Patent Publication Number: US-2023162905-A1

Title: Planar transformer including noise cancellation for auxiliary winding

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. provisional patent application No. 63/147,005 filed on Feb. 8, 2021, entitled “PLANAR TRANSFORMER INCLUDING NOISE CANCELLATION FOR AUXILIARY WINDING,” the entire contents of which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     Electronic devices are often supplied power from an electrically isolated source to protect the electronic devices from shorts, overloads and other external conditions. Transformers are often used to provide the electrical isolation between the power input (also called a primary winding) and the power output (often called a secondary winding) that supplies power to the electronic devices. Transformers can also be used to change the output voltage relative to the input voltage and to provide one or more auxiliary power supply rails that power auxiliary electronic devices. The auxiliary power supply rails often draw power from the transformer and in doing so can induce a current imbalance between the primary winding and the secondary winding, resulting in the injection of common-mode noise into the system. New transformers are needed that can generate one or more auxiliary power supply rails without injecting common-mode noise into the system. 
     SUMMARY 
     Numerous benefits are achieved by way of the present invention over conventional techniques. For example, embodiments of the present invention provide the ability to generate one or more auxiliary voltages from a transformer without generating noise in the system. These and other embodiments of the invention along with many of its advantages and features are described in more detail in conjunction with the text below and attached figures. 
     In some embodiments an electronic component comprises a magnetic core and first and second primary windings formed around the magnetic core. First and second secondary windings and first and second shield windings are also formed around the magnetic core. An auxiliary winding is formed around the magnetic core and is positioned on a same layer as the first shield winding. A compensation winding is formed around the magnetic core and is positioned on a same layer as at least one of the first and the second shield windings. 
     In some embodiments the compensation winding is formed a same layer as the first shield winding. In various embodiments the compensation winding is formed around the magnetic core in an opposite direction as the first shield winding. In some embodiments the compensation winding is formed on a same layer as the second shield winding. In various embodiments the compensation winding is formed in an opposite direction as the second shield winding. In some embodiments a first end of the compensation winding is electrically coupled to the at least one of the first and second shield windings and a second end is electrically floating. 
     In some embodiments a transformer comprises a first layer including a first secondary winding and a second layer including a first shield winding and a compensation winding. The transformer can also comprise a third layer including a first primary winding and a fourth layer including a second primary winding, as well as a fifth layer including a second shield winding and an auxiliary winding. A sixth layer includes a second secondary winding. 
     In various embodiments the transformer further comprises a magnetic core wherein the first secondary winding, the first shield winding, the compensation winding, the first primary winding the second primary winding the second shield winding, the auxiliary winding and the second secondary winding are formed at least partially around the magnetic core. In some embodiments the compensation winding is formed in an opposite direction as compared to the first shield winding. In various embodiments a first end of the compensation winding is electrically coupled to the first shield winding and a second end is electrically floating. In some embodiments the auxiliary winding is a primary auxiliary winding. In various embodiments the auxiliary winding induces a current imbalance between the second primary winding and the second secondary winding, and wherein the compensation winding at least partially cancels the current imbalance. 
     In some embodiments a transformer comprises a magnetic core, at least one primary winding formed around the magnetic core and at least one secondary winding formed around the magnetic core. At least one shield winding is formed around the magnetic core and is positioned between the at least one primary winding and the at least one secondary winding. At least one auxiliary power winding is formed around the magnetic core and is positioned on a same layer as the at least one shield winding. At least one compensation winding is formed around the magnetic core and is arranged to cancel a current imbalance in the transformer generated by the at least one auxiliary winding. 
     In some embodiments the at least one compensation winding is formed on a same layer as the at least one shield winding. In various embodiments the at least one compensation winding is formed around the magnetic core in an opposite direction as compared to the at least one shield winding. In some embodiments a first end of the compensation winding is electrically coupled to the at least one shield winding and a second end is electrically floating. In various embodiments the at least one shield winding is a first shield winding and the at least one auxiliary power winding is formed on a same layer as the first shield winding, and wherein the transformer includes a second shield winding on a different layer than the first shield winding. 
