Abstract:
A compact high current source including a homopolar generator integrally formed on a substrate. An electronic circuit also can be disposed on the substrate, homopolar generator on a single integrated circuit. The for example, with the homopolar generator to produce a pulsed electronic circuit can be coupled to the homopolar generator to produce a pulsed high current output from a continuous lower current input. The electronic circuit can include at least one electronically controlled switch responsive to a control signal for alternately connecting the homopolar to a current source and to a load. A controller can be used to generate the control signal.

Description:
BACKGROUND OF THE INVENTION 
     Statement of the Technical Field 
     The inventive arrangements relate generally to the field of energy storage, and more particularly to an energy storage device incorporated onto substrate materials. 
     Description of the Related Art 
     Shrinking geometries and increasing clock speeds have consistently driven down the supply voltages for central processing units (CPUs), digital signal processors (DSPs), and other printed circuit board devices. Currently these devices can operate in the +1.0 V to +2.0 V range, but operational voltages will decrease further as operational Importantly, the capacitors typically have relatively high values of capacitance so that the capacitors can store enough energy to supply adequate levels of current. In consequence, capacitors that are used to supplement supply current tend to be fairly large. In order to minimize the slew rate and voltage between the capacitors and the circuit device having the high current requirements, the capacitors also are usually located near the circuit device to minimize circuit resistance and inductance between the capacitors and the circuit device. Locating large capacitors on a printed circuit board at the proper location often can be challenging, however. In particular, the capacitors can limit the extent to which the size of a circuit board can be reduced. Moreover, the capacitors can interfere with the mating of the circuit board to other devices. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a compact high current source including a homopolar generator integrally formed on a substrate. An electronic circuit is disposed on the substrate as well. In one arrangement, the homopolar generator and the electronic circuit can be formed on a single integrated circuit. The electronic circuit is coupled to the homopolar generator to produce a pulsed high current output from a continuous lower current input. The electronic circuit can include at least one electronically controlled switch responsive to a control signal for alternately connecting the homopolar generator to a current source and to a load. A controller can be used to generate the control signal. Further, the load can have a duty cycle and the electronically controlled switch can cause the current source to connect to the homopolar generator during an off portion of the load duty cycle and connect the homopolar generator to the load during an on portion of the load duty cycle. 
     The substrate material can be ceramic and/or a semiconductor. For example, the substrate can be a low temperature co-fired ceramic. The homopolar generator can include a circular recess formed in the substrate and at least one conductive disk rotatably disposed within the circular recess. The homopolar generator also can include a magnetic field source and a controller in the electronic circuit for selectively controlling an intensity of a magnetic field produced by the magnetic field source. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an exemplary micro-mechanical homopolar generator in accordance with the present invention. 
     FIG. 2 is a side view of the exemplary micro-mechanical homopolar generator in accordance with the present invention. 
     FIGS. 3A-3D illustrate an exemplary process for manufacturing the micro-electromechanical homopolar generator on a ceramic substrate in accordance with the present invention. 
     FIGS. 4A-4H illustrate an exemplary process for manufacturing the micro-electromechanical homopolar generator on a silicon substrate in accordance with the present invention. 
     FIG. 5 is an exemplary circuit incorporating a micro-mechanical homopolar generator in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to a micro-electromechanical homopolar generator (MEHG) manufactured on a substrate. Notably, the MEHG is an energy storage device that can be used in place of a capacitor in a variety of applications. For example, the MEHG can be used as a compact current source, thereby eliminating the need for large capacitors that are commonly used to supplement a power supply during peak current demand. Such capacitors are generally too large to be incorporated into an integrated circuit (IC) package, having energy storage densities on the order of 0.1 mJ/mm 3 . By comparison, the MEHG can provide a typical energy storage density on the order of 10 mJ/mm 3 , and in some instances on the order of 1 J/mm3. Accordingly, the present invention provides the circuit designer with an added level of flexibility by permitting the incorporation of an MEHG into a circuit board substrate or an IC package. This added flexibility enables improved circuit performance and circuit density not otherwise possible. 
