Pulse transformer with high transformation ratio and fast pulse output capability

Abstract

The invention discloses a pulse transformer giving consideration to both high transformation ratio and fast pulse output capability, and relates to the technical field of pulse transformers, the pulse transformer comprises an insulating inner core, a variable impedance line and an insulating film wound on the insulating inner core; the variable impedance line has a gradual change width corresponding to a transformation ratio demand and a transmission demand. The pulse transformer has the advantages that impedance change is achieved through gradual change of the variable impedance line serving as the conducting layer part on the pulse transformer, multiple times of reflection and transmission occur in the electromagnetic wave propagation process through impedance change, pulse width compression is achieved, and therefore the pulse transformer has the high boosting capacity and the fast pulse output capacity at the same time.

Description

Technical Field

[0001] This application relates to the technical field of pulse transformers, and particularly to a pulse transformer that takes into account both a high turns ratio and a fast pulse output capability. Background Art

[0002] A pulse transformer is a transformer specifically designed to generate high-voltage short pulses. Its core function is to convert a fast transient signal (such as a square wave or a step pulse) at the low-voltage end into a high-voltage pulse output through magnetic coupling. It plays an important role in the field of high-voltage pulse generation, especially suitable for application scenarios that require electrical isolation, high voltage gain, and fast rise time. However, pulse transformers also have significant drawbacks: with a high turns ratio, it results in a large internal resistance and limited output capability on low-impedance loads; its voltage boosting ability is usually positively correlated with structural parameters, that is, the more turns and the larger the structural size, the stronger the voltage boosting ability, but the more turns and the larger the structural size, it will also cause the output voltage to slow down. As a result, the pulse transformer cannot take into account both a high voltage boosting ability and a fast pulse output.

[0003] The patent "A High-Voltage Spiral Doubler", publication number: CN118487490A, publication date: July 12, 2024, specifically discloses including an outer metal film, an inner metal film, a first insulating film, and a second insulating film. The outer metal film and the inner metal film are wound in a spiral double-wire structure. A first insulating film is provided between the outer metal film and the inner metal film, and a second insulating film is provided between the inner metal film and the outer metal film. The outer metal film and the inner metal film are wound in a spiral double-wire structure to form N turns of winding, and the central positions of any two adjacent turns are at least different by a set offset distance in the axial direction. This solution improves the insulation effect of the spiral transformer by increasing the insulation distance. However, there is still a problem that it cannot take into account a fast pulse output when a high voltage boosting ability is required.

[0004] The patent "Coaxial Spiral Reentrant Multiplier Forming Line", publication number: CN106301294A, publication date: August 19, 2016, specifically discloses including three parts: an outer wire of the forming line, a spiral reentrant inner wire, and a main switch. The spiral reentrant wire includes multiple spiral wire sections with different pitches. This solution enables the pulse power device to develop in the direction of higher voltage through pitch differences. However, the problem of reduced pulse output efficiency caused by an increased voltage boosting ability has still not been solved. Summary of the Invention

[0005] In view of the technical problem in the prior art that a pulse transformer cannot balance high step-up ability and fast pulse output, the present application provides a pulse transformer that can balance high turns ratio and fast pulse output ability. By gradually changing the impedance of the variable impedance line that is part of the conductive layer on the pulse transformer, the change of impedance is realized. Through the impedance change, multiple reflections and transmissions occur during the propagation of electromagnetic waves, realizing the compression of the pulse width, so as to balance the fast pulse output ability while the pulse transformer has high step-up ability.

[0006] To achieve the above technical purpose, a technical solution provided by the present application is a pulse transformer that can balance high turns ratio and fast pulse output ability, including: an insulating inner core, a variable impedance line, and an insulating film wound around the insulating inner core; wherein, the variable impedance line has a gradually changing width corresponding to the turns ratio requirement and the transmission requirement.

