Isolated resonant power supply circuit, magnetic resonance imaging system and air-core transformer

Abstract

The embodiment of the invention provides an isolated resonant power supply circuit, a magnetic resonance imaging system and an air-core transformer, the isolated resonant power supply circuit is arranged in a scanning room of the magnetic resonance imaging system, the isolated resonant power supply circuit comprises an inverter circuit, a resonant transformation circuit and a rectifying circuit, the inverter circuit is connected with the resonant transformation circuit, and the resonant transformation circuit is connected with the rectifying circuit. The converter is connected with the resonant transformation circuit and is used for converting input direct current into alternating current and outputting the alternating current to the resonant transformation circuit; the resonant transformation circuit is used for carrying out resonant conversion and transformation on the alternating current and then outputting the alternating current to the rectifying circuit; the rectifying circuit is used for rectifying the alternating-current output voltage output by the resonant transformation circuit into direct-current voltage to be output for power supply; wherein the resonant transformation circuit comprises a variable capacitance circuit and an inductor, and the equivalent capacitance value of the variable capacitance circuit is changed by changing the input voltage of the variable capacitance circuit.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of medical equipment technology, and in particular to an isolated resonant power supply circuit, a magnetic resonance imaging system, and an air-core transformer. Background Art

[0002] Magnetic resonance (MR) imaging systems have been widely used in the field of medical diagnosis. Magnetic resonance systems usually have a main magnet, a gradient amplifier, a radio frequency amplifier, a gradient coil, a transmission chain module, a transmission / receiving coil, a receiving chain module, etc. Among them, the transmission chain module generates a radio frequency pulse signal and transmits it to the transmission / receiving coil. The transmission / receiving coil generates a radio frequency excitation signal to excite the scanned object to generate a magnetic resonance signal. After the excitation is completed, the transmission / receiving coil collects the magnetic resonance signal after spatial encoding to reconstruct the medical image.

[0003] At present, it is hoped that the gradient amplifier, gradient coil assembly, radio frequency amplifier, and radio frequency coil assembly are all arranged in the scanning room of the magnetic resonance imaging system. In addition, the power supply also needs to be placed in the scanning room to supply power to one or more of the above components in the scanning room. The commonly used power supply is based on a non-isolated buck topology structure, using a switch tube as a switch, and the switching frequency is high enough, that is, a stable voltage can be output to supply power. Summary of the invention

[0004] Embodiments of the present application provide an isolated resonant power supply circuit, a magnetic resonance imaging system, and an air-core transformer.

[0005] According to one aspect of an embodiment of the present application, there is provided an isolated resonant power supply circuit, which is arranged in a scanning room of a magnetic resonance imaging system, wherein the isolated resonant power supply circuit comprises: an inverter circuit, a resonant transformer circuit and a rectifier circuit;

[0006] The inverter circuit is connected to the resonant transformer circuit and is used to convert the input direct current into alternating current and output it to the resonant transformer circuit;

[0007] The resonant transformer circuit is used to perform resonant conversion on the alternating current and then output the transformed alternating current to the rectifier circuit;

[0008] The rectifier circuit is used to rectify the AC output voltage output by the resonant transformer circuit into a DC voltage output power supply;

[0009] The resonant voltage transformer circuit includes a variable capacitance circuit and an inductor, and the equivalent capacitance value of the variable capacitance circuit is changed by changing the input voltage of the variable capacitance circuit.

[0010] According to one aspect of an embodiment of the present application, a magnetic resonance imaging system is provided, the system comprising:

[0011] A main magnet, used for generating a main magnetic field;

[0012] Gradient coil assembly;

[0013] a gradient amplifier, for exciting the gradient coil assembly to generate a gradient magnetic field on a selected gradient axis so as to apply the gradient magnetic field to the main magnetic field;

[0014] Radio frequency coil assembly;

[0015] A radio frequency amplifier, used to excite the radio frequency coil assembly to generate a radio frequency signal;

[0016] The isolated resonant power supply circuit of the aforementioned aspect is arranged in a scanning room of the magnetic resonance imaging system and supplies power to devices in the scanning room.

[0017] According to one aspect of an embodiment of the present application, there is provided an air-core transformer, the air-core transformer comprising a skeleton and a first number of windings wound on the skeleton, each winding being formed by a wire harness being wound multiple times on the skeleton, each wire harness comprising a second number of winding wires twisted together;

[0018] Among them, the third number of winding wires in each winding serves as the primary winding, and both ends of the third number of winding wires are connected to the primary circuit of the air-core transformer; the fourth number of winding wires in each winding serves as the secondary winding, and both ends of the fourth number of winding wires are connected to the secondary circuit of the air-core transformer; the first number is an integer greater than or equal to 1, and the second number, the third number, and the fourth number are all integers greater than 1.

[0019] According to one aspect of an embodiment of the present application, a magnetic resonance imaging system is provided, comprising:

[0020] A main magnet, used for generating a main magnetic field;

[0021] Gradient coil assembly;

[0022] a gradient amplifier, for exciting the gradient coil assembly to generate a gradient magnetic field on a selected gradient axis so as to apply the gradient magnetic field to the main magnetic field;

[0023] Radio frequency coil assembly;

[0024] A radio frequency amplifier, used to excite the radio frequency coil assembly to generate a radio frequency signal;

[0025] A power supply circuit, which is arranged in a scanning room of the magnetic resonance imaging system and supplies power to devices in the scanning room;

[0026] The air-core transformer of the aforementioned aspect is provided in the power supply circuit.

[0027] One of the beneficial effects of the embodiment of the present application is that: through the isolated resonant power supply circuit in the embodiment of the present application, a zero voltage switching (ZVS) soft switching method can be adopted, so even in the case of high input voltage, the effect of reducing switching loss can be achieved. In addition, there is no need to adjust the switching frequency, and the power supply circuit can operate at a fixed switching frequency of more than 1MHz, which can avoid the noise interference of the power supply circuit to the magnetic resonance imaging system and make the output voltage more stable.

[0028] One of the beneficial effects of the embodiments of the present application is that the air-core transformer in the embodiments of the present application can solve the problem that the traditional magnetic core cannot work in a strong magnetic field environment, and can improve the coupling coefficient between the primary and secondary sides of the transformer.

