Atmospheric plasma generator

Abstract

The invention discloses an atmosphere plasma generator, which comprises a driving power supply and a spray gun, and is characterized in that the driving power supply comprises a rectifier, at least two half-bridge inverters and at least two transformers in one-to-one correspondence with the half-bridge inverters; the input end of the rectifier is connected with an AC power supply; the at least two half-bridge inverters are arranged at the output end of the rectifier in parallel; the primary side of each transformer is connected with the output end of the corresponding half-bridge inverter, the secondary sides of the multiple transformers are connected in series to form an output port, and the output port is connected with the spray gun. According to the atmospheric plasma generator, the specification requirement on a single related power device is reduced, so that higher total power output can be realized, the requirement of equipment such as the plasma generator on high voltage of several kilovolts can be met, and the controllability and adaptability of voltage output are improved. And when the power demand is increased, flexible expansion can be realized by increasing the number of the parallel modules, the whole system does not need to be redesigned, and the power expansion capability is improved.

Description

Technical Field

[0001] This invention relates to the field of plasma equipment technology, and more particularly to an atmospheric plasma generator. Background Technology

[0002] Plasma generators are commonly used in industrial cutting, surface treatment, waste gas treatment, and medical sterilization. Their working principle relies on high-voltage, high-frequency electrical energy to excite gas and form plasma. To meet the needs of different applications, the plasma power supply in a plasma generator often needs to provide several kilowatts or more of output power, with output voltages potentially reaching several kilovolts, and operating frequencies typically in the tens of kilohertz range, to accommodate the dynamic impedance characteristics of the plasma spray gun.

[0003] In existing technologies, high-power power supplies typically employ a single inverter structure, achieving power conversion and voltage boosting through a single high-specification power device and transformer. For example, common half-bridge or full-bridge inverter topologies are widely used to convert DC to high-frequency AC, which is then coupled to the spray gun via a transformer. However, this inverter structure faces numerous challenges in high-power applications. First, the single inverter must handle the entire power load, resulting in extremely high specifications for power devices and magnetic components. This not only increases design complexity and manufacturing costs but also reduces system heat dissipation performance and lifespan due to heat concentration. Second, as power demands increase further, the scalability of a single inverter is limited, making power upgrades difficult through simple adjustments and often requiring a complete redesign of the circuit system. Furthermore, in terms of reliability, the single inverter structure carries a single point of failure risk. If a critical component fails, the entire power system will malfunction, which is particularly detrimental in continuous production or high-safety applications. Summary of the Invention

[0004] The purpose of this invention is to provide an atmospheric plasma generator that achieves higher power output, better modular expansion capabilities, and better system stability.

[0005] To achieve the above objectives, the present invention provides an atmospheric plasma generator, which includes a driving power supply and a spray gun. The driving power supply includes a rectifier, at least two half-bridge inverters, and at least two transformers corresponding to the half-bridge inverters. The input terminal of the rectifier is connected to an AC power source, and the rectifier is used to convert AC power into DC power. At least two half-bridge inverters are connected in parallel at the output of the rectifier; The primary side of each transformer is connected to the output terminal of the corresponding half-bridge inverter, and the secondary sides of multiple transformers are connected in series to form an output port. The output port is connected to the spray gun, and the spray gun outputs a plasma stream based on the power supplied by the output port.

[0006] Preferably, the output port is further provided with an impedance matching network adapted to the impedance of the spray gun.

[0007] Preferably, the impedance matching network includes a plurality of first resonant inductors respectively disposed on the secondary side of each of the transformers and resonant capacitors connected to both ends of the output port.

[0008] Preferably, the impedance matching network further includes a second resonant inductor connected in series across the resonant capacitor and a variable resistor with adjustable resistance.

[0009] Preferably, the output port is connected to the spray gun via a coaxial cable.

[0010] Preferably, the input terminal of each half-bridge inverter is connected to the output terminal of the rectifier through a power factor correction circuit.

[0011] Preferably, the input terminal of the rectifier is connected to an AC power supply via a filter.

[0012] Compared to existing technologies, the atmospheric plasma generator provided by the above-mentioned technical solution uses a multi-channel parallel connection to share the input power, reducing the specification requirements of individual related power devices. This enables a higher total power output, meeting the high voltage requirements of plasma generators and other equipment, such as those requiring thousands of volts, and improving the controllability and adaptability of the voltage output. Furthermore, when power demand increases, flexible expansion can be achieved by adding more parallel modules without redesigning the entire system, thus enhancing power scalability. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the atmospheric plasma generator in an embodiment of the present invention. Detailed Implementation

[0014] To illustrate the technical content, structural features, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0015] This embodiment discloses an atmospheric plasma generator, such as... Figure 1 It includes a drive power supply and a spray gun, wherein the drive power supply includes a rectifier DC, at least two half-bridge inverters UC and at least two transformers T corresponding one-to-one with the half-bridge inverters UC.

[0016] In this embodiment, there are four half-bridge inverters UC and four transformers T.

