Isolated resonant power supply circuit and magnetic resonance imaging system

Abstract

The embodiment of the utility model provides an isolated resonant power supply circuit and a magnetic resonance imaging system, the isolated resonant power supply circuit is arranged in a scanning room of the magnetic resonance imaging system, and the isolated resonant power supply circuit comprises an inverter circuit, a resonant transformation circuit and a rectification circuit; the inverter circuit 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; and 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 an air-core transformer, a first capacitor, a second capacitor and an inductor, the first capacitor, the second capacitor and the inductor are connected in series, and the second capacitor is connected with a primary winding of the air-core transformer in parallel.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of medical equipment, and in particular to an isolated resonant power supply circuit and a magnetic resonance imaging system. 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 transmitting / receiving chain module, a transmitting / receiving coil, etc., wherein the transmitting / receiving chain module generates a radio frequency pulse signal and transmits it to the transmitting / receiving coil, and the transmitting / 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 transmitting / receiving coil collects the magnetic resonance signal after spatial encoding, and the transmitting / receiving chain module receives and processes the magnetic resonance signal to reconstruct a 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, in order to reduce the volume and reduce the cost, 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. Utility Model Content

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

[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 resonance conversion on the alternating current and then output the transformed alternating current to the rectifier circuit; and

[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 transformer circuit comprises an air-core transformer, a first capacitor, a second capacitor and an inductor, wherein the first capacitor, the second capacitor and the inductor are connected in series, and the second capacitor is connected in parallel with the primary winding of the air-core transformer.

[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; and

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

[0017] 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

[0018] 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:

[0019] Figure 1 is a schematic diagram of a magnetic resonance imaging system according to an embodiment of the present application;

[0020] Figure 2 is a schematic diagram of an isolated resonant power supply circuit according to an embodiment of the present application;

[0021] Figure 3 is a schematic diagram of an inverter circuit of an embodiment of the present application;

[0022] Figure 4 is a schematic diagram of a voltage stabilizing circuit according to an embodiment of the present application;

[0023] Figure 5 is a schematic diagram of a resonant transformer circuit according to an embodiment of the present application;

[0024] Figure 6 is a schematic diagram of a voltage doubler rectifier circuit according to an embodiment of the present application;

[0025] Figure 7 is a schematic diagram of an isolated resonant power supply circuit in a scanning room of an embodiment of the present application;

[0026] Figure 8 is a schematic diagram of a magnetic resonance imaging system according to an embodiment of the present application;

[0027] Fig. 9 Schematic diagram of an isolated resonant power supply circuit according to an embodiment of the present application. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0032] For ease of understanding, Figure 1 A magnetic resonance imaging (MRI) system 10 of some embodiments of the present application is shown.

[0033] 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 an interactive graphical interface.

[0034] 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.

[0035] 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.

[0036] In some embodiments, the pulse generator 38 may be integrated into a scanner device (e.g., a resonance assembly 52). The system controller 32 receives commands from an operator via a 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 a gradient amplifier 42 and generates data called gradient waveforms that control the timing and shape of the gradient pulses to be used during scanning.

[0037] 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.

[0038] 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 transceiver 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 transceiver switch 62. Alternatively, the signals emitted by the excited nuclei can be sensed by a separate receiving 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 transceiver switch 62 is controlled by a signal from the pulse generator 38 to electrically connect the radio frequency amplifier 60 to the whole body radio frequency coil 56 during the transmit mode and to connect the preamplifier 64 to the whole body radio frequency coil 56 during the receive mode. The transceiver 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.

[0039] 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 the memory 66 in the system controller 32. 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, most commonly Fourier transforms. 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.

[0040] 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 power supply must have a high switching frequency, 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 power supply voltage V and V cannot be very high due to the charging and discharging. If the voltage becomes larger, the switching loss will increase significantly. Therefore, this conventional power supply circuit cannot be used in high input / output voltage occasions.

[0041] In order to solve at least one of the above problems, the present application provides an isolated resonant power supply circuit and a magnetic resonance imaging system, which will be described below in conjunction with the embodiments.

[0042] 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. The one or more devices require a high voltage power supply.

