High voltage pulsed source excited plasma sterilization apparatus for closed package food

Abstract

The application relates to a high-voltage pulse source excited closed package food plasma sterilization device, which comprises a high-voltage pulse source including a multi-stage pulse output circuit for generating bipolar high-voltage pulse output; and a long-gap dielectric barrier discharge electrode device, wherein the bipolar high-voltage pulse is loaded to an upper electrode and a lower electrode to form a long-gap discharge area for placing closed package food. The application combines the multi-stage high-voltage pulse source with the long-gap dielectric barrier discharge structure to form long-gap dielectric barrier discharge in the normal-pressure air environment, the high-voltage pulse electric field can be coupled to the inside of the package bag through the capacitor to ionize and activate the gas in the bag, so that the closed package food can receive low-temperature plasma sterilization treatment without opening the package bag, secondary pollution caused by re-packaging or external contact after sterilization is avoided, and the health safety and preservation effect of the food are improved.

Description

Technical Field

[0001] This invention relates to the fields of food sterilization and low-temperature plasma technology, and in particular to a plasma sterilization device for sealed packaged food excited by a high-voltage pulse source. Background Technology

[0002] Food is susceptible to contamination by bacteria, mold, and other microorganisms during production, processing, logistics, transportation, and final storage, affecting its quality, safety, and shelf life. This is especially true for products with high hygiene requirements, such as meat products, ready-to-eat foods, fresh foods, and pre-prepared foods. If the packaging is reopened for subsequent sterilization or processing after sealing, external microorganisms can easily re-enter the packaging, leading to secondary contamination. This not only affects sterilization effectiveness but may also reduce shelf life. Therefore, achieving food sterilization while maintaining intact, sealed packaging has become an important research direction in the fields of food preservation and aseptic packaging. Currently, common food sterilization methods include high-temperature heat treatment, ultraviolet irradiation, chemical fumigation, and radiation sterilization. High-temperature sterilization can easily alter the taste, nutritional components, and texture of food; chemical sterilization may pose a risk of residue; and radiation sterilization equipment is expensive and has limitations in some applications. Therefore, novel sterilization technologies suitable for low-temperature conditions that can balance sterilization effectiveness with food quality preservation have attracted widespread attention.

[0003] Low-temperature plasma technology generates a large number of highly reactive particles, including electrons, ions, reactive oxygen species, reactive nitrogen species, ozone, and ultraviolet radiation, at near-room temperature. These particles have a strong destructive effect on the cell walls, proteins, and genetic material of microorganisms, thereby inactivating bacteria, fungi, and viruses. Compared to traditional heat sterilization methods, low-temperature plasma technology has advantages such as lower processing temperatures, faster reaction speeds, less chemical residue, and suitability for heat-sensitive foods, making it a promising technology for food sterilization.

[0004] Among existing methods for generating low-temperature plasma, dielectric barrier discharge (DBD) is a common form of discharge under normal pressure conditions. This method typically involves placing an insulating dielectric layer between electrodes to limit the discharge current and suppress the formation of a continuous arc, allowing the discharge process to occur in the form of micro-discharge or filamentary discharge, thus obtaining a relatively stable low-temperature plasma. However, existing DBD devices are mostly used for sterilization of open food surfaces, medical device surfaces, or confined spaces. Their discharge area is usually small, and the electrode spacing is limited, making them unsuitable for sealed packaged foods with a certain volume and thickness.

[0005] For food packaging sealed with non-metallic insulating materials such as plastic film and composite polymer materials, a certain amount of gas space is usually retained inside. Existing devices often struggle to allow the externally applied high-voltage electric field to effectively penetrate the packaging material and couple into the internal space when processing such sealed food packaging. This makes it difficult for the gas inside the packaging to be effectively ionized and activated, thus preventing sufficient sterilization of the internal environment and food surface without opening the package. Furthermore, if the discharge gap is too small, it may be limited by the packaging size, making it difficult to meet the placement requirements of actual food packaging.

[0006] Therefore, how to achieve long-gap dielectric barrier discharge suitable for sealed packaged food under normal air pressure, and how to ensure the integrity of the packaging while effectively applying a high-voltage pulse electric field to the gas space inside the packaging bag, and simultaneously forming an effective plasma reaction zone inside and outside the packaging, so as to achieve sterilization of sealed packaged food and its internal environment, remains a technical problem that urgently needs to be solved in the existing technology. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a plasma sterilization device for sealed packaged food excited by a high-voltage pulse source.