[0029] With reference to the following description and accompanying drawings, the specific implementation of the embodiment of the present application is disclosed in detail, indicating the way in which the principle of the embodiment of the present application can be adopted. It should be understood that the implementation of the present application is not limited in scope. Within the scope of the spirit and clauses of the attached claims, the implementation of the present application includes many changes, modifications and equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The included drawings are used to provide a further understanding of the embodiments of the present application, which constitute a part of the specification, are used to illustrate the implementation methods of the present application, and together with the text description, explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other implementation methods can be obtained based on these drawings without creative work. In the drawings:

[0031] Figure 1 is a schematic diagram of a magnetic resonance imaging system according to an embodiment of the present application;

[0032] Figure 2 is a schematic diagram of an isolated resonant power supply circuit according to an embodiment of the present application;

[0033] Figure 3 is a schematic diagram of a resonant transformer circuit 202 according to an embodiment of the present application;

[0034] Figure 4 is a schematic diagram of a voltage feedback circuit according to an embodiment of the present application;

[0035] Figure 5 is a schematic diagram of an air-core transformer according to an embodiment of the present application;

[0036] Figure 6is a schematic diagram of a transformer winding method in an embodiment of the present application;

[0037] Figure 7 is a line end schematic diagram of a transformer winding according to an embodiment of the present application;

[0038] Figure 8 is a schematic diagram of the transformer structure after series-parallel connection in an embodiment of the present application;

[0039] Fig. 9 is a schematic diagram of a transformer winding method in an embodiment of the present application;

[0040] Fig.10 is a schematic diagram of the transformer structure after series-parallel connection in an embodiment of the present application;

[0041] Fig.11 is a schematic diagram of a magnetic resonance imaging system according to an embodiment of the present application. DETAILED DESCRIPTION

[0042] With reference to the accompanying drawings, the foregoing and other features of the embodiments of the present application will become apparent through the following description. In the description and the accompanying drawings, specific embodiments of the present application are specifically disclosed, which show some embodiments in which the principles of the embodiments of the present application can be adopted. It should be understood that the present application is not limited to the described embodiments. On the contrary, the embodiments of the present application include all modifications, variations and equivalents that fall within the scope of the attached claims.

[0043] In the embodiments of the present application, the terms "first", "second", etc. are used to distinguish different elements in terms of title, but do not indicate the spatial arrangement or temporal order of these elements, etc., and these elements should not be limited by these terms. The term "and / or" includes any one and all combinations of one or more of the associated listed terms. The terms "comprising", "including", "having", etc. refer to the presence of the stated features, elements, components or components, but do not exclude the presence or addition of one or more other features, elements, components or components.

[0044] In the embodiments of the present application, the singular forms "a", "the", etc. include plural forms and should be broadly understood as "a kind" or "a type" rather than being limited to the meaning of "one"; in addition, the term "said" should be understood to include both singular and plural forms, unless the context clearly indicates otherwise. In addition, the term "according to" should be understood as "at least in part according to...", and the term "based on" should be understood as "at least in part based on...", unless the context clearly indicates otherwise.

[0045] Features described and / or shown for one embodiment may be used in one or more other embodiments in the same or similar manner, combined with features in other embodiments, or replace features in other embodiments. The term "includes / comprising" when used herein refers to the presence of a feature, an entirety, a step, or a component, but does not exclude the presence or addition of one or more other features, entireties, steps, or components.

[0046] For ease of understanding, Figure 1 A magnetic resonance imaging (MRI) system 10 of some embodiments of the present invention is shown.

[0047] The operation of the magnetic resonance imaging system 10 can be controlled from an operator console 12, which includes a keyboard or other input device 13, a control panel 14, and a display 16. The console 12 communicates with a computer system 20 via a link 18 and provides an interface for an operator to use to prescribe a magnetic resonance scan, display the resulting images, perform image processing on the images, and archive the data and images. The input device 13 may include a mouse, a joystick, a keyboard, a trackball, a touch screen, a light wand, a voice control device, or any similar or equivalent input device, and may be used for interactive geometry prescriptio.

[0048] The computer system 20 includes a plurality of modules that communicate with each other through electrical and / or data connections provided, for example, by utilizing a backplane 21. The data connection may be a direct wired link or a wireless communication link, etc. The modules of the computer system 20 include an image processor 22, a central processing unit 24, and a memory 26. The memory 26 may include a frame buffer for storing an array of image data. In an alternative embodiment, the image processor 22 may be replaced by an image processing function running on the central processing unit 24. The computer system 20 may be linked to an archival media device, a permanent or backup memory storage device, or a network. The computer system 20 may also communicate with an independent system controller 32 via a link 34.

[0049] In some embodiments, the system controller 32 includes a set of modules that communicate with each other via electrical and / or data connections 31. The data connection 31 can be a wired link or a wireless communication link, etc. In alternative embodiments, the computer system 20 and the modules of the system controller 32 can be implemented on the same computer system or multiple computer systems. The modules of the system controller 32 include a central processor 36 and a pulse generator 38 connected to the operator console 12 via a communication link 40.

[0050] In some embodiments, the pulse generator 38 may be integrated into a scanner device such as the resonance assembly 52. ​​The system control computer receives commands from an operator via the link 40 indicating that a scanning sequence is to be executed. The pulse generator 38 operates the system components that emit (i.e., execute) the desired pulse sequence by sending instructions, commands, and / or requests describing the timing, intensity, and shape of the radio frequency pulses and pulse sequence to be generated, as well as the timing and length of the data acquisition window. The pulse generator 38 is connected to the gradient amplifier 42 and generates data called gradient waveforms that control the timing and shape of the gradient pulses to be used during scanning.

[0051] In some embodiments, the pulse generator 38 may also receive patient data from a physiological acquisition controller 44, which receives signals from a plurality of different sensors connected to the patient, such as electrocardiogram signals from electrodes attached to the patient. The pulse generator 38 is connected to a scan room interface 46, which receives signals associated with the condition of the patient and the magnet system from various sensors. The patient positioning system 48 also receives commands to move the patient table to a desired position for scanning through the scan room interface 46.

[0052] In some embodiments, the gradient waveform generated by the pulse generator 38 is applied to the gradient amplifier 42. The gradient amplifier 42 includes an X-axis gradient amplifier, a Y-axis gradient amplifier, and a Z-axis gradient amplifier. Each gradient amplifier excites a corresponding physical gradient coil in the gradient coil assembly 50 and generates a magnetic field gradient pulse for spatial encoding of the acquired signal. The gradient coil assembly 50 forms a part of the resonance assembly 52, which includes a polarized superconducting magnet with a superconducting main coil 54. The resonance assembly 52 may include a whole-body radio frequency coil 56, a surface or parallel imaging coil 76, or both. The coils 56, 76 of the radio frequency coil assembly may be configured for transmission and reception, or only transmission, or only reception. The patient or imaging subject 70 may be placed in the cylindrical patient imaging volume 72 of the resonance assembly 52. ​​The transceiver 58 in the system controller 32 generates pulses, which are amplified by the radio frequency amplifier 60 and coupled to the radio frequency coils 56, 76 through the transmit / receive switch 62. The resulting signals emitted by the excited nuclei in the patient can be sensed by the same radio frequency coil 56 and coupled to the preamplifier 64 through the transmit / receive switch 62. Alternatively, the signals emitted by the excited nuclei can be sensed by a separate receive coil such as a parallel coil or a surface coil 76. The amplified magnetic resonance signals are demodulated, filtered, and digitized in the receiver portion of the transceiver 58. The transmit / receive switch 62 is controlled by a signal from the pulse generator 38 to electrically connect the radio frequency amplifier 60 to the radio frequency coil 56 during the transmit mode and to connect the preamplifier 64 to the radio frequency coil 56 during the receive mode. The transmit / receive switch 62 can also enable the use of a separate radio frequency coil (e.g., a parallel or surface coil 76) in the transmit or receive mode.