     An exemplary MEHG is shown in FIG.  1 . The MEHG  100  includes a conductive disc (disc)  105 , or rotor, having a central portion  110  and radial: edge  115 . The disc  105  can be positioned proximate to a substrate surface, for example within an aperture  130  formed within a substrate  125 . In one arrangement. The disc  105  can be provided with an axle  120  to facilitate rotation about a central axis  135  of the disc  105  and maintain the disc  105  in the proper operating position. But other arrangements can be provided as well. For example, in another arrangement the aperture  130  can be structured with a low friction peripheral surface  140  that maintains the disc  105  within the aperture  130 . In yet another arrangement a hole can be provided at the central axis  135  of the disc  105 . The hole can fit over a cylindrical structure, such as a bearing, to maintain the operating position of the disc  105 . 
     Referring to FIG. 2, the rotatable conductive disc  105  is immersed in a magnetic field, illustrated with magnetic field lines  205 , which are typically perpendicular to a surface  210  of the disc  105 . One or more magnets  230  can be provided above and/or below the conductive disc  105  to generate the magnetic field. The magnets  230  can include permanent magnets and/or electromagnets. A first contact brush  215  can contact. The disc near its central portion  110 , which is proximate to the disc axis of rotation  135 . A second contact brush  220 , which is radially spaced from the first contact brush  215 , can contact the radial edge  115  of The disc  105 . In one arrangement, a contact brush (not shown) can be provided to contact the axle  120 . Additional contact brushes also can be provided. For example, contact brushes can be spaced in a circular pattern to contact multiple points on the radial edge  115 . Likewise, contact brushes can be spaced near the central portion  110  of the disc  105  to contact the central portion  110  at multiple points or to contact the axle  120  at multiple points. 
     When voltage is applied across the contact brushes  215  and  220 , causing current to flow through the disc  105 , magnetic forces are exerted on the moving charges. The moving charges in turn exert the force to the disc  105 , thereby causing the disc  105  to rotate and store kinetic energy. When the voltage source is replaced with an electrical load, the kinetic energy stored in the rotating disc  105  can be used to generate electricity. As the conductive disc  105  rotates within the magnetic field, an electromotive force (emf) is induced in the disc  105 , thereby causing current flow through the load. 
     The amount of voltage (V t ) that is generated by the MEHG  105  is approximately given by the formula            V   t     =         ω   m          B        (       r   2   2     -     r   1   2       )         2       ,                          
     where ω m  is angular velocity of disc, B is the flux density of the magnetic field that is perpendicular to the motor, r 1  is the radial distance between the center of the disc  105  and the first contact brush  215 , and r 2  is the radial distance between the center of the disc  105  and the second contact brush  220 . Further, the impedance (Z) of the MEHG is given by the formula          Z   _     =         B   2       2      π                 t                 ρ            1       j      ω                                             
     and the equivalent capacitance (C) is given by          C   =       2      π                 t                 ρ       B   2         ,                          
     where t is the thickness of the rotor, and ρ is the mass density of the rotor material. Further, the time constant (t) for charging the MEHG  105  is proportional to          ρ     B   2       .                          
     Accordingly, the flux density of the magnetic field can be varied to adjust the charge time, output current, impedance, and equivalent capacitance of the MEHG  105 . For example, if an electromagnet is provided to generate at least a portion of the magnetic field, the current in the electromagnet can be adjusted to adjust the flux density. In particular, reducing current flowing through the conductor of an electromagnet can reduce the magnetic flux density and increasing the current flowing through the conductor of the electromagnet can increase the magnetic flux density. A myriad of devices can be used to vary the current flowing through the conductor of the electromagnet, for example, an amplifier circuit, a rheostat, a potentiometer, a variable resistor, or any other device having an adjustable output current or voltage. 