[0008] This invention is achieved through the following technical solution: A high-voltage pulse source-excited closed-package food plasma sterilization device includes: A high-voltage pulse source includes a multi-stage pulse output circuit for generating bipolar high-voltage pulse output. Each stage of the pulse output circuit includes a capacitor charging and discharging module, a full-bridge inverter circuit module, and a pulse transformer module. A long-gap dielectric barrier discharge electrode device includes an upper electrode and a lower electrode. A bipolar high-voltage pulse is applied to the upper electrode and the lower electrode to form a long-gap discharge region for placing sealed packaged food.

[0009] According to the above technical solution, preferably, the secondary outputs of the pulse output circuits at each stage are connected in series and superimposed to form the bipolar high-voltage pulse output.

[0010] According to the above technical solution, preferably, each stage of the pulse output circuit is provided with a PCB board, and the high voltage pulse source is provided with five stages of PCB board.

[0011] According to the above technical solution, preferably, the output terminal of the capacitor charging and discharging module is connected to the input terminal of the full-bridge inverter circuit module, the output terminal of the full-bridge inverter circuit module is connected to the primary side of the pulse transformer module, the secondary side of the pulse transformer module serves as the boost output terminal of the pulse output circuit of that stage, and the secondary sides of each stage of the pulse transformer module are connected in series to achieve voltage superposition, forming the bipolar high-voltage pulse output.

[0012] According to the above technical solution, preferably, the capacitor charging and discharging module includes a DC power input, a charging resistor, a charging and discharging capacitor, a fast recovery diode, a switching transistor, and an MCP1407 driver chip for controlling the switching transistor to turn on.

[0013] According to the above technical solution, preferably, the full-bridge inverter circuit module includes a full-bridge inverter circuit composed of four switching transistors and four isolation drive modules that drive each switching transistor respectively. The isolation drive module includes a UCC23313 driver chip and a QA151C isolation power supply for realizing high and low voltage isolation.

[0014] According to the above technical solution, preferably, the pulse transformer module uses a 1K107B iron-based amorphous nanocrystalline alloy core magnetic ring, and the winding uses DC silicone high-voltage wire. The pulse transformer module is wound with primary and secondary windings wound in parallel. Furthermore, the pulse transformer module is immersed in insulating oil, which covers the windings and high-voltage output parts of the pulse transformer module.

[0015] According to the above technical solution, preferably, both the upper electrode and the lower electrode are FPC flexible electrodes, including a copper conductive layer and a polyimide dielectric layer. The copper conductive layer of the upper electrode adopts a multi-parallel strip structure design, and the copper conductive layer of the lower electrode adopts a rectangular planar structure design. The upper electrode and the lower electrode are placed in a staggered relative manner, forming the long gap discharge region between them.

[0016] According to the above technical solution, preferably, both the upper electrode and the lower electrode are provided with pads, the pads are electrically connected to the corresponding copper conductive layer, the positive polarity output terminal of the high voltage pulse source is connected to the pad of the upper electrode through a wire, and the negative polarity output terminal of the high voltage pulse source is connected to the pad of the lower electrode through a wire.

[0017] The beneficial effects of this invention are: This invention employs a structure combining a high-voltage pulse source and a long-gap dielectric barrier discharge electrode device. A long-gap dielectric barrier discharge is generated in a normal-pressure air environment using a bipolar high-voltage pulse. The packaging bag is made of non-metallic insulating material. Utilizing the capacitive coupling characteristics of the high-voltage pulse electric field, the pulse electric field can penetrate the packaging bag material and act on the gas space inside the bag. This generates or activates active components with sterilization effects, such as electrons, ions, ozone, active oxygen particles, and active nitrogen particles, in situ inside the bag, thereby achieving sterilization of the internal space of the packaging and the surface of the food.

[0018] This method does not rely on external plasma to directly penetrate the packaging material, but rather creates an active environment inside the bag through electric field coupling, thus improving the internal sterilization effect while maintaining the integrity of the packaging.

[0019] Therefore, the present invention can achieve long-gap low-temperature plasma sterilization treatment suitable for sealed packaged food under normal air pressure environment, and achieve in-situ sterilization of the internal space of the packaging while maintaining the integrity of the packaging. It has the advantages of low sterilization temperature rise, low risk of secondary contamination, suitability for heat-sensitive foods and high discharge stability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the connection principle of the high-voltage pulse source part of the present invention.