     In some embodiments the at least one compensation winding is positioned on a same layer as the second shield winding. In various embodiments the at least one compensation winding is positioned on a same layer as the at least one shield winding and the at least one auxiliary winding. In some embodiments the auxiliary power winding induces a current imbalance between the at least one primary winding and the at least one secondary winding, and wherein the at least one compensation winding at least partially cancels the induced current imbalance. 
     To better understand the nature and advantages of the present disclosure, reference should be made to the following description and the accompanying figures. It is to be understood, however, that each of the figures is provided for the purpose of illustration only and is not intended as a definition of the limits of the scope of the present disclosure. Also, as a general rule, and unless it is evident to the contrary from the description, where elements in different figures use identical reference numbers, the elements are generally either identical or at least similar in function or purpose. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a top plan view of a first layer of a PCB that forms a portion of a planar transformer, according to an embodiment of the disclosure; 
         FIG.  2    illustrates a simplified partial cross-sectional view through region  2 - 2  of the transformer shown in  FIG.  1   ; 
         FIG.  3    illustrates a simplified schematic illustration of the windings of the transformer shown in  FIGS.  1  and  2   ; 
         FIG.  4    shows a top plan view of the second layer within the PCB of the transformer shown in  FIGS.  1  and  2   ; 
         FIG.  5    shows a top plan view of the fifth layer within the PCB of the transformer shown in  FIGS.  1  and  2   ; 
         FIG.  6    shows a top plan view of the third layer within the PCB of the transformer shown in  FIGS.  1  and  2   ; 
         FIG.  7    shows a top plan view of the fourth layer within PCB of the transformer shown in  FIGS.  1  and  2   ; 
         FIG.  8    shows a top plan view of the first layer within PCB of the transformer shown in  FIGS.  1  and  2   ; 
         FIG.  9    shows a top plan view of the sixth layer within PCB of the transformer shown in  FIGS.  1  and  2   ; 
         FIG.  10    shows a top plan view of a layer of a PCB-based transformer that includes a compensation winding, according to embodiments of the disclosure; 
         FIG.  11    illustrates a top plan view of another layer of the transformer shown in  FIG.  10   ; 
         FIG.  12    illustrates a simplified partial cross-sectional view through a region of a PCB-based transformer, according to embodiments of the disclosure; 
         FIG.  13    illustrates a simplified partial cross-sectional view through a region of a PCB-based transformer, according to embodiments of the disclosure; and 
         FIG.  14    shows a simplified schematic illustration of the windings of the transformer shown in  FIG.  13   . 
     
    
    
     DETAILED DESCRIPTION 
     Several illustrative embodiments will now be described with respect to the accompanying drawings, which form a part hereof. The ensuing description provides embodiment(s) only and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the embodiment(s) will provide those skilled in the art with an enabling description for implementing one or more embodiments. It is understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of this disclosure. In the following description, for the purposes of explanation, specific details are set forth in order to provide a thorough understanding of certain inventive embodiments. However, it will be apparent that various embodiments may be practiced without these specific details. The figures and description are not intended to be restrictive. The word “example” or “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or design described herein as “exemplary” or “example” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. 
     Techniques disclosed herein relate generally to electronic transformers. More specifically, techniques disclosed herein relate to electronic transformers that include one or more auxiliary windings in addition to primary and secondary windings. Various inventive embodiments are described herein, including methods, processes, systems, devices, and the like. 
     For example, in some embodiments a transformer is formed from a multilayer PCB that includes windings formed around a magnetic core. The transformer includes a primary winding arranged to receive an input AC voltage which induces a varying magnetic flux in the magnetic core. The varying magnetic flux induces a varying electromotive force across other windings formed around the magnetic core. In this particular example there is a secondary winding formed around the magnetic core that produces an AC output signal for a load where the input signal is electrically isolated from the output signal via the transformer. In addition, by varying the number of turns of the primary and the secondary windings (e.g., turns ratio) the voltage of the output signal can be stepped up or down as compared to the voltage of the input signal. Often one or more shielding windings and/or layers are formed between the primary and secondary windings to minimize the coupling of electrical noise from the primary winding to the secondary winding. 