[0017] Specifically, the input terminal of the rectifier DC is connected to the AC power supply to convert the input AC power into DC power, providing a stable DC input for subsequent circuits. For example, the rectifier DC can use a three-phase bridge rectifier circuit, with the input AC power being a three-phase 380V, 50Hz industrial power supply, and the output DC voltage after rectification being approximately 540V.

[0018] Four half-bridge inverters (UCs) are connected in parallel at the output of the rectifier (DC) to convert DC power into high-frequency AC power.

[0019] Each half-bridge inverter UC uses two IGBT power devices to form a half-bridge topology to accommodate the dynamic impedance characteristics of the spray gun.

[0020] The input of each half-bridge inverter UC is connected to the output of the rectifier DC, sharing the DC current output by the rectifier DC. This reduces the current load and power load of a single inverter, reduces the specification requirements of power devices, and lowers the design difficulty and heat concentration issues.

[0021] The output of each half-bridge inverter UC is connected to the primary side of the corresponding transformer T to achieve initial voltage boost and isolated transmission of high-frequency signals.

[0022] For example, each transformer T has a turns ratio of 1:5, a primary input voltage of approximately 500V high-frequency AC, and a secondary output voltage of approximately 2500V.

[0023] In addition, the secondary sides of multiple transformers T are connected in series to form an output port OUT. The output port OUT is connected to the spray gun, and the spray gun outputs a plasma stream based on the power supplied by the output port OUT.

[0024] For example, taking the secondary output voltage of each transformer T as approximately 2500V as an example, the four output voltages are superimposed, and finally a high voltage output of approximately 10000V is formed at the output port OUT, which meets the plasma generator's requirement for several kilovolts of high voltage.

[0025] In this embodiment, the drive power supply is configured through the parallel connection of multiple half-bridge inverters UC, distributing the total input power across multiple paths. Each inverter only needs to handle a portion of the total power, reducing the specification requirements of individual inverters and related power devices, while improving the system's heat dissipation performance and lifespan. Furthermore, the series connection of the secondary side of transformer T enables the superposition of output voltages, satisfying high voltage requirements while reducing the design complexity of a single transformer T.

[0026] Furthermore, the drive power supply in this embodiment features modularity, with multiple half-bridge inverters UC and their corresponding transformers T functioning identically and operating independently. When power demand increases, power expansion can be achieved by adding more parallel half-bridge inverters UC and transformers T without redesigning the entire circuit, demonstrating excellent scalability and versatility. Simultaneously, if one module fails, other modules can continue to operate, avoiding the risk of overall system failure. Moreover, the modular design facilitates maintenance; faulty modules can be replaced or repaired individually, reducing maintenance costs.

[0027] On the other hand, an impedance matching network is added between the output port OUT and the spray gun. The impedance matching network is adapted to the impedance of the spray gun to achieve the matching of the output impedance of the drive power supply and the impedance of the spray gun, thereby maximizing the power transmission efficiency and reducing reflection loss.

[0028] Specifically, the impedance matching network includes several first resonant inductors L1 respectively disposed on the secondary side of each transformer T and resonant capacitors C connected to the two ends of the output port OUT.

[0029] Each first resonant inductor L1 is connected in series with the corresponding transformer T secondary side to provide a specific inductive impedance during high-frequency signal transmission, thereby compensating for the imaginary impedance of the spray gun and achieving local resonance. Each first resonant inductor L1 is a high-Q coil element, and the inductance value is designed according to the output frequency of the transformer T secondary side (e.g., 40kHz) and the impedance characteristics of the spray gun. For example, each first resonant inductor L1 is 10μH to ensure the formation of an effective series resonant circuit at the operating frequency.

[0030] The resonant capacitor C, together with the first resonant inductor L1, forms an overall resonant network. This combination of the resonant capacitor C and all the first resonant inductors L1 achieves overall tuning of the impedance matching network, ensuring that the equivalent impedance of the output port OUT matches the impedance of the plasma spray gun. Specifically, when the high-voltage AC output is achieved by connecting the secondary side of transformer T in series, the first resonant inductors L1 help adjust the impedance characteristics of each path, while the resonant capacitor C provides a parallel or series resonance effect at the output port OUT, thereby minimizing reflection losses and optimizing power transmission.

[0031] In this embodiment, it is assumed that the impedance of the plasma spray gun is a dynamically changing 50 ohms (real part) plus 30 ohms (imaginary part). By adjusting the value of the first resonant inductor L1 and the resonant capacitor C, the impedance matching network forms a matching impedance of approximately 50 ohms at the 40kHz operating frequency, thereby achieving conjugate impedance matching.

[0032] On the other hand, the impedance matching network also includes a second resonant inductor L2 connected in series across the resonant capacitor C and a variable resistor RT with adjustable resistance.

[0033] The second resonant inductor L2 is used to further adjust the overall inductance characteristics of the impedance matching network, providing additional resonant compensation to accommodate dynamic changes in the spray gun impedance.

[0034] A variable resistor RT is also connected in series across the resonant capacitor C, working together with the second resonant inductor L2. This variable resistor RT provides adjustable impedance matching, achieving compensation for the real impedance of the spray gun, reducing reflection loss, and stabilizing the circuit output.

