Plasma Generation System

Abstract

A power circuit for cold plasma generation (optionally therapeutic plasma). Cold plasma generation occurs at the distal end of a catheter-like device that is flexible, narrow (e.g., less than 5 mm in diameter), and long, extending, for example, 50-100 cm into a body cavity. The cable used for power transmission is part of the power generation circuit, and its inherent impedance is the primary contributor and limiting factor to the time constant of the synchronizing RC circuit, which has a resonant frequency that synchronizes the power generation frequency. In some embodiments, an inductive transformer coupling is used to generate voltage gain in the synchronizing / transmission line circuit. In some embodiments, the transformer coupling is split into multiple stages. This allows for practically higher transmission frequencies and allows for higher gain, reduced sensitivity to variations in the distal part of the synchronizing RC circuit, and / or longer transmission lines compared to a single-stage transformer configuration.

Description

[Technical Field]

[0001] Related Applications This application is a continuation of U.S. Patent Application No. 18 / 130,163, filed April 3, 2023, which is a continuation-in-part (CIP) of U.S. Patent Application No. 17 / 866,700, filed July 18, 2022, and issued April 11, 2023, as U.S. Patent No. 11,627,652.

[0002] This application is also a continuation-in-part (CIP) of U.S. Patent Application No. 18 / 129,116, filed March 31, 2023, which is a continuation-in-part of U.S. Patent Application No. 17 / 971,737, filed October 24, 2022, and issued April 4, 2023, as U.S. Patent No. 11,621,587, which is a continuation-in-part (CIP) of U.S. Patent Application No. 17 / 866,700, filed July 18, 2022, and issued April 11, 2023, as U.S. Patent No. 11,627,652.

[0003] This application is also related to a concurrently filed international patent application entitled "CONFIGURABLE PLASMA GENERATING SYSTEM" (Applicant's Attorney Internal Docket No. 95982).

[0004] The contents of each of the above applications cited in this application are hereby incorporated by reference in their entirety. [Background technology]

[0005] Some embodiments of the present invention relate to the field of plasma generation, and more particularly, but not exclusively, to the generation and therapeutic delivery of low-temperature plasma.

[0006] Non-thermal atmospheric plasma (NTAP), also known as cold atmospheric plasma (CAP), is an ionized gas at near-room temperature composed of a variety of neutral and charged species. Its beneficial properties in medicine are well established, and it is widely used in various application fields and industries. The application of NTAP to tissues has complex and unique effects at both the cellular / tissue and systemic levels.

[0007] NTAP can be generated by dielectric barrier discharge (DBD), in which a flowing gas (typically a noble gas such as helium or argon) is ionized by an electrode to which a high voltage is periodically applied. The electrode is covered by a dielectric barrier, preventing a direct ohmic path between the driving source and the target tissue. Summary of the Invention

[0008] According to one aspect of some embodiments of the present disclosure, a power supply circuit for a non-thermal plasma generator includes a gain transformer having a primary coil and a secondary coil, a driver circuit electrically connected to pass current through the primary coil, and a load circuit having a distal end having a plasma generation site and a proximal end coupled to the secondary coil of the gain transformer, the load circuit including at least one decoupling transformer inductively connecting the plasma generation site and the secondary coil.

[0009] According to some embodiments of the present disclosure, the load circuit has an impedance that determines the frequency of oscillation of the load circuit as a function of the current generated by the secondary coil.

[0010] According to some embodiments of the present disclosure, the load circuit synchronizes the oscillation of the driver circuit.

[0011] According to some embodiments of the present disclosure, the oscillation of the load circuit is synchronized by feedback from a gain transformer.

[0012] According to some embodiments of the present disclosure, the frequency of oscillation of the load circuit is high enough so that plasma generation at the plasma generation site does not die out during at least one complete oscillation period.

[0013] According to some embodiments of the present disclosure, the gain transformer provides a gain of at least 20.

[0014] According to some embodiments of the present disclosure, the at least one decoupling transformer provides a total gain of less than or equal to one.

[0015] According to some embodiments of the present disclosure, the at least one decoupling transformer provides a total gain that is at least two times less than the gain provided by the gain transformer.

[0016] According to some embodiments of the present disclosure, the gain transformer and at least one coupling transformer have an air core or a ferrite core.

[0017] According to some embodiments of the present disclosure, the at least one decoupling transformer comprises a plurality of decoupling transformers.

[0018] According to some embodiments of the present disclosure, a gain transformer and at least one coupling transformer isolate the plasma generation site from ground.

[0019] According to some embodiments of the present disclosure, the load circuit includes a transmission line and a distal transformer of at least one decoupling transformer, the distal transformer being inductively interconnected with a primary coil of the distal transformer and having a secondary coil of the distal transformer connected to a proximal side of the transmission line; a driver circuit electrically interconnected with the proximal side of the transmission line via the primary coil and the secondary coil of the distal transformer, providing an electrical signal to the transmission line at an operating frequency of 1 to 10 MHz, the electrical signal being transmitted to the distal end of the transmission line with an operating amplitude of at least 0.5 kV RMS; and an impedance of the secondary coil of the distal transformer in combination with a capacitance of the transmission line is sufficiently small so that a circuit portion including the transmission line and the secondary coil operates at resonance upon receiving the electrical signal.

[0020] According to some embodiments of the present disclosure, the driver circuit stops generating an electrical signal when the transmission line is disconnected, but continues to generate the electrical signal for values of the transmission line capacitance that vary within a range that has at least a 10% difference between the minimum and maximum values.

[0021] According to some embodiments of the present disclosure, the operating amplitude is at least 1 kV RMS.

[0022] According to some embodiments of the present disclosure, the transmission line has a length of at least 50 cm and is flexible.

[0023] According to some embodiments of the present disclosure, the load circuit provides a feedback signal to the driver circuit via a feedback network.

[0024] According to some embodiments of the present disclosure, oscillations in the load circuit synchronize, via a feedback network, the driver circuit to generate an electrical signal at the operating frequency.

[0025] According to some embodiments of the present disclosure, the power supply circuit is provided with a gas supply lumen that is directed along a transmission line to the plasma generation site, the gas supply lumen and transmission line together being elements of a flexible probe having an overall diameter of less than 10 mm.

[0026] According to some embodiments of the present disclosure, the plasma generation site generates a non-thermal plasma when powered by an electrical signal.

[0027] According to some embodiments of the present disclosure, the at least one decoupling transformer and the gain transformer together comprise a plurality of transformers interconnecting the proximal end of the transmission line and a low voltage signal oscillating at the operating frequency and having a voltage amplitude at least 20 times smaller than the operating amplitude.

[0028] According to some embodiments of the present disclosure, the primary coil of the gain transformer has an inductance in the range of approximately 1-5 μH, and the secondary winding of the gain transformer has an inductance in the range of approximately 1000-5000 μH.

[0029] According to some embodiments of the present disclosure, the gain transformer has a feedback winding that provides a feedback signal to the driver circuit via a feedback network, the feedback winding having an inductance in the range of approximately 1-10 μH.

[0030] According to some embodiments of the present disclosure, a feedback signal synchronizes the oscillation of the driver circuit to the operating frequency and is received at the feedback winding via the load circuit at the frequency of the electrical oscillation of the transmission line.

[0031] According to some embodiments of the present disclosure, the secondary winding of the distal transformer has an inductance in the range of approximately 20-80 μH, and the primary winding of the distal transformer has an inductance in the range of approximately 5-20 μH.

[0032] According to some embodiments of the present disclosure, the secondary winding of the distal transformer is connected to the conductor of the transmission line via an electrical contact.

[0033] According to some embodiments of the present disclosure, the power supply circuit includes a pulse modulation circuit operable to modulate the operating frequency at a low frequency, including frequencies in the range of 0.1 to 1 KHz.

[0034] According to some embodiments of the present disclosure, a method for decoupling gain and frequency constraints for non-thermal plasma generation includes providing an output electrical signal having an operating frequency and voltage amplitude sufficient to generate a plasma to a plasma generation site, the plasma generation site being electrically interconnected via at least two transformer stages to an input electrical signal oscillating at the operating frequency and at a voltage at least 20 times lower than the output electrical signal.

[0035] According to some embodiments of the present disclosure, the voltage amplitude is at least 1 kV.