     The MEHG  100  can be manufactured on a variety of substrates, for example, ceramic, silicon, gallium arsenide, gallium nitride, germanium, indium phosphide, and any other substrate material suitable for a micro-electromechanical manufacturing process. FIGS. 3A-3D represent an exemplary manufacturing process for manufacturing the MEHG  100  on a ceramic substrate. The ceramic substrate can be made of any suitable ceramic substrate material, for example low temperature co-fired ceramic (LTCC) material. One such LTCC material is Green Tape™ provided by DuPont, 14 NW Alexander Drive, Research Triangle Park, N.C. 27709. 
     Referring to FIG. 3A, a first ceramic substrate layer 305 can be provided. The ceramic substrate material that is to be used in each of the ceramic substrate layers can be preconditioned before being used in a fabrication process. For example, the ceramic material can be baked at an appropriate temperature for a specified period of time or left to stand in a nitrogen dry box for a specified period of time. Common preconditioning cycles are 120° C. for 20-30 minutes or 24 hours in a nitrogen dry box. Both preconditioning process are well known in the art of ceramic substrates. 
     Once the first ceramic substrate layer (first ceramic layer)  305  is preconditioned, a conductive via  340  can be formed in the first ceramic layer  305  to provide electrical conductivity through the ceramic layer. Many techniques are available for forming conductive vias in a ceramic substrate. For example, vias can be formed by mechanically punching holes or laser cutting holes into the ceramic substrate. The holes then can be filled with a conductive material, such as a conventional thick film screen printer or extrusion via filler. Vacuum can be applied to the first ceramic layer through a porous stone to aid via filling. Once the conductive via  340  has been formed in the first ceramic layer  305 , the conductive material can be dried in a box oven at an appropriate temperature and for an appropriate amount of time. For example, a common drying process is to bake the ceramic substrate having the conductive material at 120° C. for 5 minutes. 
     After the conductive filler in the via has dried, a first conductive circuit trace  330  and a second conductive circuit trace  335  can be provided. The circuit traces  330  and  335  can be deposited onto the first ceramic layer  305  using a conventional thick film screen printer, for example, standard emulsion thick film screens. In one arrangement the circuit traces  330  and  335  can be deposited onto opposite sides of the first ceramic layer  305 , with the first circuit trace  330  being in electrical contact with the conductive via  340 . Further, the second circuit trace  335  can extend around, and concentric with, the conductive via  340 . Nonetheless, a myriad of other circuit layouts can be provided, as would be known to the skilled artisan. As with the via filling process, once the circuit traces have been applied to the first ceramic layer  305 , the circuit traces can be dried in a box oven at an appropriate temperature and for an appropriate amount of time. 
     Subsequent ceramic substrate layers can be laminated to the first ceramic layer  305  after appropriate preconditioning and drying of circuit traces and/or via fillers. In particular, a second ceramic substrate layer (second ceramic layer)  310  can be stacked onto the first ceramic layer  305 . The second ceramic layer  310  can insulate circuit traces on the top of the first ceramic layer  305 . The second ceramic layer also can include vias  341  and  342 , which can be filled with material to form an axial contact brush  350  and at least one radial contact brush  355 , respectively. The vias can be positioned so that the contact brushes make electrical contact with respective circuit traces  330  and  335 . In one arrangement, a plurality of radial contact brushes  355  or a continuous radial edge contact brush, can be disposed concentric with, and at a uniform radius from, the axial contact brush  350  to reduce a net contact resistance between the a conductive object and the brushes. 
     The contact brushes can include any conductive material suitable for use in a contact brush, for example a carbon nano composite or a conductive liquid. In the case that the contact brushes are a solid material, such as carbon nano composite, the contact brushes can be screen printed into the vias in the second ceramic layer  310  using a conventional thick film screen printer. In the case that a conductive liquid is used as contact brushes, ferromagnetic properties can be incorporated into the conductive liquid so that a magnetic field can contain the conductive liquid within the vias  341  and  342 . In one arrangement, the axial contact brush  350  can fill only part of the via  341  so that a top surface of the via is disposed below a top surface of the second layer  310 . Accordingly, the via  341  also can function as a bearing. 