[0053] The magnetic resonance signals sensed by the radio frequency coil 56, or the parallel or surface coil 76, are digitized by the transceiver 58 and transmitted to a memory 66 in the system control computer. Typically, frames of data corresponding to the magnetic resonance signals are temporarily stored in the memory 66 until they are subsequently transformed to create an image. The array processor 68 creates images from the magnetic resonance signals using known transformation methods, the most common of which is the Fourier transform. These images are transmitted via the link 34 to the computer system 20, where they are stored in memory. This image data may be archived in a long-term storage device, or it may be further processed by the image processor 22, transmitted to the operator console 12, and presented on the display 16 in response to commands received from the operator console 12.

[0054] Unlike power supplies in other fields, power supplies used in the scanning room of an MRI system cannot contain any magnetic components. In addition, in order to avoid the influence of switching noise on MRI scanning (such as a 1.5T MRI system), the switching frequency of the power supply must be fixed above 1MHz. The operating frequency of the current BUCK topology-based power supply is 1.4MHz, and the energy loss of one switching cycle is about In order to limit the switching losses (mainly caused by parasitic capacitance C s The input voltage V of the power supply needs to be small because the input voltage is large (caused by charging and discharging). If the input voltage increases, the switching loss will increase significantly. If the switching frequency is further increased to meet the higher requirements of the MRI system (such as a 3T MRI system), the switching loss will also increase linearly with the increase in frequency. Therefore, the power supply circuit is not flexible and cannot be used in high input voltage and high switching frequency situations. In addition, the ferromagnetic material used in the transformer of the commonly used power supply circuit is not suitable for working in the strong magnetic field environment of the MRI system.

[0055] In order to solve at least one of the above problems, the embodiments of the present application provide an isolated resonant power supply circuit, a magnetic resonance imaging system, and a transformer, which are described below in conjunction with the embodiments.

[0056] The embodiment of the present application provides an isolated resonant power supply circuit, which is arranged in a scanning room of a magnetic resonance imaging system and is used to power one or more devices in the scanning room of the magnetic resonance imaging system. For example, the isolated resonant power supply circuit can be used to power any one of a gradient amplifier and a radio frequency amplifier in the scanning room. By arranging the isolated resonant power supply circuit in the scanning room, cables and filters can be saved, so that the cost of the magnetic resonance imaging system is reduced.

[0057] Figure 2 is a schematic diagram of an isolated resonant power supply circuit according to an embodiment of the present application. Figure 2 As shown, the isolated resonant power supply circuit 200 includes: an inverter circuit 201, a resonant transformer circuit 202 and a rectifier circuit 203;

[0058] The inverter circuit 201 is connected to the resonant transformer circuit 202 and is used to convert the input direct current into alternating current and output it to the resonant transformer circuit 202;

[0059] The resonant transformer circuit 202 is used to perform resonant conversion on the alternating current and then transform the alternating current and output it to the rectifier circuit 203;

[0060] The rectifier circuit 203 is used to rectify the AC output voltage output by the resonant transformer circuit 202 into a DC voltage output power supply.

[0061] In some embodiments, the inverter circuit 201 can convert direct current into alternating current (e.g., a high-frequency square wave), and the inverter circuit 201 includes a direct current positive input terminal, a direct current negative input terminal, an inverter output terminal 1, and an inverter output terminal 2. The direct current positive input terminal and the direct current negative input terminal are used for the input of direct current. The inverter circuit 201 can be a full-bridge inverter circuit (e.g., including 4 power switch tubes), or a half-bridge inverter circuit (e.g., including 2 power switch tubes), and the embodiments of the present application are not limited to this. In addition, the above switch tubes are various power semiconductor switching devices including power metal oxide semiconductor field effect transistors (Metal Oxide Semi-Conductor Field Effect Transistors, MOSFET), insulated gate bipolar transistors (Insulated Gate Bipolar Transistor, IGBT), BJT, thyristor, IGCT, etc. The above inverter circuit 201 components and connection relationships are only examples, and specific reference can be made to the relevant technology, and the present application is not limited to this.

[0062] In some embodiments, the inverter output terminal 1 and the inverter output terminal 2 of the inverter circuit 201 are connected to the AC input terminal 1 and the AC input terminal 2 of the resonant transformer circuit 202. The AC power (high-frequency square wave) output by the inverter circuit 201 is applied to the AC input terminal 1 and the AC input terminal 2 of the resonant transformer circuit 202 to generate high-frequency resonance, eliminate the harmonics of the square wave, and output a fundamental frequency sine wave. The sine wave is transmitted from the primary side to the secondary side through the transformer, and the voltage is boosted or stepped down according to application requirements and then connected to the rectifier circuit 203 through the AC output terminal 1 and the AC output terminal 2, and the transformed sine wave is output to the rectifier circuit 203.

[0063] Figure 3 Schematic diagram of the resonant transformer circuit 202 in the embodiment of the present application. Figure 3As shown, the resonant transformer circuit 202 includes a variable capacitance circuit 301, an inductor 302 and an air-core transformer 303. By changing the input voltage of the variable capacitance circuit 301, the equivalent capacitance value of the variable capacitance circuit 301 is changed. The variable capacitance circuit 301 includes a first capacitor 3011, a second capacitor 3012 and a variable resistor 3013, wherein one end of the second capacitor 3012 is connected to one end of the variable resistor 3013, the other end of the second capacitor 3012 is connected to one end of the first capacitor 3011, and the other end of the first capacitor 3011 is connected to the other end of the variable resistor 3013. The two ends of the first capacitor 3011 can also be regarded as two terminals of the variable capacitance circuit. The equivalent circuit model of the air-core transformer 303 includes inherent lumped circuit parasitic elements, which include a primary inductance Lp. The primary inductance Lp is not a real component. Figure 3 The effect of the existence of the primary inductance is only illustrated as an example.