[0036] According to some embodiments of the present disclosure, the operating frequency is between 1 and 10 MHz.

[0037] According to some embodiments of the present disclosure, the plasma generation site is interconnected with an input electrical signal via a transmission line, and oscillation of a circuit including the transmission line synchronizes oscillation of the input electrical signal.

[0038] According to some embodiments of the present invention, a non-thermal plasma generator includes a gain transformer having a primary coil and a secondary coil; a driver circuit electrically connected to conduct current through the primary coil; and a load circuit having a distal end having a plasma generation site that generates non-thermal plasma and a proximal end coupled to the secondary coil of the gain transformer, the load circuit including at least one decoupling inductor providing inductance including an inductance connected in parallel with the secondary coil and an inductance connected in parallel with the plasma generation site.

[0039] According to some embodiments of the present invention, the load circuit has an impedance that determines the frequency of oscillation of the load circuit as a function of the current produced by the secondary coil.

[0040] According to some embodiments of the present invention, the load circuit synchronizes the oscillation of the driver circuit.

[0041] According to some embodiments of the present invention, the oscillation of the driver circuit is synchronized by feedback from a gain transformer.

[0042] According to some embodiments of the present invention, the frequency of oscillation of the load circuit is high enough that plasma generation at the plasma generation site does not die out during at least one complete oscillation period.

[0043] According to some embodiments of the present invention, the non-thermal plasma generator comprises a pulse modulation circuit operable to modulate the frequency of oscillation at a low frequency in the range of 0.1 to 1 KHz.

[0044] According to some embodiments of the present invention, the gain transformer provides a gain of at least 20.

[0045] According to some embodiments of the present invention, the at least one decoupling inductor comprises at least one decoupling transformer providing a total gain of less than or equal to one.

[0046] According to some embodiments of the present invention, the at least one decoupling inductor comprises a decoupling transformer that collectively provides a gain that is at least two times less than the gain provided by the gain transformer.

[0047] According to some embodiments of the present invention, the gain transformer has an air core or a ferrite core.

[0048] According to some embodiments of the present invention, the at least one decoupling inductor comprises a plurality of decoupling transformers.

[0049] According to some embodiments of the present invention, the at least one decoupling inductor comprises an inductor coil connected in parallel to the secondary coil and in parallel to the plasma generation site.

[0050] According to some embodiments of the present invention, the driver circuit stops oscillating when the plasma generation site is disconnected from the load circuit, but maintains oscillation at values of the frequency of oscillation of the load circuit that vary within a range having at least a 10% difference between the minimum and maximum values of the range.

[0051] According to some embodiments of the present invention, the operating voltage amplitude at the plasma generation site, generated by passing a current through the primary coil of the gain transformer, is at least 1 kV RMS.

[0052] According to some embodiments of the present invention, the transmission line has a length of at least 50 cm and is flexible.

[0053] According to some embodiments of the present invention, a non-thermal plasma generator is provided with a gas supply lumen that is directed to the plasma generation site along a transmission line, the gas supply lumen and transmission line together being elements of a flexible probe having an overall diameter of less than 10 mm.

[0054] According to some embodiments of the present invention, the at least one decoupling inductor and the gain transformer together comprise one or more transformers that deliver an operating voltage to the plasma generation site at an amplitude at least 20 times the voltage amplitude at the primary coil of the gain transformer.

[0055] According to some embodiments of the present invention, the primary coil of the gain transformer has an inductance in the range of approximately 1-5 μH, and the secondary coil of the gain transformer has an inductance in the range of approximately 1000-5000 μH.

[0056] According to some embodiments of the present invention, feedback from the gain transformer is provided by a feedback winding of the gain transformer, the feedback winding having an inductance in the range of approximately 1-10 μH.

[0057] According to some embodiments of the present invention, the at least one decoupling inductor comprises at least one decoupling transformer, the distal coil of the at least one decoupling transformer having an inductance in the range of approximately 20-80 μH, and the distal decoupling transformer coil of the at least one decoupling transformer having a primary coil with an inductance in the range of approximately 5-20 μH.

[0058] According to some embodiments of the present invention, at least one decoupling inductor is connected to the plasma generation site via releasable electrical contacts.

[0059] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this disclosure belongs.Although methods and materials similar or equivalent to those described herein can be used to practice or test the embodiments of this disclosure, exemplary methods and / or materials are described below.In case of conflict, the patent specification, including definitions, shall prevail.In addition, materials, methods, and examples are merely illustrative and are not necessarily intended to be limiting.

[0060] Several embodiments of the present disclosure are described herein, by way of example only, with reference to the accompanying drawings. With detailed reference to the following drawings, it is emphasized that the particulars shown are exemplary and are for the purpose of explaining embodiments of the present disclosure. Similarly, from viewing the description in conjunction with the drawings, it will become apparent to those skilled in the art how embodiments of the present disclosure may be practiced. [Brief explanation of the drawings]

[0061] [Figure 1A]1 is a schematic diagram of a plasma generation device according to some embodiments of the present disclosure. [Figure 1B] 1 is a graph of a typical current-voltage waveform of a low frequency (<100 KHz) atmospheric pressure plasma according to some embodiments of the present disclosure. [Figure 1C] FIG. 1 is a graphical representation of a typical high frequency (e.g., greater than 1 MHz) atmospheric pressure plasma current-voltage waveform, according to some embodiments of the present disclosure. [Figure 2A] FIG. 1 is a schematic diagram of an intracorporeal plasma application system illustrating potential issues in the design of plasma generation systems that are addressed in some embodiments of the present disclosure. [Figure 2B] FIG. 1 is a schematic diagram of an intracorporeal plasma application system illustrating potential issues in the design of plasma generation systems that are addressed in some embodiments of the present disclosure. [Figure 3A] FIG. 1 is a schematic block diagram of a resonant high-voltage plasma generation system according to some embodiments of the present disclosure. [Figure 3B] FIG. 10 is a flow chart illustrating a method of operating a resonant high-voltage plasma generation system, according to some embodiments of the present disclosure. [Figure 3C] FIG. 1 is a schematic circuit diagram of a resonant high-voltage plasma generation system according to some embodiments of the present disclosure. [Figure 3D] FIG. 10 is a diagram that schematically illustrates a reduction in the theoretical dependence of Cequiv on Ccoax at gain levels M=1 and M=2, in accordance with some embodiments of the present disclosure. [Figure 4A] FIG. 1 is a schematic diagram of a resonant high-voltage plasma generation system according to some embodiments of the present disclosure. [Figure 4B] FIG. 1 is a schematic diagram of a resonant high-voltage plasma generation system according to some embodiments of the present disclosure. [Figure 5A] FIG. 1 is a schematic diagram of a variation of a resonant high voltage plasma generation system using a decoupling coil, according to some embodiments of the present disclosure. [Figure 5B]FIG. 1 is a schematic diagram of a variation of a resonant high voltage plasma generation system using a decoupling coil, according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0062] Some embodiments of the present invention relate to the field of plasma generation, and more particularly, but not exclusively, to the generation and therapeutic delivery of low-temperature plasma.

[0063] overview One aspect of some embodiments of the present disclosure relates to the design of an electrical circuit operable at high frequency to generate power for plasma generation. In some embodiments of the present disclosure, an alternating electric field is used to generate a non-thermal atmospheric pressure plasma (NTAP) via a dielectric barrier discharge (DBD).

[0064] The alternation helps overcome the alternating "shielding" effect caused by charge mobility. During the positive cycle of the voltage (anode electrode), highly mobile electrons generated in the plasma are attracted to the electrode barrier. This creates an electrical shielding effect, causing the plasma to quickly extinguish. During the reverse cycle, when the electrode acts as a cathode, these electrons become the ionization source to reignite the plasma. This continues until the cathode is once again shielded by positive ions being attracted to it. To keep the plasma generating continuously, the electric field (proportional to the voltage applied to the electrode) is continuously alternated between the polarities of these two cycles. On minute time scales, the plasma is emitted as discrete plasma bullets, but the frequency of the alternation is high enough that the plasma output appears continuous.

