Abstract:
Embodiments of the present invention provide novel techniques for creating a high speed transformer such as a pulse transformer. In particular, a secondary coil of the high speed transformer may include a single turn. The use of a single turn secondary coil simplifies the design and manufacture of the transformer and aids in more efficient inspections. Further, the single turn secondary coil transformer may reduce the number of vias used to interconnect the components of the transformer. Additionally, the embodiments described herein may significantly improve voltage isolation by single turn coils, and eliminate vias between board layers.

Description:
BACKGROUND 
       [0001]    The present invention relates generally to the field of electrical transformers such as those used to control the transfer electrical energy from one circuit to another as well as provide voltage isolation between the control and power circuits. More particularly, the present invention relates to transformers that may be made on or in control electrical circuit boards, and to methods for making such transformers. 
         [0002]    High speed transformers are used in a wide range of applications. For example, in power converters capable of converting electrical energy for use with centrifuges, magnetic clutches, pumps and more generally, in electric motor drive controllers that transform and condition incoming AC power for supply to motor drive circuitry. In certain motor drive circuits, silicon controlled rectifiers (SCRs) or other solid state switches are utilized to redirect and rectify incoming AC power and to deliver variable voltage and frequency three-phase power to control the speed of an induction motor. Accordingly, pulse transformers may be employed to provide voltage isolation and drive, i.e., switch solid state switches, according to different phases of the incoming AC power. However, pulse transformers may not provide adequate voltage isolation. 
       BRIEF DESCRIPTION 
       [0003]    Embodiments of the present disclosure provide novel techniques for using a high speed transformer, such as a pulse transformer, to provide for high speed switching, electrical isolation, and/or generation of a gate signal pulses. The high speed transformer embodiments described herein are simple to manufacture, are more reliable to use, are manufactured of less expensive components, and are capable of high speed switching of signals. In particular, certain embodiments of the transformer embodiments described herein can incorporate a single trace winding (e.g., single turn secondary coil and/or single turn primary coil) capable of allowing high frequency switching speeds and a SCR drive current. Indeed, the transformer embodiments described herein are capable of reducing circuit board real estate and reducing the number of vertical interconnect accesses (vias) interconnecting the primary and secondary windings of a pulse transformer. 
         [0004]    In a first embodiment, a transformer system is provided which includes a primary coil, a core, and a single-turn secondary coil. The single-turn secondary coil is formed on a layer of a circuit board. A first current flow through the primary coil creates a magnetic flux in the core. The magnetic flux induces a second current flow in the single-turn secondary coil. 
         [0005]    In a second embodiment, a transformer system is provided which includes a primary coil formed on at least one layer of a printed circuit board, a core, and a single-turn secondary coil. The single-turn secondary coil is formed on a layer of the printed circuit board. A first current flow through the primary coil creates a magnetic flux in the core. The magnetic flux induces a second current flow in the single-turn secondary coil. 
         [0006]    In a third embodiment, a transformer system is provided which includes a primary coil circuit configured to provide an input current, a transformer, and a secondary coil circuit. The transformer includes a primary coil coupled to the primary coil circuit to receive the input current, a core, and a single-turn secondary coil formed on a layer of a printed circuit board. The secondary coil circuit is configured to receive output current from the single-turn secondary coil for provision of current to a load 
     
    
     
       DRAWINGS 
         [0007]    These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0008]      FIG. 1  is a schematic diagram of an embodiment of a high speed transformer; 
           [0009]      FIG. 2  is a perspective view of an embodiment of a multi-layer printed circuit board; 
           [0010]      FIG. 3  is an exploded view of the printed circuit board of  FIG. 2 ; 
           [0011]      FIG. 4  is top view of an embodiment of a layer of a first layer printed circuit board; 
           [0012]      FIG. 5  is top view of an embodiment of a second layer of a printed circuit board; 
           [0013]      FIG. 6  is top view of an embodiment of a third layer of a printed circuit board; 
           [0014]      FIG. 7 . is an exploded view of embodiments of a printed circuit board and a transformer core; 
           [0015]      FIG. 8  is a side view of embodiments of a printed circuit board and a transformer core; 
           [0016]      FIG. 9  is an exploded view of embodiments of a printed circuit board and a transformer core; 
           [0017]      FIG. 10  is an exploded view of embodiments of a printed circuit board and a transformer core; and 
           [0018]      FIG. 11  is a schematic view of a motor controller circuit. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    It may be beneficial to first discuss embodiments of certain transformer systems that may incorporate the techniques described herein. With this in mind and turning now to  FIG. 1 , the figure is a schematic diagram of an embodiment of an electric circuit  10  including a transformer  12 . The electrical circuit  10  of  FIG. 1  may be incorporated into electric motor control embodiments, power converter embodiments, photographic flash embodiments, light dimmer embodiments, and so forth. Indeed, the circuit  10  may be used in any number of electrical examples. In certain embodiments, the transformer  12  may be a pulse transformer  12  suitable for high duty cycles (e.g., in excess of 50%) and frequencies in excess of 2 MHz. The transformer  12  includes a primary coil  14 , a core  16 , and a secondary coil  18 . A primary side circuit (e.g., control circuit)  20  enables flow of current into the primary coil  14  of the transformer, which in turn produces a magnetic field. The core  16  may increase the magnetic field strength (i.e., increase a magnetic flux), and also aid in confining and guiding the magnetic field. The magnetic field induces a current flow in the secondary coil  18  of the transformer  12 . Accordingly, electrical energy is transferred from the control circuit  20  to a secondary side circuit (e.g., solid state switching circuitry)  22 . 