[0043] For example, the isolated resonant power supply circuit can be used to power the RF switch in the scanning room. The RF switch can be a diode (such as a PIN tube), which is set in the transmitting / receiving coil and is used to switch the state of the transmitting / receiving coil (such as a body coil) to be a transmitting coil or a receiving coil. For example, the RF switch can be Figure 1The transceiver conversion switch 62 in the scanning room. The isolated resonant power supply circuit can be integrated on the circuit board of the RF transceiver controller in the scanning room, and the RF transceiver controller is connected to the RF switch in the transmitting / receiving coil through a cable. When the RF switch is provided with current conduction by the RF transceiver controller, the transmitting / receiving coil acts as a transmitting coil, and the RF pulse signal is transmitted to the transmitting coil. The transmitting coil generates a RF excitation signal to excite the scanning object to generate a magnetic resonance signal, and then the RF transceiver controller provides a reverse voltage (provided by the isolated resonant power supply circuit) to the RF switch, and the RF switch is reversely cut off, and the RF pulse signal cannot be transmitted to the coil. The transmitting / receiving coil acts as a receiving coil to receive and process the magnetic resonance signal. The above is only an example, and the embodiment of the present application is not limited to this. The isolated resonant power supply circuit can also power other devices. By setting 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.

[0044] 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;

[0045] 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;

[0046] 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;

[0047] 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;

[0048] In some embodiments, the inverter circuit 201 can convert direct current into alternating current. Figure 3 Schematic diagram of the inverter circuit structure of the embodiment of the present application. Figure 3As shown, the inverter circuit 201 includes a voltage-frequency converter 301, an isolation drive circuit 302 and a plurality of switch tubes 303, and the voltage-frequency converter 301 is used to generate a square wave voltage with a duty cycle of 50%. The input end of the isolation drive circuit 302 is connected to the output end of the voltage-frequency converter 301, and the output end of the isolation drive circuit 302 is connected to the plurality of switch tubes 303, which is used to generate a complementary drive signal, and sequentially drive at least one of the plurality of switch tubes 303 to be turned on, and the plurality of switch tubes can constitute a full-bridge circuit (for example, including 4 power switch tubes), or a half-bridge circuit (for example, including 2 power switch tubes), and the embodiment of the present application is not limited to this. In addition, the isolation drive circuit 302 can be connected to the plurality of switch tubes through a resistor, and the resistance value of the resistor can be designed as needed. The above switching tubes are various power semiconductor switching devices including power Metal Oxide Semi-Conductor Field Effect Transistors (MOSFET), Insulated Gate Bipolar Transistor (IGBT), BJT, thyristor, IGCT, etc.

[0049] Figure 3 Taking a half-bridge circuit (including two power switches M1 and M2) as an example, the isolation drive circuit 302 generates two complementary drive signals DA and DB, DA and DB are respectively connected to the G poles (bases) of M1 and M2 via resistors, and the D pole (collector) of M1 is connected to the input DC voltage V in The S pole (emitter) of M1 is connected to the D pole of M2 (as the output end of the inverter circuit) and then connected to the input end of the resonant transformer circuit. The S pole of M2 is grounded. The two complementary drive signals DA and DB make M2 cut off when M1 is turned on, and M1 cut off when M2 is turned on.

[0050] The above components and connection relationships of the inverter circuit 201 are only examples for illustration. For details, please refer to the relevant technology, and this application is not limited to this.

[0051] In some embodiments, the square wave voltage is frequency-adjustable, and the frequency of the square wave voltage generated by the voltage-frequency converter can be adjusted according to the output voltage feedback of the isolated resonant power supply circuit. The isolated resonant power supply circuit can also include a voltage stabilizing circuit 204, the output end of the voltage stabilizing circuit 204 is connected to the input end of the voltage-frequency converter 301, and the input voltage of the voltage stabilizing circuit 204 is the output DC voltage Vo of the isolated resonant power supply circuit. The frequency of the square wave voltage generated by the voltage-frequency converter 301 can be adjusted according to the dynamic change of the output DC voltage of the resonant power supply circuit with the load, which will cause the power flowing from the primary side to the secondary side to change accordingly, and the change of the power can further compensate for the dynamic change of the output DC voltage, so as to achieve the effect of output voltage stabilization. For example, when the output DC voltage increases, the input voltage of the voltage-frequency converter 301 (the output voltage of the voltage stabilizing circuit 204) will change greatly, so that the resonant frequency is reduced (away from the maximum resonant frequency), and the power flowing from the primary side to the secondary side is reduced, thereby reducing the output voltage and making the output DC voltage more stable.

