Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F17/00—Fixed inductances of the signal type
  • H01F17/04—Fixed inductances of the signal type with magnetic core
  • H01F17/045—Fixed inductances of the signal type with magnetic core with core of cylindric geometry and coil wound along its longitudinal axis, i.e. rod or drum core
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F17/00—Fixed inductances of the signal type
  • H01F17/04—Fixed inductances of the signal type with magnetic core
  • H01F17/043—Fixed inductances of the signal type with magnetic core with two, usually identical or nearly identical parts enclosing completely the coil (pot cores)
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F3/00—Cores, Yokes, or armatures
  • H01F3/10—Composite arrangements of magnetic circuits
  • H01F3/14—Constrictions; Gaps, e.g. air-gaps
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F21/00—Variable inductances or transformers of the signal type
  • H01F21/02—Variable inductances or transformers of the signal type continuously variable, e.g. variometers
  • H01F21/06—Variable inductances or transformers of the signal type continuously variable, e.g. variometers by movement of core or part of core relative to the windings as a whole
  • H01F21/065—Measures for obtaining a desired relation between the position of the core and the inductance
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/0206—Manufacturing of magnetic cores by mechanical means
  • H01F41/0213—Manufacturing of magnetic circuits made from strip(s) or ribbon(s)
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/04—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing coils
  • H01F41/041—Printed circuit coils
  • H01F41/045—Trimming

