Abstract:
In described examples, an inductive structure includes a power coil and a data coil. The data coil is substantially centered within the power coil. A first portion of the data coil is for conducting current in a first direction. A second portion of the data coil is for conducting current in a second direction opposite the first direction. The first portion of the data coil is connected at a ground node to the second portion of the data coil. The power coil is for: receiving power without data; and outputting the received power without data.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 14/026,515 filed Sep. 13, 2013, which claims priority to: (a) U.S. Provisional Patent Application Ser. No. 61/841,765, filed Jul. 1, 2013, entitled A METHOD TO IMPROVE COMMON MODE TRANSIENT IMMUNITY FOR INDUCTIVE STRUCTURES, naming Rajaram Subramonian et al. as inventors; and (b) U.S. Provisional Patent Application Ser. No. 61/876,796, filed Sep. 12, 2013, entitled A METHOD TO IMPROVE COMMON MODE TRANSIENT IMMUNITY FOR INDUCTIVE STRUCTURES, naming Rajaram Subramonian et al. as inventors. All of the above-identified applications are hereby fully incorporated herein by reference for all purposes. 
         [0002]    This application is related to co-owned co-pending U.S. patent application Ser. No. 14/311,354, filed on Jun. 23, 2014, entitled INDUCTIVE STRUCTURES WITH REDUCED EMISSIONS AND INTERFERENCE, naming Rajaram Subramonian et al. as inventors. 
     
    
     BACKGROUND 
       [0003]    The disclosures herein relate in general to electronic structures, and in particular to inductive structures with reduced emissions and interference. 
         [0004]    An inductively coupled structure (or “inductive structure”) is useful for transmitting power and/or data from one or more transmitters to one or more receivers across an isolation barrier. If such power and data are transmitted through a single channel of an inductive structure, then various challenges and limitations may arise. However, if such power and data are transmitted through multiple channels of an inductive structure, then other challenges and limitations may arise (e.g., increased size, cost, emissions and/or interference). 
       SUMMARY 
       [0005]    In described examples, an inductive structure includes a power coil and a data coil. The data coil is substantially centered within the power coil. A first portion of the data coil is for conducting current in a first direction. A second portion of the data coil is for conducting current in a second direction opposite the first direction. The first portion of the data coil is connected at a ground node to the second portion of the data coil. The power coil is for: receiving power without data; and outputting the received power without data. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a block diagram of a system of the illustrative embodiments. 
           [0007]      FIG. 2  is a schematic plan view of an inductive structure of  FIG. 1 . 
           [0008]      FIG. 3  is a schematic perspective view of the inductive structure of  FIG. 1 . 
           [0009]      FIG. 4  is a structural perspective view of the inductive structure of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIG. 1  is a block diagram of a system, indicated generally at  100 , of the illustrative embodiments. A transmitter  102  outputs data and power to a receiver  104  through a device that includes inductive structures  106   a  and  106   b  (collectively, “inductive structure  106 ”). The inductive structure  106   a:  (a) receives the data from the transmitter  102  through differential TX Data lines; (b) receives the power from the transmitter  102  through differential TX Power lines; and (c) outputs the data and power by inductive coupling across an isolation barrier  108  to the inductive structure  106   b.  The inductive structure  106   b:  (a) receives the data and power by inductive coupling across the isolation barrier  108  from the inductive structure  106   a;  (b) outputs the data to the receiver  104  (which receives the data) through differential RX Data lines; and (c) outputs the power to the receiver  104  (which receives the power) through differential RX Power lines. 
         [0011]      FIG. 2  is a schematic plan view of the inductive structure  106 . As shown in  FIG. 2 , the inductive structure  106   a  includes: (a) a standard power coil  202  connected to the differential TX Power lines, namely TX Power+ and TX Power−; and (b) data coils  204   a  and  204   b  (collectively, “data coil  204 ”) connected to the differential TX Data lines, namely TX Data+ (connected to the data coil  204   a ) and TX Data− (connected to the data coil  204   b ). Also, the data coil  204   a  is connected to the data coil  204   b  at a node  206 , which is coupled through a center tap ground line  208  to a first ground. 
         [0012]    The data coil  204  is substantially centered within the power coil  202 . Accordingly, the data coil  204  is smaller than the power coil  202 . Because the data coil  204  is located (e.g., formed) within the center of the power coil  202 , the inductive structure  106  has reduced size and cost. 
         [0013]    Also, the data coil  204  is formed to have a relatively symmetric shape (e.g., symmetric 8-shape). As shown in  FIG. 2 , the data coil  204   b  is substantially identical to (yet reversed from) the data coil  204   a.  If current flows through the data coil  204   a  in one direction (e.g., clockwise), then current flows through the data coil  204   b  in an opposite direction (e.g., counterclockwise). Moreover, the center tap ground line  208  helps to substantially equalize a voltage between TX Data+ and the ground line  208  (“TX Data+ voltage”), relative to a voltage between TX Data− and the ground line  208  (“TX Data+ voltage”). 
