Patent Document

BACKGROUND 
     Technical Field 
       [0001]    The present disclosure relates to shielding of planar magnetic devices, such as those used in an electrosurgical generator. In particular, the present disclosure relates to shielding members disposed on a printed circuit board containing the planar magnetic devices, such as current sense coils and transformers. The shielding members according to the present disclosure are configured to shield planar magnetics from stray electromagnetic fields. 
       Background of Related Art 
       [0002]    Electrosurgery involves application of high radio frequency (“RF”) electrical current to a surgical site to cut, ablate, desiccate, or coagulate tissue. In monopolar electrosurgery, a source or active electrode delivers RF alternating current from the electrosurgical generator to the targeted tissue. A patient return electrode is placed remotely from the active electrode to conduct the current back to the generator. 
         [0003]    In bipolar electrosurgery, return and active electrodes are placed in close proximity to each other such that an electrical circuit is formed between the two electrodes (e.g., in the case of an electrosurgical forceps). In this manner, the applied electrical current is limited to the body tissue positioned between the electrodes. Accordingly, bipolar electrosurgery generally involves the use of instruments where it is desired to achieve a focused delivery of electrosurgical energy between two electrodes. 
         [0004]    Electrosurgical generators may include planar magnetic devices, (e.g., transformers and/or inductors), which are constructed using multilayered printed circuit boards. Planar magnetic devices are commonly used to increase magnetic coupling between conducting layers while decreasing skin effect by taking advantage of the proximity and large surface areas of the parallel planes. However, this also increases voltage coupling. This can result in decreased high frequency performance of the planar components, such as increased crosstalk and susceptibility to external electromagnetic interference (“EMI”) from the electrosurgical generator. Conventional, e.g., non-planar, magnetic devices usually include EMI shields, such as solid or mesh copper shields, which are not suitable in planar magnetic devices. Although adding a solid or mesh electrostatic shield to a planar magnetic device would shield the device, it would also render the device non-functional. In conventional magnetic devices, a solid shield can be added incorporated into the device because the three dimensional shape of the magnetic device allows the shield to be placed orthogonally to the magnetic field, thereby avoiding any interaction between the field and the shield. However, a planar magnetic device, which is effectively a two dimensional structure, construction techniques limit placement of the solid shields in the desired location, with respect to blocking EMI. 
         [0005]    Furthermore, any such shielding conductors disposed near the winding of the planar component would diminish the magnetic field of the signal, which would generate strong currents, effectively shorting the windings of the planar component. Thus, there remains a need to shield planar magnetics from stray electromagnetic fields. 
       SUMMARY 
       [0006]    According to one embodiment of the present disclosure, an electronic device includes: a multilayered dielectric substrate including a plurality of dielectric layers; a planar magnetic device disposed on at least one internal dielectric layer of the plurality of the dielectric layers; and an overlapping shield assembly including a first shield layer and a second shield layer separated by at least one of the plurality of dielectric layers. 
         [0007]    According to one aspect of the above embodiment, the planar magnetic device is a sense transformer. The sense transformer includes: a first outer coil configured to detect a first magnetic field generated by a current; a second outer coil configured to detect the first magnetic field, the second outer coil further configured to cancel an electrical field induced in the first outer coil; and an inner conductor disposed between the first outer coil and the second outer coil, the inner conductor configured to detect a second magnetic field generated by the current. Each of the first outer coil, the second outer coil, and the inner conductor is disposed on a corresponding internal dielectric layer of the plurality of dielectric layers. 
         [0008]    According to another embodiment of the present disclosure, an electrosurgical generator is disclosed. The electrosurgical generator includes: a power supply configured to output a direct current; a power converter coupled to the power supply, the power converter configured to convert the direct current into a radio frequency current; at least one lead coupling the power converter to a terminal configured to couple to an electrosurgical instrument; and a current sensor configured to sense the radio frequency current. The current sensor includes: a multilayered dielectric substrate including a plurality of dielectric layers; at least one component of the current sensor disposed on at least one internal dielectric layer of the plurality of the dielectric layers; and an overlapping shield assembly including a first shield layer and a second shield layer separated by at least one of the plurality of dielectric layers. 