     A third ceramic substrate layer (third ceramic layer)  315  can be stacked above the second ceramic layer  310 . The third ceramic layer  315  can incorporate an aperture having a radius edge  343  aligned with an outer radius of vias  342  (a portion of the via furthest from the via  341 ). A fourth ceramic substrate layer (fourth ceramic layer)  320  can be stacked below the first ceramic layer  305  to insulate circuit traces on the bottom of the first ceramic layer  305 . Lastly, a fifth ceramic substrate layer (fifth ceramic layer)  325  can be stacked below the fourth ceramic layer  320 . As with the third ceramic layer, the fifth ceramic layer also can include an aperture  345  having a radius aligned with the outer radius of vias  342 . 
     Once the ceramic substrate layers have been stacked to form the substrate structure shown in FIG. 3B, the structure can be laminated using a variety of lamination methods. In one method, the ceramic substrate layers can be stacked and hydraulically pressed with heated platens. For example, a uniaxial lamination method presses the ceramic substrate layers together at 3000 psi for 10 minutes using plates heated to 70° C. The ceramic substrate layers can be rotated 180° following the first 5 minutes. In an isotatic lamination process, the ceramic substrate layers are vacuum sealed in a plastic bag and then pressed using heated water. The time, temperature and pressure can be the same as those used in the uniaxial lamination process, however, rotation after 5 minutes is not required. Once laminated, the structure can be fired inside a kiln on a flat tile. For example, the ceramic substrate layers can be baked between 200° C. and 500° C. for one hour and a peak temperature between 850° and 875° can be applied for greater than 15 minutes. After the firing process, post fire operations can be performed on the ceramic substrate layers. 
     Referring to FIG. 3C, a conductive disc (disc)  360  having an upper surface  361  and an opposing lower surface  362  can be provided in the MEHG for use as a rotor for storing kinetic energy. In one arrangement, a plurality of conductive discs can be provided to achieve greater energy storage capacity. The disc  360  can include a central contact  365  axially located on the lower surface  362 , and at least one radial contact  370 , also located on the lower surface  362 . In one arrangement, the radial contact  370  can extend around the lower peripheral region  373  of the disc  360 . The disc  360  can be positioned above the second ceramic substrate layer  310  so that the central contact  365  makes electrical contact with the axial contact brush  350  and the radial contact  370  makes electrical contact with the radial edge contact brush  355 . Accordingly, electrical current can flow between an inner portion  372  of the disc  360  and the peripheral region  373  when voltage is applied across the contact brushes  350  and  355 . The radial wall  358  of the aperture  341  can function as a bearing surface for the central contact  365  of the disc  360 . Alternatively, bearings (not shown) can be installed between the radial wall  358  and the central contact  365 . The bearings can be, for example, electromagnetic or electrostatic bearings. 
     Referring to FIG. 3D, a lid  375  can be provided above the disc  360  to provide an enclosed region  380  in which the disc  360  can rotate. Dust and other contaminants that enter the enclosed region  380  can increase friction between the contacts  365  and  370  and the contact brushes  350  and  355 , which can reduce the efficiency of the MEHG. To reduce contamination, a seal layer  385  can be provided between the third ceramic layer  315  and the lid  375  to form a continuous seal around a periphery of the disc  360 . 
     One or more magnets can be fixed above and/or below the disc  360  to provide a magnetic field aligned with an axis of rotation  135  of the disc  360 . For example a magnet  390  can be attached to the bottom of the lid  375 , spaced from the upper surface of the disc  361 . A magnet  395  also can be spaced from the lower surface  362  of the disc  360 . For example, a magnet can be provided beneath the fourth ceramic substrate layer  320 , within the aperture  345  of the fifth ceramic substrate layer  325 . The magnets  390  and  395  can be permanent magnets, such as magnets formed of magnetic material. For example, the magnets  390  and  395  can be made of ferrite, neodymium, alnico, ceramic, and or any other material that can be used to generate a magnetic field. 