[0007] Further, the variable impedance line has an exponentially gradually changing width corresponding to the turns ratio requirement and the transmission requirement.

[0008] Further, the variable impedance line has a linearly gradually changing width corresponding to the turns ratio requirement and the transmission requirement.

[0009] Further, one or more segments of the variable impedance line have an exponentially gradually changing width, and one or more segments of the variable impedance line have a linearly gradually changing width.

[0010] Further, the insulating film, the variable impedance line, the insulating film, and the variable impedance line are sequentially wound around the outer layer of the insulating inner core from the inside out.

[0011] Further, the decreasing coefficient of the gradually changing width is calculated according to the step-up ratio, the pulse front time, and the pulse peaking degree.

[0012] Further, the exponentially gradually changing width ratio and the linearly gradually changing width ratio are comprehensively calculated according to the manufacturing process cost of the exponentially gradually changing width, the manufacturing process cost of the linearly gradually changing width, the pulse front time corresponding to the exponentially gradually changing width, and the pulse front time corresponding to the linearly gradually changing width.

[0013] Further, the variable impedance line is a metal foil with a gradually changing width.

[0014] Further, the variable impedance line is printed on the insulating film.

[0015] Further, the thickness of the variable impedance line is obtained according to the skin effect parameter.

[0016] Advantages of the present application: By gradually changing the width of the variable impedance line, the impedance change of the variable impedance line is achieved. Using the impedance change, multiple reflections and transmissions occur during the propagation of electromagnetic waves. The reflected wave and the transmitted wave are superimposed in the transmission line to form a complex waveform. According to the variable ratio requirement and the transmission requirement, the trend of the width change of the variable impedance line is calculated, so that the reflected wave and the transmitted wave interfere with each other at specific positions and times, thereby compressing the pulse width and achieving both the requirement of high voltage boost multiple and the fast pulse output ability. Brief Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the gradually changing width of a pulse transformer that takes into account both high variable ratio and fast pulse output ability of the present application.

[0018] Figure 2 It is a schematic diagram of the structure of a pulse transformer that takes into account both high variable ratio and fast pulse output ability of the present application. Detailed Embodiment

[0019] To make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only the best embodiments of the present application, which are only used to explain the present application and do not limit the protection scope of the present application. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present application.

[0020] As Figure 1 shown, as Embodiment 1 of the present application, a pulse transformer that takes into account both high variable ratio and fast pulse output ability includes: An insulating inner core, a variable impedance line, and an insulating film wound around the insulating inner core; Among them, the variable impedance line has a gradually changing width corresponding to the variable ratio requirement and the transmission requirement.

[0021] In this embodiment, the variable impedance line and the insulating film are wound around the insulating inner core to form a spiral structure, and the insulating film and the variable impedance line are wound at intervals. Among them, the insulating film, the variable impedance line, the insulating film, and the variable impedance line are successively wound from the inside to the outside of the insulating inner core. The gradually changing width of the variable impedance line is set according to the variable ratio requirement and the transmission requirement of the pulse transformer. The impedance changes along the direction of electromagnetic wave transmission through the width change of the variable impedance line, thereby compensating for the problem of waveform change during the voltage boost process of the spiral transformer.

[0022] Specifically, a spiral transformer is usually composed of two alternating layers of metal tape and two layers of insulating layer. The metal layer mostly uses highly conductive copper tape, which is mainly used for the transmission and coupling of electromagnetic energy, while the insulating layer functions as electrical isolation and electric field control, preventing electric breakdown or interlayer short circuit while carrying high-voltage transmission. The core working mechanism of the spiral transformer is based on the basic principle of the propagation and reflection of electromagnetic waves in a transmission line: when a high-voltage wave is excited at the input end, it will propagate along the spiral transmission path until it reaches the open-circuit boundary at the end of the spiral. Since there is no load connected at the end, the electromagnetic wave cannot continue to move forward and is reflected back. The reflected wave propagates in the reverse direction and superimposes with the remaining forward wave along the way. This process forms the voltage output waveform at the load end. However, as the number of turns of the spiral increases, the path length of the electromagnetic wave transmission inside increases, resulting in an increase in its electrical pulse width. In order to obtain fast-pulse high voltage, it is usually necessary to shape and peak the electrical pulse output by the spiral transformer. The shaping and peaking structure works at high voltages of hundreds of kilovolts or even hundreds of kilovolts. Limited by the insulation characteristics, it is difficult to miniaturize the device structure parameters.