Definitions

• the present invention relates generally to components used in electronics applications, and particularly to an improved inductive devices used in, inter alia, filter and splitter apparatus for a digital subscriber line (DSL) or similar telecommunications system.
• DSL digital subscriber line
• DSL Digital Subscriber Line
• Fig. 1 illustrates a typical installation of such in-line filters.
• the self-installable micro-filter is a challenging design, largely because it must have sufficient stop band in the DSL band to protect and preserve DSL performance, but at the same time should also have negligible effect on the voice band performance.
• Fig. la illustrates a typical prior art in-line filter configuration used in DSL applications.
• Such prior art filter designs often do not satisfy some of the telecom customer's requirements for both return loss and DSL stop band.
• One significant problem is that the total capacitance required for the DSL stop band requirements also produce excessive side tone in the upper band of the telephones, a highly undesirable result.
• the return loss problem becomes worse as more micro-filters are added for each of the subscriber's phones.
• inductance characteristic refers generally to the inductance profile, or variation in inductance as a function of dc current through the inductor.
• Figs. 2a and 2b illustrate the inductance characteristics associated with typical prior art inductors having either fixed inductance or variable inductance, respectively. Note that in the typical "fixed” inductor, the inductance characteristic 102 is essentially flat or constant as a function of current, until comparatively high currents are reached.
• Fig. 2b is generally representative of the types of prior art device manufactured by, inter alia, Coilcraft Corporation of Cary, Illinois, USA, such as the DT1608 Series SMT power inductors.
• Fig. 3 illustrates the construction of the aforementioned Coilcraft device.
• the device 300 comprises a two-piece core 302 having a base 304 with an off-centered post 306.
• the upper core piece 308 has an aperture 310 which is oversized with respect to the diameter of the post 306. This arrangement creates what amounts to a continuously variable gap between the outer surface of the post 306 and the interior surface of the aperture 310, ranging from a minimum gap at the closest point of approach of the two surfaces, to a maximum at the diametric opposite of the point of closest approach.
• This continuously variable gap has at least two disabilities, including: (i) a continuously variable or "soft stepped” inductance characteristic, which is undesirable or less than optimal in certain applications, and (ii) high cost of manufacturing, since two core pieces with precise relative tolerances must be provided (including precise alignment of the upper core piece 308 with the base 304. Furthermore, there is additional cost associated with manufacturing the "off-center" post 306, irrespective of its tolerances with the other core piece 308. Such off-center arrangement is also not generally conducive to use of well known alignment aids, such as the split-pin arrangement described subsequently herein.
• an improved inductive device having both low cost of manufacturing and desirable inductance characteristics is needed for use in, inter alia, digital subscriber line (DSL) signals.
• Such improved apparatus would ideally (i) have the desired inductance characteristics in the on-hook and off-hook states, so as to support for example functions such as Caller ID which require higher on-hook stop band loss (ii) be highly cost- effective to manufacture, (iii) be reliable, and (iv) be physically compact in both volume and footprint.
• the present invention satisfies the aforementioned needs by providing an improved inductive device suitable for use in, for example, DSL filter circuit applications, and a method of manufacturing the same.
• an improved inductive device for use in an electronic circuit generally comprises a magnetically permeable core with a controlled saturation element, the core and element cooperating to produce a desired inductance characteristic (e.g., a substantially "stepped" or discrete inductance versus dc current profile).
• the device comprises a substantially cylindrical potentiometer ("pot") core having a first core element and a second core element, with a variable geometiy gap formed between at least a portion of the core elements.
• the variable geometry gap comprises, for example, a first portion having a first gap width and a second, adjacent portion having a second gap width.
• the variable geometry gap helps control the saturation of the device at various current levels, thereby providing the substantially stepped inductance characteristic in the bands of interest.
• An integral or separate terminal array is also provided for electrically interfacing the device to external components such as a printed circuit board (PCB).
• PCB printed circuit board
• the improved device of the present invention comprises a unitary or multi-part wound "dual" drum core with first and second end elements, wherein a controlled core saturation element is disposed across all or a portion of the periphery of the dram end elements.
• the controlled saturation element comprises, in one exemplary configuration, a thin strip of Nickel-Iron (Ni-Fe) tape. By virtue of its ferrous content, this material contains magnetic domains which interact with the magnetically permeable drum core to provide the aforementioned stepped inductance characteristic.
• the improved inductive device comprises a "triple" drum core having first and second end elements, as well as a central element disposed between the ends. Ni-Fe tape is used to bridge between at least a portion of the peripheries of the two end elements and the central element.
• an improved DSL filter apparatus generally comprises a DSL filter circuit incorporating one or more of the aforementioned inductive devices, thereby being adapted for enhanced stop band performance.
• the filter circuit comprises a dynamically switched filter circuit adapted to reduce shunt capacitance, and thereby allow multiple distributed filters to be used on a given telecommunications circuit without producing undesirably low return loss.
• the aforementioned pot core and or dual drum core devices are used to provide increased input inductance during the on-hook state.
• a circuit board assembly comprising a substrate (e.g.,