     The magnets  390  and  395  also can be non-permanent magnets, for example, electromagnets. In another arrangement, the magnets can be a combination of permanent magnets and non-permanent magnets, for example, an electromagnet adjacent to one or more layers of magnetic material. As previously noted, the strength of the magnetic field generated by an electromagnet can be varied by varying the current through the conductor of the electromagnet, which can be useful for varying the output current of the MEHG, also as previously noted. 
     In another exemplary embodiment, the MEHG  100  can be manufactured on a semiconductor substrate, for example on a silicon substrate using a polysilicon microfabrication process. Polysilicon microfabrication is well known in the art of micromachining. One such process is disclosed in David A. Koester et al.,  MUMPs Design Handbook  (Rev. 7.0, 2001). An exemplary polysilicon microfabrication process is shown in FIGS. 4A-4H. It should be noted, however, that the invention is not limited to the process disclosed herein and that other semiconductor microfabrication processes can be used. 
     Importantly, the MEHG  100  can be fabricated on a substrate of an integrated circuit (IC) to provide a built-in current source. The need for external energy storage capacitors can be thereby eliminated. For example, modern computer systems commonly include a bank of energy storage capacitors immediately next to a central processing unit (CPU). Using the MEHG, energy storage capacity can be fabricated into the CPU chip itself. Further, the MEHG can be incorporated into digital signal processors (DSPs), or any other type of integrated circuit. Moreover, other circuits requiring substantial energy storage capacity can be compactly fabricated onto a single IC chip. 
     Referring to FIG. 4A, a first silicon substrate layer (first silicon layer)  405  can be provided to begin forming the MEHG structure  400 , for example, a silicon wafer typically used in IC manufacturing. It may be desirable to for the first silicon layer  405  to have electrically insulating properties. Accordingly, the first silicon layer  405  can be formed without doping or have only a light doping. Alternatively, an electrically insulating layer can be applied over the first silicon layer  405 . For example, a layer of silicon dioxide can be applied over the first silicon layer  405 . A conductive layer can be deposited onto the substrate, from which circuit traces  410  can be etched. For example, a conductive layer of doped polysilicon or aluminum can be deposited onto the substrate. After deposition of the conductive layer, conductive traces  410  can be defined using known lithography and etching techniques. 
     After the circuit traces are formed, an electrically insulating layer  415 , such as silicon nitride (SiN), can be deposited over the first substrate and circuit traces. For example, low pressure chemical vapor deposition (LPCVD) involving the reaction of dichlorosilane (SiH 2 Cl 2 ) and ammonia (NH 3 ) can be used for this purpose to deposit an insulating layer. A typical thickness for the SiN layer is approximately 600 nm. 
     Inner vias  420  and outer vias  425  then can be formed through the insulating layer  415  and filled with electrically conductive material (e.g. Aluminum) to electrically contact the circuit traces  410  at desired locations. Axial contact brushes  430  then can be deposited on inner vias  420  and radial edge contact brushes  435  can be deposited on outer vias  425  so that the contact brushes  430  and  435  can be electrically continuous with the respective vias  420  and  425 . Accordingly, the electrical contact brushes are electrically continuous with respective ones of circuit traces  410 . Two axial contact brushes  430  and two radial edge contact brushes  435  are shown in the figure, but additional axial and radial edge contact brushes can be provided. Further, the contact brushes can include any conductive material suitable for use in a contact brush, for example a carbon nano composite, which can be applied using a thermo spray method commonly known to the skilled artisan. In another arrangement the contact brushes can be a conductive liquid. 
     A first structural layer of polysilicon (poly  1 )  440  can be deposited onto the insulating layer  415  using LPCVD. The poly  1  layer then can be etched to form a radial aperture  445  which exposes the contact brushes  430  and  435 . In an alternate arrangement, the aperture  445  region can be masked prior to application of the poly  1  layer  440 , thereby preventing deposition in the aperture  445  region. 