[0065] However, there is a potential impact on efficiency insofar as extinguished plasma generation must be reignited each half-cycle. The energy required to maintain an ignited plasma per cycle is significantly lower than the energy required to reignite it. One way to mitigate this is to shorten the period of time during which the moving ions / electrodes move and increase shielding, which could, in principle, be achieved by increasing the cycle frequency. The frequency at which transient shielding effects no longer cause intermittent extinction of plasma generation is referred to herein as the "transition frequency."

[0066] The transition frequency from bullet plasma to continuous plasma depends on the physical configuration of the system (e.g., electrode size, gas chamber dimensions, and / or electrode placement), as well as gas composition and environmental influences such as pressure and temperature. In typical DBD plasma jet applications, the transition frequency is typically around 1 MHz. Even at this frequency, shielding effects below the plasma extinction threshold can still interfere with ionization efficiency. Therefore, at even higher frequencies, the power output required to generate the plasma can continue to increase, other parameters being equal.

[0067] As a result, adjusting the plasma generation frequency can be used as a method of controlling plasma power. For example, the plasma generation frequency may be controllable from near the transition frequency of the device to about 10 times that frequency. For example, the frequency may be variable from about 1 MHz to about 10 MHz, or even within a portion of this range.

[0068] The adjustment of frequency in a practical electrical circuit is subject to various constraints that are determined and / or influenced by the remaining requirements for plasma generation and performance. In some embodiments of the present disclosure, the plasma generator is implemented to operate with an AC (e.g., sinusoidal) voltage of about 0.5 to 2 kV RMS (e.g., 1 kV RMS).

[0069] Here, "continuous plasma" refers to continuity through a single high-frequency signal cycle of 100 kHz or greater. Optionally, the term also refers to a train of multiple such cycles. However, such trains of cycles may be interrupted. For example, the plasma may be pulse-width modulated (PWM) at a frequency in the range of approximately 0.1 to 1 kHz (e.g., 600 Hz). The duty cycle is optionally adjusted to a suitable percentage up to 100% (e.g., 66%). In some embodiments, the plasma generation system may include, for example, a PWM circuit operable at least within this range.

[0070] Apart from the specific characteristics of plasma generation, generator performance and efficiency more generally depend strongly on the load characteristics and required bandwidth. In particular, a generator may be most efficient at a certain operating frequency of the circuit. For a plasma generator, this operating frequency may fall, for example, in the 1 MHz to 10 MHz range, but other frequencies within that range may potentially be significantly less efficient. The operating frequency may be at or near the circuit's natural resonant frequency. Alternatively, the generator design may sacrifice efficiency and performance (e.g., frequency stability, distortion, and / or power loss) to support a wider range of resistive and capacitive loads.

[0071] In some embodiments of the present disclosure, the plasma generator is configured for use in medical applications. This configuration includes, among other things, spatially separating the plasma generation site from the power generation unit that drives the plasma generation unit. The power generation unit may be too cumbersome to place near the organ and / or patient being treated. In intracorporeal plasma applications where the plasma delivery probe penetrates or passes through tight spaces, the electrical drive circuitry of the probe is too large to be associated with the probe itself.

[0072] The usefulness of plasma generated outside the body (relatively close to the driving circuitry) and delivered into the body may be reduced by the short half-life of the plasma products, and the electrical properties of plasma may prevent their transport more than a few centimeters within the body.

[0073] Alternatively, a high-voltage signal is transmitted to the distal end of the probe, generating plasma, which is then applied to the target tissue. Signal transmission may occur via a coaxial cable, allowing safe transmission of electrical signals over relatively long distances (e.g., 1 meter or more, e.g., at least 1, 2, 3, 4, or 5 meters) while maintaining power and signal integrity. The coaxial cable structure has potential advantages in terms of miniaturization and flexibility when used within the body, for example, in catheter-type devices that can be advanced over distances of several centimeters (e.g., 10 centimeters, 50 centimeters, 100 centimeters or more) from an opening into the body, such as a natural orifice and / or keyhole incision.

[0074] As explained further below, the use of coaxial transmission lines is a practical solution for transmitting power to relatively distant sites of plasma generation, but it is part of a system of interacting parameters, and some embodiments of the present disclosure are believed to limit the transmission frequency to around a particular resonant frequency of the transmission line (and the RC network of which the coaxial transmission line is a part) for best efficiency.

[0075] If the transmission line is part of an RC network with a resonant frequency that is far from the transmission frequency, this may result in excessive losses in the transmission line itself (e.g., causing heating, potentially to the point of imposing limitations on operation such as reduced duty cycle) and / or inefficiencies in delivering power to the transmission line, e.g., increasing the size, cost, and / or robustness requirements of the power supply. At resonance, inductance and capacitance can cancel each other, reducing power losses due to resistance.

[0076] In particular, the effect of electrical losses causing heating is potentially more significant when transmitted through a low diameter transmission line, e.g., due to the corresponding low thermal mass. In some embodiments of the present disclosure, the diameter of the transmission line (e.g., less than 5 mm, 3 mm, 2 mm, or 1.5 mm) is a constraint on the minimum diameter of the accessible body cavity to the extent that the transmission line is used as part of a probe that advances through the body cavity toward the target of plasma delivery.

[0077] Further, problems arise due to the high slew rates required to provide high voltage signals (e.g., 0.5 kV RMS or greater) at high frequencies (e.g., 1 MHz or greater). It can be difficult to keep a transmit load up to such slew rates without resonant drive. Resonant drive also, in some embodiments, incorporates a power outage feature in the event of accidental disconnection or sufficiently severe damage to the transmission line, insofar as such disconnection prevents the generation of a feedback signal that synchronizes the frequency of the power generation.

[0078] These considerations result in an interlocking system of engineering constraints. A simple example of how these constraints work together is presented below, with further details provided below. (1) The voltage requirement at the plasma generator can be 1 kV RMS to achieve plasma discharge. (2) To reach 1 kV RMS from a reasonable input voltage of 20 to 33 V, the gain of the power-generation transformer should be in the range of approximately 30 to 50 (optionally greater than 20, greater than 25, or greater than 30). (3) This ratio is also proportional to the square-root ratio of the two inductances (primary and secondary) used in the transformer capable of producing this gain. (4) However, the output inductance (secondary inductance) is constrained to a low level by the same efficiency constraints that motivate the selection of a high resonant frequency (e.g., a frequency of approximately 2 MHz) to power the plasma-generation probe. If the inductance were too high, this frequency would not be met without significantly reducing the capacitance instead (6), which in some embodiments is provided primarily by the inherent capacitance of the coaxial cable required to transmit the power. Finally, (7) the input inductance (primary inductance) is limited to be even lower than the secondary inductance. However, this is potentially an impractically low value. This may manifest as design pressure to forgo one or more of the following requirements, for example: low input voltage, high operating frequency, or long power transmission lines.

[0079] In some embodiments of the present disclosure, design pressures are alleviated through another solution: the use of a dual-transformer configuration comprising a gain transformer and a decoupling transformer (which may be split into one or more stages). The interposition of the decoupling transformer allows the gain transformer to use a practically reasonable inductance value to generate voltage gain. Indeed, isolation allows the output side of the gain transformer to have a substantially low capacitance. And because the isolation transformer does not require gain (or only a relatively low gain), the primary inductance of the isolation transformer can be equal to its secondary inductance, rather than being forced to an impractically small value by the requirement to generate voltage gain. In some embodiments, the decoupling effect is created using the same inductor coil connected in parallel to both the plasma load (distal) and another inductor coil (proximal, e.g., the secondary coil of the gain transformer). This can mimic the effect of an interposed unity-gain transformer while avoiding losses due to non-ideal inductive coupling.

[0080] As potential practical consequences, the introduction of a separation stage offers potential advantages to one or more of the following: · Separating constraints on voltage gain and operating frequency. The ability to run coaxial cable longer without compromising the ability to meet other design constraints. - Reducing frequency fluctuations caused by changes in load impedance.

[0081] Details of these potential benefits are discussed further below.

[0082] It should be noted that in some embodiments, the plasma generation site (which is subject to high voltage) is coupled to power via one or more ground isolation transformers, thereby providing electrical isolation from ground.

