Method and apparatus for providing input EMI filtering in power supplies

• US 20050041442A1
• Filed: 09/23/2004
• Published: 02/24/2005
• Est. Priority Date: 11/18/2002
• Status: Active Grant

• Current Assignee: Balu Balakrishnan
• Original Assignee: Balu Balakrishnan
• Inventors: Balakrishnan, Balu
• Granted Patent: US 7,609,535 B2
• Time in Patent Office: Days
• US Class Current: 363/44
• CPC Class Codes: H02M 1/126 using passive filters
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters

Abstract

A power supply electromagnetic interference (EMI) filter circuit and technique. In one embodiment, a method of filtering EMI in a power supply includes rectifying an AC signal from an AC source, smoothing the rectified AC signal with a bulk storage capacitor to provide a DC output as an input to a power conversion circuit and filtering the EMI generated by the power conversion circuit from reaching the AC source by using the bulk capacitor and one or more inductors in combination with the AC source capacitance as an EMI filter. In one embodiment the method also includes the use of one or more of the inductors as a fusing element.

Claims

1-46. -46. (Canceled).

47. A circuit, comprising:

a power supply input circuit including a rectifier coupled to a capacitor and coupled to an inductor, the power supply input circuit to be further coupled to a Line Impedance Stabilization Network (LISN) having a LISN capacitance; and

a power conversion circuit coupled to the power supply input circuit, wherein the LISN capacitance, the inductor and the capacitor form an electromagnetic interference (EMI) pi filter circuit to filter EMI.

48. The circuit of claim 47 wherein the inductor is to be coupled between the LISN capacitance and the rectifier.

49. The circuit of claim 47 wherein the inductor is coupled between the rectifier and the capacitor.

50. The circuit of claim 47 wherein the inductor is a first inductor, wherein the power supply input circuit further includes a second inductor coupled to the rectifier circuit.

51. The circuit of claim 50 wherein the first and second inductors are to be coupled between LISN capacitance and the rectifier.

52. The circuit of claim 50 wherein the first and second inductors are to be coupled between the rectifier and the capacitor.

53. The circuit of claim 47 wherein the capacitor is coupled between the rectifier and the power conversion circuit to provide bulk storage for a direct current (DC) input of the power conversion circuit.

54. The circuit of claim 47 wherein the rectifier is a half wave rectifier circuit.

55. The circuit of claim 47 wherein the rectifier is a full wave rectifier circuit.

56. The circuit of claim 47 wherein the inductor is adapted to function as a fuse to limit an abnormal amount of current flow.