[0064] In some embodiments, the variable capacitance circuit 301, the inductor 302, and the primary inductance (ie, the excitation inductance) Lp are connected in series, but the present application does not limit the connection sequence of the inductor 302, the primary inductance, and the variable capacitance circuit 301. Figure 3 As shown, the primary inductor is located between the variable capacitance circuit 301 and the inductor 302, that is, one terminal of the variable capacitance circuit 301 and one end of the inductor 302 serve as the AC input terminal 1 and the AC input terminal 2 of the resonant transformer circuit 202, and are respectively connected to the inverter output terminal 1 and the inverter output terminal 2 of the inverter circuit 201. Alternatively, as not shown in the figure, the inductor 302 may be located between the variable capacitance circuit 301 and the primary inductor Lp, that is, one terminal of the variable capacitance circuit 301 and one end of the primary inductor Lp serve as the AC input terminal 1 and the AC input terminal 2 of the resonant transformer circuit 202, and are respectively connected to the inverter output terminal 1 and the inverter output terminal 2 of the inverter circuit 201. Examples are not given one by one here.

[0065] In some embodiments, the rectifier circuit 203 can convert a sine wave into a stable DC voltage output, which can be a full-bridge rectifier circuit or a half-bridge rectifier circuit. The rectifier circuit 203 includes a first connection terminal, a second connection terminal, a DC positive output terminal and a DC negative output terminal. The DC positive output terminal and the DC negative output terminal are used for the output of DC power. The first connection terminal and the second connection terminal can be connected to the AC output terminal 1 and the AC output terminal 2 of the resonant transformer circuit 202, respectively. The rectifier circuit 203 includes a rectifier tube, which includes at least one diode and / or at least one synchronous rectifier tube, that is, the rectifier tubes can all be diodes, or all are synchronous rectifier tubes, or a combination of diodes and synchronous rectifier tubes. The above components and connection relationships of the rectifier circuit 203 are only examples, and specific reference can be made to the relevant technology. This application is not limited to this.

[0066] In some embodiments, the isolated resonant power supply circuit 200 may further include an output capacitor 204 , the two ends of which are respectively connected to the DC positive output terminal and the DC negative output terminal of the rectifier circuit 203 , that is, connected in parallel with the output terminal of the rectifier circuit 203 .

[0067] The inventors have found that in the existing resonant circuit, the switching frequency can be adjusted to move away from or close to the resonance point, thereby adjusting the power flowing from the primary side to the secondary side. However, in the magnetic resonance imaging system, in order to avoid the influence of switching noise on the magnetic resonance imaging scan (such as the receiver receiving frequency, etc.), the switching frequency of the power supply cannot be changed arbitrarily. Therefore, the resonant capacitance value can be adjusted by designing a variable capacitance circuit, thereby adjusting the power flowing from the primary side to the secondary side.

[0068] The operating principle of the variable capacitance circuit is described below.

[0069] In some embodiments, the input voltage of the variable resistor can be changed to change the input voltage of the variable capacitance circuit, so that the equivalent capacitance value of the variable capacitance circuit changes. That is, the equivalent resistance value of the variable resistor is changed by changing the input voltage of the variable resistor, thereby changing the equivalent capacitance value of the variable capacitance circuit, and the equivalent capacitance value of the variable capacitance circuit changes between a first value and a second value, wherein the first value is the capacitance value of the first capacitor, and the second value is the sum of the capacitance values ​​of the first capacitor and the second capacitor.

[0070] In some embodiments, the variable resistor is a switch tube operating in a linear region. The linear conduction degree of the switch tube is changed by changing the input voltage of the variable resistor to change the equivalent capacitance value of the variable capacitance circuit, wherein the switch tube can be a MOS tube, but the embodiment of the present application is not limited to this. One end and the other end of the variable resistor 3013 are the source terminal and the drain terminal of the switch tube, respectively. The switch tube operates in the linear region, that is, the switch tube operates in a resistive state, and the linear conduction degree of the switch tube is different, that is, the equivalent resistance value (between the source and drain) corresponding to the switch tube is different. When the switch tube is fully turned on, the switch tube can be regarded as a short circuit (a wire), and the resistance value is regarded as 0. The variable capacitance circuit can be regarded as a parallel circuit of the first capacitor and the second capacitor, and its equivalent capacitance value is the second value. When the switch tube is completely disconnected, the switch tube can be regarded as an open circuit, that is, the resistance value is regarded as infinite, and the variable capacitance circuit can be regarded as only including the first capacitor, that is, the equivalent capacitance value of the variable capacitance circuit is the first value. If the switch tube is between fully on and fully off, its resistance value is related to its degree of conduction, and the equivalent capacitance value of the variable capacitance circuit varies between a first value and a second value, and the variation is monotonic, that is, the greater the degree of conduction, the closer the equivalent capacitance value of the variable capacitance circuit is to the second value, and the smaller the degree of conduction, the closer the equivalent capacitance value of the variable capacitance circuit is to the first value.

[0071] In some embodiments, the equivalent capacitance value of the variable capacitance circuit can be changed according to the dynamic change of the feedback voltage of the resonant power supply circuit with the load, such as Figure 3 As shown ( Figure 2 (not shown), the isolated resonant power supply circuit also includes: a voltage feedback circuit 205, which is respectively connected to the variable capacitor circuit and the rectifier circuit, and is used to feed back the DC voltage output by the rectifier circuit to the variable capacitor circuit; and the feedback voltage VFB of the voltage feedback circuit 205 is used as the input voltage of the variable resistor.

[0072] Figure 4 205 is a schematic diagram of the voltage feedback circuit 205 of the present application. Figure 4 As shown, the voltage feedback circuit 205 includes an optocoupler isolator 401, a terminal X of the optocoupler isolator 401 is used to input the DC voltage Vo output by the rectifier circuit (via a resistor R1), a terminal Y of the optocoupler isolator 401 is used to be grounded (via a diode D8), a terminal M of the optocoupler isolator 401 is used to input a power supply voltage (for example, 5V or 8V or 10V, etc.), a terminal N of the optocoupler isolator 401 is used to be connected to a variable capacitor circuit (via a resistor R2) to output a feedback voltage VFB, and the parameters of the optocoupler isolator 401 and the values ​​of R1 and R2 can be designed as needed, and the embodiments of the present application are not limited thereto.

[0073] In some embodiments, when the variable resistor is the aforementioned switch tube, the voltage feedback circuit is connected to the gate of the switch tube, for example, the terminal N of the optocoupler isolator 401 is connected to the gate of the switch tube (via the resistor R2), and the feedback voltage is used as the input voltage of the variable resistor to control the equivalent resistance value of the variable resistor, that is, the gate voltage of the switch tube is used to control the size of the channel resistance of the switch tube. In other words, the size of the channel resistance of the switch tube changes through the change of the feedback voltage (or when the feedback voltage changes, the channel resistance of the switch tube will change accordingly), thereby causing the equivalent capacitance value of the variable capacitance circuit to change between the first value and the second value.