[0023] In this embodiment, the insulating film is a PP film (polypropylene film), and the variable-impedance line is a metal foil with a gradually changing width. By changing the width of the variable-impedance line, the impedance change of the variable-impedance line is realized. The impedance change causes the electromagnetic wave to undergo multiple reflections and transmissions during the propagation process. The complex waveform is formed by the superposition of the reflected wave and the transmitted wave in the transmission line. According to the turn ratio requirement and the transmission requirement, the trend of the width change of the variable-impedance line is calculated, so that the reflected wave and the transmitted wave interfere with each other at a specific position and time, thereby compressing the pulse width and achieving both the requirement of a high step-up multiple and the ability of fast-pulse output.

[0024] Taking the strip-wound pulse transformer as an example, the inductance per unit length is: ; where L represents the inductance per unit length of the winding, represents the number of turns of the winding, represents the vacuum permeability, represents the average radius of the winding, represents the width of the winding.

[0025] Its capacitance per unit length is: ; where C represents the capacitance per unit length of the winding, represents the relative permittivity, represents the vacuum permittivity, represents the thickness of a single insulating layer.

[0026] A pulse transformer with a strip transmission line as the basic structure, its wave impedance is determined by the capacitance and inductance per unit length, and is: ; wherein, represents the wave impedance of the pulse transformer, represents the equivalent inductance of the variable impedance line calculated according to the inductance per unit length, represents the equivalent capacitance of the variable impedance line calculated according to the inductance per unit length.

[0027] When an electrical pulse is transmitted in the variable impedance line, the variable impedance line redistributes the energy of the incident wave in time through the impedance gradient distributed in space, and realizes pulse compression by coherent superposition. Therefore, by setting the width of the variable impedance line with different gradient amplitudes according to the turns ratio requirement and transmission requirement to adapt to different input pulse shapes, efficient pulse compression is achieved. The voltage and current on the variable impedance line satisfy the modified telegraph equation: ; wherein, represents the partial derivative of voltage V with respect to time t, represents the equivalent inductance of the variable impedance line at the z position, represents the partial derivative of current I with respect to time t, represents the equivalent capacitance of the variable impedance line at the z position.

[0028] During the transmission of the electrical pulse, the phase velocity of the electromagnetic wave can be described as: ; Since the specific values of the equivalent inductance and equivalent capacitance of the variable impedance line change with position, reflection and refraction of the electromagnetic wave occur during transmission. By designing the impedance gradient to gradually decrease, the phase velocities at different stages of the electrical pulse are different. After passing through the variable impedance line, significant pulse compression will occur.

[0029] As Figure 2 shown, the winding composed of the variable impedance line and the insulating film passes through the protection resistor and the primary switch to the high-voltage DC power supply voltage . When the primary switch is closed, while the electrical pulse is being pulse-compressed during transmission in the variable impedance line, it also reaches the inner open port from the outer feeding end of the pulse transformer.

[0030] The implementation process of this embodiment is mainly as follows: Determine the turns ratio requirement and transmission requirement of the pulse transformer; Calculate the gradient width data of the variable impedance line according to the turns ratio requirement, transmission requirement and basic parameters of the pulse transformer; Process the variable impedance line and the insulating film with corresponding specifications according to the gradient width data; Wind the variable impedance line and the insulating film on the insulating inner core in the pattern of insulating film - variable impedance line - insulating film - variable impedance line to construct a pulse transformer.

