Abstract:
A system for driving an electromagnetic field generator. In one aspect, the system may include a plurality of transistors arranged in an H-bridge configuration, the H-bridge having first and second output terminals, first and second switching inputs, and a power input. The system may further include a control transistor coupling the power input to a power supply, and a diode having a cathode coupled to the power input and an anode coupled to ground. The first and second output terminals may be coupled to the electromagnetic field generator and the first and second switching inputs may receive switching signals based on an output of the electromagnetic field generator.

Description:
[0001]    This application claims the benefit of provisional patent application Ser. No. 60/930,221, filed May 15, 2007, the entire contents of which are hereby incorporated by reference into the present disclosure. This application further hereby incorporates by reference U.S. non-provisional patent application Ser. No. ______, titled “System and Method for Forming and Controlling Electric Arcs,” filed May 15, 2008 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an system and method for controlling an electromagnetic field generator. 
       BACKGROUND OF THE INVENTION 
       [0003]    Various types of solid state Tesla coil (SSTC) speakers are known. With high frequency (1-5 MHz) E-class SSTC speakers as the E-class exception, SSTC speakers typically create audio via modulating the dead times on the gates of the 4H-bridge transistors. High frequency E-class SSTC speakers modulate the wave via controlling a MOSFET gate or by applying a ˜100V ˜400 watt audio signal over an E-class system. 
       SUMMARY OF THE INVENTION 
       [0004]    The present disclosure relates to a system for driving an electromagnetic field generator. In one aspect, the system may include a plurality of transistors arranged in an H-bridge configuration, the H-bridge having first and second output terminals, first and second switching inputs, and a power input. The system may further include a control transistor coupling the power input to a power supply, and a diode having a cathode coupled to the power input and an anode coupled to ground. The first and second output terminals may be coupled to the electromagnetic field generator and the first and second switching inputs may receive switching signals based on an output of the electromagnetic field generator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Features and other aspects of embodiments of the present invention are explained in the following description taken in conjunction with the accompanying drawings, wherein like references numerals refer to like components, and wherein: 
           [0006]      FIG. 1  illustrates an apparatus for forming an electric arc from electromagnetic field generator with control circuitry in accordance with embodiments of the present invention; 
           [0007]      FIG. 2  illustrates control circuitry in accordance with embodiments of the present invention; 
           [0008]      FIG. 3A  shows a graph of voltage inputs and output with a standard center of oscillation over time in accordance with embodiments of the present invention; 
           [0009]      FIG. 3B  shows a graph of voltage inputs and output with a lower center of oscillation over time in accordance with embodiments of the present invention; 
           [0010]      FIG. 3C  shows a graph of PWM signal from a standard center of oscillation over time in accordance with embodiments of the present invention; 
           [0011]      FIG. 3D  shows a graph of PWM signal from a lower center of oscillation over time in accordance with embodiments of the present invention; 
           [0012]      FIG. 4  illustrates a control circuit PWM output from  FIG. 3A  in accordance with an embodiment of the present invention; 
           [0013]      FIG. 5A  illustrates an input signal and reference wave in accordance with embodiments of the present invention; 
           [0014]      FIG. 5A  illustrates an output wave in accordance with embodiments of the present invention; 
           [0015]      FIG. 6  illustrates circuitry in accordance with embodiments of the present invention; 
       
    
    
       [0016]    The drawings are exemplary, not limiting. 
       DETAILED DESCRIPTION 
       [0017]    Various embodiments of the present invention will now be described in greater detail with reference to the drawings. 
         [0018]    In one aspect, the system of the present disclosure may use a transistor or paralleled transistors to pulse energy into a bridge system that turns the pulsed DC wave into a pulsed high frequency AC waveform. This design may allow for bridge resonation to continue without interruption while modulated energy can be pulsed into the bridge. 