[0021] Figure 2 This is the basic circuit diagram of the high-voltage pulse source part of the present invention.

[0022] Figure 3 This is a circuit connection diagram of the capacitor charging and discharging module in this invention.

[0023] Figure 4 This is a circuit connection diagram of the isolation drive module in this invention.

[0024] Figure 5 This is a schematic diagram of the planar structure of the upper electrode in the long gap dielectric barrier discharge electrode device of the present invention.

[0025] Figure 6 This is a schematic diagram of the planar structure of the lower electrode in the long-gap dielectric barrier discharge electrode device of the present invention.

[0026] Figure 7 This is a schematic diagram illustrating the application scenario of the plasma sterilization device in this invention.

[0027] In the figure: 21, polyimide dielectric layer; 22, copper conductive layer; 23, long gap discharge region; 24, sealed packaged food. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] This invention provides a high-voltage pulse source-excited closed-package food plasma sterilization device, comprising: A high-voltage pulse source includes a multi-stage pulse output circuit for generating bipolar high-voltage pulse output. Each stage of the pulse output circuit includes a capacitor charging / discharging module, a full-bridge inverter circuit module, and a pulse transformer module. A long-gap dielectric barrier discharge electrode device includes an upper electrode and a lower electrode. The bipolar high-voltage pulse is applied to the upper and lower electrodes to form a long-gap discharge region for placing sealed packaged food. The sealed packaged food is placed within the long-gap dielectric barrier discharge region and undergoes plasma sterilization without opening the packaging bag. Specifically, the positive and negative output terminals of the high-voltage pulse source device are connected to the upper and lower electrodes of the long-gap dielectric barrier discharge electrode device via wires, respectively. The sealed packaged food is located between the upper and lower electrodes. The packaging bag is made of non-metallic insulating packaging material and has a gas space inside.

[0030] The packaging bag uses non-metallic insulating packaging material. Utilizing the capacitive coupling characteristics of a high-voltage pulsed electric field, the pulsed electric field can penetrate the packaging material and act on the internal gas space of the bag. This generates or activates active components with sterilization effects, such as electrons, ions, ozone, reactive oxygen particles, and reactive nitrogen particles, in situ within the bag, thereby achieving sterilization of both the internal space of the packaging and the surface of the food. This method does not rely on external plasma directly penetrating the packaging material; instead, it creates an active environment within the bag through electric field coupling. Therefore, it can improve the internal sterilization effect while maintaining the integrity of the packaging.

[0031] In this high-voltage pulse source, each stage of the pulse output circuit is equipped with a printed circuit board (PCB). Each stage includes a capacitor charging / discharging module, a full-bridge inverter circuit module, and a pulse transformer module. The output terminal of the capacitor charging / discharging module is connected to the input terminal of the full-bridge inverter circuit module, and the output terminal of the full-bridge inverter circuit module is connected to the primary side of the pulse transformer module. The secondary side of the pulse transformer module serves as the boost output terminal of the pulse output circuit at that stage. The secondary sides of each stage of the pulse transformer module are connected in series to achieve voltage superposition, forming the bipolar high-voltage pulse output. In this example, the high-voltage pulse source adopts a multi-stage pulse output circuit and a series superposition structure of the secondary sides of the pulse transformer. By combining full-bridge inverter and pulse boost, a high-amplitude bipolar high-voltage pulse output can be obtained, thereby improving the long-gap air discharge capability. Furthermore, the output voltage, pulse width, and repetition frequency can be adjusted according to different food packaging sizes and discharge requirements, improving the adaptability and discharge control capability of the device.