     Referring to FIG. 4B, a first sacrificial layer  450 , for example silicon dioxide (SiO 2 ) or phosphosilicate glass (PSG), can be applied to the substrate over the previously applied layers. The first sacrificial layer  450  is removed at the end of the process, as is further discussed below. The sacrificial layer can be deposited by LPCVD and annealed to the circuit. For example, in the case that PSG is used for the sacrificial layer, the sacrificial layer can be annealed at 1050° C. In argon. The first sacrificial layer  450  then can be planarized within the aperture  445  using a planarizing etch-back process to form a flat base  455  within the aperture  445  that is recessed from an upper elevation  460  of the first sacrificial layer, as shown in FIG.  4 C. 
     Referring to FIG. 4D, a conductor then can be deposited into the aperture  445  to form a conductive disc (disc)  465  having opposing upper surface  466 , a lower surface  467 , an inner region  468 , and a peripheral region  469 . Further, the disc  465  can be wholly contained within the aperture  445  so that the only material contacting the conductive disc  465  is the sacrificial layer. The thickness of the disc  465  can be determined by the thickness of the first sacrificial layer  450  and the amount of etch-back. Importantly, the equivalent capacitance of MEHG is proportional to thickness of disc  465 . Accordingly, the thickness of the disc  465  can be selected to achieve a desired equivalent capacitance. Further, mechanical characteristics, such as rigidity, should be considered when selecting a thickness for the disc  465 . 
     A second aperture  470  then can be etched through the inner region  468  of the disc  465  and through the first sacrificial layer below the center of the disc to expose the second silicon substrate layer  415 , as shown in FIG.  4 E. Notably, the second aperture  470  can be sized to form a hole in the disc  465  having a radius equal to or smaller than the radial distance between opposing axial contact brushes  430  and  435 . Further, the first sacrificial layer in contact with the SiN layer  415  also can be etched away to expose a region  473  of the SiN layer  415  within the second aperture  470 . Known etching techniques can be used, for example reactive ion etch (RIE), plasma etching, etc. 
     A second sacrificial layer  475 , for example SiO 2  or PSG, then can be applied over an upper surface of the disc  465  and over the radial wall  480  formed by the second aperture  470 . Importantly, the region  473  of the SiN layer  415  should be masked during the application of the second sacrificial layer  475  to prevent the second sacrificial layer  475  from adhering to the SiN layer in the region  473 . Alternatively, a subsequent etching process can be performed to clear away the second sacrificial layer from the region  473 . 
     Referring to FIG. 4F, using LPCVD, a second layer of polysilcon (poly  2 )  490  can be deposited over the previously applied layers, for example the poly  1  layer. 440  surrounding the disc  465 , thereby adding an additional silicon structure. Notably, the poly  2  layer  490  also can fill the second aperture  470 . A washer shaped region  487  then can be etched to remove a washer shaped portion of the poly  2  layer  490  located above the disc  465 . Notably, the inner radius of the washer shaped region  487  can be larger than the inner radius of the disc  465 . Accordingly, the etching of the poly  2  layer  490  can leave a structure  485 , having a “T” shaped cross section, within the second aperture  470 . An upper portion  488  of the structure  485  can extend over the inner portion  468  of disc  465 , thereby limiting vertical movement of the disc  465  once the sacrificial layers are removed. Further, the structure  485  can operate as a bearing around which the disc  465  can rotate. Alternatively, electromagnetic or electrostatic bearings can be provided in the second aperture  470 . 
     Referring to FIG. 4G, the first and second sacrificial layers  450  and  475  then can be released with a hydrogen fluoride (HF) solution as is known to the skilled artisan. For example, the MEHG structure  400  can be dipped in an HF bath. HF does not attack silicon or polysilicon, but quickly etches SiO 2 . Notably, the HF can etch deposited SiO 2  approximately 100× faster than SiN. The release of the sacrificial layers  450  and  475  enables the disc  465  to rest upon, and make electrical contact with, the axial and radial edge contact brushes  430  and  435 . Moreover, the release of the sacrificial layers  450  and  475  frees the disc  465  to rotate about its axis. 
