US-12620523-B2 - Inductor apparatus optimized for low power loss in class-D audio amplifier applications and method for making the same

US12620523B2US 12620523 B2US12620523 B2US 12620523B2US-12620523-B2

Abstract

An inductor is provided, comprising: a first ferrite core piece and a second ferrite core piece, each of which are made of substantially similar materials, exhibit desired electromagnetic properties, and which are fashioned in a substantially similar manner and shape, and wherein each of the first and second ferrite core pieces comprises a substantially planar mating surface, a center post, and a wire core assembly channel, and wherein a first substantially planar mating surface of the first ferrite core piece is adapted to planarly mate with a second substantially planar mating surface of the second ferrite core piece; and a wire core assembly adapted to be substantially self-locating and self-centering about a first or second center post when located in a respective first or second wire core assembly channel.

Inventors

Robert N. Buono

Assignees

CRESTRON ELECTRONICS, INC.

Dates

Publication Date: 20260505
Application Date: 20190610

Claims (3)

1 . An inductor, comprising: a first ferrite core piece and a second ferrite core piece, each of which are fashioned in a substantially similar manner and shape, and wherein each of the first and second ferrite core pieces comprises a substantially planar mating surface, a center post, and a wire core assembly channel, and wherein a first substantially planar mating surface of the first ferrite core piece is adapted to planarly mate with a second substantially planar mating surface of the second ferrite core piece; and a wire core assembly made of substantially flat wire, formed as a coil, the coil comprising a coiled portion, a first lead, and a second lead, the first and second leads extending from the coiled portion, and wherein the wire core assembly is formed as a spring and with such dimensions that when the first lead and second lead are pulled towards each other, the wire core assembly is adapted to be substantially self-locating and self-centering about a first or second center post when located in a respective first or second wire core assembly channel.
2 . An inductor, comprising: a first ferrite core piece and a second ferrite core piece, each of which are fashioned in a substantially similar manner and shape, and wherein each of the first and second ferrite core pieces comprises a substantially planar mating surface, a center post, and a wire core assembly channel comprising an inner channel wall, outer channel wall, and channel floor, the inner channel wall comprising an outer surface of the center post, and wherein a first substantially planar mating surface of the first ferrite core piece is adapted to planarly mate with a second substantially planar mating surface of the second ferrite core piece; and a wire core assembly adapted to be substantially self-locating and self-centering about a first or second center post when located in a respective first or second wire core assembly channel, wherein such self-locating and self-centering occurs through operation of a spring-like characteristic built into the wire core assembly, and further wherein when the wire core assembly is located about the first or second center post, an outer surface of the wire core assembly is mated to a portion of the outer channel wall.
3 . An inductor, comprising: a first ferrite core piece and a second ferrite core piece, each of which are fashioned in a substantially similar manner and shape, and wherein each of the first and second ferrite core pieces comprises a substantially planar mating surface, a center post, and a wire core assembly (WCA) channel, wherein the WCA channel surrounds the center post, and comprises a WCA channel inner wall that is also a center post radial outer wall; a WCA channel outer wall that comprises a substantially circular portion and two substantially linear portions, and wherein the substantially circular portion is centered between and in contact with the two substantially linear portions to form a substantially smooth wall surface, and wherein the substantially circular portion comprises a WCA channel outer wall radius; and a substantially planar WCA channel surface; and a WCA made of substantially flat wire, formed as a coil, the coil comprising a coiled portion, a first lead, and a second lead, and wherein the first and second leads extending from the coiled portion, and further wherein the wire core assembly formed as a spring and with such dimensions that when the first lead and second lead are pulled towards each other, the wire core assembly is adapted to be substantially self-locating and self-centering about a first or second center post when located in a respective first or second wire core assembly channel.