         [0019]    As shown in  FIG. 1 , one embodiment of the present invention may include insulated gate bipolar transistors (IGBTs)  031 ,  032 ,  033 , and  034  in an H-bridge configuration with a Q-bridge IGBT  039  controlling the bus voltage between the DC supply  028  and the positive DC input of the H-bridge configuration. In further aspects, this solid state bridge system may drive an electromagnetic field generator or other resonant system. In one aspect, the electromagnetic field generator may be a solid state Tesla coil having a primary winding  001 , which may be wrapped around a non-conductive form  006 . Primary winding  001  may induce a current into the secondary winding  002  which may act as a Tesla resonator and may be wrapped on a non-conductive form  005 . Secondary winding  002  is connected to discharge electrode  003  (not pictured). 
         [0020]    In further aspects, when voltages ring up in the secondary winding  002 , a voltage drop between the ground  008  and the discharge electrode  003  may emit lightning  007 , which may be modulated to create sound waves. This may result in some electrons being ripped from air molecules around the discharge electrode  003 , creating an arc or plasma formations around the discharge electrode  003 . In further aspects, the resultant plasma may have power added or reduced, and in doing so may make sound wave concussions. Power in the plasma may be added or reduced by the secondary winding  002 , which may receive its energy from primary winding  001 . Primary winding  001  may receive its AC energy from an H-bridge including IGBTs  031 ,  032 ,  033 , and  034 . IGBTs  031 ,  032 ,  033 , and  034  may receive their energy from DC source  028 , which may be regulated by Q-bridge IGBT  039 , which may be controlled by signal  022 , which may be a pulse width modulation (PWM) digital signal (for example, signals  058  and  059  as shown in certain aspects of the invention presently disclosed in  FIGS. 3A-3D ). 
         [0021]    In further embodiments, IGBTs  032  and  033  may receive and be controlled by signal  021  and IGBTs  031  and  034  may receive control signal  020 . The signal  021  may switch the IGBTs at or near the resonant frequency phase of the electromagnetic field generator such that the energy driven into the primary winding  001  may prove energy to the secondary winding  002 . In further aspects, when the secondary winding  002  is highly energized and/or when the primary winding  001  is in resonance with the secondary winding  002 , high peak current may damage IGBTs  031 ,  032 ,  033 , and  034 , unless IGBTs  031 ,  032 ,  033 , and  034  are switched at the zero current crossings. This window where IGBTs  031 ,  032 ,  033 , and  034  may be switched may limit the dead time controls over IGBTs  031 ,  032 ,  033 , and  034  and the frequency at which they may switch. In further embodiments, Q-bridge IGBT  039  may have no such limitations when, for example, high currents are present in the secondary winding  002 . In further aspects, the Q-bridge IGBT  039  may switch at any frequency or pulse width and may not be limited to the resonant frequency of the secondary winding  002 . 
         [0022]    As shown in  FIG. 2 , one embodiment of the present invention may include a Q-bridge IGBT configuration connected to a primary winding acting as a Tesla resonator (represented here by inductor  041 ) with a self capacitance in the secondary of capacitor  045  and secondary winding grounded with a current drive transformer (CDT)  046  located in between the bottom of the secondary winding and ground  008 . In further embodiments, CDT  046  may send analog signal  047  to inverting driver  048  that may output digital signal  020  and non-inverting driver  049  that may output digital signal  021  to drive H-bridge IGBTs  031 ,  032 ,  033 , and  034 . It is instructive to note, for purposes of this drawing, full depiction of an electromagnetic field generator, such as a Tesla resonator, is not shown in its entirety to better focus on the currents in the Q-bridge. Furthermore, inductor  041  may be shown to represent an electromagnetic field generator, such as a Tesla resonator, for purposes of showing that embodiments of the invention may include a device to drive and store electromagnetic resonate energy into the Q-bridge so that the electromagnetic field generator may be used to generate a feedback signal, where a digital signal may be acquired to drive the H-bridge IGBTs  031 ,  032 ,  033 , and  034 . The electromagnetic field generator may be an AC resonant system and the primary winding inductor  041  and primary capacitor  040  may be said to be holding electromagnetic energy such that they resonate at some natural resonant frequency. The logic system that generates signals  021  and  020  may receive feedback from resonations of inductor  041  and capacitor  040  such that they may switch the DC bus current to aid in these resonations. The logic system may include inverter  048  and non-inverter  049 , such as may be found in a Hex-inverter, to generate digital signals. If, for example, the gate logic control signals  021  and  020  are zero (low), then the H-bridge may no longer resonate and any electromagnetic energy inside the Tesla resonator and/or primary winding inductor  041  and primary capacitor  040  may flow back into the bridge system, in direction shown via current indicators  043  and  042 , one current path for each direction in which the resonate energy flows. In further aspects, this current then may be rectified via diodes  035 ,  036 ,  037 , and  038 . Energy may then flow through diode  101  to charge the DC bus capacitors  025 ,  026 , and  027 . In effect, when IGBTs  031 ,  032 ,  033 ,  034 , are turned off, all the energy in the electrodynamic dimension may charge the DC bus line and the Tesla coil may be off or may no longer be in oscillation. 