         [0020]    In certain embodiments, the primary coil  14  of the transformer  12  may have more turns than the secondary coil  18 . Such embodiments of the transformer  12  may “step down” or reduce the voltage resulting in the secondary coil when compared to the voltage in the primary coil  14 . Such voltage reduction capabilities may enable the use of a higher voltage to drive devices requiring a lower voltage. In other embodiments, the primary coil  14  of the transformer  12  may have fewer turns than the secondary coil  18 . In these embodiments, the transformer  12  may “step up” or increase the voltage resulting in the secondary coil when compared to the voltage in the primary coil  14 . Such a voltage increase capability may enable the use of a lower voltage to drive devices requiring a higher voltage. In yet other embodiments, the number of turns of the primary coil  14  and the secondary coil  18  may be approximately equal. In these embodiments, the voltage of the secondary coil  18  may be approximately equal to the voltage of the primary coil  18 . Such embodiments may be useful in providing electrical isolation between the control circuit  20  and the solid state switching circuit  22 . Indeed, the “step down” and “step up” embodiments may also be capable of enabling electrical isolation between the control circuit  20  and the solid state switching circuit  22 , thus protecting any electrically sensitive equipment that may be connected to the transformer  12 . 
         [0021]    The pulse transformer  12  enables high speed switching (i.e., modulation) of certain devices, such as electric motors. In these embodiments, the pulse transformer  12  and circuitry  20  may be optimized so as transmit electrical pulses, such as rectangular pulses, having fast rise and a fall times and relatively constant amplitudes. That is, the pulse transformer may be suitable for adequately reproducing pulsed signals such as square pulse signals, being generated by the control circuit  20 . Indeed, in certain embodiments, the pulse transformer  12  and circuitry  20 ,  22  may be capable of operating at frequencies of approximately 2 MHz and upwards, while also enabling a driving current suitable for switching a variety of solid state devices (e.g., SCRs, NPN transistors, insulated-gate bipolar transistors, thyristors) and a load voltage of approximately 690 volts and upwards. Accordingly, certain embodiments of the pulse transformer  12  may use, for example, a diode  24  as a current rectifier, a Zener diode  26  as a voltage peak limiter (e.g., regulator), a resistor  28  as a current limiter, and a second diode  30  as a current rectifier. It is to be understood that other electrical and electronic components may also be used, instead of or in addition to the components  24 ,  26 ,  28 , and  30 , such as the components of the control circuit  20  and the solid state switching circuit  22 . 
         [0022]    Historically, the pulse transformer  12  has included multiple turns in each primary and secondary coils  14  and  18 , sometimes in excess of twenty or more turns. The techniques disclosed herein enable a transformer, such as the pulse transformer  12 , to include a secondary coil having a single turn. Such a transformer  12  may enable the elimination of multiple vias that are typically used to connect the multiple turns on a circuit board, thus increasing the ease of circuit board construction and lowering manufacturing cost. Further, the size of the transformer  12  may be reduced, gaining valuable circuit board real estate. Additionally, the transformer  12  having a single-turn secondary coil may increase the reliability of the electric circuit  10  and reduce failures due to, for example, over over-voltage breakdown. Further, the transformer  12  may be printed or formed (e.g., by etching) at multiple levels of a circuit board, as described in more detail below. The ability to select multiple board levels for the formation of the transformer  12  may reduce or eliminate the need for potting compounds and/or bismaleimide-triazine (BT) board materials that are typically used to prevent electrical creepage (i.e., unwanted current leaks) and meet clearance distances (i.e. distance between conductive parts) at higher working voltages (e.g., approximately 120 volts or higher). 