• an improved method of providing controlled induction using an inductive device generally comprises: providing an inductor having a core and a controlled saturation element; selecting the parameters of the controlled saturation element to provide (i) comparatively higher inductance during no-current conditions; (ii) comparatively lower inductance during non-zero current conditions above a given current threshold; and operating the device within a circuit capable of generating no- current and non-zero current conditions through the device.
• the act of selecting the parameters comprises selecting the material, thickness, and geometry of the controlled saturation element in order to control the magnetic saturation thereof.
• a method of manufacturing an inductive component generally comprises: providing a first core element and a second core element adapted for mating; configuring a first portion of the gap formed between the first and second elements to a first width; configuring a second portion of the gap to a second width; winding the core with conductors; and assembling the first and second elements.
• the method generally comprises: providing a drum core having first and second end elements and a spool region; winding at least one conductor on the spool region; and bridging the first and second end elements using a controlled saturation element.
• the method comprises: providing a drum core having first and second end elements, a central element, and at least one spool region; winding at least one conductor on the at least one spool region; and bridging the first and second end elements and the central element using at least one controlled saturation element.
• Fig. 1 is a block diagram of a typical prior art DSL installation in a home or small business environment, including prior art micro-filters installed on multiple phone extensions.
• Fig. la is a schematic of the prior art DSL micro-filters shown in Fig. 1.
• Fig. 2a is a graphical representation of the inductance versus dc current characteristic ("inductance characteristic") of a typical fixed inductance prior art device.
• Fig. 2b is a graphical representation of the inductance characteristics of typical variable inductance (linear and "soft stepped") prior art devices.
• Fig. 3 is top plan view of an exemplary prior art inductive device (Coilcraft) having a varying inductance characteristic.
• Fig. 4 is a perspective view of a first embodiment of an improved pot core inductive device with controlled saturation according to the invention.
• Fig. 4a is a side cross-sectional view of the inductive device of Fig. 4, taken along line 4-4.
• Fig. 4b is a bottom plan view of the first core element of the inductive device of Fig. 4, illustrating the variable geometry gap.
• Fig. 4c is an exemplary graph of inductance versus dc current for the inductive device of Fig. 4.
• Figs. 4d-4f illustrate alternate embodiments of the variable geometry gap of the inductive device of the present invention, illustrating the use of (i) a three-tiered gap; (ii) a concentric two-tiered gap; and (iii) a intermittent concentric two-tiered gap, respectively.
• Fig. 5 is a perspective view of a first embodiment of an improved drum core inductive device (single spool) with controlled saturation according to the invention.
• Fig. 5 a is a perspective view of a first alternate embodiment of the drum core device of the invention having multiple controlled saturation elements.
• Fig. 5b is a cross-sectional view of a second alternate embodiment of the drum core device of the invention having a substantially continuous sheet for the controlled saturation element.
• Fig. 5 c is a perspective view of a third alternate embodiment of the drum core device of the invention having L-shaped terminals adhesively mounted within the drum core.
• Fig. 6 is a perspective view of a first embodiment of an improved drum core inductive device (multi-spool) with controlled saturation according to the invention.
• Fig. 7 is a schematic diagram of a first exemplary filter circuit using the improved inductive device of the invention.
• Fig. 8 is a schematic diagram of a second exemplary filter circuit using the improved inductive device of the invention, utilizing the dual-spool drum core device of Fig. 6.
• Fig. 9 is a schematic diagram of the filter circuit of Fig. 8, including optional third- order filter.
• Fig. 10a is a logical flow diagram illustrating an exemplary method of manufacturing the pot core inductive device of Figs. 4-4f.
• Fig. 10b is a logical flow diagram illustrating an exemplary method of manufacturing the drum core inductive devices of Figs. 5-6.
• signal conditioning or “conditioning” shall be understood to include, but not be limited to, signal voltage transformation, filtering and noise mitigation, signal splitting, impedance control and correction, current limiting, capacitance control, and time delay.
• digital subscriber line shall mean any form of DSL configuration or service, whether symmetric or otherwise, including without limitation so- called “G.lite” ADSL (e.g., compliant with ITU G.992.2), RADSL: (rate adaptive DSL), VDSL (very high bit rate DSL), SDSL (symmetric DSL), SHDSL or super-high bit-rate DSL, also known as G.shdsl (e.g., compliant with ITU Recommendation G.991.2, approved by the ITU-T February 2001), HDSL: (high data rate DSL), HDSL2: (2nd generation HDSL), and IDSL (integrated services digital network DSL), as well as In-Premises Phoneline Networks (e.g., HPN).
• G.lite ADSL
• RADSL rate adaptive DSL
• VDSL very high bit rate DSL
• SDSL symmetric DSL
• SHDSL or super-high bit-rate DSL also known as G.shdsl (e.g., compliant with ITU Re
• site and “subscriber's site” as used herein shall include any location (or group of locations) having telecommunications line service provided thereto, including without limitation residential houses, apartments, offices, and businesses.
• extension device is meant to include any type of telecommunications device compatible with use on existing telecommunications lines, including without limitation conventional telephones, answering machines, facsimile machines, wireless or satellite receivers, and multi-line phones.
• the present invention in effect solves the problem of being able to cost-efficiently tailor the inductance characteristic of an inductive device to provide two or more substantially discrete inductance values as a function of dc current.
• this substantially discrete characteristic allows for significantly higher input impedance for the filter in the on-hook state.
• low shunt capacitance and the desired high stop band loss are advantageously provided in a single circuit.
• the improved inductive devices of the present invention are both cost efficient to manufacture and spatially compact as well.