     A lid  495  can be provided above the disc  465  to provide an enclosed region  497  in which the disc  475  can rotate, as shown in FIG.  4 H. As previously noted, dust and other contaminants that enter the enclosed region  497  can reduce the efficiency of the MEHG. A magnet  499  can be fixed above and/or below the disc  465  to provide a magnetic field aligned with the axis of rotation of the disc  465 . For example a magnet can be attached to the bottom of the lid  495 , spaced from the upper surface  466  of the disc  465 . Further, a magnet can be attached to the bottom of the first silicon substrate below the disc  465 , for example with a third silicon substrate layer. 
     As previously noted, the magnet  499  can be a permanent magnet, non-permanent magnets, or a combination of a permanent magnet and a non-permanent magnet. For example, the magnet can include an electromagnet and one or more layers of magnetic material. The strength of the magnetic field generated by an electromagnet can be varied by varying the current through the conductor of the electromagnet, which can be useful for varying the output current of the MEHG, also as previously noted. In operation, a voltage applied across axial contact brush  430  and radial edge contact brush  435  causes current to flow between a region near the inner radius  472  of the disc  465  and a peripheral region  469  of the disc  465 , thereby causing the disc to rotate, as previously described. 
     An exemplary circuit  500  in which the MEHG can be used to provide pulsed current to a circuit device  510  is shown in FIG.  5 . In addition to the circuit device  510 , the circuit can include a power supply  505 , at least one MEHG  515 , a controller  520 , and at least one two-way switch (switch)  525 . The power supply  505  can be a conventional DC power supply. For example, the power supply can incorporate batteries or a transformer and rectifier. The switch can include a first terminal connected to the MEHG  515 , a second terminal connected to the power supply  505 , and a third terminal connected to the circuit device  510 . The circuit device  510  can be any circuit device requiring an input current. For example, the circuit device can be an integrated circuit (IC), such as a CPU, a DSP, or any other processor. The circuit device also can be an output device such as a pulsed current digital antenna, a micro electromechanical system (MEMS) actuator, a light emitter, microrobotics devices, and any other output device that requires an input current. Nonetheless, the present invention is not limited to these examples. 
     Because the MEHG  515  can be manufactured as a mini device or micro device on a substrate, the MEHG can be incorporated into a circuit board or an IC package, thereby enabling the MEHG  515  to be used as a current source in microelectronic circuits. In one arrangement, the circuit device  510 , the controller  520 , the at least one switch  525 , and the at least one MEHG  515  can be incorporated on a circuit in a single substrate, for example on a single wafer or in a single IC package. In particular, the single substrate can include a controller  520 , a switch  525  an MEHG  515 , and a processor. Moreover, pluralities of these circuits can be provided on a single IC package as well. 
     In some circuits the energy charge time associated with a MEHG  515  can be longer than the discharge time, which can have the benefit of relieving the power supply from having to supply the instantaneous power requirement of a particular load. But a single MEHG  515  having a charge time longer than the discharge time may not be able to adequately supply a particular current pulse rate required by a specific load  510 . To compensate, a plurality of MEHGs  515  can be used to supply current pulses to the load  510 , thereby increasing the current pulse rate that a circuit is capable of generating. For example, three MEHGs  515  can be provided in the circuit  500 . 
     The controller  520  can be provided to control the opening and closing of the switches  525 , thereby distributing the current requirements among the MEHGs  515  and keeping the MEHGs  515  synchronized. In one arrangement, the closing of the switches  525  can be sequentially synchronized wherein multiple MEHGs  515  generate current pulses in a specific order with no two MEHGs  515  generating simultaneous current pulses. Accordingly, multiple MEHGs  515  can present to the power supply a load that is more steady than when a single MEHG  515  is used. In another arrangement, the MEHGs  515  can be synchronized to simultaneously generate current pulses, thereby increasing an amount of current generated with the pulses. 
     In addition to MEHG synchronization, the controller  520  also can preform signal processing, such as analog to digital conversion, signal encoding, modulation, etc. For example, the controller  520  can receive an input signal, encode, modulate and digitize the signal, and activate the switches  525  as required to send current pulses corresponding to the digitized signal to a broadcast antenna. 
     While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as described in the claims.