         [0023]    In further aspects, if the Q-bridge gate input logic  022  is at zero volts or is held low, IGBT  039  may be off and no power may travel from the DC bus capacitor  027  or from the DC power source  028  to the resonate system (inductor  041  and capacitor  040 ). In one example, electrically turning off the Q-bridge IGBT  039  may be similar to removing the DC bus power supply  028  completely. The turning off of the Q-bridge IGBT  039  may not result in stopping the Tesla resonator oscillations, but may result in a dip in the electrodynamic energy in the Tesla resonator for the duration that the Q-bridge IGBT  039  may be off. In further examples, when the Q-bridge IGBT  039  may be off, current  044  may not flow and a freewheel diode  029  may be added so that current  201  may flow from the bottom to the top of the H-bridge. This diode may protect the IGBT  039  from stray inductance loops, which in the case of high current, may result in very high peak voltages that may destroy the IGBT  039 . 
         [0024]    As shown in  FIG. 3A , one embodiment of the present invention may include an input wave  051 , such as an audio wave, oscillating around a center point  052  and the input wave  051  is referenced against the triangle wave  050 . For correct pulse width modulations, audio wave  051  and triangle wave  050  may input directly to the + and − pins of a comparator or op-amp, respectively, such that when the input wave  051  is above the triangle wave  050 , the op-amp or comparator&#39;s output may be “1”, and when the input wave  051  is below the triangle wave  050 , the op-amp or comparator&#39;s output may be “0.” The resulting digital “1” and “0” pulse width modulated signal  058  may then be input into the gate of the Q-bridge IGBT  039  at any triangle wave frequency or may be used to control dead times (i.e., dead time controls (DTC)) on the H-Bridge IGBTs  031 ,  032 ,  033 , and  034 . In one embodiment, this may result in creating a high power audio signal to feed into a Tesla resonator through an H-bridge. 
         [0025]    In further aspects, sound waves from plasma may be created by changing the surface area of the plasma. As shown in  FIG. 3B , one embodiment of the present invention may include the input wave  056  oscillating around a center point  057 , which may be below the middle of the triangle reference wave  055 . This may allow for larger changes of plasma at the discharge electrode which may result in louder and more “booming” sounds. This effect may be referred to as the “boom factor”. In further aspects, the farther the center point  057  of audio oscillation may be from the center of the reference triangle wave  055 , the larger the boom factor. When using pulse width modulation of triangle wave  055  and input wave  056 , with the boom factor enabled, i.e., lowered center point  057 , less energy overall may be used. In further embodiments, this may be shown by pausing the audio signal shown in  FIG. 3   d.    
         [0026]    As shown in  FIGS. 3C and 3D , digital PWM output  059  may have a smaller duty cycle than PWM non-boom factor wave  058 , yet the boom factor  059  may result in louder plasma output, shown as  007  in  FIG. 1 , as it may expand and contract the plasma output  007  more than the non-boom factor wave  058 . The width of the “1 s”, or on-times, of the PWM digital wave  058  may be larger than the “1 s”, or on-times of the PWM digital boom factor  059  as shown in  FIG. 3C  and  FIG. 3D . In such embodiments, the boom factor may increase audio output while decreasing the power input. 