[0032] Preferably, in this example, the high-voltage pulse source is equipped with a five-stage pulse output circuit, which corresponds to five PCB boards. The structure of each stage of the pulse output circuit is completely identical, and they are respectively labeled as PCB board 1, PCB board 2, PCB board 3, PCB board 4, and PCB board 5. The positive and negative terminals of the pulse transformer of each stage of the pulse output circuit serve as the output terminals of that stage of the pulse circuit. The negative terminal of the pulse transformer on PCB 1 serves as the negative output terminal of the entire high-voltage pulse source. The positive terminal of the pulse transformer on PCB 1 is connected to the negative terminal of the pulse transformer on PCB 2. The positive terminal of the pulse transformer on PCB 2 is connected to the negative terminal of the pulse transformer on PCB 3. The positive terminal of the pulse transformer on PCB 3 is connected to the negative terminal of the pulse transformer on PCB 4. The positive terminal of the pulse transformer on PCB 4 is connected to the negative terminal of the pulse transformer on PCB 5. The positive terminal of the pulse transformer on PCB 5 serves as the positive output terminal of the entire high-voltage pulse source. Through the series superposition of the secondary sides of the five pulse transformers, the high-voltage pulse source device achieves a voltage boost capability of approximately 50 times relative to the input voltage of a single primary side.

[0033] The capacitor charging / discharging module includes a DC power input, a charging resistor, a charging / discharging capacitor, a fast recovery diode, a switching transistor, and an MCP1407 driver chip to control the switching transistor's conduction. When the switching transistor is off, the DC power supply charges the capacitor through the charging / discharging capacitor and the diode. When the switching transistor is on, the charging / discharging capacitor and the switching transistor form a discharging circuit for discharge output. The output terminal of the MCP1407 driver chip is connected to the gate of the switching transistor to control its conduction.

[0034] like Figure 2As shown, the basic circuit of the high-voltage pulse source consists of a five-stage pulse output circuit. Taking two stages as an example, the high-voltage DC charging point is connected to the corresponding energy storage node via charging resistors R1 and R2. The energy storage node of the upper branch is connected to the charging / discharging capacitor C1, the fast recovery diode D1, and the controlled switch Q1. The energy storage node of the lower branch is connected to the charging / discharging capacitor C2, the fast recovery diode D2, and the controlled switch Q2. The output side of C1 is connected to a full-bridge inverter unit composed of Q3, Q4, Q5, and Q6, and the output side of C2 is connected to a full-bridge inverter unit composed of Q7, Q8, Q9, and Q10. The AC output terminal of each full-bridge inverter unit is connected to the primary side of the pulse transformer, and the secondary sides of the two pulse transformers are connected in series to achieve voltage superposition.

[0035] Figure 2 When the circuit shown is operating, when Q1 is off, the high-voltage DC charging point charges C1 through the path containing R1, C1, and D1; when Q1 is on, C1 forms a discharge path through Q1, outputting a unipolar pulse. When Q3 and Q6 are on and Q4 and Q5 are off, the full-bridge inverter unit outputs a positive pulse wave; when Q4 and Q5 are on and Q3 and Q6 are off, the full-bridge inverter unit outputs a negative pulse wave, thus forming an alternating polarity pulse voltage on the primary side of the pulse transformer. In the lower branch, the connection and operation of Q2, C2, D2, R2, and Q7, Q8, Q9, and Q10 correspond to those of the upper branch. By controlling the alternating conduction of the two sets of diagonal switches Q7 and Q10, and Q8 and Q9, the lower branch also outputs pulses of alternating polarity.

[0036] The specific circuit connection diagram of the capacitor charging and discharging module is as follows: Figure 3 As shown, in the capacitor charging and discharging module, the control signal SIGNAL is connected to the INPUT terminal of the driver chip U7 (MCP1407-E / P); the VDD terminal of U7 is connected to the +12V power supply terminal, the GND terminal of U7 is grounded, and the decoupling capacitor U8 (4.7μF) is connected between the +12V power supply terminal and ground to stabilize the driving power supply of U7. The output terminal OUT of U7 is connected to the gate of the switching transistor Q4 (IXBHN250) through the isolation resistor R4 (1Ω). The gate of Q4 is also grounded through the pull-down resistor R5 (10kΩ) to reliably turn off Q4 when the control signal is removed. The high-voltage charging input terminal INPUT is connected to the energy storage node via the charging resistor U170 (10kΩ) in the figure. The charging and discharging capacitor C4 (470nF) is connected between the energy storage node and the output terminal OUTPUT1. The fast recovery diode D3 (EM520) is connected between the output terminal OUTPUT1 and the ground terminal, and together with C4 and Q4, they form a unidirectional charging and pulse discharging path.