     An auxiliary winding is also formed around the magnetic core and is used to produce an auxiliary AC output signal that can be a different voltage than the output signal and is used to supply power to auxiliary circuitry. In further embodiments the auxiliary winding is used to supply power to circuitry associated with the primary side of the transformer where the voltage supplied by the auxiliary winding is different than the voltage of the input signal. 
     In some embodiments the presence of the auxiliary winding induces a current imbalance (e.g., common mode noise injection) between the primary and secondary windings and/or couples noise from the primary winding to the secondary winding which can result in an unacceptable level of noise on the output signal. To compensate for the imbalance induced by the auxiliary winding a compensation winding can be added on the same layer as one of the shielding windings, where the compensation winding is wound in an opposite direction as compared to the shielding winding which it shares a layer with. In some embodiments a first end of the compensation winding can be electrically floating and a width and a number of turns of the compensation winding can be adjusted to cancel the current imbalance caused by the addition of the auxiliary winding. In further embodiments the compensation winding can be formed on a same layer as the auxiliary winding or on an adjacent layer. 
     In order to better appreciate the features and aspects of the present disclosure, further context for the disclosure is provided in the following section by discussing one particular implementation of a planar transformer that includes an auxiliary winding according to embodiments of the disclosure. These embodiments are for explanatory purposes only and other embodiments may be employed in other transformers. For example, embodiments of the disclosure can be used with any transformer that includes one or more auxiliary windings that induce imbalance and/or electrical noise in the system. In some instances, embodiments of the disclosure are particularly well suited for use with computing systems because of their need for auxiliary windings and their susceptibility to electrical noise in the system. 
       FIG.  1    shows a top plan view of a first layer of a PCB that forms a portion of a planar transformer  100 , according to an embodiment of the disclosure. As shown in  FIG.  1   , first layer  105  includes a first secondary winding  110  wound in a clockwise direction around central region  115 . More specifically, first secondary winding  110  is a patterned layer of copper that integrally forms a portion of printed circuit board (PCB)  120 . In this particular embodiment all of the windings of transformer  100  are formed within a PCB structure, however, this disclosure is not limited to this configuration and other embodiments may include windings formed from one or more conductors that are not integrated within a PCB and are wrapped around a magnetic core. In some embodiments, central region  115  of PCB  120  is removed and a magnetic core (not shown in  FIG.  1   ) is positioned within the central region to couple AC power from the primary winding to the secondary winding. In some embodiments a bobbin-style core is used while in other embodiments a planar core, E-core, I-core, C-core, pot-core, laminated core, toroidal core or other suitable style of magnetic core can be used. Transformer  100  includes a noise cancellation winding (not shown in  FIG.  1   ) that compensates for an auxiliary winding, as described in more detail below. 
       FIG.  2    illustrates a simplified partial cross-sectional view through region  2 - 2  of transformer  100  shown in  FIG.  1   . As shown in  FIG.  2   , transformer  100  includes a magnetic core  205  positioned within central region  115  of PCB  120 . In this embodiment, PCB  120  includes six separate metal layers each separated by a dielectric layer (not shown), however other embodiments can contain a fewer number or a greater number of layers. More specifically, PCB  120  includes first and second secondary windings  110 ,  210 , respectively, disposed on first layer  105  and sixth layer  215 , respectively, of the PCB. In some embodiments one or more secondary auxiliary windings  220   a,    220   b  can be formed on first and/or sixth layers  105 ,  215 , respectively. Because secondary auxiliary windings  220   a,    220   b  are positioned on the outer layers (e.g., first layer  105  and sixth layer  215 ) they may have a negligible effect on current balance within transformer  100  and may not need to be compensated. In this particular embodiment first and second secondary windings,  110 ,  210 , respectively, are each shown as having approximately one turn, however other embodiments may have a fraction of a turn or more than one turn. 