[0074] In some embodiments, when the switch tube is fully turned on by the feedback voltage control, that is, the feedback voltage increases so that the gate voltage of the switch tube increases to greater than or equal to the switch tube turn-on voltage V1, so that the switch tube is fully turned on, the switch tube can be regarded as a short circuit (a wire), and the resistance value is regarded as 0. The variable capacitance circuit can be regarded as a parallel circuit of the first capacitor and the second capacitor, and its equivalent capacitance value is the second value. When the switch tube is completely disconnected by the feedback voltage control, that is, the feedback voltage decreases so that the gate voltage of the switch tube is reduced to less than or equal to the switch tube turn-off voltage V2, so that the switch tube is disconnected, the switch tube can be regarded as an open circuit, that is, the resistance value is regarded as infinite, and the variable capacitance circuit can be regarded as only including the first capacitor, that is, the equivalent capacitance value of the variable capacitance circuit is the first value. When the feedback voltage changes between V1 and V2, the degree of conduction of the switch tube changes, and then the equivalent capacitance value of the variable capacitance circuit changes between the first value and the second value. The values ​​of V1 and V2 are related to the switch tube, and the embodiments of the present application are not limited to this.

[0075] In some embodiments, the magnitude of the feedback voltage is affected by the load, that is, a change in the load will cause the output voltage to change, and then the feedback voltage to change, so that the equivalent resistance of the variable resistor changes, and then the equivalent capacitance value of the variable capacitor circuit changes. On the other hand, the change in the equivalent capacitance value of the variable capacitor circuit will cause the power flowing from the primary side to the secondary side to change accordingly, and the change in power can further compensate for the impact of the load change on the output voltage, thereby making the output voltage more stable. The following is a detailed description.

[0076] For example, when the load is light, it is equivalent to a larger load resistance, which will increase the output voltage, the feedback voltage, the degree of conduction of the switch tube, the on-resistance of the switch tube, and the equivalent capacitance of the variable capacitor circuit. This will reduce the resonant frequency (away from the maximum resonant frequency) and reduce the power flowing from the primary side to the secondary side, thereby reducing the output voltage. In other words, the problem of output voltage rise caused by a lighter load is avoided, making the output voltage more stable.

[0077] For example, when the load is large (for example, when the load changes from no-load to full-load), it is equivalent to the load resistance becoming smaller, the output voltage will drop (drop, hereinafter referred to as voltage drop), the feedback voltage VFB will also decrease, the conduction degree of the switch tube becomes smaller, the on-resistance of the switch tube becomes larger, and the equivalent capacitance of the variable capacitor circuit becomes smaller, so that the resonant frequency increases (close to the maximum resonant frequency), and the power flowing from the primary side to the secondary side becomes larger, thereby increasing the output voltage. In other words, the problem of output voltage drop caused by a large load is avoided, making the output voltage more stable.

[0078] It can be seen from the above embodiments that the existing common switch tubes are all hard switches. When turning on and off, the drain-source voltage and current of the switch tube will overlap. The area where the voltage and current overlap is the turn-on loss and turn-off loss of the switch tube. Especially when the input voltage of the power supply circuit is increased, the switching loss will increase significantly. In the embodiments of the present application, the ZVS soft switching method can be adopted through the above-mentioned isolated resonant power supply circuit. Therefore, even in the case of high input voltage, the effect of reducing switching loss can be achieved. In addition, there is no need to adjust the switching frequency, and the power supply circuit can operate at a fixed switching frequency of more than 1MHz, which can avoid the noise interference of the power supply circuit to the magnetic resonance imaging system and make the output voltage more stable.

[0079] In the above examples, the variable resistor is a switch tube working in the linear region, but the embodiment of the present application is not limited to this. The variable resistor can also be a digital adjustable resistor, and the corresponding relationship between the feedback voltage and the resistance value of the digital adjustable resistor can be preset. The resistance value of the digital adjustable resistor is adjusted according to the value of the feedback voltage and the corresponding relationship to change the equivalent capacitance value of the variable capacitance circuit, which will not be described one by one here. The variable resistor can also adopt other implementations, and the present application is not limited to this.

[0080] The following describes how to design the capacitance of the first capacitor and the second capacitor.

[0081] In some embodiments, the inductance value Lr (resonant inductance) of the inductor can be predetermined according to the circuit requirements, and the first value and the second value can be determined according to the resonant inductance and the output power under different load conditions. For example, in the case of light load, the value of the first capacitor is determined according to the resonant inductance and the output power, that is, the first value. In the case of heavy load or full load, the value of the second capacitor is determined according to the resonant inductance, the output power and the first value, that is, the second value. The specific value can be obtained by referring to the simulation of the relevant technology. The first value and the second value can take values ​​with a large difference in numerical value, so that the adjustable range of the equivalent capacitance of the variable capacitance circuit becomes larger. For example, the first value is 1nF and the second value is 100nF. This is only an example, and the embodiments of the present application are not limited to this.

[0082] In some embodiments, Figure 3 As shown, the resonant transformer circuit also includes a third capacitor 304, one end of the third capacitor is connected to the other end of the first capacitor, and the other end of the third capacitor is connected to the gate of the switch tube. Since the channel resistance value of the switch tube is relatively sensitive to the change of the feedback voltage, for example, if the feedback voltage increases by a very small value, the channel resistance value will decrease by a large value, and the feedback is prone to oscillation. By adding the third capacitor to the resonant transformer circuit, the change speed of the channel resistance value of the switch tube is slowed down, and the sensitivity of the change of the channel resistance value of the switch tube can be reduced. The capacitance value of the third capacitor can be determined as needed, for example, set to 100nF, but the embodiment of the present application is not limited to this.

[0083] In some embodiments, the air-core transformer 303 is applicable to the structure of any air-core transformer, but in the absence of a magnetic core, if the primary winding and the secondary winding are placed separately, the coupling between the windings is poor, resulting in a low coupling coefficient, high noise, and low efficiency. Therefore, in order to further improve the coupling coefficient between the primary winding and the secondary winding. The embodiment of the present application also provides an air-core transformer, the air-core transformer includes a skeleton and a first number of windings wound on the skeleton, each winding is formed by a wire harness wound on the skeleton for multiple turns, and each wire harness includes a second number of winding wires twisted together; the first number is an integer greater than or equal to 1, and the second number is an integer greater than 1, for example, the second number is greater than or equal to a second threshold, and the second threshold can be determined as needed. The winding wire can be an enameled wire, such as an insulated copper wire, and a wire harness is formed by twisting a second number of winding wires together, and the wire harness is tightly wound on the skeleton for multiple turns to form a winding. The formation method of each winding is the same, and it will not be repeated here.