         [0009]    According to one aspect of any of the above embodiments, the first shield layer includes a plurality of first strips and the second shield layer includes a plurality of second strips. Each of the plurality of first strips has a first width and the plurality of first strips are separated by a first gap width. Each of the plurality of second strips has a second width and the plurality of second strips are separated by a second gap width. The first width is substantially equal to the second gap width and the second width is substantially equal to the first gap width. 
         [0010]    According to another aspect of any of the above embodiments, the first shield layer includes a first perimeter conductor coupled to each of the plurality of first strips and the second shield layer includes a second perimeter conductor coupled to each of the plurality of second strips. The first shield layer is electrically coupled to the second shield layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present disclosure may be understood by reference to the accompanying drawings, when considered in conjunction with the subsequent detailed description, in which: 
           [0012]      FIG. 1  is a perspective view of an electrosurgical system according to an embodiment of the present disclosure; 
           [0013]      FIG. 2  is a front view of an electrosurgical generator of the electrosurgical system of  FIG. 1 ; 
           [0014]      FIG. 3  is a schematic diagram of the electrosurgical generator of  FIG. 2 ; 
           [0015]      FIG. 4  is a schematic diagram of a planar magnetic device disposed on a printed circuit board; 
           [0016]      FIG. 5  is a cross-sectional side view taken along a sectional line  5 - 5  of the planar magnetic device of  FIG. 4  according to an embodiment of the present disclosure; 
           [0017]      FIG. 6  is a cross-sectional side view of a planar magnetic device having an overlapping shield assembly according to another embodiment of the present disclosure; 
           [0018]      FIG. 7  is a plan view of a first layer of the overlapping shield assembly of  FIG. 6 ; 
           [0019]      FIG. 8  is a plan view of a second layer of the overlapping shield assembly of  FIG. 6 ; and 
           [0020]      FIG. 9  is a perspective view of the overlapping shield assembly of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Particular embodiments of the present disclosure will be described below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Those skilled in the art will understand that embodiments of the present disclosure may be adapted for use with any electrosurgical system, generator, and/or instrument. It should also be appreciated that different electrical and mechanical connections and other considerations may apply to each particular type of instrument. 
         [0022]    Briefly, an overlapping shield assembly according to the present disclosure is described below with respect to shielding planar magnetic devices in an electrosurgical generator. Although the present disclosure is described with respect to an electrosurgical generator, it is envisioned that the overlapping shield assembly may be utilized with any planar magnetic device in any electronic device in which EMI protection is desired. 
         [0023]    The electrosurgical generator according to the present disclosure may be used in monopolar and/or bipolar electrosurgical procedures, including, for example, cutting, coagulation, ablation, and vessel sealing procedures. The generator may include a plurality of outputs for interfacing with various electrosurgical instruments (e.g., monopolar instruments, return electrode pads, bipolar electrosurgical forceps, footswitches, etc.). Further, the generator may include electronic circuitry configured to generate radio frequency energy specifically suited for powering electrosurgical devices operating in various electrosurgical modes (e.g., cut, blend, coagulate, division with hemostasis, fulgurate, spray, etc.) and procedures (e.g., monopolar, bipolar, vessel sealing). 
         [0024]    Referring to  FIG. 1 , an electrosurgical system  10  according to the present disclosure includes one or more monopolar electrosurgical instruments  20  having one or more active electrodes  23  (e.g., electrosurgical cutting probe, ablation electrode(s), etc.) for treating tissue of a patient. Electrosurgical alternating RF current is supplied to the instrument  20  by a generator  200  via a supply line  24  that is connected to an active terminal  350  ( FIG. 3 ) of the generator  200 , allowing the instrument  20  to cut, coagulate, and/or otherwise treat tissue. The RF current is returned to the generator  200  through a return electrode pad  26  via a return line  28  at a return terminal  352  ( FIG. 3 ) of the generator  200 . For monopolar operation, the system  10  may include a plurality of return electrode pads  26  that, in use, are disposed on a patient to minimize the chances of tissue damage by maximizing the overall contact area with the patient. In addition, the generator  200  and the return electrode pads  26  may be configured for monitoring tissue-to-patient contact to ensure that sufficient contact exists therebetween. 