[0083] Before describing at least one embodiment of the present disclosure in detail, it is to be understood that the disclosure is not necessarily limited in its application to the details of construction and the arrangement of components and / or methods set forth in the following description and / or illustrated in the drawings. Features described in the present disclosure, including features of the present invention, can be implemented in other embodiments or can be carried out in various ways.

[0084] Plasma Treatment Device Reference is made to FIG. 1A, which schematically illustrates a plasma generation device 100 according to some embodiments of the present disclosure.

[0085] In some embodiments, the plasma generation apparatus 100 includes a high-voltage power generator 201 and an ionized gas supply 61 interconnected to a plasma probe assembly 62. The high-voltage power generator 201 supplies an ionizing voltage to the plasma probe assembly 62 via a cable 203 (e.g., a coaxial cable or other impedance-controlled electrical conduit). The ionized gas supply 61 supplies an ionized gas to the plasma probe assembly 62 via tubing 72. The supplied gas may include, for example, one or more noble gases, such as neon, argon, or helium, and / or other gases suitable for ionization into the plasma plume 90. Optionally, the cable 203 and the tubing 72 are integrated into a single cable unit that connects to the plasma probe assembly 62. Optionally, the high-voltage power generator 201 and the ionized gas supply 61 are housed together.

[0086] The plasma probe assembly 62 optionally includes a handle 80. The handle 80 optionally includes controls 81, 82 for controlling operation of the probe conduit 73 and / or the plasma delivery tip 66, and / or for controlling the function of the power generation section 201, and / or for controlling the delivery of ionized gas from the gas supply 61. Optionally, the plasma probe assembly 62 physically integrates power and gas delivery functions into the probe conduit without using a dedicated handle. In some embodiments, the probe conduit 73 includes a lumen for delivery of ionized gas and a high-voltage transmission line (e.g., an extension of the cable 203 and tubing 72). In some embodiments, the probe conduit includes multiple lumens, such as a lumen attached to the gas supply 61 that supplies ionized gas, and optionally a lumen for collecting (removing) the ionized gas under suction. In some embodiments, one or more of the lumens in the probe conduit 73 are optionally used as a working path by insertion of a tool. The handle 80 , in some embodiments, includes one or more ports 83 for introducing such tools into the lumen of the probe conduit 73 .

[0087] In some embodiments of the invention, the probe conduit 73 and plasma delivery tip 66 are sized and otherwise configured (e.g., at a safety setting) to deliver non-thermal plasma to an intrabody location. The intrabody location may be remotely located relative to the point of insertion, e.g., 25 cm or more from the point of insertion into the body, e.g., 80 cm, 100 cm, or 120 cm. To the extent that the plasma tip 60 comprises the site of plasma generation (as in some embodiments), the device must supply an ionization level voltage to the tip 60 (e.g., 1 kV or greater). This length may impose constraints on the minimum capacitance of the cable 203.

[0088] In some embodiments, the probe conduit 73 (including both the lumen for delivery of ionized gas and the high voltage transmission line) has an overall diameter of less than 12 mm, less than 10 mm, less than 8 mm, or less than 5 mm. The narrower the overall diameter, the narrower the minimum size body cavity through which the probe conduit can pass, such as a catheter. For example, a ureter, blood vessel, or other subcutaneous access route to the target treatment site.

[0089] Figure 1B is a graph showing a typical current-voltage waveform of atmospheric pressure plasma at low frequencies (<100 KHz), and Figure 1C is a graph showing a typical current-voltage waveform of atmospheric pressure plasma at high frequencies (e.g., 1 MHz or higher).

[0090] The excitation voltages 103, 101 are sinusoidal in both cases, but in Figure 1B, the current 104 can be seen to spike as plasma bullets are ignited on each half-cycle. In the high frequency example of Figure 1C, the current waveform 102 more closely tracks the input voltage (with a phase shift) because the continuous plasma generation maintains uniform resistance within the plasma plume.

[0091] Plasma high voltage generator 2A-2B, which schematically illustrate an intracorporeal plasma application system 200 illustrating potential issues in plasma generation system design that are addressed in some embodiments of the present disclosure. Figure 2A is a schematic block diagram of system 200, and Figure 2B illustrates a component-level implementation of the schematic block diagram of Figure 2A.

[0092] In the illustrated example, the power generation unit 201 and the coaxial cable 203 work together to generate a high voltage drive signal for the plasma gun. The power generation unit 201 includes a primary coil driver circuit 204 that is activated by an input voltage 202 and includes an amplifier 208 that drives a primary coil of a transformer 205. In some embodiments, the coaxial cable 203 includes a flexible electrical transmission line electrically connected to the secondary coil of the transformer 205 and configured to conduct high voltage to a plasma generation site near its end, where plasma comprising the plasma load 206 is generated.

[0093] To generate the plasma, an ionized gas is also introduced to the plasma generation site, optionally through a conduit extending along the coaxial cable 203. In some embodiments, the coaxial cable 203 is inserted into the subject's body (e.g., inserted along the lumen of a body cavity) while a high voltage is transmitted along with the ionized gas to generate the plasma. The voltage alternates at a high frequency, for example, at a frequency of several kilohertz, e.g., 100 kHz or higher. Note that dosimetry of the generated plasma can be performed in one or more of several locations and / or methods. For example, the signal used to generate the plasma (e.g., its power, frequency, and / or waveform) can be monitored in dosimetry circuitry (e.g., circuitry in communication with the optional dosimeter 505) arranged to measure the signal immediately prior to entering the coaxial cable 203 and / or at other locations in the circuitry of the overall system. Optionally, the plasma itself is monitored, for example optically or electrically, by a sensor close to the plasma generation site (plasma load 206 ) in communication with a dosimeter 505 .

[0094] The implementation of FIG. 2B is similar to that of the coaxial cable 203, except that the capacitance C coax, which in some embodiments adds a significant capacitance to the total load driven by power generation section 201 via primary coil driver circuit 204. This capacitance is a typical characteristic expected for any type of transmission line.

[0095] As the target frequency of operation increases, this additional capacitance eventually limits the bandwidth that power generation section 201 can achieve at a given voltage amplitude. At relatively low frequencies of a few kHz, the additional capacitance C coax is negligible for realistic cable lengths of 2-3 m.

[0096] However, to increase the frequency into the MHz range, it is potentially advantageous to use a resonant generator configuration such as that shown in Figure 2B. The resonant generator relies on cable capacitance to form an "LC" type resonant circuit (with transformer 205) that can be tuned to a specific resonant frequency. This generated frequency is supplied directly to the plasma generation site, with high voltage supplied from the high voltage side of the transformer (transformer secondary coil).

[0097] Note that this approach to power signal generation differs from simply generating a power signal at a frequency selected to match the load's time constant. Matching is necessary for efficient transmission of the generated signal. Integrating the load and its electrical characteristics into the power generation circuit itself potentially compromises the flexibility of power generation parameters. For example, while frequency-selective adjustment in a standard power supply must match the load impedance for efficient transmission to the load, the frequency of the power signal itself may be relatively freely selectable without interfering with its generation. Once the load becomes part of the signal generation circuit, adjusting the frequency outside a limited range implies coordinated adjustment of the electrical characteristics of the load and driver circuit. If the adjustment is not coordinated, the signal generation circuit may simply stop generating the signal.

[0098] In some embodiments of the present disclosure, matching goes beyond providing efficient transmission of the power signal and also affects the generation of the power signal itself. The frequency of that power signal is generated essentially (i.e., proximately and not merely as a matter of predetermined choice) as a function of the load characteristics. Changing the load also changes the frequency. This is due to the fact that C coax This does not mean that power can be efficiently generated at any frequency selected by the resonance of the LC circuit comprising L1 and L2; the power supply must operate within its own limits. Excessive load characteristic changes will impair power signal generation. In the complete absence of load resonance, extreme network mismatch will cause power signal generation to cease.

[0099] In effect, the transmission line capacitance serves as a key component of the timing signal providing portion of the power signal generating portion, in that the transmission line can either accept the frequency at which the power signal is generated (or can accept it after generating the frequency), or there is no valid power signal to accept. In effect, the load side of the circuit oscillates with the driver circuit, rather than simply being selected to match its oscillation frequency.