[0035] In this embodiment, the secondary side of each transformer T is connected to a first resonant inductor L1. These first resonant inductors L1 are connected to the resonant capacitor C at the output port OUT. A second resonant inductor L2 and a variable resistor RT are further connected in series across the resonant capacitor C, forming a composite matching network. During operation, this network achieves real-time matching of the plasma spray gun by adjusting the resistance value of the variable resistor RT and the fixed characteristics of the second resonant inductor L2, ensuring maximum power transmission efficiency.

[0036] On the other hand, the output port OUT is connected to the spray gun (such as a plasma generator) via a coaxial cable. A coaxial cable is a shielded transmission line consisting of an inner conductor, an outer insulation layer, a shielding layer, and an outer sheath, capable of effectively transmitting high-frequency signals and minimizing signal loss. One end of the coaxial cable is connected to the positive and negative terminals of the output port OUT, and the other end is connected to the input terminal of the spray gun, ensuring that the high-voltage signal remains stable during transmission and is unaffected by external electromagnetic interference.

[0037] To achieve optimal transmission performance, this embodiment incorporates impedance matching design for the coaxial cable. Specifically, the equivalent impedance of the output port OUT (e.g., 50 ohms) is matched to the characteristic impedance of the coaxial cable, preventing reflection losses in the transmission line. Simultaneously, simple matching pads (such as small capacitors or inductors) can be added at the connection points to compensate for any minor impedance differences. In high-frequency operating environments (e.g., 40kHz), this connection method reduces signal attenuation, ensures power transmission efficiency of over 95%, and prevents system interference due to electromagnetic radiation.

[0038] On the other hand, the input of each half-bridge inverter UC is connected to the output of the rectifier DC through a power factor correction circuit PFC.

[0039] Power factor correction (PFC) circuits are used to improve the waveform of the input current, making it closer to a sine wave, thereby improving the power factor of the power supply. In this embodiment, the selected PFC circuit includes a boost converter, whose input is connected to the output of the rectifier DC and whose output is connected to the input of the half-bridge inverter UC.

[0040] Specifically, the boost converter's controller adjusts the on-time of the switching elements based on the input current and output voltage signals to achieve dynamic regulation of the input current. In this way, the power factor correction (PFC) circuit ensures that the input current remains constant throughout the power cycle, reducing harmonic components and thus improving the power factor to above 0.95, meeting international power quality standards.

[0041] On the other hand, the input terminal of the rectifier DC is connected to the AC power supply via a filter EF. The filter EF is used to filter out high-frequency noise, harmonic components, and other electromagnetic interference signals from the AC power supply, ensuring a cleaner AC signal input to the rectifier DC. In this embodiment, the selected filter EF is an electromagnetic interference (EMI) filter EF, comprising a common-mode inductor, a differential-mode inductor, and a combination of X and Y capacitors. The input terminal of the filter EF is connected to the AC power supply (e.g., three-phase 380V, 50Hz mains power), and the output terminal is connected to the input terminal of the rectifier DC.

[0042] In practical applications, the filter EF can also protect the rectifier DC and subsequent circuits from sudden voltage spikes or surges in the AC power supply. For example, when the AC power supply is subjected to transient interference caused by lightning strikes or switching operations, the filter EF can absorb or attenuate these interference signals, preventing them from damaging the diodes or other sensitive components in the rectifier DC, thereby improving the overall reliability of the system.

[0043] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. An atmospheric plasma generator, characterized in that, It includes a drive power supply and a spray gun. The drive power supply includes a rectifier, at least two half-bridge inverters, and at least two transformers corresponding to each half-bridge inverter. The input terminal of the rectifier is connected to an AC power source, and the rectifier is used to convert AC power into DC power. At least two half-bridge inverters are connected in parallel at the output of the rectifier; The primary side of each transformer is connected to the output terminal of the corresponding half-bridge inverter, and the secondary sides of multiple transformers are connected in series to form an output port. The output port is connected to the spray gun, and the spray gun outputs a plasma stream based on the power supplied by the output port.

2. The atmospheric plasma generator according to claim 1, characterized in that, The output port is also equipped with an impedance matching network adapted to the impedance of the spray gun.

3. The atmospheric plasma generator according to claim 2, characterized in that, The impedance matching network includes several first resonant inductors respectively disposed on the secondary side of each transformer and resonant capacitors connected to both ends of the output port.

4. The atmospheric plasma generator according to claim 3, characterized in that, The impedance matching network also includes a second resonant inductor connected in series across the resonant capacitor and a variable resistor with adjustable resistance.

5. The atmospheric plasma generator according to claim 1, characterized in that, The output port is connected to the spray gun via a coaxial cable.

6. The atmospheric plasma generator according to claim 1, characterized in that, The input terminal of each half-bridge inverter is connected to the output terminal of the rectifier through a power factor correction circuit.

7. The atmospheric plasma generator according to claim 1, characterized in that, The input terminal of the rectifier is connected to the AC power supply via a filter.

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