[0052] Figure 4 204 is a schematic diagram of the voltage stabilizing circuit 204 of the embodiment of the present application. Figure 4 As shown, the voltage stabilizing circuit 204 includes an optocoupler isolator 401, a terminal T1 of the optocoupler isolator 401 is used to input the output DC voltage Vo of the rectifier circuit 203 (via a resistor, a capacitor), a terminal T2 of the optocoupler isolator 401 is used for grounding, a terminal T3 of the optocoupler isolator 401 is used to input the power supply voltage (via a resistor), and a terminal T4 of the optocoupler isolator 401 is used to connect to the input end of the voltage-frequency converter 301 (via a resistor). The parameters of the optocoupler isolator 401 and the values ​​of each resistor can be designed as needed. The voltage stabilizing circuit can also include other circuit devices or use other circuit structures. For details, please refer to the relevant technology, and the embodiments of the present application are not limited to this.

[0053] In some embodiments, the voltage-to-frequency converter 301 may also be connected to a third capacitor 3011. After the voltage is input, the third capacitor 3011 enters a charging state to achieve a slow increase in voltage and realize soft start.

[0054] In some embodiments, the isolation drive circuit 302 may also input a control signal 3021, through which the isolation drive circuit 302 is controlled to be turned on or off. The control signal may be a voltage signal. For example, when the voltage signal is 5V, the isolation drive circuit 302 is turned on to generate a complementary drive signal. When the voltage signal is 0V, the isolation drive circuit 302 is turned off and no drive signal is generated.

[0055] In some embodiments, the alternating current (high-frequency square wave) output by the inverter circuit 201 is applied to the resonant transformer circuit 202 to generate resonance, eliminate the harmonics of the square wave, and output a sine wave. The sine wave is transmitted from the primary side to the secondary side through the transformer, and the voltage is boosted according to application requirements and connected to the rectifier circuit 203 to output the transformed sine wave to the rectifier circuit 203.

[0056] Figure 5 Schematic diagram of the resonant transformer circuit 202 according to an embodiment of the present application. Figure 5 As shown, the resonant transformer circuit 202 includes an air-core transformer 2021 and a resonant component, and the resonant component includes a first capacitor 2022, a second capacitor 2023 and an inductor 2024. The first capacitor 2022, the second capacitor 2023 and the inductor 2024 are connected in series, but the embodiment of the present application does not limit the series connection order. For example, the first capacitor 2022 can be located between the inductor 2024 and the second capacitor 2023, and the other end of the inductor 2024 is connected to the output end of the inverter circuit 201 as the input end of the resonant transformer circuit 202; or, the inductor 2024 can be located between the first capacitor 2022 and the second capacitor 2023, and the other end of the first capacitor 2022 is connected to the output end of the inverter circuit 201 as the input end of the resonant transformer circuit 202, and no more examples are given here.

[0057] In some embodiments, the second capacitor 2023 is connected in parallel with the primary winding of the air-core transformer 2021. The equivalent circuit model of the air-core transformer 2021 includes inherent lumped circuit parasitic elements, which include a primary inductance Lp. The primary inductance Lp is not a real component. Figure 5 Only for the purpose of exemplifying the effect of the existence of the primary inductance, the second capacitor 2023 can be regarded as being connected in parallel with the primary inductance Lp (i.e., the excitation inductance). By connecting the second capacitor 2023 in parallel with the primary winding of the air-core transformer 2021 to form a parallel resonance, a high resonant voltage can be obtained on the primary inductance of the transformer. In addition, the first capacitor 2022 and the inductor 2024 resonate to achieve zero voltage switching (zero voltage switching, ZVS) soft switching on multiple switch tubes in the inverter circuit, thereby reducing switching losses. The capacitance values ​​of the first capacitor, the second capacitor, and the inductance value of the inductor can be designed according to the resonant frequency, and the embodiments of the present application are not limited thereto.