         [0023]      FIG. 2  is a perspective view depicting multiple layers  40 ,  42 , and  44  that may be used to construct a circuit board, such as a printed circuit board (PCB)  46 . In the depicted embodiment, the PCB  46  may be assembled by bonding each of the layers  40 ,  42 , and  44  on top of each other. That is, the layers  40 ,  42 , and  44  may first be printed or plated, for example, with a copper trace and then stacked on top of each another. The stacked layers  40 ,  42 , and  44  may then be heated, pressed and/or cured, thus forming the multi-layer PCB  46 . It is to be understood that, in other embodiments, the PCB  46  may include more or less layers. 
         [0024]      FIG. 3  is an exploded view depicting the layers that  40 ,  42 , and  44  that make up the embodiment of the PCB  46  of  FIG. 2 . The first layer  40  includes a trace  48  placed on a top surface  49  of the layer  40 . The trace  48  may be used as one turn of the primary coil  14 . The trace  48  may be a copper trace  48 , but any suitable conductive trace may be used. Three openings or holes  50 ,  52 , and  54  are disposed on the layer  40 , which enable the core  16  to be placed on the PCB  46  as described in more detail below with respect to  FIG. 3 . Indeed, approximately identical openings or holes  56 ,  58 ,  60 ,  62 ,  64 , and  66  are placed on the middle layer  42  and on the bottom layer  44 , respectively. The openings or holes  50 ,  52 ,  54 ,  56 ,  58 ,  60 ,  62 ,  64 , and  66  are through-holes, that is, they traverse the entirety of the layers  40 ,  42 , and  44 . 
         [0025]    In one embodiment, a via  68  may disposed on the top layer  40  that allows one end of the trace  48  to connect to a second trace  70  disposed on the bottom layer  44 , thus forming the two-turn primary coil  14 . The via  68  traverses the entirety of the layer  40 . That is, the via  68  extends from the top surface  49  through the interior of the layer  40  to a bottom surface  72  of the layer  40 . Likewise, an electrically conductive via  74  is disposed on the middle layer  42 , which traverses the layer  42  from a top surface  76  to a bottom surface  78 . In the depicted embodiment, an electrically conductive via  80  is disposed on the third layer  44  so as to traverse the third layer  44  from a top surface  82  to a bottom surface  84 . Accordingly, electrical conductivity is established between the top trace  48  and the bottom trace  70  through the electrically conductive vias  68 ,  74 , and  80 . Indeed, the depicted layers  40 ,  42 , and  44  may be used to print the primary and secondary coils of the transformer  12  using only a single via at each of layers  40 ,  42 , and  44 . Having a single via at each layer  40 ,  42 , and  44  increases the reliability of the transformer  12  because such a transformer is simpler to manufacture and inspect. Additionally, the features described herein improve voltage isolation between the primary and secondary coils of the transformer  12 . 
         [0026]    The secondary coil  18  of the transformer  12  includes a single-turn trace  86 . The single-turn trace  86  does not require any vias because there is no need to connect with any other layer. Indeed, the secondary coil  18  can be printed as a single trace on a surface of the layer  42 , such as the top surface  76 . In another embodiment, such as a single turn primary coil embodiment, the single trace  86  may be printed on the bottom surface  78  of the layer  42 . In this embodiment, the clearance distance between the traces  48  and  86  is increased because of the additional separation between the two traces  48  and  86 . The increased clearance distance may improve reliability of the transformer  12  and aid in preventing over-voltage breakdown. In yet another embodiment, the trace  86  may be printed on the bottom surface  72  of the layer  40 . In this embodiment, the PCB  46  may then consist of the layer  40  disposed on top of the layer  44 . Having a PCB  46  with two layers may additionally improve the ease of manufacture and inspection of the PCB  46  while also reducing cost. Likewise, the trace  86  may be printed on the bottom surface  84  of the layer  44 . Printing the trace  86  on the bottom surface  84  allows for an easier interconnection with electronic components such as diodes, resistors, capacitors, and so forth, that may be placed on the bottom surface  84 . 