• Figs. 4-4f various exemplary embodiments of the improved inductive device of the invention are described in detail. It will be recognized by those of ordinary skill 5 that the embodiments described herein are merely exemplary of the broader concept of providing a controlled saturation inductive device which is both cost efficient to manufacture, and generates a desired inductance characteristic. Many different variations of physical configuration (some of which are described herein) may be employed consistent with the invention.
• a first embodiment of the inductive device 400 is illustrated.
• the device 400 comprises generally a potentiometer or "pot" type core 402 having two elements 402a, 402b designed for mating with one another.
• the two elements 402a, 402b are in the present embodiment substantially cylindrical in shape when joined, and each include a centrally disposed post 406a, 406b around which a channel or recess 5 408a, 408b is formed. It will be recognized, however, that other core shapes (including for example the well-known "E” core shape, which is effectively two “E” shapes in mirror image disposition, or the "U” core design) may be utilized consistent with the present invention.
• the recess 408 provides an interior volume in which the windings of the device 410 are disposed.
• the elements 402 are each formed from a magnetically permeable material, such as Mn-Zn, as
• Apertures 409 are formed in the sides of the core elements (at the mating joint of the two elements 402a, 402b) so as to permit conductor ingress/egress.
• Other mechanisms for ingress/egress of the conductors may be used, including penetrations through the top or bottom surfaces of the core, etc.
• certain core shapes such as the aforementioned "E" core) are open by design, thereby inherently providing
• the inductive device 400 also includes one or more electrically conductive windings 413 formed by winding the desired type(s) of conductor around the center post 406 of the core 402.
• so-called "magnet wire” of the type well known in the electronics art is used for both its comparatively low cost and good electrical and mechanical
• Magnet wire is commonly used to wind transformers and inductive devices, and comprises wire is made of copper or other conductive material coated by a thin polymer insulating film or a combination of polymer films such as polyurethane, polyester, polyimide (aka “KaptonTM”), and the like.
• the thickness and the composition of the film coating determine the dielectric strength capability of the wire.
• Magnet wire in the range of 31 to 42 AWG is most commonly used in microelectronic transformer or inductor applications, although other sizes may be used in certain applications.
• the inductive device 400 of Fig. 4 may also optionally include a terminal array 425 for connection of the aforementioned winding(s) to an external device such as a PCB pad or trace.
• Inductive devices generally of the type disclosed herein are often disposed on substrates such as PCBs and surface-mounted thereto, advantageously providing a low profile and low cost assembly.
• the terminal array 425 includes a non-conductive array frame 427 and a plurality of individual substantially flat cross-section terminals 429 which are insulated from each other by the array frame 427. To each or the respective terminals are terminated to the free ends of the inductive device windings 413, such as by soldering and/or wire wrapping into notches formed on the ends of the terminals 429 (not shown).
• each of the terminals 429 are adapted for surface mounting (e.g., soldering) to corresponding PCB contact pads (not shown) or other similar conductive counterparts.
• the core 402 of the inductive device 400 sits atop the frame 427, and may be mounted thereto such as through use of an adhesive on the bottom surface of the second core element 402b or any other number of different well known means.
• the terminals 429 may be mounted directly into or onto the core
• the region 414 between the facing surfaces 412a, 412 of the respective core element posts 406a, 406b includes a "variable" geometry, the latter designed so as to provide the desired inductance characteristic (described below with respect to Fig. 4c).
• this variably geometry comprises two regions 416, 418 disposed between the posts 406, each region having a different gap width ("two- tiered").
• the first region 416 has a first gap width Wi which is approximately 0.010 in. (0.254 mm), while the second region 418 has a gap of width W 2 which is approximately 0.001 in. (0.0254 mm), which is less than Wi.
• the two regions 416, 418 comprise two adjacent components which form in sum the total cross-sectional area of the posts 406.
• the first region 416 comprises in the present embodiment about 90% of the total surface area of the cross-section of the post 406, this region being divided from the second region by a chord edge 419.
• the second region 418 comprises the remaining approximately 10% of the cross-sectional area.
• the gap(s) is/are filled with air; however, it will be appreciated that one or more other materials having desirable properties may be used.
• the gap may be filled with a high magnetic reluctance compound so as to further control the inductance profile of the core.
• the series inductor's core(s) must have an air gap to prevent the cores from being saturated by the off-hook dc loop current in the telephone lines.
• the inductive device of Fig. 4 provides the desired "stepped" inductive characteristic. Specifically, the inductor's on-hook inductance value becomes on the order of 2 - 10 times larger (depending on the parameters chosen, as discussed below) than the off-hook value.
• the width W 2 of the second region 418 described above is sufficiently small to allow saturation of the core with the prevailing off-hook dc loop current. This results in the inductance of the device falling to the desired off-hook value.
• the values of Wi and W 2 , as well as the relative apportionment of the cross- sectional areas of the first and second regions 416, 418 help determine the specific off-hook inductance value, as well as the shape of the "stepped" induction characteristic.
• a two-step characteristic is provided to generate the two desired inductance values (i.e., for on-hook and off-hook states).
• Fig. 4c illustrates the inductance characteristic 450 associated with the exemplary device of Fig. 4.
• the characteristic has a first portion 452 having a comparatively higher and substantially constant inductance value (at low dc current through the device), a second substantially vertical portion 454 with decreasing inductance as dc current increases, a third portion 456 with comparatively lower inductance at higher dc current (also substantially constant), and a fourth portion 458 wherein the device core is completely saturated.