[0037] Figure 3When the capacitor charging / discharging module shown is working, when SIGNAL is active, U7 outputs a drive pulse. This drive pulse is applied to the gate of Q4 via R4, turning Q4 on. The energy stored in C4 is rapidly released through Q4 and the OUTPUT1 circuit, forming a unipolar pulse output at the OUTPUT1 terminal. When SIGNAL is inactive, U7 outputs a low level, R5 clamps the gate of Q4 to ground, and Q4 turns off. At this time, the high-voltage charging input terminal INPUT charges C4 through the charging path defined by the 10kΩ charging resistor and D3, storing energy for the next pulse output. R4 is used to suppress gate drive circuit oscillation, U8 is used to reduce voltage fluctuations at the U7 power supply terminal, and D3 is used to limit the direction of the circuit current and improve the pulse recovery speed. In this embodiment, three parallel charging / discharging capacitors can be set in each stage of the capacitor charging / discharging module to improve the current output capability of this stage of the circuit, reduce the current stress of a single capacitor, and improve the energy release capability and discharge load driving capability during the pulse output process.

[0038] The full-bridge inverter circuit module includes a full-bridge inverter circuit composed of four switching transistors and four isolation drive modules that drive each switching transistor respectively. The isolation drive module includes a UCC23313 driver chip and a QA151C isolation power supply to achieve high and low voltage isolation.

[0039] like Figure 4 As shown, in the isolated drive module, the control signal SIGNAL is connected to the ANODE terminal of U1 (UCC23313DWYR) via the input current-limiting resistor R2 (150Ω), and the CATHODE terminal of U1 is grounded via resistor R1 (150Ω), forming the control signal loop on the input side of U1. The +VIN terminal of the isolated power supply U2 (QA151C) is connected to the 15V power supply terminal, and the GND terminal is grounded. The input-side decoupling capacitor C1 (4.7μF) is connected between the 15V power supply terminal and ground. The +VOUT terminal of U2 is connected to the VCC terminal of U1, the COM terminal is grounded, and the -VOUT terminal is connected to the VEE terminal of U1. Capacitors C2 (4.7μF) and C3 (4.7μF) are connected between the terminals of the isolated output power supply for filtering and voltage regulation. The VOUT terminal of U1 is connected to the OUT terminal via the output isolation resistor R3 (1Ω), and the OUT terminal is then connected to... Figure 2 The corresponding gates are Q3, Q4, Q5, Q6 or Q7, Q8, Q9, Q10 of the full-bridge switching transistors. Each switching transistor in the full-bridge inverter circuit is equipped with a corresponding isolation drive module to provide a drive signal, thereby achieving high and low voltage isolation.

[0040] Figure 4When the isolation drive module shown is working, the control signal is applied to the input side of U1 via R2 and R1. Under the action of the isolation power supply provided by U2, U1 generates an isolation drive pulse corresponding to the control signal at the output side VOUT terminal. This isolation drive pulse is output to the OUT terminal via R3 and drives the gate of the corresponding full-bridge switch, so that the full-bridge inverter unit realizes the alternating conduction of the diagonal switches according to the set timing. Since U2 electrically isolates the output side of U1 from the control side, even if the full-bridge inverter unit is in a high-voltage pulse and rapid potential change environment, the control signal can still be stably transmitted to the corresponding switch, thereby reducing false triggering and drive interference.

[0041] To further enhance the bipolar pulse output voltage amplitude, a pulse transformer module is connected to the output of the full-bridge inverter circuit module. The pulse transformer module uses a 1K107B iron-based amorphous nanocrystalline alloy core magnetic ring, wound with DC silicone high-voltage wire. The primary to secondary turns ratio of the pulse transformer is 7:70, resulting in approximately a 10-fold voltage boost for each stage of the pulse output circuit. To further reduce transformer leakage inductance and improve the pulse waveform's leading edge and quality, the pulse transformer module is wound with the primary and secondary windings wound in parallel.

[0042] Because the secondary output voltage of the pulse transformer is relatively high, to improve insulation reliability, the pulse transformer module is immersed in insulating oil in this example. The insulating oil covers the windings and high-voltage output parts of the pulse transformer module, which can improve the insulation strength on the high-voltage side and reduce the risk of local breakdown or surface discharge at the high-voltage terminal on the secondary side, thereby improving the operational stability of the high-voltage pulse source device. In addition, high-voltage insulated wires are used in this example, and insulating encapsulation layers can also be set in the non-discharge areas of the upper and lower electrodes and at the pad connections to reduce the risk of surface discharge near the high-voltage output terminal and pads. By setting an insulating oil-immersed structure on the high-voltage side of the pulse transformer and setting an insulating encapsulation layer in the high-voltage output area, the risk of surface discharge and local breakdown can be reduced, improving the insulation reliability and operational stability of the high-voltage pulse source device under high-voltage pulse operation.

