Grid voltage control method, grid voltage control circuit and x-ray machine suitable for x-ray machine

Abstract

The application discloses a grid voltage control method suitable for an X-ray machine, the X-ray machine comprising a carbon nanotube, and the grid voltage control method comprises the following steps: setting the voltage of the cathode as the reference ground of the grid power supply, so that the voltage of the grid floats on the voltage of the cathode; setting a series-connected switch assembly and an adjusting assembly between the grid power supply input and the grid, the switch assembly is used for realizing the conduction and the shutdown between the grid power supply and the grid, and the adjusting assembly is used for realizing the adjustment of the grid voltage between the minimum value and the maximum value, and the set tube current is obtained. The grid voltage control method has the advantages of fast switching speed of the grid voltage, can realize fast pulse exposure of the carbon nanotube ray source, has a narrow grid voltage range and high precision, can make the carbon nanotube current ripple small and the overshoot low, the grid voltage floats on the high voltage of the cathode, the voltage pressure difference is small, the insulation is good, the volume is small, and the cost is low.

Description

Technical Field

[0001] The present invention specifically relates to a gate voltage control method for an X-ray machine, a gate voltage control circuit for performing the gate voltage control method, and an X-ray machine including the gate voltage control circuit. Background Technology

[0002] Carbon nanotubes, a novel type of X-ray tube that has emerged in recent years, primarily utilize the tunneling effect of field emission cathode materials (also known as "cold cathodes") in a strong electric field environment. Internal electrons overcome the surface potential barrier and enter the external vacuum electric field, where they are accelerated and bombard the anode target, emitting X-rays. This strong electric field is called the grid voltage. Field emission electrons are almost entirely emitted from near the Fermi level of the material, resulting in significantly less energy dispersion compared to thermionic emission. The direction of field emission electrons is concentrated along the surface normal, making its directionality far superior to that of thermionic emission. This improved current emission consistency and more concentrated energy distribution lead to higher effective energy utilization of field emission materials, a significantly reduced proportion of ineffective energy absorbed by the target, and easier focusing. Furthermore, field emission does not require heating the cathode; it can be emitted instantaneously upon application of electricity, resulting in high speed.

[0003] Current solutions require boosting the gate voltage to -80KV using a voltage multiplier circuit, but the voltage rise time is slow, around 100ms, which fails to leverage the fast current response of carbon nanotubes. While using a multi-module series voltage multiplier can solve the voltage rise time problem, it requires a larger transformer with increased windings and a larger volume for insulation, significantly increasing cost and size. Furthermore, due to the low gate power, the rapid drop in gate voltage (i.e., the rapid decrease in tube current) during pulse exposure also poses a problem.

[0004] On the other hand, the tube current of carbon nanotubes is highly sensitive to changes in gate voltage. Within a tube current variation range of 0-1.2mA, a gate voltage change of around 0.8mA and approximately 10V will result in a 0.1mA change in tube current. Therefore, adjusting a 10V voltage accuracy within a -80KV gate voltage range is difficult and challenging to achieve. Existing technology designs result in poor current accuracy and high ripple. Furthermore, achieving a -80KV gate voltage from a 4KV requirement would lead to higher costs and increase product size to ensure safe insulation distances.

[0005] The above background information is provided only to aid in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this invention. In the absence of clear evidence that the above information was disclosed before the filing date of this invention, the above background information should not be used to evaluate the novelty and inventiveness of this invention. Summary of the Invention

[0006] In view of this, in order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a gate voltage control circuit with fast gate voltage switching speed and fast response speed.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A gate voltage control method for an X-ray machine, the X-ray machine including a carbon nanotube, the carbon nanotube including an anode, a cathode and a gate, the gate being connected to a gate power input; The gate voltage control method includes the following steps: The voltage of the cathode is set as the reference ground of the gate power supply, so that the voltage of the gate floats on the voltage of the cathode; A switching assembly and an adjustment assembly are connected in series between the gate power input and the gate. The switching assembly is used to turn the gate power supply and the gate on and off, and the adjustment assembly is used to adjust the gate voltage between a minimum value and a maximum value, and to obtain a set tube current.

[0008] According to some preferred embodiments of the invention, the switching and / or regulating components comprise four metal-oxide-semiconductor field-effect transistors connected in series. A first group of MOSFETs serves as a switch, i.e., the switching assembly; the second group adjusts the gate voltage of this design by changing the on-resistance of the MOSFETs through control of their drive voltage. The two groups are used together to achieve the function of fast switching of the X-ray tube, i.e., pulse exposure.