• the first portion 452 represents dc current values producing little or no core saturation, and higher inductance corresponding in the exemplary DSL filter circuit to the on- hook condition.
• the core is beginning to saturate, and there is a sharp (precipitous) drop in inductance with increasing dc current.
• This sharp drop is related to, inter alia, the increased magnetic flux density through the small gap with increased current saturating this portion which effectively removes it electrically from the circuit.
• the core saturates further, and the device enters the third portion 456 of the curve 450.
• the inductance is essentially constant with increasing current, until the saturation region 458 is reached. Once complete saturation of the core is achieved, inductance falls off again rapidly to a very small value in comparison to the inductance achieved in the first, second, and third regions 452, 454, 456.
• Fig. 4 uses a two-region arrangement for the central post 406, other arrangements may be utilized to produce the desired electrical performance.
• a third region 470 is added to the mating surfaces of the core post 406, thereby adding a third step in the induction characteristic ("three-tiered").
• the two tiers or regions 416, 418 of the gap area are made concentric to one another, such that the second region 418 with the smaller gap W 2 surrounds the first region 416 with the larger gap Wi.
• the thickness Di of the wall or annulus 474 associated with the second region 418 is controlled to provide the desired inductance characteristic.
• this wall or annulus 474 may be tapered as a function of vertical height, such that for example its width Di is smaller nearer the gap W 2 than at a point higher above the gap.
• the annulus 474 can additionally (or alternatively) be made non-continuous; e.g., punctuated with one or more regions along its circumference where the gap is increased, such as by removal of material in these regions as shown in Fig. 4f.
• variable geometry gap arrangement of the illustrated embodiment may be readily applied to other core configurations, including for example "E” and "U” cores.
• Figs. 4a-4f can be manufactured for low cost, since (as described below in greater detail) they can use readily available or "off-the- 0 shelf low-cost pot cores which are simply modified as described herein to provide the desired inductance characteristic. These devices advantageously require no more space than the traditional pot core, since the variable geometry gap is entirely contained within the interior volume of the device.
• a drum (or spool) core 502 of the type well known in the art is utilized in conjunction with a controlled saturation element 508.
• the drum core 502 includes a central spool region 504 as well as two end elements (e.g., flanges) 506a, 506b disposed on the ends of the spool region 504.
• the spool region 504 contains the windings 510, which are concentrically wound around the spool.
• the core 502 is formed from a magnetically permeable material.
• the core 502 of the illustrated embodiment is one-piece in construction for, among other reasons, reduced cost, although it will be appreciated that a multi-piece core may be substituted.
• the controlled saturation element 508 of the illustrated device comprises a thin (approx. 0.001 in., or 0.0254 mm, thick) elongated strip of nickel-iron (Ni-Fe) alloy, which is :5 disposed longitudinally along the core 502 such that it bridges the two end elements 506a, 506b.
• the element 508 is in the present embodiment glued or bonded by adhesive to the two end elements 506.
• Ni-Fe is chosen for the controlled saturation element 508 since (i) it is magnetically permeable (and electrically conductive) due to the ferrous content, and (ii) physically rugged and sufficiently hard due to the Nickel content.
• the illustrated element 508 0 has a percentage of 80% Nickel and 20 % Iron, although other alloys may be substituted based on the desired properties. For example, different percentages of Nickel and Iron may be used. Alternatively, different types of alloys such as Ni-Fe-Cr (commonly known as Inconel) or so- called "stainless steel" (primarily Fe-C-Cr, whether Martensitic or otherwise) may be used alone or in combination.
• Ni-Fe-Cr commonly known as Inconel
• stainless steel primarily Fe-C-Cr, whether Martensitic or otherwise
• One advantage of Chromium content is passivation of the element 508, thereby largely mitigating the effects of ferrous degradation mechanisms including iron 5 oxide formation ("rust") and corrosion.
• the controlled saturation element 508 may advantageously fabricated as a tape in larger sheets, including the pre-application of adhesive thereto as described in greater detail below, thereby facilitating easy and cost-effective manufacture due to their ready availability.
• .0 saturation element 508 can affect the point at which device saturation occurs, as well as the relative inductance values for different currents.
• an approximately 0.001 in. (0.0254 mm) thick flat strip is used in the illustrated embodiment, other thickness and/or cross- sectional profiles may be used.
• the device 500 may be outfitted with two or more smaller diameter strips 508 disposed around the periphery of the device, thereby bridging the two end elements 506 at multiple locations (see Fig. 5a).
• the strip 508 shown in Fig. 5 may be replaced with one or more continuous sheets of the alloy "tape" 561 which extend partly or completely around the periphery of each end element 506 (Fig. 5b).
• Heat- shrink tubing 563 of the type well known in the art such as that manufactured by the Raychem Corporation of Menlo Park, CA
• composite saturation elements 508 may be used, wherein two or more different alloys may be used in conjunction with each other, such as being formed into substantially discrete, side-by-side or over-under strips. 0 Without the controlled saturation element 508 in place, the inductance of the core 502
• the saturation element 508 in place, the air gap between the ends 506 is bridged, thereby substantially increasing the inductance of the device 500 in the low or no- current condition (e.g., on-hook).
• the dc current increases, thereby increasing the flux 5 density in the comparatively thin element 508. This causes the element 508 to rapidly saturate, thereby substantially reducing the inductance of the device ("step").
• the inductive device 500 of Fig. 5 may also optionally include a terminal array such as that described with respect to Fig. 4 above for connection of the aforementioned winding(s) to an external device such as a PCB pad or trace.
• the terminals 529 may be
