductance; and the normal mode noise suppressing means incorporates two capacitors for a normal mode that are located at positions that sandwich the two windings, each of the two capacitors having an end connected to the first conductor line and the other end connected to the second conductor line, and reducing normal mode noise in cooperation with the leakage inductance produced by the two windings.