     Positioned within central region  115  of PCB  120  are first and second primary windings  225   a . . .  225   d,    230   a  . . .  230   d,  respectively positioned on third layer  235  and fourth layer  240 , respectively. In this particular example each of first and second primary windings  225   a  . . .  225   d,    230   a  . . .  230   d,  respectively, include approximately four turns as illustrated by the four separate windings shown in each layer, however other embodiments can have fewer or more turns. Positioned between first secondary winding  110  and first primary winding  225   a  . . .  225   d  is a first shield winding  245  formed on second layer  250 . Similarly, positioned between second secondary winding  210  and second primary winding  240   a  . . .  240   d  is a second shield winding  255  formed on a fifth layer  260 . First and second shield windings  245 ,  255 , respectively, can shield noise from being coupled from first and second primary windings  225   a  . . .  225   d,    230   a  . . .  230   d,  respectively, to first and second secondary windings  110 ,  210 , respectively. 
     In this particular embodiment, an auxiliary primary winding  265   a  . . .  265   n  is formed on fifth layer  260 , adjacent second shield winding  255  and has n turns (e.g., shown as four turns in  FIG.  2   ). As discussed above, magnetic core  205  can induce a varying electromotive force across auxiliary primary winding  265   a  . . .  265   n  which can supply power to auxiliary circuitry. The number of turns of auxiliary primary winding  265   a  . . .  265   n  can be adjusted to deliver a particular voltage that is suitable for powering the auxiliary circuitry. 
     In this embodiment, auxiliary primary winding  265   a  . . .  265   n  is positioned on fifth layer  260  between second primary winding  230   a  . . .  230   d  and second secondary winding  210 . This location of auxiliary primary winding  265   a  . . .  265   n  not only disrupts the shielding provided by second shield winding  255  (e.g., exposes second secondary winding  210  to the electromagnetic field of second primary winding  230   a  . . .  230   d ), it also causes imbalanced current flow in transformer  100  (e.g., shown by the arrows proximate auxiliary primary winding) resulting in common mode electrical noise in the system. In this particular embodiment the current imbalance is compensated by a compensation winding  270  that is positioned on second layer  250  adjacent first shielding winding  245 . Compensation winding  270  is wound in an opposite direction as first shielding winding  245  to balance the current flow within transformer  100 . As appreciated by one of ordinary skill in the art having the benefit of this disclosure, a width and a number of turns of compensation winding  270  can be varied to provide a suitable level of current flow to cancel the common mode noise. Each metal layer in transformer  100  can be electrically insulated from adjacent metal layers by one or more dielectric materials including FR4, bismaleimide triazin (BT), polyamide or other suitable electrical insulator. 
       FIG.  3    shows a simplified schematic illustration of the windings of transformer  100  shown in  FIGS.  1  and  2   . As shown in  FIG.  3    transformer  100  has a primary side  305  electrically isolated from a secondary side  310 . Primary side  305  includes first and second primary windings  225   a  . . .  225   d,    230   a  . . .  230   d,  respectively, coupled in series with an AC power source (shown in  FIG.  3    as a DC power source  315  controlled by a switch  320 ) that induces a varying magnetic flux in magnetic core  205  (see  FIG.  2   ). The varying magnetic flux induces a varying electromotive force across first and second secondary windings  110 ,  210 , respectively which are coupled in series and produce an AC output signal  325  for a load. First and second primary windings  225   a  . . .  225   d,    230   a  . . .  230   d,  respectively, are shielded from first and second secondary windings  110 ,  210 , respectively, by first and second shield windings  245 ,  255 , respectively. 
     Transformer  100  also includes primary auxiliary winding  265   a  . . .  265   n  that generates a primary auxiliary output voltage  330 , and a secondary auxiliary winding  220   a  . . .  220   b  that produces a secondary output voltage  335 . Because primary auxiliary winding  265   a  . . .  265   n  is formed on fifth layer  260  (see  FIG.  2   ), between second primary winding  230   a  . . .  230   d  and second secondary winding  210 , it induces a current imbalance in transformer  100  which is compensated by compensation winding  270 . Compensation winding  270  is formed on second layer  250 , adjacent first shield winding  245  and is wound in an opposite direction as the first shield winding. Compensation winding  270  has a first end  340  coupled to the AC power source and a second, distal end  345  that is electrically floating. 