[0100] In simple terms, the capacitance C coax is used, together with the secondary coil inductance L3, as the main parameter that determines the time constant at which not only they but also the driver circuit 204 on the primary side of the coil 205 oscillates. However, at sufficiently high frequencies, it becomes difficult to realize this theoretical circuit in practice, for example because voltage gain requirements force the selection of an unrealistically low inductance for the primary coil of the transformer 205 (including inductors L1 and L2).

[0101] 2B, a primary coil driver circuit 204 is powered by an input voltage source 202 measuring, for example, up to 100V DC. A transformer unit 205 is connected between the driver circuit 204 and a transmission line (coaxial cable 203). It comprises three coupled inductors: a primary coil L1, a feedback coil L2, and a secondary coil L3.

[0102] The output 206 of amplifier 208 is connected to the primary coil L1 through a decoupling capacitor C4, and feedback in opposite polarity to amplifier 208 is connected to input 207 through a compensation network C_FB and L_FB. The feedback network consisting of L2, L_FB, and C_FB provides a compensation network for L3 and C coax By matching the time constants of the LC network consisting of

number

[0103] Considering a typical use case, for example, one may aim for a resonance of 2 MHz. For example, the typical capacitance of 2 m of coaxial cable is about 200 pF. Given these assumptions, the inductance of the secondary coil may be selected to measure 31 μH.

[0104] In some embodiments, the capacitance of the transmission line (e.g., a transmission line including a coaxial cable, twisted pair cable, or other conductor configuration) is at least 50 pF, 100 pF, 150 pF, or 200 pF. In some embodiments, the length of the transmission line is at least 50 cm, 100 cm, 150 cm, or 200 cm. The secondary coil inductance is selected accordingly.

[0105] As a further design parameter, a conservative high operating voltage of 1 kV RMS at the plasma load 206 may be allocated, although higher operating voltages may be desirable, for example, at least 1.5 kV RMS, or at least 2 kV RMS.

[0106] For reasonable input voltages, transformer 205 has a gain ratio in the range of approximately 30 to 50. Insofar as the gain ratio is proportional to the square root of the inductance ratio, this imposes a constraint that the primary coil inductance be in the range of approximately 0.01 to 0.03 μH.

number

[0107] It is impractical to use such low primary inductance in a transformer design for use at such high voltages. Due to physical constraints, single-coil inductors of a few nH typically have a typical size of a few millimeters (e.g., 4 mm or less) in their maximum dimension. A corresponding transformer, even if constructed somehow, would need to handle enormous current loads at the target voltage (0.01 μH corresponds to approximately 0.1 Ω at 2 MHz), causing transformer saturation and other parasitic effects such as skin effect. There are also concerns about heating and electrical insulation. Increasing the input voltage (which could reduce the gain while maintaining the target output voltage) significantly reduces the generator's efficiency (and generates heat), making it impractical beyond a certain point.

[0108] At more moderate frequencies, the constraints are relaxed and the use of a transformer 205 may be practical. For example, for a plasma generating unit driven at 1 MHz with 1 kV RMS into a 100 pF cable, a driver circuit with a configuration such as 100 μH secondary inductance, 1 μH primary inductance (resulting in a gain of approximately 10), and an input voltage of 90 V may be used. The inductance of the transformer's feedback coil, although typically less critical, is typically approximately the same as the inductance of the primary coil.

[0109] In the above example, the capacitance of the coaxial cable 203 is C coax = 100pF (other factors being equal), we would expect a sharp increase in frequency, a decrease in efficiency, and even a complete loss of resonance if further reductions in capacitance are made. Similarly, increasing the cable capacitance (e.g., increasing the length of the cable) would result in a decrease in frequency and a decrease in efficiency. In either case, the decrease in efficiency is due to the effect of the feedback (C_FB, L_FB, and L2) LC network and the primary (L3 and C coax ) This is due to the introduction of mismatch between the LC network.

[0110] High voltage generation unit with dual transformer stages Referring to Figures 3A and 3C, a resonant high-voltage plasma generation system 300 is schematically illustrated in accordance with some embodiments of the present disclosure. Also, Figures 5A and 5B, in accordance with some embodiments of the present disclosure, schematically illustrate a variation of the resonant high-voltage plasma generation system 300 using a decoupling coil 501. Compared to the block diagram of Figure 2A, the power generation section 301 of Figures 3A and 5A splits the transformer 205 into two transformer stages: a gain transformer 305A and a decoupling transformer 305B or decoupling coil 501. The discussion regarding Figures 3A and 3C also applies to the embodiment of Figures 5A and 5B, modified accordingly, in that a decoupling coil 501 is used instead of the decoupling transformer 305B. This substitution is further relevant below.

[0111] In some embodiments, this allows for driving relatively high capacitance loads while retaining the potential advantages of a resonant architecture for achieving high frequency and potentially true sinusoidal output while generating plasma.

[0112] Considering the driver circuit 204, including the amplifier 308, output 306, and feedback input 307, in combination with the gain transformer 305A, a fundamental resonance is achieved by matching the time constant of the LC network of L3 and C5 to the time constant of the feedback LC network (C_FB, L_FB, and L2). C5 can be selected to be small (e.g., within 10 times 1-5 pF). This allows the corresponding secondary coil inductance L3 to be substantially high. This allows the primary coil and / or feedback coil inductance (e.g., L1 and / or L2) to be substantially high, potentially within a practical range that enables previously unobtainable gains at frequencies, for example, 1-2 MHz. In some embodiments, the primary coil L1 has an inductance in the range of approximately 1-5 μH, the secondary coil L3 has an inductance in the range of approximately 1000-5000 μH, and the feedback coil L2 has an inductance in the range of approximately 0.1-10 μH.

[0113] The remainder of the circuit delivers the high-frequency, high-voltage signal to the load. Capacitor C6 isolates the generated signal. It may range, for example, from tens of nanofarads to hundreds of nanofarads (e.g., 0.1 to 900 nF (e.g., 0.5 to 2 nF, 2 to 10 nF, 0.1 to 10 nF, 5 to 20 nF, 20 to 100 nF, 50 to 500 nF, or other capacitance ranges)). A relatively low capacitance has the potential advantage of increasing the system response speed, such as the rate at which the oscillation frequency and voltage stabilize (i.e., the voltage reaches the drive value faster because less capacitance is charged). A relatively high capacitance has the potential advantage of reducing common instability characteristics, such as a tendency to overshoot the intended voltage and not necessarily reach the same voltage (e.g., cycle-to-cycle instability and / or unstable operating modes).

[0114] Further ahead, an additional decoupling transformer 305B is used, with a primary inductance L4 and a secondary inductance L5. Optionally, this transformer is set to unity gain (L4 = L5, optionally selected to a value on the order of 10 times approximately 100 μH, e.g., in the range of 20-200 μH). Alternatively, this transformer is used as a second stage gain. For example, by setting L4 to a value in the range of approximately 5-20 μH and L5 to a value in the range of approximately 20-80 μH, an effective second stage gain of, e.g., 1-4 (e.g., 2) can be obtained. Finally, L5 and C coax is designed to match the resonant frequency set by the driver circuit 204 and the gain transformer.

[0115] Dosimetry is preferably performed using optional dosimeter 505. Dosimetry may be performed, for example, using one or more of the implementations described in connection with Figure 2A.

[0116] In some embodiments, the role of decoupling transformer 305B, as shown in FIGS. 3A and 3C, is performed by a single decoupling coil 501 electrically connected in parallel with plasma load 206, as shown in FIGS. 5A and 5B. In embodiments in which decoupling transformer 305B provides unity gain, it can be appreciated that there is a potential loss of ideal behavior if the coupling between the primary and secondary is non-ideal. This potentially includes a reduction in efficiency. However, in some embodiments, decoupling coil 501 is used as a substitute equivalent to unity-gain decoupling transformer 305B, i.e., equivalent in terms of its function of providing inductance that affects the resonant frequency of the circuit. This substitution offers the potential advantage of avoiding the losses of the transformer while maintaining some of the potential advantages described in the following discussion (i.e., advantages that do not depend on having a gain other than unity).