         [0027]    As shown in  FIG. 4 , one embodiment of the present invention may include a MOSFET  063  in a class-E configuration, with a resonant system including a resonate capacitor  060  and resonate inductor  061 . The MOSFET  063  may be driven by a logic wave  023 , which, for example, may be around 1 Mhz-6 Mhz, and may be derived from an oscillator, for example, a crystal oscillator, and may be amplified (if needed) depending on the size of the MOSFET  063  gate capacitance. 
         [0028]    In further aspects, the class-E MOSFET operation may allow for high frequency operation, where transient audio waves may be beyond the range of the human ear. However, the human ear may detect the amount of change in plasma surface area. Such embodiments may allow for resonant frequencies of the Tesla resonator to be above 2 MHz, where audio may be clear and that of high fidelity omnidirectional sound. In further aspects, the freewheel diode  069  may allow the class E operation to resonate without interruption and Q-bridge IGBT  062  may pulse energy directly into the class-E bridge. In further aspects, when the Q-bridge IGBT  062  may be off, resonant energy and stray inductance current may bypass the DC power supply  028  and Q-bridge IGBT  062  via freewheel diode  069 . Such embodiments that may include this configuration of class-E MOSFET  063  operation with a pulsing Q-bridge IGBT  062  and freewheel diode  069  may increase the sensitivity and small bandwidth frequency window of a set E-class operation resonator. 
         [0029]    In further aspects, the class-E MOSFET  063  may switch when voltage over the collector to emitter is zero, which may result in its fast 1-5 MHz operation. In one example, when the gate of the MOSFET  063  is turned on or off to the beat of music, and not to the zero voltage crossing from drain to source, a power loss may occur. When reproducing audio using a class-E operation MOSFET, the plasma modulate by controlling the MOSFET gate, using low powers. Further embodiments may modulate the voltage over the class-E operation system by applying a high wattage audio signal. While this may create clear audio at medium and high power levels, a large, high powered, costly amplifier may be used. In further embodiments, use of the Q-bridge IGBT  062  and freewheel diode  069  may supplant the use of such an audio amplifier, as a single IGBT may act as the amplifier with, for example, over 1 Kwatt output capabilities. 
         [0030]    As shown in  FIG. 5A , one embodiment of the present invention may include a signal  071  that may be referenced against a reference wave  070 . A PWM signal generated from the signal wave  071  (here, a saw-tooth wave), and the reference wave  070  (here a triangle wave), may yield a pulsing signal with steadily increasing pulse widths. If signal  022 , as shown in one embodiment in  FIG. 1 , is a PWM signal generated from signal wave  071  and reference wave  070 , then the output of the Tesla coil may be graphed as shown in one embodiment of  FIG. 5B , which may resemble a slowly increasing output waveform conducive to straight arc growth. 
         [0031]    As shown in  FIG. 6 , one embodiment of the present invention may include input jack  080 , e.g., a 3.5 mm audio jack, coupled to printed circuit board ground  077  and op-amp  081 , which sends a signal to op-amp  082 , which outputs audio signal  056 . Resistors  087 ,  089 ,  090 ,  091  may be static resistors, and  092 ,  093 ,  094  may be variable resistors that change in resistance value depending on the audio input voltage and the and the amount of boom-factor desired. In one aspect, audio input voltage may be ˜2 volts peak to peak. Diodes  095  and  096 , e.g., 20 v Schottky diodes, allow one side of the audio wave to rise higher than the other side so that the full voltage range of the audio wave  056  may span the voltage range of the triangle reference wave  055 . Positive and negative voltage supplies  085  and  086  may supply op-amps  081 ,  082 , and variable resistor  093  with voltage, respectively. 
         [0032]    Although illustrative embodiments have been shown and described herein in detail, it should be noted and will be appreciated by those skilled in the art that there may be numerous variations and other embodiments that may be equivalent to those explicitly shown and described. For example, the scope of the present invention is not necessarily limited in all cases to execution of the aforementioned steps in the order discussed. Unless otherwise specifically stated, terms and expressions have been used herein as terms of description, not of limitation. Accordingly, the invention is not to be limited by the specific illustrated and described embodiments (or the terms or expressions used to describe them) but only by the scope of claims.