[0009] According to some preferred embodiments of the present invention, a transformer module and a voltage multiplier module are disposed between the gate power input and the gate. One side of the transformer module is connected to the gate power input, and the other side is connected to the voltage multiplier module. The switching assembly and the regulating assembly are disposed between the voltage multiplier module and the gate. The transformer module enables the gate power supply to float isolated on the cathode high voltage.

[0010] According to some preferred embodiments of the present invention, the transformer module, the voltage multiplier module, the switching assembly, and the regulating assembly are arranged sequentially; or, the transformer module, the voltage multiplier module, the regulating assembly, and the switching assembly are arranged sequentially.

[0011] According to some preferred embodiments of the present invention, the transformer module includes a primary coil, a secondary coil, and a core, wherein the primary coil is connected to a gate power input, and the secondary coil is connected to the voltage multiplier module.

[0012] According to some preferred embodiments of the present invention, the voltage multiplier module is a voltage doubler circuit.

[0013] According to some preferred embodiments of the present invention, the transformer module, voltage multiplier module, switching assembly and regulating assembly constitute a gate voltage control circuit, the output of which is 0.1~4kV.

[0014] According to some preferred embodiments of the present invention, the anode is connected to a high-voltage circuit; the output voltage of the high-voltage circuit is 40kV~80kV.

[0015] The present invention also provides a gate voltage control circuit for performing the gate voltage control method described above, and an X-ray machine including the gate voltage control circuit described above.

[0016] Compared with the prior art, the advantages of the present invention are: the gate voltage control method of the present invention has a fast gate voltage switching speed, which enables the carbon nanotube X-ray source to achieve rapid pulse exposure; the gate voltage range is narrow and the precision is high, resulting in small current ripple and low overshoot in the carbon nanotube; the gate voltage floats on the cathode high voltage, resulting in small voltage difference, good insulation, small size, and low cost. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram showing the connection between the gate voltage control circuit, the high voltage circuit, and the carbon nanotube in a preferred embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] like Figure 1As shown, the X-ray machine in this embodiment includes a housing and carbon nanotubes (carbon nanotube X-ray tubes) located inside the housing, a high-voltage circuit, a grid voltage control circuit, a signal feedback circuit, an arc detection circuit, and other conventional components. The carbon nanotube includes an anode, a cathode, and a grid. The output of the high-voltage circuit is connected to the anode, and the output voltage of the high-voltage circuit is 40kV~80kV. In this embodiment, the voltage of the cathode is set as the reference ground of the grid power supply, so that the voltage of the grid floats on the voltage of the cathode. In this embodiment, the cathode is also grounded.

[0021] In this embodiment, the gate power supply is a fixed 4KV. The gate power supply is isolated and floated on the high voltage of the cathode through a transformer (hereinafter referred to as the transformer module), and the voltage of the cathode serves as the reference ground for this gate power supply. This achieves a voltage difference between the cathode and the gate, and the 4KV voltage is easier to obtain by directly using a voltage multiplier circuit.

[0022] The gate voltage control circuit is located between the gate power input and the gate, and includes a transformer module, a voltage multiplier module, a switching assembly, and a regulating assembly. One side of the transformer module is connected to the gate power input, and the other side is connected to the voltage multiplier module. The switching assembly and the regulating assembly are located between the voltage multiplier module and the gate.

[0023] The positions of the switching component and the regulating component can be interchanged, i.e., the transformer module, voltage multiplier module, switching component, and regulating component are arranged sequentially; or, the transformer module, voltage multiplier module, regulating component, and switching component are arranged sequentially. In this embodiment, the transformer module, voltage multiplier module, switching component, and regulating component are preferably arranged sequentially. The output of the gate voltage control circuit is 0.1~4kV.

[0024] The switching and regulating components comprise four series-connected metal-oxide-semiconductor field-effect transistors (MOSFETs). Using MOSFETs to control the gate voltage of the carbon nanotubes enables fast switching and high-precision voltage regulation.

[0025] In this embodiment, two sets of four 1.5KV MOSFETs connected in series are added between the gate power input and the gate connection (switching and regulation components). The first set of four MOSFETs in series acts as a fast switching component. When turned on, a 4KV gate power supply is applied to the gate, providing the maximum voltage. When turned off, the gate voltage is zero, and there is no tube current. This enables rapid pulse exposure of carbon nanotubes. The second set of four MOSFETs in series acts as a voltage regulation component. Different V-GS voltages result in different on-resistances. By adjusting the V-GS voltage, the V-DS voltage is changed. This allows for adjustment of the gate voltage from 0-4KV, thereby achieving a closed-loop control to obtain the set tube current. The magnitude of the tube current is controlled by the gate voltage; the higher the gate voltage, the higher the tube current; the lower the gate voltage, the lower the tube current; below a certain value, there is no tube current. The purpose of this embodiment is to achieve adjustable tube voltage and tube current. Furthermore, the cathode grounding method in this embodiment can leverage the advantage of rapid current rise in the sub-tube, making it applicable in the medical field.