• .0 mounted directly into or onto the core 502 (as shown), such by frictionally and/or adhesively embedding them into apertures 535 in the core element 502, and then terminating the free ends of the windings 413 thereto. See also the alternate embodiment of Fig. 5c, wherein the drum core contains recesses 588 which are adapted to receive L-shaped terminals 586. The free ends 580 of the device windings 513 are disposed within the recesses 588 to allow electrical
• L5 termination to the terminals 586 Numerous other configurations for terminals and their mounting (either directly or indirectly) to the core 502 exist, such as in the well known ball grid array approaches, or pins (such as used in pin grid arrays). Such alternative configurations being readily recognized by those of ordinary skill.
• the device 600 comprises a dual drum core 602 5 having first and second end elements 602a, 602b and a central element (e.g., flange) 605 disposed between the two end elements 602.
• Two spool regions 604 are provided to each contain one or more sets of concentrically wound windings 610.
• a unitary controlled saturation element 608 is disposed longitudinally along the axis 611 of the device and in contact with each of the three elements 602a, 602b, 605, thereby bridging the two air gaps 0 formed there between.
• two discrete saturation elements 608 may be used to bridge the two air gaps of the dual-spool core 602.
• the various alternate configurations described above with respect to the single-spool drum core of Fig. 5, such as use of different alloys, continuous tape, multiple saturation elements, etc., may be equally applied to the dual-spool core of Fig. 6.
• the inductive device of the present invention solves the problem of being able to cost-efficiently tailor the inductance characteristic of an inductive device to provide two or more substantially discrete inductance values as a function of dc current.
• this substantially discrete characteristic allows for significantly higher input impedance for the filter in the on-hook state.
• the improved inductor of the present invention when combined with the dynamic filter circuit of Fig. 7, provides for a single filter circuit which provides a low impedance filter in the off-hook state and a high impedance filter in the on-hook state, yet advantageously maintains the same (or similar) frequency cutoff performance.
• synergies are created through the combination of these two elements (i.e., the "stepped" inductive devices and the dynamically switched filter circuits).
• the inductive device of the present invention is combined into the filter circuit(s) of Figs. 8 and 9
• excellent stop band performance is provided at extremely low cost, through among other things the use of the combined or dual-spool inductor of Fig. 6.
• Fig. 7 a first embodiment of the dynamic micro-filter configuration with improved inductive devices is described. It will be appreciated that while the embodiment of Fig. 7 comprises an exemplary design adapted to meet the requirements for use in the United Kingdom (UK), the dynamic filter of the present invention may be adapted for use in literally any application, through proper component selection and configuration. Such alternate applications and adaptations are readily determinable to those of ordinary skill based on the present disclosure, and accordingly are not described further herein.
• UK United Kingdom
• the filter circuit 700 generally comprises an input section 702 having a plurality of input terminals (line side jack) 704 and two input inductors 706, 708. These two input inductors 706, 708 each comprise in the present embodiment an controlled saturation inductor of the type previously described herein. This provides the circuit with desired input inductance characteristic previously discussed.
• An output section 720 comprises two additional inductors 724, 726 (L3, L4) and three capacitors 727, 228, 730 (C4, C9, C6).
• the filter's input "stepped" inductors (LI, L2) 706, 708 are connected to the line side jack 704, while the filter's capacitive output section 720 is connected to the filter's phone side jack 740.
• the line and phone side jacks 704, 740 a UK-type modular jack of the type commonly used in the United Kingdom, although it will be recognized that other types of modular plugs and connectors may be substituted.
• the filter 700 further includes a DSL jack 750 that, in the illustrated embodiment, comprises and RJ-11 type DSL jack, although others may be substituted as well.
• the DSL jack 750 passes directly via electrical pathways 752 to the line side jack 704 (or plug) to provide a convenience DSL or home phone network (HPN) jack.
• HPN home phone network
• FIG. 7 is a fourth-order elliptical low pass filter that consists of the two input inductors 706, 708 (LI, L2), two output section inductors 724, 726 (L3, L4), and three bridge capacitors 727, 728, 730 (C4, C9, and C6, respectively).
• the input inductors 706, 708 provide the required input inductance characteristic and prevent loading on the DSL circuit, while the two capacitors 734, 736 (CI, C7) in the output section 720 are added to the output inductors 724, 726 (L3, L4) to produce a resonance on the order of 30 KHz, although it will be appreciated that other reactance and capacitance values can be selected in order to obtain other resonance frequencies. Accordingly, the embodiment of Fig.
• the filter 7 is a fourth-order elliptical filter which produces a sharp 30 KHz cut-off.
• the elliptical stop band feature allows the design to minimize the total capacitance to typically ⁇ 40 nF off-hook and 5 nF on-hook (i.e., ⁇ 40E-09 Farad off-hook, and 5E-09 Farad on-hook), which minimizes the effect of the capacitance on the phone's voice band performance.
• two reed switches 762, 764 KI, K2 are added to remove most of the filter capacitance for the on hook (idle) phones.
• Both of the reed switches 762, 764 are, in the embodiment of Fig. 7, magnetically coupled to the dual inductor 770 (L5A), as described in U.S. Patent Nos. 6,181,777 and 6,212,259 entitled “Impedance Blocking Filter Circuit", issued January 30, 2001 and April 3, 2001, respectively, and assigned to Assignee hereof.
• the reed switches 762, 764 are coupled to a dual inductor 770 by virtue of their physical proximity to the windings of the inductor, and therefore the magnetic field generated thereby.
• the inductor/reed switch device 766 of the present embodiment is formed of cylindrical housing and contains the dual inductor and the two reed switches 762, 764.
• the dual inductor/reed switch device 766 can be replaced with two single inductor/switch units (not shown) so as to render the same functionality.
• the reed switches 762, 764 are disposed horizontally with their longitudinal axis substantially parallel with that of the bobbin of the device. This configuration provides the aforementioned magnetic coupling between the windings of the inductor 770 and the switches to operate the latter.
