Common mode signal suppressing circuit and normal mode signal suppressing circuit

A common mode signal suppressing circuit for suppressing common mode signals propagating with identical phases through two conductor lines, the common mode signal suppressing circuit comprising:

• a first winding inserted to one of the conductor lines at a specific first point;
• a second winding that is inserted to the other of the conductor lines at a second point corresponding to the first point and is coupled to the first winding, the second winding suppressing the common mode signals in cooperation with the first winding;
• a third winding coupled to the first and second windings such that a mutual inductance is generated between the third winding and the first and second windings;
• and
• a phase-inverted signal transmitting means connected to the third winding and to the one of the conductor lines at a third point different from the first point, the transmitting means being further connected to the other of the conductor lines at a fourth point corresponding to the third point and different from the second point, the transmitting means transmitting a phase-inverted signal for suppressing the common mode signals, wherein:
• when a source of the common mode signals is located at a point closer to the third and fourth points than the first and second points except a point between the first and third points and a point between the second and fourth points, the transmitting means detects a common mode signal and supplies the phase-inverted signal to the third winding, the phase-inverted signal having a phase opposite to a phase of the common mode signal detected, and the third winding injects the phase-inverted signal to the two conductor lines through the first and second windings;
• when the source of the common mode signals is located at a point closer to the first and second points than the third and fourth points except a point between the first and third points and a point between the second and fourth points, the third winding detects a common mode signal, and the transmitting means injects the phase-inverted signal to the two conductor lines, the phase-inverted signal having a phase opposite to a phase of the common mode signal detected by the third winding;
• and
• a coupling coefficient between the third winding and the first and second windings is 0.7 or greater.

A normal mode signal suppressing circuit for suppressing normal mode signals transmitted by two conductor lines and creating a potential difference between the two conductor lines, the normal mode signal suppressing circuit comprising:

• a first inductance element inserted to one of the conductor lines at a specific first point;
• a second inductance element coupled to the first inductance element such that a mutual inductance is generated between the first and second inductance elements;
• a phase-inverted signal transmitting means connected to the second inductance element and to the one of the conductor lines at a second point different from the first point, the transmitting means transmitting a phase-inverted signal for suppressing the normal mode signals;
• and
• an impedance element provided on the one of the conductor lines at a point between the first and second points, the impedance element reducing a peak value of a normal mode signal passing therethrough, wherein:
• when a source of the normal mode signals is located at a point closer to the second point than the first point except a point between the first and second points, the transmitting means detects a normal mode signal and supplies the phase-inverted signal to the second inductance element, the phase-inverted signal having a phase opposite to a phase of the normal mode signal detected, and the second inductance element injects the phase-inverted signal to the one of the conductor lines through the first inductance element;
• and
• when the source of the normal mode signals is located at a point closer to the first point than the second point except a point between the first and second points, the second inductance element detects a normal mode signal, and the transmitting means injects the phase-inverted signal to the one of the conductor lines, the phase-inverted signal having a phase opposite to a phase of the normal mode signal detected by the second inductance element.