[0026] The transformer module includes a primary coil, a secondary coil, and a core. The primary coil is connected to the gate power input, and the secondary coil is connected to the voltage multiplier module. The voltage multiplier module is a voltage doubler circuit.

[0027] Preferably, in this embodiment, a sampling module is further provided between the regulating component and the gate for detecting the gate voltage.

[0028] The gate voltage control method for X-ray machines based on the above gate voltage control circuit includes the following steps: Set the cathode voltage as the reference ground for the gate power supply, so that the gate voltage floats on the cathode voltage. A switching component and a regulating component are connected in series between the gate power input and the gate. The switching component is used to turn the gate power supply and the gate on and off, while the regulating component is used to adjust the gate voltage between its minimum and maximum values ​​to obtain the set transistor current. The transistor current is set by the user, and the circuit automatically adjusts the gate voltage to obtain the corresponding transistor current based on the user's settings.

[0029] In this embodiment, the anode is connected to high voltage, and the cathode is grounded. The gate does not need to float on the high voltage of the cathode. Only the 4KV insulation withstand voltage needs to be considered, and the MOSFET drive isolation voltage is reduced. This invention connects the anode to an eight-times high-voltage power supply input. The advantage of this design is that the cathode can be grounded, the gate only has a 4KV high voltage, and insulation is easy to implement because the distance between the gate and the cathode tube is very close. With a traditional high-voltage cathode, the insulation of the tube itself needs to be considered. The gate voltage only needs to be stepped up by a normal transformer, connected in series with the MOSFET, and then connected to the gate. The MOSFET controls the magnitude and switching of the gate voltage. This invention controls the 4KV voltage applied to the gate by the switching on / off state of two sets of MOSFETs, while the 4KV high-voltage power supply remains unchanged, achieving both fast response and high control accuracy, and is also safer and more reliable. It has the following advantages: 1. The fast gate voltage switching speed and fast response speed enable the carbon nanotube X-ray source to achieve rapid pulse exposure, giving full play to the rapid start-up advantage of carbon nanotubes.

[0030] 2. Narrow gate voltage range and high precision result in low current ripple and low overshoot in carbon nanotubes.

[0031] 3. The gate voltage floats on the cathode high voltage, resulting in a small voltage difference, good insulation, small size, and low cost.

[0032] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A grid voltage control method suitable for X-ray machines, characterized in that: The X-ray machine includes carbon nanotubes, each carbon nanotube comprising an anode, a cathode, and a gate, wherein the gate is connected to a power input. The gate voltage control method includes the following steps: The voltage of the cathode is set as the reference ground of the gate power supply, so that the voltage of the gate floats on the voltage of the cathode; A switching assembly and an adjustment assembly are connected in series between the gate power input and the gate. The switching assembly is used to turn the gate power supply and the gate on and off, and the adjustment assembly is used to adjust the gate voltage between a minimum value and a maximum value, and to obtain a set tube current.

2. The gate voltage control method according to claim 1, characterized in that: The switching and / or regulating components include four metal-oxide-semiconductor field-effect transistors connected in series.

3. The gate voltage control method according to claim 1, characterized in that: A transformer module and a voltage multiplier module are provided between the gate power input and the gate. One side of the transformer module is connected to the gate power input, and the other side is connected to the voltage multiplier module. The switching assembly and the regulating assembly are provided between the voltage multiplier module and the gate.

4. The gate voltage control method according to claim 3, characterized in that: The transformer module, voltage multiplier module, switch assembly, and regulating assembly are arranged in sequence; or, the transformer module, voltage multiplier module, regulating assembly, and switch assembly are arranged in sequence.

5. The gate voltage control method according to claim 3, characterized in that: The transformer module includes a primary coil, a secondary coil, and a core. The primary coil is connected to the gate power input, and the secondary coil is connected to the voltage multiplier module.

6. The gate voltage control method according to claim 3, characterized in that: The voltage multiplier module is a voltage multiplier circuit.

7. The gate voltage control method according to claim 3, characterized in that: The transformer module, voltage multiplier module, switching assembly, and regulating assembly constitute a gate voltage control circuit, and the output of the gate voltage control circuit is 0.1~4kV.

8. The gate voltage control method according to claim 1, characterized in that: The anode is connected to a high-voltage circuit; the output voltage of the high-voltage circuit is 40kV~80kV.

9. A gate voltage control circuit for performing the gate voltage control method as described in any one of claims 1-8.

10. An X-ray machine including the gate voltage control circuit as described in claim 9.

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