[0084] In some embodiments, a third number of winding wires in each winding serves as a primary winding, and both ends of the third number of winding wires are connected to the primary circuit of the air-core transformer. A fourth number of winding wires in each winding serves as a secondary winding, and both ends of the fourth number of winding wires are connected to the secondary circuit of the air-core transformer. Both the third number and the fourth number are integers greater than 1. The third number of winding wires and the fourth number of winding wires may be randomly selected, and the present application is not limited thereto. For example, the third number may be equal to the fourth number, which is equal to half of the second number, but the present application is not limited thereto. That is to say, the second number of winding wires in a wiring harness are divided into primary winding wires and secondary winding wires. For example, 40 winding wires are twisted together to form a wiring harness, and the wiring harness is tightly wound around the skeleton in circles. 20 winding wires are randomly selected from one end of the wiring harness (winding wires) as primary winding wires, and the other end of the 20 winding wires is determined. One end and the other end of the 20 winding wires are connected to the primary circuit of the air-core transformer, and the remaining 20 winding wires are used as secondary winding wires, and both ends of the remaining 20 winding wires are connected to the secondary circuit of the air-core transformer.

[0085] Figure 5 is a cross-sectional schematic diagram of a winding in an embodiment of the present application, such as Figure 5 As shown, although the primary winding wire and the secondary winding wire are randomly selected, since the primary winding wire and the secondary winding wire are mixed and twisted together in one winding, it is still possible to ensure that the primary winding wire and the secondary winding wire are evenly distributed in the one winding. Since each winding wire in the primary winding is surrounded by multiple secondary winding wires, the magnetic flux generated by the primary winding can be coupled with the secondary winding to a greater extent. Similarly, the magnetic flux generated by the secondary winding can be coupled with the primary winding to a greater extent. Therefore, the coupling coefficient between the primary and secondary windings can be improved.

[0086] In some embodiments, a transformer operating at a high frequency (e.g., greater than 1 MHz) may experience a skin effect. In order to alleviate the skin effect and reduce losses, the diameter of each winding wire is less than or equal to a first threshold value. The first threshold value can be set to a relatively small value as needed. For example, the diameter of each winding wire can be 0.1 mm, but the embodiments of the present application are not limited to this.

[0087] In some embodiments, in order to obtain the best coupling coefficient, the number of turns (winding turns) of the primary and secondary sides are the same, that is, the primary and secondary turns ratio of the transformer is 1:1. In this case, when the input voltage is 48V and the output voltage is 15V, the duty cycle is (15×2) / 48=0.625, but when the output voltage is 5V, the duty cycle is (5×2) / 48=0.208, that is, in the case of low output voltage, if the primary and secondary turns ratio is still 1:1, it will result in a low duty cycle, thereby limiting the primary and secondary power conversion efficiency. Therefore, in the case of low output voltage, for the case of large transformation ratio, the primary and secondary turns ratio of the transformer can be made greater than 1 to obtain a higher switching duty cycle and improve efficiency. The following describes how the embodiment of the present application achieves a primary and secondary turns ratio of the transformer greater than 1.

[0088] In some embodiments, the first number can be set to an integer greater than 1, that is, the transformer has multiple (first number) windings, or is formed by multiple (first number) wire harnesses winding around a skeleton. The transformer has a first number of windings. Since each winding includes a primary winding and a secondary winding, the first number of windings indicates that the transformer has a first number of primary windings and a first number of secondary windings. Multiple (first number) primary windings in the first number of windings can be connected in series, and multiple (first number) secondary windings in the first number of windings can be connected in parallel, thereby making the primary-to-secondary turns ratio become the first number: 1, that is, the turns ratio is greater than 1, so as to obtain a higher switching duty cycle.

[0089] In some embodiments, connecting the first number of primary windings in series includes: each primary winding includes a third number of winding wires, the third number of winding wires (hereinafter referred to as a group) having two ends, and connecting the opposite ends of different groups of winding wires (different primary windings) together to complete the first number of primary windings in series, and the remaining two ends not connected together are connected to the primary circuit of the air-core transformer, for example, respectively connected to the inductor and the variable capacitor circuit.

[0090] In some embodiments, connecting the first number of secondary windings in parallel includes: each secondary winding includes a fourth number of winding wires, the fourth number of winding wires (hereinafter referred to as a group) having two ends, and connecting the same-named ends of different groups of winding wires (different secondary windings) together to complete the first number of secondary windings in parallel, and the two parallel ends are connected to the secondary circuit of the air-core transformer, for example, respectively connected to the first connection end and the second connection end of the rectifier circuit.

[0091] In some embodiments, the voltages of different secondary windings are not exactly the same. If multiple secondary windings are directly connected in parallel, a circulating current will be generated. In order to avoid the circulating current between the secondary windings, each secondary winding in the first number of windings can be connected in parallel after being rectified by a rectifier. The number of rectifiers is also the first number, and the first number of rectifiers corresponds to the first number of secondary windings one by one, that is, the two ends of each group of winding wires are first connected to the corresponding rectifier, and then the same-named ends of the two output ends of each rectifier are connected together to complete the parallel connection.

[0092] In some embodiments, the first number of windings are all wound in one slot of the skeleton. Taking the first number equal to 3 as an example, Figure 6 is a first number of winding schematic diagrams of an embodiment of the present application, Figure 7 is a schematic diagram of the line ends of the first number of windings in an embodiment of the present application, such as Figure 6 and Figure 7 As shown, a slot is provided on the skeleton, and the three windings (wiring harnesses) are all wound in the slot, the two ends of the third number of primary winding wires in the first wiring harness are end A and end B, the two ends of the third number of primary winding wires in the second wiring harness are end C and end D, and the two ends of the third number of primary winding wires in the third wiring harness are end E and end F. The third number of primary winding wires in the first wiring harness and the third number of primary winding wires in the second wiring harness are connected together at the opposite ends B and C, and the third number of primary winding wires in the second wiring harness and the third number of primary winding wires in the third wiring harness are connected together at the opposite ends D and E, to complete the series connection of the three primary windings, and the remaining A and F ends of the third number of primary winding wires are connected to the primary circuit (such as an inductor and a variable capacitor circuit). The two ends of the fourth number of secondary winding wires in the first wiring harness are A' and B', the two ends of the fourth number of secondary winding wires in the second wiring harness are C' and D', and the two ends of the fourth number of secondary winding wires in the third wiring harness are E' and F'. The same-named ends B', D' and F' of the fourth number of secondary winding wires in the first wiring harness, the fourth number of secondary winding wires in the second wiring harness and the fourth number of secondary winding wires in the third wiring harness are connected together, and the same-named ends A', C' and E' of the fourth number of secondary winding wires in the first wiring harness, the fourth number of secondary winding wires in the second wiring harness and the fourth number of secondary winding wires in the third wiring harness are connected together to complete the parallel connection of the three secondary windings, and the A' and B' ends are connected to the secondary circuit (for example, a rectifier circuit). Figure 8 Schematic diagram of the transformer structure after series-parallel connection in the embodiment of the present application. Figure 8 As shown, three primary windings are connected in series and three secondary windings are connected in parallel.