         [0027]    The layers of the PCB  46 , including layers  40 ,  42 , and  44 , may include a number of substrates, including dielectric substrates. Some example substrates include polytetrafluoroethylene (e.g., Teflon®), fire retardant (FR) substrates, composite epoxy material (CEM) substrates, glass (G) substrates, and national electrical manufacturers association (NEMA) substrates (e.g., XPC, X, XX, and XXX). Such substrates may include FR-1 (e.g., phenolic paper), FR-2 (e.g., phenolic cotton paper), FR-3 (e.g., cotton paper and epoxy), FR-4 (e.g., woven glass and epoxy), FR-5 (e.g., woven glass and epoxy), FR-6 (e.g., matte glass and polyester), CEM-1 (e.g., cotton paper and epoxy), CEM-2 (e.g., cotton paper and epoxy), CEM-3 (e.g., woven glass and epoxy), CEM-4 (e.g., woven glass and epoxy), CEM-5 (e.g., woven glass and polyester), and G-10 (e.g., woven glass and epoxy). Because of the ease of forming the primary coil  14  (e.g., traces  48  and  70 ) and the secondary coil  18  (e.g., trace  86 ), the PCB  46  may be assembled with any number of substrates, including the substrates listed above. Such flexibility of manufacture allows the transformer  12  to be formed on a variety of board materials and assembled more quickly, efficiently, and inexpensively. 
         [0028]      FIG. 4  is a top view of embodiments of the trace  48  and through holes  50 ,  52 , and  54  of the layer  40  of  FIG. 3 . Additionally, the figure depicts an area  90  that may be used to position, for example, an “I” component of the core  16  on top of the trace  48 , as described in more detail below with respect to  FIGS. 7 and 8 . The single via  68  is depicted at one end  92  of the trace  48 , while the second end  94  of the trace  48  may be connected to, for example, embodiments of the control circuit circuitry  20 . In the depicted embodiment, the trace  48  is an approximately rectangular trace  48 . In other embodiments, the trace  48  may include other shapes such as circular shapes, curved shapes, angled shapes, and so forth. Additionally, the trace  48  may be of width W 1  and length L 1  that enables the reduction or elimination of electrical creepage and that improves clearance distances. In certain embodiments, W 1  may be approximately between 0.05 inches and 10 inches. In these embodiments, L 1  may be approximately between 0.05 and 10 inches. Indeed, the transformer  12  may be manufactured so as to have a small footprint, in some embodiments, of less than 1 inch while operating at frequencies of approximately 2 MHz and above. 
         [0029]      FIG. 5  is a top view of an embodiment of the trace  86  (i.e., secondary coil  18 ) and through holes  56 ,  58  and  60  of the layer  42  of  FIG. 3 . In the depicted embodiment, the trace  86  is an approximately rectangular trace  86  having an end  96  and an end  98 . The ends  96  and  98  may be suitable for interconnection with other electronic and/or electrical components of the solid state switching circuitry  22 . In other embodiments, the trace  86  may have other shapes such as a circular shapes, curved shapes, triangle shapes, and so forth. In the depicted embodiment, the trace  86  is designed to be positioned approximately under the trace  48  of  FIG. 4 . Accordingly, in one embodiment, the trace  86  may be printed in the same layer (e.g., layer  40 ) as the trace  48  but on the surface opposite to the surface used to print the trace  48 . In other embodiments, including the depicted embodiment, the trace  86  may be printed in a layer below the layer containing the trace  48  (e.g., layer  42 ). The trace  86  may have a width W 2  and a length L 2  similar to the width W 1  and length L 1  of trace  48 . In certain embodiments, the width W 2  may be approximately between 0.05 inches and 10 inches. In these embodiments, the length L 2  may be approximately between 0.05 and 10 inches. As mentioned above, the trace  86  may be designed to reduce or eliminate electrical creepage and to improve clearance distances. 
         [0030]    The depicted embodiment also illustrates a placement of the via  74  so that the via  74  is positioned approximately directly under the via  68  depicted in  FIG. 4 . The placement of the vias  68 ,  74  (and  80 ) allows them to be manufactured by placing all of the layers of the PCB  46  on top of one another and then using a single vertical drilling operation to create via through holes. The vias  68 ,  74  (and  80 ) may then be made electrically conductive, for example, by plating, or disposing a conductive surface or conductor (e.g., copper) in the interior of the vias. Further, the middle layer  42  does not require a via for the single-turn secondary coil  18  (e.g., trace  86 ). Reducing the number of vias used to manufacture the PCB  46  reducing the time and costs associated with manufacturing and inspection of the PCB  46 . 