         [0025]    The system  10  may also include one or more bipolar electrosurgical instruments, for example, a bipolar electrosurgical forceps  30  having one or more electrodes for treating tissue of a patient. The electrosurgical forceps  30  includes a housing  31  and opposing jaw members  33  and  35  disposed at a distal end of a shaft  32 . The jaw members  33  and  35  have one or more active electrodes  34  and a return electrode  36  disposed therein, respectively. The active electrode  34  and the return electrode  36  are connected to the generator  200  through cable  38  that includes the supply and return lines  24 ,  28 , which may be coupled to the active and return terminals  350 ,  352 , respectively ( FIG. 3 ). The electrosurgical forceps  30  is coupled to the generator  200  at a port having connections to the active and return terminals  350  and  352  (e.g., pins) via a plug (not shown) disposed at the end of the cable  38 , wherein the plug includes contacts from the supply and return lines  24 ,  28  as described in more detail below. 
         [0026]    With reference to  FIG. 2 , a front face  240  of the generator  200  is shown. The generator  200  may include a plurality of ports  250 - 262  to accommodate various types of electrosurgical instruments (e.g., monopolar electrosurgical instrument  20 , electrosurgical forceps  30 , etc.). 
         [0027]    The generator  200  includes a user interface  241  having one or more display screens  242 ,  244 ,  246  for providing the user with variety of output information (e.g., intensity settings, treatment complete indicators, etc.). Each of the screens  242 ,  244 ,  246  is associated with a corresponding port  250 - 262 . The generator  200  includes suitable input controls (e.g., buttons, activators, switches, touch screen, etc.) for controlling the generator  200 . The screens  242 ,  244 ,  246  are also configured as touch screens that display a corresponding menu for the instruments (e.g., electrosurgical forceps  30 , etc.). The user can adjust inputs by simply touching corresponding menu options. 
         [0028]    Screen  242  controls monopolar output and the devices connected to the ports  250  and  252 . Port  250  is configured to couple to a monopolar electrosurgical instrument (e.g., electrosurgical instrument  20 ) and port  252  is configured to couple to a foot switch (not shown). The foot switch provides for additional inputs (e.g., replicating inputs of the generator  200 ). The port  254  is configured to couple to the return electrode pad  26 . Screen  244  controls monopolar and bipolar output and the devices connected to the ports  256  and  258 . Port  256  is configured to couple to other monopolar instruments. Port  258  is configured to couple to a bipolar instrument (e.g., electrosurgical forceps  30 ). 
         [0029]    Screen  246  controls the electrosurgical forceps  30  that may be plugged into one of the ports  260  and  262 , respectively. The generator  200  outputs energy through the ports  260  and  262  suitable for sealing tissue grasped by the electrosurgical forceps  30 . In particular, screen  246  outputs a user interface that allows the user to input a user-defined intensity setting for each of the ports  260  and  262 . The user-defined setting may be any setting that allows the user to adjust one or more energy delivery parameters, such as power, current, voltage, energy, etc. or sealing parameters, such as energy rate limiters, sealing duration, etc. The user-defined setting is transmitted to a controller  324  ( FIG. 3 ) where the setting may be saved in a memory (not shown). In embodiments, the intensity setting may be a number scale, such as for example, from one to ten or one to five. In embodiments, the intensity setting may be associated with an output curve of the generator  200 . The intensity settings may be specific for each electrosurgical forceps  30  being utilized, such that various instruments provide the user with a specific intensity scale corresponding to the electrosurgical forceps  30 . The active and return terminals  350  and  352  ( FIG. 3 ) may be coupled to any of the desired ports  250 - 262 . 
         [0030]    With reference to  FIG. 3 , the generator  200  also includes a controller  324 , a power supply  326 , and a power converter  332 . The power supply  326  may be a high voltage, DC power supply connected to an AC source (e.g., line voltage) and provides high voltage, DC power to the power converter  332 , which then converts high voltage, DC power into RF energy and delivers the energy to the active terminal  350 . ( FIG. 2 ) The energy is returned thereto via the return terminal  352 . In particular, electrosurgical energy for energizing the monopolar electrosurgical instrument  20  and/or electrosurgical forceps  30  is delivered through the active and return terminals  350  and  352 . The active and return terminals  350  and  352  are coupled to the power converter  332  through an isolation transformer  340 . More specifically, the isolation transformer  340  includes a primary winding  340   a  coupled to the power converter  332  and a secondary winding  340   b  having an active lead  342  coupled to the active terminal  350  and a return lead  344  coupled to the return terminal  352 . The output of power converter  332  transmits current through the isolation transformer  340  to the load “Z”, e.g., tissue being treated. 