       FIG.  4    shows a top plan view of second layer  250  within PCB  120 , shown in  FIGS.  1  and  2   . As shown in  FIG.  4   , second layer  250  includes first shield winding  245  wound in a clockwise direction, positioned adjacent compensation winding  270  wound in a counterclockwise direction. First end  340  of compensation winding  270  is electrically coupled to first shield winding  245  and second, distal end  345 , is electrically floating. 
       FIG.  5    shows a top plan view of fifth layer  260  within PCB  120 , shown in  FIGS.  1  and  2   . As shown in  FIG.  5   , fifth layer  260  includes second shield winding  255 , positioned adjacent primary auxiliary winding  265   a  . . .  265   n.    
       FIG.  6    shows a top plan view of third layer  235  within PCB  120 , shown in  FIGS.  1  and  2   . As shown in  FIG.  6   , third layer  235  includes first primary winding  225   a  . . .  225   d.    
       FIG.  7    shows a top plan view of fourth layer  240  within PCB  120 , shown in  FIGS.  1  and  2   . As shown in  FIG.  7   , fourth layer  240  includes second primary winding  230   a  . . .  230   d.    
       FIG.  8    shows a top plan view of first layer  105  within PCB  120 , shown in  FIGS.  1  and  2   . As shown in  FIG.  8   , first layer  105  includes first secondary winding  110  positioned adjacent a first portion of secondary auxiliary winding  220   a.    
       FIG.  9    shows a top plan view of sixth layer  215  within PCB  120 , shown in  FIGS.  1  and  2   . As shown in  FIG.  9   , sixth layer  215  includes second secondary winding  210  positioned adjacent a second portion of secondary auxiliary winding  220   b.    
     As appreciated by one of skill in the art having the benefit of this disclosure, the metal patterns of the PCB layers described herein are for example only and other embodiments can have different geometries, numbers of turns and/or configurations, some of which are described below. For example, in one embodiment the primary windings may be formed on exterior layers and the secondary windings may be formed on interior layers. As defined herein the term winding can refer to a partial, a full or multiple turns around the magnetic core. 
       FIG.  10    shows a top plan view of a layer of a PCB-based transformer  1000  that includes a compensation winding, according to embodiments of the disclosure. As shown in  FIG.  10   , transformer  1000  is similar to transformer  100  shown in  FIGS.  1 - 9   , however transformer  1000  is formed in an oval shape. Compensation winding  1005  is formed on a same layer as shielding winding  1010  where the compensation winding is arranged in a counterclockwise direction and the shielding winding is arranged in a clockwise direction. 
       FIG.  11    illustrates a top plan view of another layer of transformer  1000  that includes a first shielding winding  1105  positioned adjacent a secondary auxiliary winding  1110 . 
       FIG.  12    illustrates a simplified partial cross-sectional view through a region of a PCB-based transformer  1200  that is similar to transformer  100  shown in  FIG.  1   . As shown in  FIG.  12   , transformer  1200  includes a primary auxiliary winding  1205   a  . . .  1205   n  on a same layer as a second shielding winding  1210 . Transformer  1200  also includes a compensation winding  1215   a  . . .  1215   n  on a same layer as a first shielding winding  1220 , where the compensation winding has n turns. In this embodiment magnet  1225  is illustrated as an E-core configuration having an air gap  1230  at a central portion  1235 . 
       FIG.  13    illustrates a simplified partial cross-sectional view through a region of a PCB-based transformer  1300  that is similar to transformer  100  shown in  FIG.  1   . As shown in  FIG.  13   , transformer  1300  includes a primary auxiliary winding  1305   a  . . .  1305   n  on a same layer as a second shielding winding  1310 . However, instead of positioning a compensation winding on the other shielding layer (e.g., a first shielding layer  1315 ), compensation winding  1320   a  . . .  1320   n  is positioned on the same layer as second shielding winding  1310  and primary auxiliary winding  1305   a  . . .  1305   n.    