         [0031]      FIG. 6  is a top view of embodiments of the trace  70  (i.e. second turn of the primary coil  14 ) and through holes  60 ,  62 , and  64  of the layer  44  of  FIG. 3 . Additionally, the figure depicts an area  100  that may be used to position, for example, an “E” component of the core  16  on top of the trace  70 , as described in more detail with respect to  FIGS. 7 and 8  below. The single via  80  is also depicted at one end  102  of the trace  70 , while the second end  104  of the trace  70  may be connected to, for example, embodiments of the control circuitry  20 . In the depicted embodiment, the trace  70  is an approximately rectangular trace  70 . As mentioned above, other embodiments of the traces, such as the trace  70 , may include shapes such as circular shapes, curved shapes, angled shapes, and so forth. In a preferred embodiment, the trace  70  is of approximately equal dimensions to the trace  48  of  FIG. 4 . Accordingly, the trace  70  may have width W 3  approximately equal to W 1  and a L 3  approximately equal to L 1  of the trace  48  of  FIG. 4 . 
         [0032]    In a presently contemplated embodiment, the trace  70  is formed on the lower surface  84  of the layer  44 . Forming the trace  70  on the lower surface  84  may aid in connecting other components to the primary coil  14 , such as electrical and/or electronic components of the control circuitry  20  residing on the lower surface  84 . In other embodiments, the trace  70  may be formed on the top surface  82  of the layer  44  or on the bottom surface  78  of the layer  42 . In the depicted example, the via  80  is positioned approximately directly under the via  74 , which in turn is positioned directly under the via  68 . Accordingly, the trace  70  may be electrically coupled to the trace  68 , thus forming the two-turn primary coil  14 . The design of the transformer  12 , including the two-turn primary coil  14  and/or single-turn secondary coil  18 , may be used to create boards  46  having any number of layers, including two layer boards, three layer boards, four layer boards, five layer boards, six layer boards, and so on, as described in more detail with respect to  FIGS. 7 and 8  below. Such flexibility in layering the components of the transformer  12  enhances the design flexibility and implementation of various circuits, such as the example circuit of  FIG. 11 . 
         [0033]      FIG. 7  is an exploded view depicting embodiments of an “E” core component  106 , an “I” core component  108 , and the assembled board  46 . The core components  106  and  108  may include materials such as ferrite, carbonyl iron, soft iron, vitreous metal, and so forth. Indeed, any material suitable for directing a magnetic flux may be used. The “E” core component  106  includes three posts (e.g., “legs”),  112 ,  114 , and  116 . In a preferred embodiment, the center leg  114  may be approximately twice the width of the lateral legs  112  or  114 . In this embodiment, the center leg may carry approximately twice the flux of either of the legs  112  or  114 . 
         [0034]    The legs  112 ,  114 , and  116  may be inserted through openings of the PCB  46 , such as the through holes of  50 ,  52 , and  54  of the layer  40 , through holes  56 ,  58 , and  60  of the layer  42 , and through holes  62 ,  64  and  66  of the layer  44 . Indeed, the “E” core component  106  may be inserted through the openings of all of the layers that make up the board  46 , as depicted. The “I” core component  108  may then be placed on top of the legs  112 ,  114 , and  116  of the “E” core component  106 , thus forming the core  16  of the transformer  12 . In certain embodiments, a fastener such as a metal tab may then be used to mechanically fasten the components  106  and  108  to each other. In other embodiments, the two components  106  and  108  may be secured to each other with solder, conductive adhesive, and so forth. Indeed, any type of fastening device capable of securing the “E” core component  106  to the “I” core component  108  while maintaining flux conductivity between the two components  106  and  108  may be used. It is also to be understood that, in other embodiments, the core  16  may be constructed out of two “E” core components  106 . That is, the “I” core component  108  may be replaced by another “E” core component  106 , as depicted in  FIG. 9 . Indeed, other core components may include laminated core components, cylindrical rod core components, C-shaped core components, toroidal core components, and so forth. 
         [0035]      FIG. 8  is a side view of embodiments of the “E” core component  106 , a board  118 , and the “I” core component  108 . In the depicted embodiments, the “E” core component  106  is traversing all layers of the board  118  so as to allow the legs  112 ,  114 , and  116  to protrude from the top of the board  118 . The “I” core component  108  may then be positioned on top of the legs  112 ,  114 , and  116  of the “E” core component  106 , as depicted. The two core components  106  and  108  may then be fastened to each other using a variety of fastening techniques such as a metal tab, a solder, a conductive adhesive, and so forth. In this embodiment, the board  118  includes six layers. Indeed, boards having any number of layers, such as two, three, four, five, six, seven, eight, nine, ten layers may be used. By adding or removing layers, specific distances may be achieved between the single-turn secondary coil  18  and the turns of the primary coil  16 . Such distances enable fine tuning of the clearance distances between the single-turn secondary coil  18  and the turns of the primary coil  14 . Additionally, such distances enable a fine tuning of the magnetic flux properties of the transformer  12  as described below. 