Description

CROSS REFERENCE TO RELATED APPLICATIONS Related subject matter is disclosed in co-pending U.S. Non-Provisional patent application Ser. No. 16/436,465, filed on Jun. 10, 2019, and co-pending U.S. Non-Provisional patent application Ser. No. 16/436,522, filed on Jun. 10, 2019, the entire contents of both of which are expressly incorporated herein by reference. BACKGROUND Technical Field Aspects of the embodiments relate generally to inductors used in class D audio amplifiers, and more specifically to systems, method, and modes for an inductor that can be used in a demodulation filter in a class D audio amplifier to minimize certain negative performance parameters, while maximizing other positive performance parameters according to aspects of the embodiments. Background Art As those of skill in the art can appreciate, Class-D audio amplifiers use a demodulation filter that in its simplest implementation consists of an inductor-capacitor (L-C) filter in a low-pass arrangement. The purpose of this filter is to attenuate, as much as practically possible, the high-frequency switching waveform generated by the Class-D switching stage, typically in excess of 200 KHz, and leave unchanged, as much as practically possible, the low frequency audio content, typically in the audible range of 20 Hz to 20 KHz. In addition to this basic function, the LC filter has additional, more nuanced effects on the overall performance of the Class-D amplifier, and for that reason, its selection is critical to the performance of the Class-D amplifier. The performance parameters that the Class-D filter, and specifically the inductive component of that filter can effect are: total harmonic distortion (THD), noise and residual modulation, bandwidth and flatness of frequency response, power dissipation and efficiency, step-response, damping factor, feedback loop stability, overcurrent and short-circuit protection response, as well as size and cost. FIG. 1 illustrates a side view of an inner portion of a first half and second half of a conventional ferrite core (first half, second half) 102a,b, respectively, of conventional inductor 100, without a conventional wire core assembly for use in a conventional LC demodulation filter. Conventional inductor 100 comprises first half 102a, second half 102b, and conventional wire core assembly 200 (shown and described in regard to FIG. 2, below). Each of the first and second halves 102a,b consist of the substantially identical components, so, in fulfillment of the dual purposes of clarity and brevity, only one half will be discussed. First half 102a consists of lead wire channel 104a, wire core channel 106a, center post 108a, and inner surface 110a. Lead wire channel 104a is sized to fit lead wire 202a of conventional wire core assembly 200. Wire core channel 106a is sized and arranged to locate within it wire core body 204 of conventional wire core assembly 200 about substantially circular center post 108a. Substantially planar inner surface 110a of first half 102a is designed to mate with equally substantially planar second inner surface 110b of second half 102b. Both first and second halves 102a,b are substantially equal in all dimensions, so as to create a substantially uniform environment of ferrite material about conventional wire core assembly 200. FIG. 2 illustrates a side view of an inner surface of first half 102a with conventional wire core assembly 200 for use in a conventional LC demodulation filter. It should be noted that although shown and/or described as “substantially circular,” conventional wire core assembly 200 is generally only roughly or approximately circular, and this leads to the inherent problems of conventional inductor 100, as described below In assembly (and, as those of skill in the art can appreciate, the order of assembly can change, and therefore this description should not be considered as limiting in any manner whatsoever), either or both of inner surfaces 110a,b are coated with epoxy, and conventional wire core assembly 200 is located about either of center post 108a or center post 108b. Then, first and second halves 102a,b, are pressed together and retained until the epoxy sets. Alternatively, instead of epoxy, tape can be used to keep first and second halves 102a,b together. During assembly, prior to the mating of first and second halves 102a,b, lead wires 202a,b are located within lead wire channel 104a,b, respectively. As can be seen in FIG. 2, following insertion of conventional wire core assembly 200 about center post 108a, first variable spacing 206a and second variable spacing 208a present themselves. First variable spacing 206a exists between inner surface of wire core assembly 214 of conventional wire core assembly 200 and inner wall of wire core channel 210, wherein “inner” refers to a position closer to the center of center post 108. Second variable spacing 208a exists between outer surface of wire core assembly 216 of conventional wire core assembly 200 a