[0117] The embodiments of the two pairs of figures (one pair of FIGS. 3A and 3C and the other pair of FIGS. 5A and 5B) can be commonly characterized in that they provide isolation of the plasma probe impedance from the impedance characteristics of the gain transformer. More specifically, they isolate the constraints of the probe lead capacitance (coaxial cable capacitance) from the constraints of the gain transformer design, which affect characteristics such as the system operating voltage, carrier frequency, and / or efficiency. They are commonly characterized by including inductances connected between the conductors of the coaxial cable 203 and / or in parallel with the plasma load 206, and by including inductances connected in parallel with the secondary coil of the transformer 305A (the secondary coil inductance of L3) and / or in parallel with the capacitance C5. 5A-5B, each defined "parallel connected inductance" is embodied in the same inductance provided by the same inductive component (e.g., an inductor coil), while in the embodiments of Figures 3A and 3C, there are two separately provided inductive components (e.g., two inductor coils of a transformer). Thus, in each case, at least one decoupling inductor is provided, providing an inductance including an inductance connected in parallel to the secondary coil and an inductance connected in parallel to the plasma generation portion.

[0118] While it is potentially convenient to provide each inductive component as a single inductive coil, there is nothing inherently impeding providing the inductive components in a configuration of other inductive subcomponents arranged electrically in series and / or electrically in parallel as appropriate to provide a target effective inductance that influences the remainder of the circuit. Also, nothing specifically prevents the partial sharing and partial isolation of separately defined inductances, which are optional in some embodiments of the present disclosure. In some embodiments, some non-shared portions of the differently defined inductances may optionally be provided in the form of a transformer with non-unity gain.

[0119] While there are electrical differences due to the substitutions, these can reasonably be understood as not impairing or distorting the essential function of the circuit. For example, note that in FIG. 3C , only one side of each coil providing inductances L4 and L1 is conductively connected, whereas in an embodiment using decoupling coil 501, both sides are effectively conductively connected. However, the use of unity gain means that in either case (again, ideally) there is no potential difference on either side of the coils, so conductively interconnecting them does not affect their behavior. In non-ideal cases, voltage and / or phase differences that may occur in an embodiment using decoupling transformer 305B are not particularly dependent and are not essential to the device's function.

[0120] There may also be differences in single coil current carrying: Optionally, decoupling coil 501 is designed (e.g., designed with a heavier conductor) to withstand a higher current (e.g., twice as high) than any of the individual coils of decoupling transformer 305B would carry alone.

[0121] It has been found that one or more of these configurations achieve at least three substantial potential advantages over conventional resonant transformer configurations.

[0122] First, it loosens the coupling between frequency and gain by providing additional design freedom. In the designs of Figures 2A-2B,

number

[0123] where the capacitance C coaxis absorbed into the design requirement fixed constant K, so long as it is constrained to a relatively large value. This results in the previously discussed inverse relationship between frequency f and inductance L1 and design gain. Increasing frequency requires reducing either L1 and / or gain to levels that may have impractical consequences in device construction and / or operation.

[0124] The use of a second transformer stage introduces the option (additional design freedom) of using C5 as a compensation capacitor.

number

[0125] Second, the length of the coaxial cable is less restricted. coax may be considered to have a lower limit imposed by design requirements to have a long, thin, and flexible cable to enable reaching the remote target for plasma application. In some embodiments of the present disclosure, it is a potential advantage to lengthen the coaxial cable 203 beyond the length that would result in this lower limit. Introducing C5 as a degree of design freedom also enables this. While the minimum practical value of the transformer inductance L5 remains a constraint for the selected target resonant frequency f, it can be much smaller in the decoupling transformer 305B than in the gain transformer 305A because the requirement that the primary inductance L4 still be much smaller has been removed.

[0126] Third, at least when the gain of the second stage is selected to be greater than one, it can reduce frequency variations due to changes in load impedance. Impedance can change, for example, due to damage. A potential advantage is reduced sensitivity to small variations while retaining the automatic damping effect of large impedance changes. Even with a fixed load impedance, manufacturing tolerances of a few percent (e.g., 10%) can affect important electrical characteristics of the component, which may include the capacitance of the transmission line. For example, a potential advantage is being able to reduce the sensitivity of the resonant driver circuit to variations in transmission line capacitance while retaining the benefits of a resonant circuit, allowing, for example, self-termination of high-frequency signal generation if the transmission line is disconnected.

[0127] In a single-stage resonant generator, the capacitance of the transmission line is f ∝ (C coax ) -0.5 The addition of a second stage introduces significant complications into this relationship. The transmission line and second stage together can be "seen" as an equivalent capacitance with respect to their effect on frequency, f ∝ (C equiv ) -0.5 Next, C equiv C coax The theoretical dependence on C equiv ∝C coax / M 2 where the effective gain of the second stage is M.

[0128] It can be seen that setting the gain M>1 reduces fluctuations in the oscillation frequency due to (absolute) changes in the load impedance. For simplicity, ohmic components (e.g., electrical series resistance) present in practical systems are omitted from the above equation. Taking these into account, sensitivity to the load impedance may be somewhat high.

[0129] For simplicity, referring to FIG. 3D, C at gain levels M=1 and M=2 coax C against equivSchematically illustrates the theoretical reduction of the dependence of . At the origin 361, the transmission line capacitance is zero. The effective capacitance is a reference value and is not necessarily zero.

[0130] As the gain M increases, the dependence of the effective capacitance on the transmission line capacitance decreases. The details of this relationship will vary in a real circuit depending on the presence or absence of other impedances, such as parasitic impedances.

[0131] In system 300, if coaxial cable 203 is disconnected from the circuit, a resonant circuit remains on the primary side of the decoupling transformer. However, disconnection also changes how the decoupling transformer contributes to that resonant circuit, which in turn makes it more likely to lose high frequency power.

[0132] When the coaxial cable 203 is reattached, the effective resonance on both sides of the decoupling transformer is still part of the load side of the circuit. This is true in a functional sense: if either circuit of the decoupling transformer does not allow resonance at a compatible frequency, it cannot provide the necessary frequency that allows the driver circuit 204 to perform its switching. The actual (power-consuming) load circuit still dictates to the driver circuit through and in concert with the circuit that drives the primary inductance of the decoupling transformer.

[0133] As mentioned above, the effect can become smaller as the gain of the decoupling transformer increases. However, even in embodiments with a gain higher than unity, the effect of impedance mismatch (e.g., due to damage to the coaxial cable 203) is significant. If the effect on the resonance of the decoupling transformer primary becomes large enough (despite the gain), it will lead to the same failure mode as before (i.e., loss of load resonance amplitude, loss of driver circuit synchronization, and ultimately, reduced power or failure to generate power). If the impedance mismatch is not large enough to significantly degrade the resonance of the decoupling transformer primary, the problem stops; i.e., the driver circuit 204 does not notice it. The load circuit state remains fail-safe.

[0134] FIG. 3B schematically illustrates a flowchart of a method of operating a resonant high-voltage plasma generation system according to some embodiments of the present disclosure.

[0135] In block 320, in some embodiments, the input voltage 202 is sent to a power driver circuit (eg, including block 204 of FIG. 3A).

[0136] While FIG. 3B depicts the operations of blocks 322-330 in an order appropriate for illustrating their interdependencies (e.g., the order indicated by the arrows), it should be understood that in an actual device, operations proceed simultaneously and / or at least partially in response to one another as part of the overall circuit operation. For example, the feedback signal referenced in block 322, in some embodiments, is established as a result of field interactions generated by the gain transformer referenced in block 326, and these field interactions are influenced by the second stage's generation (block 328) and transmission (block 330) of AC voltage. Thus, the influence of the operation of block 330 can be thought of as being linked back to the operation of block 322 in the sense of illustrating the interdependence of events within the circuit. Thus, one could have the condition that without the feedback of block 322, there would be no AC voltage generated and transmitted by blocks 328 and 330, but one could also say that without that AC voltage, there would be no feedback.

[0137] In block 322, in some embodiments, a feedback signal generated in response to activation by the power driver circuit is received from a load circuit including at least a transmission line (e.g., coaxial cable 203) via at least a gain transformer 305A.

[0138] In block 324, in some embodiments, the feedback signal tunes the driver circuit to oscillate, with the oscillation being adjusted (via the feedback signal) to the resonant frequency of the load circuit.

[0139] In block 326, in some embodiments, the AC voltage generated by the tuned driver circuit is stepped up to a higher voltage by inductive coupling in gain transformer 305A. The higher voltage is present on the secondary (output) side of gain transformer 305A in the first stage on the load circuit side of the overall power generation circuit.

