US 2009/0212754 A1 · NOISE REDUCTION SYSTEMS AND METHODS

Abstract

We describe a switch mode power supply having a power input, a switch, a transformer, and a power output. The transformer has a primary winding coupled to said power input via said switch, and a secondary winding coupled to said power output. The transformer further comprises an auxiliary winding and a coupling structure capacitatively coupled to said secondary winding of said transformer; wherein said coupling structure does not comprise a shield or screen between said primary and secondary windings. The switch mode power supply further comprises a coupling capacitor connected between said coupling structure and said auxiliary winding to provide a noise suppression voltage from said auxiliary winding to said secondary winding to at least partially cancel a common mode noise voltage on said secondary winding from unshielded coupling from said primary winding.

Claims19

Dependent claims

A method of reducing common-mode noise from unshielded coupling in a switch mode power supply;

said switch mode power supply having a power input, a switch, a transformer, and a power output;
said transformer having at least a primary winding on a primary side of said power supply and coupled to said power input via said switch, and a secondary winding of said transformer on a secondary side of said power supply and coupled to said power output;
said noise from unshielded coupling comprising a noise voltage on a second of said windings coupled from a first of said windings, the method comprising:
generating a noise suppression signal in antiphase to said noise from unshielded coupling using a voltage source comprising a winding of said transformer on a first one of said primary and secondary sides of said power supply;
and
coupling said noise suppression signal into said transformer using a coupling structure capacitatively coupled to a said winding of said transformer on the other one of said primary and secondary sides of said power supply;
and
wherein said coupling does not use a shield or screen between said primary and secondary windings of said transformer.

5 more elements

A switch mode power supply including a system for reducing common-mode noise from unshielded coupling in said switch mode power supply, said switch mode power supply having a power input, a switch, a transformer, and a power output, said transformer having at least a primary winding on a primary side of said power supply and coupled to said power input via said switch, and a secondary winding on a secondary side of said power supply and coupled to said power output, said noise from unshielded coupling comprising a noise voltage on a second of said windings coupled from a first of said windings, the system comprising:

means for generating a noise suppression signal in antiphase to said noise from unshielded coupling using a voltage source comprising a winding of said transformer on a first one of said primary and secondary sides of said power supply;
and
means for coupling said noise suppression signal into said transformer using a coupling structure capacitatively coupled to a said winding of said transformer on the other one of said primary and secondary sides of said power supply;
and
wherein said coupling structure comprises an electrically conducting structure disposed:
i) adjacent said winding of said transformer on said other one of said primary and secondary sides of said power supply, and ii) on a side of said winding of said transformer on said other one of said primary and secondary sides of said power supply other than a side adjacent said winding of said transformer on said first one of said primary and secondary sides of said power supply.

3 more elements

Dependencies are inferred from the claim text.

Noise reduction systems and methods

Life of this patent

Noise reduction systems and methods

Life of this patent

Abstract

Claims19