         [0031]    The power converter  332  is configured to operate in a plurality of modes, during which the generator  200  outputs corresponding waveforms having specific duty cycles, peak voltages, crest factors, etc. It is envisioned that in other embodiments, the generator  200  may be based on other types of suitable power supply topologies. Power converter  332  may be a resonant RF amplifier or a non-resonant RF amplifier. A non-resonant RF amplifier, as used herein, denotes an amplifier lacking any tuning components, e.g., inductors, capacitors, etc., disposed between the power converter and the load “Z” intended to establish a fixed operating frequency. 
         [0032]    The controller  324  includes a processor (not shown) operably connected to a memory (not shown), which may include one or more of volatile, non-volatile, magnetic, optical, or electrical media, such as read-only memory (ROM), random access memory (RAM), electrically-erasable programmable ROM (EEPROM), non-volatile RAM (NVRAM), or flash memory. The processor may be any suitable processor (e.g., control circuit) adapted to perform the operations, calculations, and/or set of instructions described in the present disclosure including, but not limited to, a hardware processor, a field programmable gate array (FPGA), a digital signal processor (DSP), a central processing unit (CPU), a microprocessor, and combinations thereof. Those skilled in the art will appreciate that the processor may be substituted for by using any logic processor (e.g., control circuit) adapted to perform the calculations and/or set of instructions described herein. 
         [0033]    The controller  324  includes output ports that are operably connected to the power supply  326  and/or the power converter  332  allowing the controller  324  to control the output of the generator  200  according to either open and/or closed control loop schemes. A closed loop control scheme is a feedback control loop, in which a plurality of sensors measure a variety of tissue and energy properties (e.g., tissue impedance, tissue temperature, output power, current and/or voltage, etc.), and provide feedback to the controller  324 . The controller  324  then controls the power supply  326  and/or the power converter  332 , which adjusts power delivered to and/or from the power converter  332 , respectively. The controller  324  also receives input signals from the input controls of the generator  200 , the electrosurgical instrument  20  and/or electrosurgical forceps  30 . The controller  324  utilizes the input signals to adjust power outputted by the generator  200  and/or performs other control functions thereon. 
         [0034]    The controller  324  may perform various mathematical computations in order to control the power supply  326  and/or the power converter  332  to generate an RF waveform having a desired shape and energy content. Examples of computations performed by the controller  324  include, but are not limited to, calculating instantaneous and/or root mean square power levels, amount of energy delivered on a cycle by cycle basis, load impedance, etc. 
         [0035]    The generator  200  according to the present disclosure may also include a plurality of sensors, namely, a voltage sensor  336  and a current sensor  338 . The voltage sensor  336  is coupled to the active and return leads  342 ,  344  and measure RF voltage supplied to the active and return terminals  350 ,  352 . The current sensor  338  is coupled to the active and/or return leads  342 ,  344  and measures RF current supplied to the active and return terminals  350 ,  352 . In embodiments, the generator  200  may also include additional sensors (not shown) coupled to the power supply  326 . 
         [0036]    With reference to  FIGS. 4 and 5 , the current sensor  338  includes a planar magnetic device  460 , e.g., a current sense coil, which is disposed on a printed circuit board (“PCB”)  400 . The PCB  400  may be a multilayer PCB formed from any suitable dielectric material, including, but not limited to composite materials composed of woven fiberglass cloth with an epoxy resin binder such as FR-4 grade as designated by the National Electrical Manufacturers Association. The PCB  400  defines an opening  402  therethrough for passage of the active lead  342 . The planar magnetic device  460  includes an outer coil  470  and an inner conductor  472 . The outer coil  470  is formed by a plurality of upper and lower conductive traces  470   a  and  470   b  interconnected by a plurality of inner conductive vias  470   c  and outer conductive vias  470   d . The upper and lower conductive traces  470   a  and  470   b  may be printed on respective upper and lower surfaces  400   a ,  400   b  ( FIG. 5 ) of the PCB  400 . The inner conductor  472  is disposed in between the upper and lower conductive traces  470   a  and  470   b  and is embedded within the PCB  400  ( FIG. 5 ). 