[0093] In some embodiments, the first number of windings are respectively wound in the first number of slots of the skeleton. Taking the first number equal to 3 as an example, Fig. 9 is a schematic diagram of the first number of windings in an embodiment of the present application, such as Fig. 9 As shown, a first number (3) of slots 901, 902, and 903 are provided on the skeleton, and each of the three windings (wiring harnesses) is respectively wound in one slot, and the opposite ends of a group of primary winding wires in the wiring harnesses wound in adjacent slots are connected, and the same ends of a group of secondary winding wires in the wiring harnesses wound in adjacent slots are connected, wherein, in order to limit the generation of circulating current, the secondary winding in each slot can be rectified by a rectifier and then the same ends can be connected in parallel, and the winding in each slot can be a wiring harness wound in a spiral shape, but the embodiments of the present application are not limited to this. Fig.10 Schematic diagram of the transformer structure after series-parallel connection in the embodiment of the present application. Fig.10 As shown, three primary windings are connected in series, and three secondary windings 1004, 1005, and 1006 are connected in parallel after passing through rectifiers 1001, 1002, and 1003 respectively.

[0094] in addition, Fig.10 The series-parallel connection method in Figure 8 Compared with the series-parallel method in the transformer, the magnetic length is shorter and therefore the transformer has less leakage flux.

[0095] Through the above example, the transformer turns ratio becomes 3:1. When the input voltage is 48V and the output voltage is 5V, the switch duty cycle is (2×5×3) / 48=0.625, thereby obtaining a higher switch duty cycle.

[0096] The isolated resonant power supply circuit in the embodiment of the present application changes the equivalent capacitance value of the variable capacitance circuit by changing the input voltage of the variable resistor, thereby, the ZVS soft switching method can be adopted, and the effect of reducing switching loss can be achieved even in the case of high input voltage. In addition, since the capacitance value can be changed, there is no need to adjust the switching frequency, and the power supply circuit can operate at a fixed switching frequency of more than 1MHz, which can avoid the noise interference of the power supply circuit to the magnetic resonance imaging system and make the output voltage more stable.

[0097] The air-core transformer in the embodiment of the present application uses multiple winding wires twisted into a wire harness, and then the wire harness is wound multiple times around a frame to form a transformer winding. This can solve the problem that traditional magnetic cores cannot work in a strong magnetic field environment, and can improve the coupling coefficient between the primary and secondary sides of the transformer.

[0098] The present application also provides a magnetic resonance imaging system. The magnetic resonance imaging system is composed of Fig.11 As shown, Figure 1The repetitive parts will not be repeated.

[0099] In some embodiments, Figure 1 The difference between the aforementioned magnetic resonance imaging system and the aforementioned magnetic resonance imaging system is that the magnetic resonance imaging system further comprises the isolated resonant power supply circuit 200 of the aforementioned embodiment, which is arranged in the scanning room of the magnetic resonance imaging system and is used to power one or more devices in the scanning room of the magnetic resonance imaging system. For example, the isolated resonant power supply circuit can be used to power any one of the gradient amplifier and the radio frequency amplifier in the scanning room.

[0100] The embodiment of the present application may also provide an air-core transformer, the air-core transformer comprising a skeleton and a first number of windings wound on the skeleton, each winding being formed by a wire harness being wound multiple times on the skeleton, and each wire harness comprising a second number of winding wires twisted together; wherein the third number of winding wires in each winding serves as a primary winding, and both ends of the third number of winding wires are connected to the primary circuit of the air-core transformer, and the fourth number of winding wires in each winding serves as a secondary winding, and both ends of the fourth number of winding wires are connected to the secondary circuit of the air-core transformer, the first number is an integer greater than or equal to 1, and the second number, the third number, and the fourth number are all integers greater than 1. The implementation method of the air-core transformer is as described above and will not be repeated here. The air-core transformer can be applied to a power supply circuit, which is not limited to the aforementioned isolated resonant power supply circuit, but can also be a power supply circuit of other structures, and the embodiment of the present application is not limited to this.

[0101] The present application also provides a magnetic resonance imaging system. The magnetic resonance imaging system is composed of Figure 1 As shown, Figure 1 The repetitive parts will not be repeated.

[0102] In some embodiments, Figure 1 The difference between the aforementioned magnetic resonance imaging system and the aforementioned magnetic resonance imaging system is that the magnetic resonance imaging system further comprises an air-core transformer according to the aforementioned embodiment, which is arranged in a scanning room of the magnetic resonance imaging system and is used in a power supply circuit for powering devices in the scanning room of the magnetic resonance imaging system.

[0103] The above devices and methods of the present application can be implemented by hardware, or by hardware combined with software. The present application relates to such a computer-readable program, which, when executed by a logic component, enables the logic component to implement the above-mentioned devices or components, or enables the logic component to implement the various methods or steps described above. The present application also relates to a storage medium for storing the above program, such as a hard disk, a magnetic disk, an optical disk, a DVD, a flash memory, etc.

[0104] The method / device described in conjunction with the embodiments of the present application may be directly embodied as hardware, a software module executed by a processor, or a combination of the two. For example, one or more of the functional block diagrams shown in the figure and / or one or more combinations of the functional block diagrams may correspond to various software modules of the computer program flow or to various hardware modules. These software modules may correspond to the various steps shown in the figure, respectively. These hardware modules may be implemented by solidifying these software modules, for example, using a field programmable gate array (FPGA).

[0105] The software module may be located in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. A storage medium may be coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium; or the storage medium may be an integral part of the processor. The processor and the storage medium may be located in an ASIC. The software module may be stored in a memory of a mobile terminal or in a memory card that can be inserted into the mobile terminal. For example, if a device (such as a mobile terminal) uses a large-capacity MEGA-SIM card or a large-capacity flash memory device, the software module may be stored in the MEGA-SIM card or the large-capacity flash memory device.

[0106] For one or more of the functional blocks described in the drawings and / or one or more combinations of functional blocks, it can be implemented as a general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware component or any appropriate combination thereof for performing the functions described in the present application. For one or more of the functional blocks described in the drawings and / or one or more combinations of functional blocks, it can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in communication with a DSP, or any other such configuration.

[0107] The present application is described above in conjunction with specific implementation methods, but it should be clear to those skilled in the art that these descriptions are exemplary and are not intended to limit the scope of protection of the present application. Those skilled in the art can make various modifications and variations to the present application based on the principles of the present application, and these modifications and variations are also within the scope of the present application.