[0058] In some embodiments, the air-core transformer 2021 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. An embodiment of the present application also provides an air-core transformer, which includes a skeleton (made of materials such as wood, rubber, or plastic), on which a primary winding and multiple (N, N is an integer greater than 1) secondary windings are wound in the same manner (winding direction and winding number of turns are the same).

[0059] In some embodiments, a first number (the first number is an integer greater than N) of insulated wires (for example, in order to adapt to the high-voltage power supply circuit and improve safety, the insulated wire can use triple insulated wires) can be twisted together to form a wire harness, and the wire harness is tightly wound around the skeleton in multiple turns, or the first number of insulated wires can be wound around the skeleton in parallel, and the embodiment of the present application is not limited to this. The second number of insulated wires in the first number of insulated wires is used as the primary winding, and the two ends of the second number of insulated wires are connected to the primary circuit of the air-core transformer. The remaining third number of insulated wires in the first number of insulated wires are used as secondary windings, and the third number of insulated wires are evenly divided into N parts, respectively as N secondary windings, and connected to the secondary circuit of the air-core transformer. The second number and the third number are both integers greater than 1 or equal to 1. The second number of insulated wires and the third number of insulated wires can be randomly selected, and the present application is not limited to this. For example, the third number is an integer multiple of N, and considering that the secondary voltage is higher than the primary voltage, therefore, the second number can be greater than the third number / N, but the present application is not limited to this. As an example, a first number of 8 insulated wires are twisted together to form a wiring harness, which is tightly wound around a skeleton in circles. Four wires are randomly selected from one end of the wiring harness as primary winding wires, and the other ends of the 4 insulated wires are determined. One end and the other end of the 4 winding wires are connected to the primary circuit of the air-core transformer, and each of the remaining 4 insulated wires is used as a secondary winding, thereby obtaining 4 secondary windings.

[0060] Since the primary winding and the secondary winding 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 insulating wire in the primary winding is surrounded by multiple secondary insulating wires, the magnetic flux generated by the primary winding can be coupled to the secondary winding to a greater extent. Similarly, the magnetic flux generated by the secondary winding can be coupled to the primary winding to a greater extent. Therefore, in the absence of a magnetic core, the coupling coefficient between the primary and secondary windings can be improved.

[0061] In order to obtain the best coupling coefficient, the number of turns of the primary winding and each of the multiple secondary windings is the same, that is, the number of turns (winding turns) of the primary and secondary windings is the same, so the transformer turns ratio is limited to 1:1.

[0062] In addition, by providing multiple (N) secondary windings, the multiple secondary windings are connected in series, thereby further achieving a boost effect. The number N can be set according to the boost requirement of the output voltage, and the embodiment of the present application is not limited thereto.

[0063] In some embodiments, the rectifier circuit 203 can convert a sine wave into a stable DC voltage output. Optionally, in order to further achieve a boost effect, the rectifier circuit 203 may include N voltage-doubling rectifier circuits connected to N secondary windings, each voltage-doubling rectifier circuit is connected to a secondary winding, and according to the voltage-doubling rectifier circuit, the voltage of the corresponding secondary side can be doubled. If the voltage boost is achieved only by a transformer without setting a voltage-doubling rectifier circuit, when the same boost effect is achieved, compared with setting a voltage-doubling rectifier circuit, there is a large voltage difference between the original secondary side of the transformer, the parasitic capacitor generates a large leakage current, and the transformer loss becomes larger. By setting the voltage-doubling rectifier circuit, the power supply can output a high voltage when the voltage on the transformer is low, thereby making the loss caused by the parasitic capacitor between the original secondary windings low. The above components and connection relationships of the rectifier circuit 203 are only examples, and specific reference can be made to the relevant technology, and this application is not limited to this.