[0043] Meanwhile, it is worth noting that the peak voltage at the output of the high-voltage pulse source is adjustable from 0-35kV, the pulse leading edge is 1μs, the pulse width is adjustable, and the repetition frequency is adjustable. In this example, when performing long-gap dielectric barrier discharge in atmospheric pressure air, a bipolar high-voltage pulse with both positive and negative pulse widths of 5μs and a repetition frequency of 1kHz is used as the excitation signal. By adjusting the output voltage amplitude, pulse width, and repetition frequency, the starting voltage, discharge intensity, and discharge distribution of the long-gap dielectric barrier discharge can be changed.

[0044] The long-gap dielectric barrier discharge electrode device includes an upper electrode and a lower electrode, with a long-gap discharge region 23 formed between the upper and lower electrodes for placing the sealed packaged food 24. Specifically, both the upper and lower electrodes are flexible printed circuit board electrodes (FPC flexible electrodes), including a copper conductive layer 22 and a polyimide dielectric layer 21. The FPC flexible electrode has a strip-like structure, preferably with a length of 50 mm and a width of 16 mm, and the effective discharge area formed between the upper and lower electrodes is 25 mm × 16 mm. The polyimide dielectric layer 21 is directly attached to the surface of the corresponding FPC electrode as a reinforcing layer. In this example, the thickness of the polyimide dielectric layer 21 is preferably 0.1 mm. The presence of the polyimide dielectric layer 21 on both the upper and lower electrodes can effectively limit the discharge current, suppress the formation of continuous arcs, and generate discharge in the form of short-duration filamentary micro-discharges, thereby reducing the risk of local overheating, improving discharge stability, and facilitating the realization of a low-temperature plasma discharge environment suitable for food processing. The copper conductive layer 22 of the upper electrode adopts a multi-parallel strip structure design, and the copper conductive layer 22 of the lower electrode adopts a rectangular planar structure design. The upper and lower electrodes are placed in a staggered manner to reduce the phenomenon of excessive local electric field in the strip starting area, so that the discharge is generated in the form of filament micro-discharge and distributed as evenly as possible in the discharge area, while suppressing local continuous conduction and reducing the possibility of discharge developing into an electric arc.

[0045] In addition, both the upper and lower electrodes are provided with pads, which are electrically connected to the corresponding copper conductive layers. The positive output terminal of the high-voltage pulse source is connected to the pad of the upper electrode via a wire, and the negative output terminal of the high-voltage pulse source is connected to the pad of the lower electrode via a wire. In this example, soldering is preferably used between the wire and the pad to ensure that the pulse voltage can be stably applied between the upper and lower electrodes.

[0046] During sterilization, the sealed packaged food is placed entirely within the long-gap discharge area between the upper and lower electrodes. When a bipolar high-voltage pulse is applied to the upper and lower electrodes, a dielectric barrier discharge is generated in the air gap outside the packaging bag. Simultaneously, the high-voltage pulse electric field couples through the non-metallic insulating packaging bag to the gas space inside the bag, ionizing or activating the gas and creating an active environment with sterilization properties inside the bag.

[0047] The working principle and workflow of this invention are as follows: When the high-voltage pulse source device is working, the DC power supply first stores energy in the charging and discharging capacitor through the capacitor charging and discharging module; the control signal is applied to the gate of the insulated gate bipolar transistor switch by the MCP1407 driver chip, causing the switch to turn on and off according to the set timing, the charging and discharging capacitor releases the stored energy and generates a unipolar pulse; after the unipolar pulse enters the full-bridge inverter circuit module, it is converted into a bipolar pulse under the control of the isolation drive module; the bipolar pulse is loaded onto the primary side of the pulse transformer, stepped up by the pulse transformer and output on the secondary side; after the secondary sides of multiple pulse transformers are connected in series and superimposed, a high-amplitude bipolar high-voltage pulse is formed and loaded onto the long gap dielectric barrier discharge electrode device through the wire.