         [0037]      FIG. 6  shows an overlapping shield assembly  500  disposed over the upper surface  400   a  of the PCB  400 . The overlapping shield assembly  500  includes a first layer  502  and a second layer  504 , which are separated by one or more dielectric layers  400   c ,  400   d , . . .  400   n  of the PCB  400 . In embodiments, the overlapping shield assembly  500  may also be disposed on the bottom surface  400   b  of the PCB  400 . In other embodiments, the overlapping shield assembly  500  may be disposed internally, i.e., within the planar magnetic device  460 , namely, between the upper conductive traces  470   a  and lower conductive traces  470   b . This configuration provides significant internal device E-field shielding and isolation and is suitable to control crosstalk and leakage currents. In further embodiments, the first layer  502  may be disposed on the upper surface  400   a  of the PCB  400  and the second layer  504  may be disposed on the lower surface  400   b  of the PCB  400 . A single layer of shielding (e.g., the first layer  502  or the second layer  504 ) may be on each surface  400   a ,  400   b  of the PCB  400  and may provide sufficient E-field shielding and may be adequate for many applications. In additional embodiments, a pair of overlapping shield assemblies  500  may be disposed on the PCB  400 , one on each surface  400   a ,  400   b , respectively, to provide an additional order of magnitude of shielding. 
         [0038]    With reference to  FIGS. 6-9 , the first and second layers  502  and  504  may be formed as conductive traces on their corresponding dielectric layers  400   c  and  400   d  ( FIG. 6 ) of the PCB  400 . Thus, the first layer  502  is disposed in a first plane “A-A” and the second layer  504  is disposed in a second plane “B-B” ( FIG. 6 ). Each of the layers  502  and  504  includes a plurality of strips  506  and  508 , respectively. The strips  506  and  508  are arranged in parallel with periodic gaps  510  and  512  that are defined therebetween. As shown in  FIG. 7 , the strips  506  of the first layer  502  have a strip width s 1  and the gaps  510  have a gap width w 1 . Similarly, the strips  508  of the second layer  504  have a strip width s 2  and the gaps  512  have a gap width w 2 . The strip width s 1  of the strips  506  is substantially equal to the gap width w 2  of the gaps  512  of the second layer  504  and conversely, strip width s 2  of the strips  508  is substantially equal to the gap width w 1  of the gaps  510  of the first layer  502 . This configuration allows for the strips  506 ,  508  and the gaps of  510 ,  512  to overlap, respectively, thus forming an EMI shield. 
         [0039]    Strip widths s 1  or s 2  may be from about 0.1 millimeters (mm) to about 10 mm, in embodiments from about 1 mm to about 5 mm. Since gap widths w 1  and w 2  are related to the strip widths s 1  and s 2 , gap widths w 1  and w 2  may also have the same dimensions. In further embodiments, the strip width s 1  or s 2  of each of the strips  506  and  508  may be different, i.e., have a non-uniform width. 
         [0040]    Each of the first layer  502  and the second layer  504  also includes a perimeter conductor  514  and  516 , respectively. The perimeter conductor  514  is coupled to each of the strips  506  of the first layer and the perimeter conductor  516  is coupled to each of the strips  508  of the second layer  504 . In addition, the first and second layers  502  and  504  are interconnected by one or more conductors  518  to form the EMI shield. 
         [0041]    Because the strips  506  and  508  are spaced apart, i.e., do not form a continuous conductive surface across one plane “A-A” or “B-B,” respectively, and are open ended, they do not form a complete circuit for stray current to flow therethrough. Furthermore, because the strips  506  and  508  are relatively narrow, Eddy currents, also known as Foucalt currents, do not have a significant impact. However, because the first and second layers  502  and  504  are separated by one or more PCB layers of the PCB  400 , the height between the layers is comparatively small, thereby forming a continuous surface when viewed along an axis “C-C,” which is transverse with respect to each of the planes “A-A” and “B-B” ( FIG. 6 ). Put differently, the first and second layers  502  and  504  complement each other to form, i.e., complete, the overlapping shield assembly  500 . 
         [0042]    While several embodiments of the disclosure have been shown in the drawings and/or described herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope of the claims appended hereto.

Technology Category: 1