         [0014]    In this example, an alternating current flows through the power coil  202 . A magnetic field induced by the power coil  202  on the data coil  204   a  results in an electromotive force that is substantially equal in magnitude to (yet opposite in polarity from) an electromotive force induced by the power coil  202  on the data coil  204   b,  so an effect of magnetic flux from the power coil  202  on the data coil  204   a  is substantially counterbalanced (e.g., cancelled) by an effect of magnetic flux from the power coil  202  on the data coil  204   b.  Accordingly, the power coil  202  induces a relatively small difference (if any) between TX Data+ voltage and TX Data− voltage, even if the data coils  204   a  and  204   b  might have slight differences (e.g., in size and/or shape) from one another. 
         [0015]    Further, an alternating current flows through the data coil  204 . A magnetic field induced by the data coil  204   a  on the power coil  202  is substantially equal in magnitude to (yet opposite in polarity from) a magnetic field induced by the data coil  204   b  on the power coil  202 , so an effect of magnetic flux from the data coil  204   a  on the power coil  202  is substantially counterbalanced (e.g., cancelled) by an effect of magnetic flux from the data coil  204   b  on the power coil  202 . Accordingly, the data coil  204  induces a relatively small difference (if any) between TX Power+ voltage and TX Power− voltage, even if the data coils  204   a  and  204   b  might have slight differences (e.g., in size and/or shape) from one another. 
         [0016]    In that manner: (a) the data coil  204  has reduced overall exposure to potential fields generated by the power coil  202 , and vice versa; (b) cross-coupling between the power coil  202  and the data coil  204  is relatively small; and (c) the relatively symmetric shape (e.g., symmetric 8-shape) of the data coil  204  reduces interference between the data coil  204  and the power coil  202  (e.g., helps to preserve integrity of the data). 
         [0017]      FIG. 3  is a schematic perspective view of the inductive structure  106 .  FIG. 4  is a structural perspective view of the inductive structure  106 .  FIGS. 3 and 4  are not necessarily drawn to scale. As shown in  FIGS. 3 and 4 , the inductive structure  106   b  is substantially identical to the inductive structure  106   a.  Further, as shown in the example of  FIG. 4 , the power coils  202  and  302  have multiple turns, and the data coils  204  and  304  have multiple turns. 
         [0018]    Accordingly, the inductive structure  106   b  includes: (a) a standard power coil  302  connected to the differential RX Power lines, namely RX Power+ and RX Power−; and (b) data coils  304   a  and  304   b  (collectively, “data coil  304 ”) connected to the differential RX Data lines, namely RX Data+ (connected to the data coil  304   a ) and RX Data− (connected to the data coil  304   b ). Also, the data coil  304   a  is connected to the data coil  304   b  at a node  306 , which is coupled through a center tap ground line  308  to a second ground that is isolated from the first ground (e.g., isolated from the center tap ground line  208 ). 
         [0019]    The data coil  304  is substantially centered within the power coil  302 . Accordingly, the data coil  304  is smaller than the power coil  302 . Because the data coil  304  is located (e.g., formed) within the center of the power coil  302 , the inductive structure  106  has reduced size and cost. 
         [0020]    Also, the data coil  304  is formed to have a relatively symmetric shape (e.g., symmetric 8-shape). As shown in  FIGS. 3 and 4 , the data coil  304   b  is substantially identical to (yet reversed from) the data coil  304   a.  If current flows through the data coil  304   a  in one direction (e.g., clockwise), then current flows through the data coil  304   b  in an opposite direction (e.g., counterclockwise). Moreover, the center tap ground line  308  helps to substantially equalize a voltage between RX Data+ and the ground line  308  (“RX Data+ voltage”), relative to a voltage between RX Data− and the ground line  308  (“RX Data+ voltage”). 
         [0021]    Further, as shown in  FIGS. 3 and 4 , the inductive structures  106   a  and  106   b  are aligned with one another (e.g., the data coils  204   a  and  304   a  are aligned with one another, and the data coils  204   b  and  304   b  are aligned with one another), so that: (a) the power coils  202  and  302  have relatively good coupling with one another; (b) the data coils  204  and  304  have relatively good coupling with one another; (c) cross-coupling between the power coil  202  and the data coil  304  is relatively small; (d) cross-coupling between the power coil  302  and the data coil  204  is relatively small; and (e) radiated emissions are relatively small (e.g., as radiated by the data coils  204  and  304 ), which helps with electromagnetic interference (“EMI”) certification. 
         [0022]    Although illustrative embodiments have been shown and described by way of example, a wide range of alternative embodiments is possible within the scope of the foregoing disclosure.