       FIG.  14    shows a simplified schematic illustration of the windings of transformer  1300  shown in  FIG.  13   . As shown in  FIG.  14    compensation winding  1320   a  . . .  1320   n  includes a first end  1405  coupled to primary auxiliary winding  1305   a  . . .  1305   n  and a second, distal floating end  1410 . 
     As appreciated by one of skill in the art having the benefit of this disclosure, primary auxiliary winding and compensation winding can be positioned on different layers or the same layer. Variations in placement of compensation winding may result in a number of turns and a width of compensation winding to compensate the current imbalance caused by auxiliary primary winding x. These and other modifications are within the scope of this disclosure. 
     In the foregoing specification, embodiments of the disclosure have been described with reference to numerous specific details that can vary from implementation to implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the disclosure, and what is intended by the applicants to be the scope of the disclosure, is the literal and equivalent scope of the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. The specific details of particular embodiments can be combined in any suitable manner without departing from the spirit and scope of embodiments of the disclosure. 
     Additionally, spatially relative terms, such as “bottom or “top” and the like can be used to describe an element and/or feature&#39;s relationship to another element(s) and/or feature(s) as, for example, illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and/or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as a “bottom” surface can then be oriented “above” other elements or features. The device can be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     Terms “and,” “or,” and “an/or,” as used herein, may include a variety of meanings that also is expected to depend at least in part upon the context in which such terms are used. Typically, “or” if used to associate a list, such as A, B, or C, is intended to mean A, B, and C, here used in the inclusive sense, as well as A, B, or C, here used in the exclusive sense. In addition, the term “one or more” as used herein may be used to describe any feature, structure, or characteristic in the singular or may be used to describe some combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example and claimed subject matter is not limited to this example. Furthermore, the term “at least one of” if used to associate a list, such as A, B, or C, can be interpreted to mean any combination of A, B, and/or C, such as A, B, C, AB, AC, BC, AA, AAB, ABC, AABBCCC, etc. 
     Reference throughout this specification to “one example,” “an example,” “certain examples,” or “exemplary implementation” means that a particular feature, structure, or characteristic described in connection with the feature and/or example may be included in at least one feature and/or example of claimed subject matter. Thus, the appearances of the phrase “in one example,” “an example,” “in certain examples,” “in certain implementations,” or other like phrases in various places throughout this specification are not necessarily all referring to the same feature, example, and/or limitation. Furthermore, the particular features, structures, or characteristics may be combined in one or more examples and/or features. 
     In some implementations, operations or processing may involve physical manipulation of physical quantities. Typically, although not necessarily, such quantities may take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, or otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to such signals as bits, data, values, elements, symbols, characters, terms, numbers, numerals, or the like. It should be understood, however, that all of these or similar terms are to be associated with appropriate physical quantities and are merely convenient labels. Unless specifically stated otherwise, as apparent from the discussion herein, it is appreciated that throughout this specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” or the like refer to actions or processes of a specific apparatus, such as a special purpose computer, special purpose computing apparatus or a similar special purpose electronic computing device. In the context of this specification, therefore, a special purpose computer or a similar special purpose electronic computing device is capable of manipulating or transforming signals, typically represented as physical electronic or magnetic quantities within memories, registers, or other information storage devices, transmission devices, or display devices of the special purpose computer or similar special purpose electronic computing device. 
     In the preceding detailed description, numerous specific details have been set forth to provide a thorough understanding of claimed subject matter. However, it will be understood by those skilled in the art that claimed subject matter may be practiced without these specific details. In other instances, methods and apparatuses that would be known by one of ordinary skill have not been described in detail so as not to obscure claimed subject matter. Therefore, it is intended that claimed subject matter not be limited to the particular examples disclosed, but that such claimed subject matter may also include all aspects falling within the scope of appended claims, and equivalents thereof.