[0031] In this embodiment, the turns ratio requirement at least includes the step-up ratio, the transmission requirement at least includes the pulse front time, the basic parameters of the pulse transformer at least include the primary and secondary electrical parameters and the structural parameters, the primary and secondary electrical parameters at least include the turns ratio, inductance, and capacitance of the primary and secondary coils, and the structural parameters at least include the structural dimensions of the pulse transformer.

[0032] As the second embodiment of the present application, the difference from the first embodiment is that the variable impedance line has an exponential gradient width corresponding to the turns ratio requirement and the transmission requirement.

[0033] When the variable impedance line changes regularly in an exponential form, its width satisfies: ; where, represents the width of the variable impedance line when the helical expansion length is z during regular change in exponential form, represents the decreasing coefficient during regular change in exponential form, represents the initial width of the variable impedance line.

[0034] At this time, calculate the decreasing coefficient of the exponential form regular change according to the step-up ratio, pulse front time, and pulse peaking degree. The pulse peaking degree is calculated according to the distortion degree of the pulse signal during transmission. The lower the pulse peaking degree, the better the quality of the pulse signal and the closer the waveform is to the ideal state. In some cases, the dimensional weights of the step-up ratio, pulse front time, and pulse peaking degree can be obtained according to the turns ratio, pulse front time, and pulse peaking degree of the historical pulse transformer and the impedance data, or the dimensional weights can also be obtained according to the laboratory data and expert experience.

[0035] As the third embodiment of the present application, the differences from the first and second embodiments are that the variable impedance line has a linear gradient width corresponding to the turns ratio requirement and the transmission requirement.

[0036] When the variable impedance line changes regularly in a linear form, its width satisfies: ; where, represents the width of the variable impedance line when the helical expansion length is during regular change in linear form, represents the decreasing coefficient during regular change in linear form, represents the initial width of the variable impedance line.

[0037] Similarly, the decreasing coefficient of the linear regular change is calculated based on the boost ratio, the pulse front time and the pulse peaking degree.

[0038] As the fourth embodiment of the present application, it is different from the first, second and third embodiments in that one or more sections of the variable impedance line have an exponential gradient width, and one or more sections of the variable impedance line have a linear gradient width.

[0039] In the actual manufacturing process, the exponential gradient width is more difficult to produce, but the exponential gradient width improves the transmission efficiency more than the linear gradient width. Therefore, the variable impedance line is designed to have at least one section of exponential gradient width and one section of linear gradient width. The exponential gradient width is used to improve the transmission efficiency, and the linear gradient width compensates for the production cost caused by the exponential gradient width. Through the mutual compensation of the exponential gradient width and the linear gradient width, the pulse transformer can meet a larger range of transmission efficiency requirements while reducing the production difficulty and cost caused by all exponential gradients.

[0040] Specifically, an optimization objective function is constructed according to the manufacturing process cost and the pulse front time. When the highest possible transmission efficiency is required, the exponential gradient width ratio and the linear gradient width ratio are comprehensively calculated according to the manufacturing process cost of the exponential gradient width, the manufacturing process cost of the linear gradient width, the pulse front time corresponding to the exponential gradient width, and the pulse front time corresponding to the linear gradient width. This can maximize the transmission efficiency of the pulse transformer under limited manufacturing process costs.

[0041] In this embodiment, the difference from the first embodiment, the second embodiment and the third embodiment is that the variable impedance line is printed on the insulating film.

[0042] In actual situations, the conductive layer of the pulse transformer is expected to be thicker to achieve better conductivity, but the conductivity of metal printing is relatively poor compared to that of metal foil, so metal foil is usually used to achieve better conductivity. In this embodiment, the conductivity degradation problem caused by metal printing is balanced by exponential gradient width, and the manufacturing difficulty caused by exponential gradient width is compensated by metal printing, thereby reducing the manufacturing difficulty and cost, and improving the transmission efficiency of the pulse transformer.