Claims

1. An isolated resonant power supply circuit, which is arranged in a scanning room of a magnetic resonance imaging system, the isolated resonant power supply circuit comprising: Inverter circuit, resonant transformer circuit and rectifier circuit; The inverter circuit is connected to the resonant transformer circuit and is used to convert the input direct current into alternating current and output it to the resonant transformer circuit; The resonant transformer circuit is used to perform resonant conversion on the alternating current and then output the transformed alternating current to the rectifier circuit; The rectifier circuit is used to rectify the AC output voltage output by the resonant transformer circuit into a DC voltage output power supply; The resonant voltage transformer circuit includes a variable capacitance circuit and an inductor, and the equivalent capacitance value of the variable capacitance circuit is changed by changing the input voltage of the variable capacitance circuit.

2. The isolated resonant power supply circuit according to claim 1, characterized in that: The variable capacitance circuit includes a first capacitor, a second capacitor and a variable resistor, wherein one end of the second capacitor is connected to one end of the variable resistor, the other end of the second capacitor is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the other end of the variable resistor, wherein the input voltage of the variable resistor is changed to change the input voltage of the variable capacitance circuit, so that the equivalent capacitance value of the variable capacitance circuit changes.

3. The isolated resonant power supply circuit according to claim 2, characterized in that: The variable resistor is a switch tube working in a linear region.

4. The isolated resonant power supply circuit according to claim 3, characterized in that: The linear conduction degree of the switch tube is changed by changing the input voltage of the variable resistor, so that the equivalent capacitance value of the variable capacitance circuit changes.

5. The isolated resonant power supply circuit according to claim 3, characterized in that: The isolated resonant power supply circuit also includes: a voltage feedback circuit, which is used to feed back the DC voltage output by the rectifier circuit to the variable capacitance circuit; and use the feedback voltage of the voltage feedback circuit as the input voltage of the variable resistor.

6. The isolated resonant power supply circuit according to claim 5, characterized in that: The voltage feedback circuit is connected to the gate of the switch tube.

7. The isolated resonant power supply circuit according to claim 5, characterized in that: By changing the feedback voltage, the equivalent capacitance value of the variable capacitance circuit changes between a first value and a second value, wherein the first value is the capacitance value of the first capacitor, and the second value is the sum of the capacitance values ​​of the first capacitor and the second capacitor.

8. The isolated resonant power supply circuit according to claim 5 or 7, characterized in that: When the switch tube is fully turned on under the control of the feedback voltage, the equivalent capacitance value of the variable capacitance circuit is a second value, and when the switch tube is fully turned off under the control of the feedback voltage, the equivalent capacitance value of the variable capacitance circuit is a first value, wherein the first value is the capacitance value of the first capacitor, and the second value is the sum of the capacitance values ​​of the first capacitor and the second capacitor.

9. The isolated resonant power supply circuit according to claim 3, characterized in that: The resonant transformer circuit also includes a third capacitor, one end of the third capacitor is connected to the other end of the first capacitor, and the other end of the third capacitor is connected to the gate of the switch tube.

10. The isolated resonant power supply circuit according to claim 1, characterized in that: The resonant transformer circuit further includes an air-core transformer, the air-core transformer including a frame and a first number of windings wound on the frame, each winding being formed by a wire harness being wound multiple times on the frame, and each wire harness including a second number of winding wires twisted together; Among them, the third number of winding wires in each winding serves as the primary winding, and both ends of the third number of winding wires are connected to the primary circuit of the air-core transformer; the fourth number of winding wires in each winding serves as the secondary winding, and both ends of the fourth number of winding wires are connected to the secondary circuit of the air-core transformer; the first number is an integer greater than or equal to 1, and the second number, the third number, and the fourth number are all integers greater than 1.

11. The isolated resonant power supply circuit according to claim 10, characterized in that: The third quantity is equal to the fourth quantity.

12. The isolated resonant power supply circuit according to claim 10, characterized in that: The diameter of each winding wire is less than or equal to a first threshold.

13. The isolated resonant power supply circuit according to claim 10, characterized in that: When the first number is greater than 1, multiple primary windings in the first number of windings are connected in series, and multiple secondary windings in the first number of windings are connected in parallel.

14. The isolated resonant power supply circuit according to claim 13, characterized in that: Each secondary winding in the first number of windings is connected in parallel after passing through a rectifier.

15. The isolated resonant power supply circuit according to claim 10, characterized in that: The first number of windings are all wound in one slot of the bobbin, or the first number of windings are respectively wound in the first number of slots of the bobbin.

16. A magnetic resonance imaging system, comprising: A main magnet, used for generating a main magnetic field; Gradient coil assembly; a gradient amplifier, for exciting the gradient coil assembly to generate a gradient magnetic field on a selected gradient axis so as to apply the gradient magnetic field to the main magnetic field; Radio frequency coil assembly; A radio frequency amplifier, used to excite the radio frequency coil assembly to generate a radio frequency signal; The isolated resonant power supply circuit according to any one of claims 1 to 15 is arranged in a scanning room of the magnetic resonance imaging system and supplies power to devices in the scanning room.

17. An air core transformer, characterized in that: The air-core transformer comprises a frame and a first number of windings wound on the frame, each winding is formed by a wire harness wound multiple times on the frame, and each wire harness comprises a second number of winding wires twisted together; Among them, the third number of winding wires in each winding serves as the primary winding, and both ends of the third number of winding wires are connected to the primary circuit of the air-core transformer; the fourth number of winding wires in each winding serves as the secondary winding, and both ends of the fourth number of winding wires are connected to the secondary circuit of the air-core transformer; the first number is an integer greater than or equal to 1, and the second number, the third number, and the fourth number are all integers greater than 1.

18. The air core transformer according to claim 17, characterized in that: The third quantity is equal to the fourth quantity.

19. The air-core transformer according to claim 17, characterized in that: The diameter of each winding wire is less than or equal to a first threshold.

20. The air core transformer according to claim 17, characterized in that: When the first number is greater than 1, multiple primary windings in the first number of windings are connected in series, and multiple secondary windings in the first number of windings are connected in parallel.

21. The air core transformer according to claim 20, characterized in that: Each secondary winding in the first number of windings is connected in parallel after passing through a rectifier.

22. The air core transformer according to claim 17, characterized in that: The first number of windings are all wound in one slot of the bobbin, or the first number of windings are respectively wound in the first number of slots of the bobbin.

23. A magnetic resonance imaging system, comprising: A main magnet, used for generating a main magnetic field; Gradient coil assembly; a gradient amplifier, for exciting the gradient coil assembly to generate a gradient magnetic field on a selected gradient axis so as to apply the gradient magnetic field to the main magnetic field; Radio frequency coil assembly; A radio frequency amplifier, used to excite the radio frequency coil assembly to generate a radio frequency signal; A power supply circuit, which is arranged in a scanning room of the magnetic resonance imaging system and supplies power to devices in the scanning room; The air-core transformer according to any one of claims 17 to 22, wherein the air-core transformer is disposed in the power supply circuit.

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