[0140] In block 328, in some embodiments, the AC voltage at the first stage (primary / input side) of decoupling transformer 305B induces a voltage at the second stage (output / secondary side) of decoupling transformer 305B. In some embodiments, the gain of decoupling transformer 305B is equal to or less than the gain of gain transformer 305A. Note that the gain of decoupling transformer 305B is approximately 1 (e.g., no gain). Optionally, decoupling transformer 305B is replaced with a decoupling coil 501 or other decoupling inductance configuration, for example, as described in connection with FIGS. 5A-5B. Optionally, the gain of gain transformer 305A is at least 1.5, 2, 3, 4, 5, or more times less than the gain of gain transformer 305B.

[0141] In block 330, in some embodiments, the second stage voltage is transmitted along a transmission line (e.g., a coaxial cable 203 or other cable design (e.g., twisted pair)) to reach the plasma generation site and provide the power used to generate the plasma.

[0142] High voltage power generation unit having multiple transformer stages Referring to Figures 4A-4B, a resonant high-voltage plasma generation system 400 according to some embodiments of the present disclosure is illustrated. Compared to the block diagram of Figure 3A, the generator 401 of Figure 4A divides the decoupling transformer 305B into a plurality of n decoupling transformers 405 (where n > 2). The decoupling transformers are shown in Figure 4B as sub-stages 405B, 405C, and 405D, which are driven from a driver circuit 204 including an amplifier 308 with a feedback input 307 and an output 306. While not all components are shown for the sub-stages after 405B, they may be understood as repeating the units of sub-stage 405B with the connectivity shown. Sub-stage 405C may be understood as representing one or more "intermediate" sub-stages. Dosimetry is preferably performed using an optional dosimeter 505. Dosimetry may be performed, for example, using one or more of the implementations described in connection with Figure 2A.

[0143] By splitting into multiple decoupling transformers 405, decoupling transformer 305B generalizes the dual-transformer architecture of Figures 3A and 3C. While more complex, the multi-stage design has the potential advantage of distributing voltage gain beyond what might be practical in a two-transformer design while maintaining a high operating (resonant) frequency.

[0144] Another potential advantage is reduced sensitivity to variations in load impedance, generalized as follows:

number

[0145] where M n is the gain of the nth transformer stage. However, impedance matching is preferably still considered to prevent signal reflections and harmonic distortion. It should be understood that each additional stage reduces the overall efficiency, especially in practical systems that include resistive losses and parasitic capacitances.

[0146] The method of Figure 3B may also be applied in some embodiments to the operation of the device of Figures 4A-4B, modified as necessary to account for additional stages, for example, with the modification that the operations of block 328 are replicated as necessary among multiple decoupling stages until the final decoupling stage is reached, where a final AC voltage is sent over the transmission line to the plasma generation site to generate the plasma.

[0147] In some embodiments, the transmission line (cable 203) itself is part of one or more of the intermediate stages, with one or more decoupling transformers placed along the transmission line, including the option of splitting the cable 203 into inductively coupled segments.

[0148] General matters As used herein, "about" means "within ±10%" with respect to an amount or value. The words "comprises," "comprising," "includes," "including," "having," and their conjugations mean "including, but not limited to."

[0149] The term "consisting of" means "including and limited to."

[0150] The term "consisting essentially of" means that a composition, method, or structure may include additional ingredients, steps, and / or moieties, provided that the additional ingredients, steps, and / or moieties do not materially alter the basic and novel characteristics of the claimed composition, method, or structure.

[0151] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. For example, "a compound" or "at least one compound" includes a plurality of compounds, and may also include mixtures thereof.

[0152] The words "example" and "exemplary" are used herein to mean "serving as an example, instance, or illustration." An embodiment described as "example" or "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and / or does not necessarily exclude features of other embodiments from being incorporated.

[0153] "Optionally" is used herein to mean "provided in some embodiments and not provided in other embodiments." Any specific embodiment of the present disclosure may include multiple "optional" features except where such features are incompatible.

[0154] As used herein, the term "method" means manner, means, techniques, and procedures for accomplishing a given task, including, but not limited to, those known to practitioners in the fields of chemistry, pharmacology, biology, biochemistry, and medicine, or those that can be readily developed by practitioners from known manners, means, techniques, and procedures.

[0155] As used herein, the term "treating" includes arresting, substantially inhibiting, slowing, or reversing the progression of a condition, substantially ameliorating the clinical or cosmetic symptoms of a condition, or substantially preventing the worsening of the clinical or cosmetic symptoms of a condition.

[0156] Throughout this application, various embodiments may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and is not an inflexible limitation on the scope of the descriptions in this disclosure. Thus, the description of a range should be considered to specifically disclose all of the possible subranges and individual numerical values within that range. For example, description of a range such as 1 to 6 specifically discloses subranges such as 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 6, 3 to 6, etc., as well as individual numerical values within that range, e.g., 1, 2, 3, 4, 5, and 6. This applies regardless of the magnitude of the range.

[0157] When a range of values is provided herein (e.g., any pair of numbers connected by "10-15," "10 to 15," or other range designations), it is intended to include any number (fractional or integer) within the limits of the range provided, unless the context clearly dictates otherwise. The phrases "range between" a first designated number and a second designated number, and "range," "range to," "range to," or "range including" (or other similar range terminology) "from" a first designated number to a second designated number, are used interchangeably herein and are meant to include the first and second designated numbers and all fractional and integer values therebetween.

[0158] While this disclosure has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims.

[0159] It should be understood that certain features of the present disclosure, which are for clarity described in the context of separate embodiments, may also be provided in any combination of these features in a single embodiment. Conversely, multiple features of the present disclosure, which are for brevity described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or with respect to other described embodiments as appropriate. A given feature described in the context of various embodiments should not be construed as essential to that embodiment, unless the particular embodiment is inoperable without that element.

[0160] It is the intention of the applicant that all publications, patents, and patent applications mentioned in this specification be incorporated herein by reference in their entirety to the same extent as if each individual publication, patent, and patent application was specifically and individually incorporated herein by reference. In addition, citation or identification of any reference in this application should not be construed as an admission that such reference is available as prior art to the present disclosure. Nor should it necessarily be construed as limiting, to the extent that section headings are used. In addition, the priority document of this application, if any, is incorporated herein by reference in its entirety.

Claims

1. 1. A power supply circuit for a non-thermal plasma generator, comprising: a gain transformer having a primary coil and a secondary coil; a driver circuit electrically connected to drive a current through the primary coil; a load circuit having a distal end with a plasma generation site and a proximal end coupled to the secondary coil of the gain transformer; the load circuit includes at least one decoupling transformer inductively connecting the plasma generation portion and the secondary coil; power circuit.

2. the load circuit has an impedance that determines a frequency of oscillation of the load circuit in response to a current generated by the secondary coil; 2. The power supply circuit according to claim 1.

3. the load circuit synchronizes the oscillation of the driver circuit; 3. The power supply circuit according to claim 2.

4. the oscillation of the load circuit is synchronized by feedback from the gain transformer; 4. The power supply circuit according to claim 2 or 3.

5. the frequency of oscillation of the load circuit is sufficiently high so that plasma generation at the plasma generation site does not die out during at least one complete oscillation period; The power supply circuit according to any one of claims 2 to 4.

6. the gain transformer provides a gain of at least 20. The power supply circuit according to any one of claims 1 to 5.

7. the at least one decoupling transformer providing a total gain of less than or equal to one; 7. The power supply circuit according to claim 6.

8. the at least one decoupling transformer provides a total gain that is at least two times less than the gain provided by the gain transformer; The power supply circuit according to any one of claims 1 to 7.

9. the gain transformer and at least one coupling transformer comprise an air core or a ferrite core; The power supply circuit according to any one of claims 1 to 8.

10. the at least one decoupling transformer comprises a plurality of decoupling transformers. The power supply circuit according to any one of claims 1 to 9.

11. the gain transformer and at least one coupling transformer isolate the plasma generation site from ground; The power supply circuit according to any one of claims 1 to 10.