[0043] At the same time, since the pulse width of the pulse voltage affects the breakdown path of the insulating material, the increase in pulse width can easily lead to insulation failure of the pulse transformer. The present application compensates for the increase in pulse width caused by the voltage boost by using the gradual width of the variable impedance line, thereby improving the insulation performance of the entire pulse transformer and reducing the possibility of insulation failure. There is no need for an overly thick insulating film, which further reduces the volume of the pulse transformer and improves the insulation reliability of the pulse transformer.

[0044] In this embodiment, the thickness of the variable impedance line is obtained according to the skin effect parameter.

[0045] The skin effect refers to the phenomenon that when an alternating current or an alternating electromagnetic field passes through a conductor, the current tends to concentrate in a thin layer on the surface of the conductor. Based on the skin effect, the skin depth is calculated according to the pulse frequency, magnetic permeability, and conductivity. The thickness of the variable impedance line is greater than or equal to the skin depth to ensure the effective conduction of the current.

[0046] The above-mentioned specific implementation manner is the preferred implementation manner of the pulse transformer of the present application that takes into account the high turns ratio and the fast pulse output ability. It does not limit the specific scope of the present application. The scope of the present application includes but is not limited to this specific implementation manner. Any equivalent changes made according to the shape and structure of the present application are within the protection scope of the present application.

Claims

1. A pulse transformer that takes into account both a high turns ratio and a fast pulse output capability, characterized in that: Comprising: An insulating inner core, a variable impedance line, and an insulating film wound around the insulating inner core; Wherein, the variable impedance line has a gradually changing width corresponding to the turns ratio requirement and the transmission requirement.

2. The pulse transformer that takes into account both a high turns ratio and a fast pulse output ability as described in claim 1, characterized in that: The variable impedance line has an exponentially gradually changing width corresponding to the turns ratio requirement and the transmission requirement.

3. The pulse transformer that takes into account both a high turns ratio and a fast pulse output ability as described in claim 1, characterized in that: The variable impedance line has a linearly gradually changing width corresponding to the turns ratio requirement and the transmission requirement.

4. The pulse transformer that takes into account both a high turns ratio and a fast pulse output ability as described in claim 1, characterized in that: One or more segments of the variable impedance line have an exponentially gradually changing width, and one or more segments of the variable impedance line have a linearly gradually changing width.

5. The pulse transformer that takes into account both a high turns ratio and a fast pulse output ability as described in claim 1, characterized in that: The insulating film, the variable impedance line, the insulating film, and the variable impedance line are sequentially wound around the outer layer of the insulating inner core from the inside out.

6. The pulse transformer that takes into account both a high turns ratio and a fast pulse output ability as described in claim 1, characterized in that: The decreasing coefficient of the gradually changing width is calculated based on the step-up ratio, the pulse front time, and the pulse peaking degree.

7. The pulse transformer that takes into account both a high turns ratio and a fast pulse output ability as described in claim 4, characterized in that: The exponentially gradually changing width ratio and the linearly gradually changing width ratio are comprehensively calculated based on the manufacturing process cost of the exponentially gradually changing width, the manufacturing process cost of the linearly gradually changing width, the pulse front time corresponding to the exponentially gradually changing width, and the pulse front time corresponding to the linearly gradually changing width.

8. The pulse transformer that takes into account both a high turns ratio and a fast pulse output ability as described in claim 1, characterized in that: The variable impedance line is a metal foil with a gradually changing width.

9. The pulse transformer that takes into account both a high turns ratio and a fast pulse output ability as described in claim 2 or 4, characterized in that: The variable impedance line is printed on the insulating film.

10. The pulse transformer that takes into account both a high turns ratio and a fast pulse output ability as described in claim 1, characterized in that: The thickness of the variable impedance line is obtained according to the skin effect parameter.

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