[0048] When a bipolar high-voltage pulse is applied between the upper and lower electrodes, a high instantaneous electric field is rapidly established within the air gap between them. This instantaneous electric field can cause atmospheric pressure air to break down and form a low-temperature plasma. Because both the upper and lower electrodes have a polyimide dielectric layer, this layer limits the discharge current and prevents the discharge channel from remaining continuously open, allowing the discharge to occur in the form of short-duration filamentary micro-discharges, thereby reducing the risk of arc discharge and localized overheating.

[0049] In this example, the object to be processed is a sealed packaged food, which can be a sealed packaged dehydrated vegetable, fruit and vegetable product, dried food, or other packaged food suitable for low-temperature plasma treatment. During sterilization, the sealed packaged food is placed in the long-gap discharge area between the upper and lower electrodes; the distance between the upper and lower electrodes is adjusted so that the entire packaging bag is within the discharge area; the output voltage, pulse width, and repetition frequency of the high-voltage pulse source device are set; after the high-voltage pulse source device is activated, a bipolar high-voltage pulse is applied between the upper and lower electrodes. The upper electrode, lower electrode, polyimide dielectric layer, packaging bag material, and the gas space inside the packaging bag together form an equivalent capacitive coupling structure. Because the sealed packaging bag is made of non-metallic insulating packaging material, the packaging bag itself does not shield the high-voltage pulse electric field like metallic materials. Therefore, under the action of the bipolar high-voltage pulse, the packaging bag material undergoes dielectric polarization, and the pulse electric field can act on the gas space inside the packaging bag through the packaging bag material via capacitive coupling.

[0050] Specifically, the bipolar high-voltage pulse output by the high-voltage pulse source device has a high voltage amplitude and a fast pulse leading edge. When this pulse voltage is applied between the upper and lower electrodes, a strong instantaneous electric field is rapidly established between them. After the sealed packaged food is placed in this strong electric field region, the barrier dielectric polyimide, the dielectric layer of the packaging bag, and the gas space inside the packaging bag constitute a series dielectric discharge region. When the local electric field strength in the gas space inside the packaging bag reaches or approaches the gas ionization condition, the gas molecules inside the bag are ionized, excited, or activated, producing active ingredients with sterilization effects such as electrons, ions, ozone, reactive oxygen particles, and reactive nitrogen particles.

[0051] Therefore, this invention does not involve the external plasma passing entirely through the packaging bag to enter the interior. Instead, it utilizes the coupling characteristic of the non-metallic insulating packaging bag to a high-voltage pulsed electric field, allowing the high-voltage pulsed electric field to penetrate the packaging material and act on the gas space inside the bag, generating or activating sterilizing particles in situ within the bag. These active particles can diffuse within the sealed packaging bag and act on the food surface and the inner surface of the bag, thus achieving plasma sterilization of sealed packaged food without opening the bag. This method avoids secondary contamination caused by repackaging or external contact after sterilization.

[0052] Based on the above embodiments, the preferred, but not limited, operation method of the technical solution of this application is as follows: (1) Check whether the high voltage pulse source device, long gap dielectric barrier discharge electrode device and connecting wires are reliably connected, and confirm that the high voltage side of the pulse transformer is immersed in insulating oil; (2) Place the upper electrode and the lower electrode opposite each other, and set the discharge gap between the upper and lower electrodes according to the thickness of the sealed packaged food; (3) Place the sealed packaged food in the long gap discharge area between the upper and lower electrodes; (4) Set the output voltage, pulse width and repetition frequency of the high-voltage pulse source device according to the thickness of the packaging bag, the packaging material, the size of the gas space inside the packaging bag and the type of food; (5) Start the control signal to make the capacitor charging and discharging module, the full-bridge inverter circuit module and the pulse transformer module work in sequence, and generate a bipolar high-voltage pulse excited dielectric barrier discharge between the upper and lower electrodes; (6) Within the predetermined processing time, the sealed packaged food is subjected to non-opening plasma sterilization treatment, so that the air gap outside the packaging bag and the gas space inside the packaging bag generate or activate particles with sterilization effect. (7) After sterilization is completed within the predetermined time, turn off the high voltage pulse source device, and perform a safe discharge process on the energy storage capacitor and output terminal before taking out the material to be processed.