• the device 766 is selected to be actuated on a predetermined loop current threshold (e.g., approximately 6-16 mA).
• the reed switch(es) may chatter during operation of the circuit, and may thus shorten the useful life of the switch(es).
• the loop current threshold is too high, then the amount of loop current may be insufficient to actuate the switch(es) in the worst case condition.
• Zener diodes 776, 778 are included across the reed switches 762, 764 as shown in Fig. 7 to clamp the peak voltage to below 12 V.
• the single diodes 776, 778 of the illustrated embodiment work satisfactorily because the capacitors are in series with the diodes, and will self bias the single diode when AC signals are present.
• the foregoing diode arrangement may be replaced dual back-to-back 6-12 V Zener diodes, a single Zener diode, or even low capacitance varistors.
• the construction and selection of such components, consistent with the present aims of providing the minimum capacitance in the device, are well known in the electronics arts, and accordingly are not described further herein.
• resistors 780, 782 are added in series with the C4 and C6 capacitors 726, 730 to limit the switching current to below the maximum current ratings of the switches.
• the resistance values of R5, R6 are chosen low enough so as not to significantly affect the filter's stop band performance.
• the resonant impedance correction circuit made from the dual inductor 770 (L5A, L5B), parallel network capacitors 790, 792 (C2, C3), and parallel network resistors 794, 796 (R4, and Rl) further improves the voice band return loss up to 10 db by adding a positive phase impendence in the 2-3 KHz band.
• the dual inductor 770 (L5A, L5B) performs a dual purpose; in addition to driving the reed switches during off hook as previously described, the dual inductor 770 (in combination with the network capacitors C2, C3 790, 792) forms a differential resonance impedance in series with the line input.
• the parallel network resistors 794, 796 (R3, R4) limit this impedance to approximately 700 ohms at resonance, which limits the maximum insertion loss to an acceptable level (i.e., on the order of 2 db).
• the circuit 700 of Fig. 7 is further provided with a 1 microfarad ringing capacitor 791
• circuit 700 embodiment of Fig. 7 advantageously uses separate inductive coils for the various circuit inductors 706, 708, 724, 726 (LI, L2, L3, L4) rather than, for example, the dual EP13 style inductor typically used in many prior art designs.
• This arrangement provides a longitudinal blocking impedance as well as differential impedances, which some applications (including for example, European telecommunications specifications) require.
• Traditional EP-based designs have effectively no longitudinal
• [0 inductors and/or dual bobbin, dual shielded inductors such as those manufactured by the Assignee hereof can provide the aforementioned longitudinal impedance as well as providing magnetic field to drive the reed switches (as applicable).
• the dynamic filter circuit 700 disclosed herein is meant to address inadequate stop band and voice band performance on telecommunications lines by providing (i) a "dynamic" filter
• an impedance correction circuit which provides, inter alia, enhanced return loss performance.
• the dynamic circuitry of the off-hook filter 0 increases its capacitance, while all the other on-hook phones on the same line remain at a low capacitance relative to the off-hook circuit.
• This dynamic capacitance feature is acceptable and compatible with existing applications, since the primary need for the enhanced DSL stop band corresponds to the off-hook phone, and the presence of the phone's polarity guard diode bridge.
• the DSL high-level up stream energy can over-drive this diode bridge in the off-hook phones,
• the incorporation in the circuit 700 of the controlled saturation inductive devices 400, 500 of the present invention advantageously addresses this problem, however, by increasing the filter's input inductance values only in the on-hook state; i.e., by providing a "stepped" inductance versus dc current characteristic. Therefore, the combination of the dynamically switched filter circuit and the controlled saturation input-side inductors provides near ideal performance in a broad range of applications (including multi-extension applications with Caller ID or similar functions) with very low cost.
• the circuit 800 of Fig. 8 comprises a line or input side having inputs 866, 868 connected to two respective input inductors 840, 842.
• the exemplary circuit 800 of Fig. 8 utilizes a dual-spool inductive device such as that of Fig. 6 herein to provide these two inductances 840, 842, although a different configuration (such as two single- spool drum core devices 500) may be substituted.
• the higher inductance provided by the dual- spool inductive device 600 advantageously produces sufficient inductance to allow the filter 800 to pass the on-hook stop band loss for more than 10 filters while allowing a larger off-hook capacitance to improve the stop band (such as for Caller ID or other functions requiring such higher stop band), yet still meeting the return loss requirements.
• Use of the dual-spool device 600 in place of the inductors 840, 842 provides significant cost benefits as well, since it is generally significantly less costly to manufacture the dual-spool device as opposed to two single-spool components.
• the circuit of Fig. 8 is extremely simple to make, requiring only two inductors 840, 842 (i.e., one dual-spool inductor), thereby allowing for a highly cost-efficient circuit with excellent stop band and filter performance.
• the circuit 900 of Fig. 9, like that of Fig. 8 described above, comprises a line or input side having inputs 966, 968 connected to two respective input inductors 940, 942, yet also includes an optional third-order filter circuit disposed in communication with the external-side jacks 960, 972. Such third order filter component may be desirable in certain circumstances.
• a method 1000 for manufacturing the improved pot core device of Fig. 4 is described.
• the second element 402b of the pot core is obtained or manufactured.
• the core 402 of the exemplary device of Fig. 4 is preferably formed from a magnetically permeable material using any number of well understood processes such as material preparation, pressing, and sintering.
• the core 402 is produced to have specified properties including magnetic flux properties, cross-sectional shape and area, height, and post diameters, as is known in the art and accordingly not described further herein.