12. The load circuit includes: A transmission line; a distal transformer of the at least one decoupling transformer, the distal transformer having a secondary coil of the distal transformer inductively interconnected with a primary coil of the distal transformer and connected to a proximal side of the transmission line; The driver circuit electrically interconnected with the proximal side of the transmission line via the primary coil and the secondary coil of the distal transformer; providing an electrical signal to the transmission line at an operating frequency of 1-10 MHz, the electrical signal being transmitted to the distal end of the transmission line with an operating amplitude of at least 0.5 kV RMS; the impedance of the secondary coil of the distal transformer is sufficiently small in combination with the capacitance of the transmission line so that a circuit portion including the transmission line and the secondary coil operates at resonance when receiving the electrical signal; The power supply circuit according to any one of claims 1 to 11.

13. the driver circuit stops generating the electrical signal when the transmission line is disconnected, but continues generating the electrical signal when the capacitance of the transmission line varies within a range having a difference of at least 10% between a minimum value and a maximum value.

13. The power supply circuit of claim 12.

14. the operating amplitude is at least 1 kV RMS; 14. The power supply circuit according to claim 12 or 13.

15. the transmission line has a length of at least 50 cm and is flexible; The power supply circuit according to any one of claims 12 to 14.

16. the load circuit providing a feedback signal to the driver circuit via a feedback network; The power supply circuit according to any one of claims 12 to 15.

17. oscillation of the load circuit synchronizes the driver circuit via the feedback network to generate the electrical signal at the operating frequency.

17. The power supply circuit of claim 16.

18. the power supply circuit is provided with a gas supply lumen that is directed along the transmission line to the plasma generation site, the gas supply lumen and the transmission line together being elements of a flexible probe having an overall diameter of less than 10 mm; The power supply circuit according to any one of claims 12 to 17.

19. the plasma generation portion generates non-thermal plasma when power is supplied by the electrical signal; The power supply circuit according to any one of claims 12 to 18.

20. the at least one decoupling transformer and the gain transformer collectively comprise a plurality of transformers interconnecting the proximal end of the transmission line and a low voltage signal oscillating at the operating frequency and having a voltage amplitude at least 20 times less than the operating amplitude. The power supply circuit according to any one of claims 12 to 19.

21. the primary winding of the gain transformer has an inductance in the range of approximately 1 to 5 μH, and the secondary winding of the gain transformer has an inductance in the range of approximately 1000 to 5000 μH; The power supply circuit according to any one of claims 12 to 20.

22. the gain transformer including a feedback winding that provides a feedback signal to the driver circuit via a feedback network, the feedback winding having an inductance in the range of approximately 1 to 10 μH; 22. The power supply circuit of claim 21.

23. the feedback signal synchronizes oscillation of the driver circuit to the operating frequency and is received at the feedback winding via the load circuit at a frequency of electrical oscillation of the transmission line; 23. The power supply circuit of claim 22.

24. the secondary winding of the distal transformer has an inductance in the range of approximately 20 to 80 μH, and the primary winding of the distal transformer has an inductance in the range of approximately 5 to 20 μH; The power supply circuit according to any one of claims 12 to 23.

25. the secondary winding of the distal transformer is connected to a conductor of the transmission line via an electrical contact; 25. The power supply circuit of claim 24.

26. a pulse modulation circuit operable to modulate the operating frequency at a low frequency, including a frequency in the range of 0.1 to 1 KHz; The power supply circuit according to any one of claims 12 to 25.

27. 1. A method for decoupling gain and frequency constraints for non-thermal plasma generation, comprising: providing an output electrical signal to a plasma generation site having an operating frequency and voltage amplitude sufficient to generate a plasma; the plasma generation site is electrically interconnected via at least two transformer stages to an input electrical signal oscillating at the operating frequency and having a voltage at least 20 times lower than the output electrical signal; method.

28. the voltage amplitude is at least 1 kV; 28. The method of claim 27.

29. the operating frequency is between 1 and 10 MHz; 29. The method of claim 27 or 28.

30. the plasma generation site is interconnected with the input electrical signal via a transmission line, and oscillation of a circuit including the transmission line synchronizes oscillation of the input electrical signal; 30. The method according to any one of claims 27 to 29.

31. a gain transformer having a primary coil and a secondary coil; a driver circuit electrically connected to drive a current through the primary coil; a load circuit having a distal end with a plasma generation site for generating a non-thermal plasma and a proximal end coupled to the secondary coil of the gain transformer; the load circuit includes at least one decoupling inductor providing an inductance including an inductance connected in parallel with the secondary coil and an inductance connected in parallel with the plasma generation portion; Non-thermal plasma generator.

32. the load circuit has an impedance that determines a frequency of oscillation of the load circuit in response to a current generated by the secondary coil; 32. The non-thermal plasma generator of claim 31.

33. the load circuit synchronizes the oscillation of the driver circuit; 33. The non-thermal plasma generator of claim 32.

34. the oscillation of the driver circuit is synchronized by feedback from the gain transformer; 34. The non-thermal plasma generator of claim 33.

35. the frequency of oscillation of the load circuit is sufficiently high so that plasma generation at the plasma generation site does not die out during at least one complete oscillation period; A non-thermal plasma generator according to any one of claims 32 to 34.

36. a pulse modulation circuit operable to modulate the frequency of said oscillation at a low frequency in the range of 0.1 to 1 KHz; The non-thermal plasma generator according to any one of claims 32 to 35.

37. the gain transformer provides a gain of at least 20. The non-thermal plasma generator according to any one of claims 31 to 36.

38. the at least one decoupling inductor comprises at least one decoupling transformer providing a total gain of less than or equal to one; 38. The non-thermal plasma generator of claim 37.

39. the at least one decoupling inductor comprises a decoupling transformer providing a total gain that is at least two times less than the gain provided by the gain transformer; A non-thermal plasma generator according to any one of claims 31 to 38.

40. the gain transformer comprises an air core or a ferrite core; 40. The non-thermal plasma generator according to any one of claims 31 to 39.

41. the at least one decoupling inductor comprises a plurality of decoupling transformers; The non-thermal plasma generator according to any one of claims 31 to 40.

42. the at least one decoupling inductor comprises an inductor coil connected in parallel to the secondary coil and in parallel to the plasma generation site; 42. The non-thermal plasma generator according to any one of claims 31 to 41.

43. the driver circuit stops oscillating when the plasma generating portion is disconnected from the load circuit, but maintains oscillation at a frequency value of the oscillation of the load circuit that varies within a range having a difference of at least 1000% between a minimum value and a maximum value of the range.

33. The non-thermal plasma generator of claim 32.

44. an operating voltage amplitude at the plasma generation site generated by passing the current through the primary coil of the gain transformer is at least 1 kV RMS; A non-thermal plasma generator according to any one of claims 31 to 43.

45. a transmission line interconnecting the plasma generation portion and the at least one decoupling inductor, the transmission line having a length of at least 50 cm and being flexible; A non-thermal plasma generator according to any one of claims 31 to 44.

46. the non-thermal plasma generator is provided with a gas supply lumen directed along the transmission line to the plasma generation site, the gas supply lumen and the transmission line together being elements of a flexible probe having an overall diameter of less than 10 mm; 46. The non-thermal plasma generator of claim 45.

47. the at least one decoupling inductor and the gain transformer together comprise one or more transformers that deliver the operating voltage to the plasma generation site at an amplitude at least 20 times a voltage amplitude at the primary coil of the gain transformer.

45. The non-thermal plasma generator of claim 44.

48. the primary coil of the gain transformer has an inductance in the range of approximately 1 to 5 μH, and the secondary coil of the gain transformer has an inductance in the range of approximately 1000 to 5000 μH; A non-thermal plasma generator according to any one of claims 31 to 47.

49. the feedback from the gain transformer is provided by a feedback winding of the gain transformer, the feedback winding having an inductance in the range of approximately 1 to 10 μH; 35. The non-thermal plasma generator of claim 34.

50. the at least one decoupling inductor comprises at least one decoupling transformer, the distal coil of the at least one decoupling transformer having an inductance in the range of about 20-80 μH, and the distal decoupling transformer coil of the at least one decoupling transformer having a primary coil with an inductance in the range of about 5-20 μH; 50. The non-thermal plasma generator according to any one of claims 31 to 49.

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