Virginia Tech Intellectual Properties Inc

Shuo Wang

Fred C Lee

Qiang Li

Williem Gerhardus Odendaal

Pengju Kong

Various examples of systems and methods for a coupled inductor winding structure for common-mode noise reduction is described herein. The coupled inductor structure can include a magnetic core including a first leg, a second leg, and a center leg; and a planar winding structure. The planar winding structures can include a first inductor winding for a forward path of a first phase of a power converter; a second inductor winding for a forward path of a second phase of the power converter; a third and fourth inductor winding for a return path. The third inductor winding having at least one turn interleaved within the number of first leg turns of the first inductor winding and configured to achieve unity coupling. The fourth inductor winding having at least one turn interleaved within the number of second leg turns of the second inductor winding and configured to achieve unity coupling.

Coupled inductor winding structure for common-mode noise reduction

Common mode (CM) and differential mode (DM) components of multi-phase conducted electromagnetic interference (EMI) noise emanating from electronic circuits such as power converters/inverters are separated by respective coupled inductors connected to each phase of three or more phases and which are coupled to each other differently for CM and DM noise of the respective phases. The inductors of the DM separation unit are coupled such that a substantially ideal zero impedance is presented to DM noise while a high impedance is presented to CM noise. Conversely, the inductors of the CM separation unit are coupled such that a substantially ideal zero impedance is presented to CM noise while a high impedance is presented to DM noise.

Multi-phase EMI noise separator

Improved performance of a noise separator circuit capable of separating common mode (CM) and differential mode (DM) components of electromagnetic interference (EMI) noise are provided by arrangement of terminating impedances such that the circuit is fully symmetric with respect of a pair of input ports. The noise separator circuit is further improved by perfecting features for canceling effects of parasitic inductances and capacitances, parasitic capacitance and inductance between circuit connections such as printed circuit board traces, minimizing leakage inductance effects of pairs of coupled inductors and mutual inductance effects between pairs of coupled inductors, providing sufficient magnetizing inductance for low frequency response, and preventing saturation of inductors using switched attenuators, providing a plurality of ground planes, choices of terminating resistors and circuit layout.

Electromagnetic interference noise separator

Common mode (CM) noise is substantially canceled in a switching power supply circuit such as a boost converter by providing a split inductor and analyzing the switching power supply circuit as a bridge circuit formed of the switch, portions of the split inductor and parasitic capacitances of respective portions of the power supply circuit. The bridge can then be balanced by addition of capacitance in parallel with the parasitic capacitance of a respective portion of the power supply circuit or dividing the split inductor such that a ratio of inductances of respective portions of the split inductor approximates a ratio of parasitic capacitances of the respective power supply circuit portions which may be measured or otherwise empirically determined. CM noise reduction of up to 40 db can be achieved without symmetric circuit design, addition of circuit elements or complex filtering having added cost, space requirements and power losses. Further, such a reduction in common mode noise allows simple EMI filtering arrangements to be employed further reducing cost and space requirements for the power supply circuit.

Reducing common mode noise of power factor correction converters using general balance concept

A negative capacitance is developed by configuring an inductor as two inversely or opposingly coupled windings having different numbers of turns and connecting a capacitance to a center tap between the two windings. The negative capacitance is developed on the side of the inductor having the winding with the greater number of turns. The negative capacitance so developed may advantageously be used to cancel any capacitance or parasitic capacitance desired for reducing power loss, increasing switching speed or reducing or eliminating common mode noise in a switched circuit such as a switched power converter

Common mode noise reduction using parasitic capacitance cancellation

An inductor device or filter such as an electromagnetic interference (EMI) filter which includes an inductor provides cancellation of parasitic capacitance of the inductor and extends high frequency performance of the inductor or filter by providing the inductor using split windings and including capacitors to couple signals corresponding to those which are passed by the equivalent parallel capacitance of the inductor to another split winding or an inductor in the ground return path. Cancellation of parasitic capacitance is provided for differential mode and common mode split windings where the split windings may be either inductively coupled or not. Forming the split windings as a bifilar winding to increase coupling coefficient further improves performance and allows cancellation (as distinct from parasitic capacitance reduction) and avoidance of resonance in circuits in which an inductor is not permitted in the ground return path.

Cancellation of inductor winding capacitance

An inductor device or filter such as an electromagnetic interference (EMI) filter which includes an inductor provides cancellation of parasitic capacitance of the inductor and extends high frequency performance of the inductor or filter by using an inductor network (a special case being split windings) and including capacitors to couple signals corresponding to those which are passed by the equivalent parallel capacitance of an inductor of a network of inductors such as in a multi-phase power supply of voltage converter to another inductor terminal, ground or an inductor in the ground return path. Cancellation of parasitic capacitance is provided for differential mode and common mode windings where the windings may be either inductively coupled or not. Forming the windings as a bifilar winding to increase coupling coefficient further improves performance and allows cancellation (as distinct from parasitic capacitance reduction) and avoidance of resonance in circuits in which an inductor is not permitted in the ground return path. Different inductance values and turns ratios of any or all inductors of the network, including multi-phase networks, may be accommodated.

Generalized cancellation of inductor winding capacitance

An electromagnetic interference (EMI) filter or frequency filters (e.g. bandpass or band reject filters) in which a capacitor has an inductance cancellation loop. Inductive coupling between capacitors can allow undesired high frequencies to propagate across a filter. This is particularly a concern when the capacitors are oriented in parallel. In the present invention, the inductance cancellation loop is disposed adjacent to one capacitor so that mutual inductance between the capacitors is reduced. The attenuation of the filter at high frequencies is thereby increased. The loop can increase voltage attenuation of an EMI filter by about 20 dB. In another aspect, inductors in the filter are oriented horizontally relative to a circuitboard. Horizontal orientation reduces leakage inductance coupling between the inductors and circuitboard traces, and between the inductor and capacitors, thereby preventing unwanted propagation of high frequencies. Both measures in combination can provide a voltage attenuation increase of 30 dB.

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Blacksburg, VA, United States of America

Shuo Wang