• the first core element 402a may be formed directly with the variable geometry gap configuration previously described herein (step 1004), such as by making the mold or form used to fabricate the first core element 402a include the desired gap features.
• the first core element 402a can be formed per step 1006 effectively as a mirror image of the second element 402b (step 1007), and then processed (step 1008) to produce the desired variable geometry gap.
• processing per step 1008 includes in one embodiment machining at least a portion of the center post 406 of the first core element 402a to the desired configuration (e.g., the 90%/10% configuration with gap widths W and W 2 ).
• Such machining comprises for example precisely grinding the desired portion of the core post 406 away.
• such processing may comprise micro-cutting or milling, or even cutting or ablation via laser energy as examples.
• the core elements 402a, 402b may be optionally coated on some or all surfaces with a layer of polymer insulation (e.g., Parylene) or other material, so as to protect the windings from damage or abrasion.
• a layer of polymer insulation e.g., Parylene
• This coating may be particularly useful when using very fine gauge windings or windings with very thin film coatings that are easily abraded during the winding process.
• Such conductor configuration may comprise for example thin gauge magnet wire wound concentrically onto the center post 406 of the core in a substantially toroidal "donut" pattern, although other types of conductors (insulated or otherwise) and wind patterns may be used.
• the two core elements 402 are next assembled and mated in their desired alignment using, for example, an adhesive compound (step 1014).
• the windings are captured within the recess formed within the core 402, with their free ends routed through the apertures 409 formed in the sides of the core elements 402 (or other comparable penetration).
• the terminal array 425 and/or terminals 429 are next provided or fabricated per step 1016.
• the terminal array frame 427 is ideally formed using an injection or transfer molding process from a suitable polymer, although other materials and techniques may be substituted.
• the terminals 429 may include desired features such as notches for wire wrapping and substrate contact pads on their bottom ends, and be molded into or subsequently inserted into the frame 427. Fabrication of such terminal arrays is well known in the electronic arts, and accordingly not described further herein.
• the wound core is next mounted to or fitted with a terminal array 425 of the type previously described herein per step 1018.
• the core 402 is adhered to the frame 427 of the terminal array using a bead or drop of suitable adhesive, such as an epoxy.
• the windings are next terminated to the terminals 429 using, for example, a soldering process over a wire-wrap into notches formed in the terminal ends (step 1020).
• the assembled inductive device 400 is then optionally tested per step 1022, thereby completing the manufacturing process.
• a method 1050 for manufacturing the improved drum core device(s) of Figs. 5 and 6 is described, with specific reference to the single-spool core of Fig. 5 for sake of simplicity.
• a drum core is obtained or manufactured.
• the core 502 of the exemplary device of Fig. 5 is preferably formed from a magnetically permeable material using any number of well understood processes such as material preparation, pressing, and sintering.
• the core 502 is produced to have specified properties including magnetic flux properties, cross-sectional shape and area, height, and post diameters, as is known in the art and accordingly not described further herein.
• the core 502 may be optionally coated on some or all surfaces with a layer of polymer insulation (e.g., Parylene) or other material, so as to protect the windings
• a layer of polymer insulation e.g., Parylene
• Such conductor configuration may comprise for example thin gauge magnet wire wound concentrically onto the spool region of the core in a substantially helical lay pattern, although other types of conductors (insulated or otherwise) and wind patterns may be used.
• the terminal 529 are next provided or fabricated per step 1058.
• the terminals 429 may include desired features such as notches for wire wrapping and substrate contact pads on their bottom ends. Fabrication of such terminals is well known in the electronic arts, and accordingly not described further herein.
• the terminals 529 are next inserted into or bonded to the wound core 502 per step
• the terminals 529 are adhered to the grooves 535 of the core 502 a bead or drop of suitable adhesive, such as an epoxy.
• suitable adhesive such as an epoxy.
• the windings are terminated to the terminals 529 during step 1060 by routing their free ends into the grooves 535 and under the terminals 529, thereby forming electrical contact therewith.
• Other method such as wire-wrapping and soldering (consistent with the chosen terminal configuration) may be
• the controlled saturation element(s) 508 is/are fabricated.
• the element 508 comprises Ni-Fe tape.
• This tape is manufactured by first forming a sheet of Ni-Fe alloy in the desired thickness (step 1064). One side of the sheet is then impregnated with a suitable aggressive adhesive (or alternatively an
• One or more of the strips 508 obtained from step 1062 above are next affixed to the core 502 longitudinally along its axis in step 1070 so as to bridge the air gap between the two end elements 502a, 502b.
• Such attachment may be by automated means (e.g., a machine
• the aforementioned process may be modified such that the sheet of appropriate size is cut and then applied to the core 502.
• the heat-shrink sleeve or tubing (if used) is then applied at least to the peripheral regions of the end flanges of the core, overlying the controlled saturation sheet 508, and then exposed to sufficient heat to shrink the sleeve to tightly bond the sheet 508 to the drum core flanges.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Coils Or Transformers For Communication (AREA)
• Filters And Equalizers (AREA)

Applications Claiming Priority (1)

Publications (2)

Family

ID=32028450

Family Applications (1)

Country Status (4)

Cited By (1)

Families Citing this family (6)

Family Cites Families (9)

• 2002
  • 2002-09-17 EP EP02775837A patent/EP1540675A4/de not_active Withdrawn
  • 2002-09-17 AU AU2002341687A patent/AU2002341687A1/en not_active Abandoned
  • 2002-09-17 CN CN02829883.7A patent/CN1695212A/zh active Pending
  • 2002-09-17 WO PCT/US2002/029480 patent/WO2004027793A1/en not_active Ceased

Also Published As

Similar Documents

Legal Events