         [0036]    In the depicted embodiment, two layers  120  and  122  are disposed between the layers  40  and  42 , and one layer  124  is disposed between the layers  42  and  44 . Clearance distances between the primary coil  14  and the secondary coil  18  may be increased by adding more layers between the layers  40 ,  42 , and  44 . Additionally, the depth of the layers, including the depth of each of the layers  40 ,  42 ,  44 ,  120 ,  122 , and  124  may be selected to meet desired clearance distances. Further, the number of layers and/or the depth of each of layers may be chosen so as to manufacture the transformer  12  with a specific magnetic field strength. For example, increasing the distances between the primary coil  14  and the secondary coil  18  reduces the magnetic field strength, while decreasing the distances between the primary  14  coil and the secondary coil  18  increases the magnetic field strength. Such fine tuning capabilities enable the transformer  12  to be used in a variety of circuitry, for example the SCR motor controller example circuitry described in more detail below with reference to  FIG. 11 . 
         [0037]      FIG. 9  is an exploded view depicting embodiments of the “E” core component  106 , a second “E” core component  127 , and the assembled board  46 . As mentioned previously, the transformer core  16  may be manufactured out of other core components, such as the two “E” core components  106  and  127 . In this embodiment, the second “E” core component  127  replaces the “I” core component of  FIGS. 7 and 8 . In yet another embodiment depicted in  FIG. 10 , a “C” core component  129  and an “I” core component  131  are used. In this embodiment, a single trace primary coil  133  and a single trace secondary coil  135  may be printed or formed onto a board. In the depicted example, the single trace primary coil  133  may be printed on the bottom surface of the layer  40 , and the single trace secondary coil  135  may be printed on the bottom surface of the layer  42 . Such a printing or forming may enable the traces  133  and  135  to be kept away from conductive core embodiments. Indeed, a variety of traces and core components may be used to manufacture the transformer  12 , as depicted. 
         [0038]      FIG. 11  is illustrative of an embodiment of a single pole of a motor controller circuit  126  that may include embodiments of the transformer  12  as described herein. Indeed, the transformer  12  may be incorporated in a variety of circuits, including motor control circuits, power conversion circuits, photographic flash circuits, light dimming circuits, and so forth. In the illustrated embodiment, the motor controller circuit  126  may include, for example, gate drive modalities that are capable of starting a motor  128 , stopping the motor  128 , regulating the speed of the motor  128 , regulating motor torque, protecting against overloads or faults, and so forth. The control circuitry  20  of the motor controller circuit  126  may include a metal-oxide semiconductor field effect transistor (MOSFET) driver integrated circuit (IC)  128 . The MOSFET driver IC  128  may be capable of converting an input signal, such as a pulse-width modulation (PWM) input signal, into an output signal capable of driving a MOSFET transistor  130 . The MOSFET transistor  130  may then be modulated by the PWM signals generated by the MOSFET driver IC  128  to switch on and off (e.g., pulse) the primary coil  14  of the transformer  12 . Such generated signals may be high speed signals. 
         [0039]    The primary coil  14  may be electrically isolated from the secondary coil  18 , as mentioned above. The electrical isolation may be capable of protecting the solid state switching circuit  22  from overloads or faults in the control circuit  20 , and vice versa. The modulation of the primary coil  14  may result in a varying magnetic field, which in turn may result in an equivalent modulation of the secondary coil  18 . In certain embodiments, the secondary coil  18  may be connected to one or more SCRs, such as SCR  132 . More specifically, the secondary coil  18  may be connected to a gate of the SCR  132 , thus enabling the switching on or off of the SCR  132 . The switching (i.e., modulation) of the SCR  132  thus allows for a current to flow into the motor  130  from the power supply  134  (e.g., approximately 690 volts). By fast switching of SCRs, such as the SCR  132 , the circuit  136  is capable of controlling motor speed, motor torque, forward direction, reverse direction, and so forth. It is to be understood that other embodiments of the motor controller circuit  126  may include insulated-gate bipolar transistor (IGBT) drives, bipolar transistor drives, or a combination thereof. 
         [0040]    While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.