[0053] In summary, this application combines a multi-stage high-voltage pulse source with a long-gap dielectric barrier discharge structure to output high-amplitude bipolar high-voltage pulses under normal atmospheric pressure, thereby improving the breakdown capability, discharge stability, and plasma generation efficiency of the long-gap discharge. Because the sealed packaging bag uses non-metallic insulating materials and has an internal gas space, the high-voltage pulse electric field can act on the inside of the packaging bag through capacitive coupling, causing ionization and activation of the gas inside the bag. This generates active particles with sterilization effects in situ inside the packaging, achieving low-temperature sterilization of the food and the internal space of the packaging without opening the bag. This avoids secondary contamination caused by repackaging after sterilization or external contact, thus improving the hygiene, safety, and preservation effect of the food.

[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A plasma sterilization device for sealed packaged food excited by a high-voltage pulse source, characterized in that, include: A high-voltage pulse source includes a multi-stage pulse output circuit for generating bipolar high-voltage pulse output. Each stage of the pulse output circuit includes a capacitor charging and discharging module, a full-bridge inverter circuit module, and a pulse transformer module. A long-gap dielectric barrier discharge electrode device includes an upper electrode and a lower electrode. A bipolar high-voltage pulse is applied to the upper electrode and the lower electrode to form a long-gap discharge region for placing sealed packaged food.

2. The plasma sterilization device for sealed packaged food excited by a high-voltage pulse source according to claim 1, characterized in that, The pulse output circuits at each stage are connected in series and superimposed with the secondary outputs of the corresponding pulse transformer modules to form the bipolar high-voltage pulse output.

3. The high-voltage pulse source-excited closed-package food plasma sterilization device according to claim 2, characterized in that, Each stage of the pulse output circuit is equipped with a PCB board, and the high-voltage pulse source is equipped with a five-stage PCB board.

4. The plasma sterilization device for sealed packaged food excited by a high-voltage pulse source according to claim 2 or 3, characterized in that, The output terminal of the capacitor charging / discharging module is connected to the input terminal of the full-bridge inverter circuit module, and the output terminal of the full-bridge inverter circuit module is connected to the primary side of the pulse transformer module. The secondary side of the pulse transformer module serves as the boost output terminal of the pulse output circuit of that stage. The secondary sides of each stage of the pulse transformer module are connected in series to achieve voltage superposition, forming the bipolar high-voltage pulse output.

5. The plasma sterilization device for sealed packaged food excited by a high-voltage pulse source according to claim 1, characterized in that, The capacitor charging and discharging module includes a DC power input, a charging resistor, a charging and discharging capacitor, a fast recovery diode, a switching transistor, and an MCP1407 driver chip for controlling the switching transistor's conduction.

6. The high-voltage pulse source-excited closed-package food plasma sterilization device according to claim 5, characterized in that, The full-bridge inverter circuit module includes a full-bridge inverter circuit composed of four switching transistors and four isolation drive modules that drive each switching transistor respectively. The isolation drive module includes a UCC23313 driver chip and a QA151C isolation power supply to achieve high and low voltage isolation.

7. The high-voltage pulse source-excited closed-package food plasma sterilization device according to claim 5 or 6, characterized in that, The pulse transformer module uses an iron-based amorphous nanocrystalline alloy 1K107B iron core magnetic ring, and the winding uses DC silicone high-voltage wire. The pulse transformer module is wound in a way that the primary winding and the secondary winding are wound in parallel.

8. The high-voltage pulse source-excited closed-package food plasma sterilization device according to claim 7, characterized in that, The pulse transformer module is immersed in insulating oil, which covers the windings and high-voltage output parts of the pulse transformer module.

9. The plasma sterilization device for sealed packaged food excited by a high-voltage pulse source according to claim 1, characterized in that, Both the upper and lower electrodes are FPC flexible electrodes, comprising a copper conductive layer and a polyimide dielectric layer. The copper conductive layer of the upper electrode adopts a multi-parallel strip structure design, and the copper conductive layer of the lower electrode adopts a rectangular planar structure design. The upper electrode and the lower electrode are placed in a staggered relative manner, forming the long gap discharge region between them.

10. The high-voltage pulse source-excited closed-package food plasma sterilization device according to claim 9, characterized in that, Both the upper and lower electrodes are provided with pads, and the pads are electrically connected to the corresponding copper conductive layers. The positive output terminal of the high-voltage pulse source is connected to the pad of the upper electrode via a wire, and the negative output terminal of the high-voltage pulse source is connected to the pad of the lower electrode via a wire.

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