[0064] Figure 6 Schematic diagram of a voltage doubler rectifier circuit according to an embodiment of the present application. Figure 6 As shown, a voltage doubler rectifier circuit includes a capacitor 61, diodes 621 and 631, and a secondary equivalent inductor 641 of a secondary winding, one end of the diode 631 is connected to one end of the secondary winding, the other end is connected to one end of the diode 621 and to one end of the capacitor 61, and the other end of the capacitor 61 is connected to the other end of the secondary winding.

[0065] In some embodiments, Figure 6 As shown, the voltage doubler rectifier circuit may further include a capacitor 65, which may filter the square wave voltage into a DC voltage. The two ends of the capacitor 65 are respectively connected to the other end of the diode 621 and one end of the diode 631. The components and connection relationships of the voltage doubler rectifier circuit are only examples, and the specifics may refer to the relevant technology. The value of the capacitor may be designed as needed, and this application is not limited to this.

[0066] In some embodiments, the isolated resonant power supply circuit 200 may further include an output capacitor 205, the two ends of which are respectively connected to the two output ends of the rectifier circuit 203, that is, connected in parallel with the output end of the rectifier circuit 203, so that the output DC voltage is more stable through the output capacitor 205.

[0067] The inventors found that due to the large parasitic capacitance generated between the primary and secondary windings, a higher switching frequency will cause higher power loss. Therefore, the switching frequency of the isolated resonant power supply circuit in the embodiment of the present application needs to be limited to a smaller value (e.g., about 500kHz). However, in a magnetic resonance system, a smaller switching frequency may cause switching noise on the sampling window. To address this problem, the isolated resonant power supply circuit is sealed in a shielding box. The input terminal and output terminal of the isolated resonant power supply circuit are respectively connected to an EMI filter to prevent the above noise from entering the sampling window.

[0068] Figure 7 is a schematic diagram of an isolated resonant power supply circuit in a scanning room of an embodiment of the present application, such as Figure 7 As shown, the isolated resonant power supply circuit 200 (integrated on PCB70) is sealed in a shielding box (e.g., a metal shell) 71, and the input and output ends of the isolated resonant power supply circuit are respectively connected to EMI filters 72 and 73, and the EMI filter may include a common mode inductor, and optionally, a capacitor, which includes two wires wound in parallel on a hollow bobbin. The shielding box can be integrated on a circuit board of a radio frequency transceiver controller in a scanning room, but the embodiment of the present application is not limited thereto.

[0069] In some embodiments, Figure 7 As shown, the isolated resonant power supply circuit introduces interference into the shielding box through the wire 74. In addition, some components in the isolated resonant power supply circuit are in contact with the shell of the shielding box via the thermal pad 75. For example, the switch tubes M1 and M2 in the isolated resonant power supply circuit may generate a lot of heat. The heat is transferred to the shielding box through the insulating thermal pad 75, which can increase the service life of the power supply circuit.

[0070] In some embodiments, Figure 7 As shown, part of the circuit functions of the isolated resonant power supply circuit can be designed on an independent control board 761 (vertical board), and the control board 761 is mounted on the PCB 70 through pins, thereby reducing the volume of the isolated resonant power supply circuit.

[0071] It can be seen from the above embodiments that existing ordinary switching tubes are hard switches. When turning on and off, the drain-source voltage and current of the switching tube will overlap. The area where the voltage and current overlap is the turn-on loss and turn-off loss of the switching tube. Especially when the voltage of the power supply circuit is increased, the switching loss will increase significantly.

[0072] In the embodiment of the present application, the second capacitor 2023 is connected in parallel with the primary winding of the air-core transformer 2021 to form a parallel resonance, and a high resonant voltage can be obtained on the primary inductance of the transformer. In addition, the first capacitor 2022 and the inductor 2024 resonate to achieve zero voltage switching (ZVS) soft switching on multiple switching tubes in the inverter circuit, thereby reducing switching losses.

[0073] 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.

[0074] In the embodiment of the present application, a plurality of (N) secondary windings are provided, and the plurality of secondary windings are connected in series, thereby further achieving a voltage boosting effect.

[0075] In the embodiment of the present application, by providing the voltage doubling rectifier circuit, the power supply can output a high voltage when the voltage on the transformer is low, thereby reducing the loss caused by the parasitic capacitance between the primary and secondary windings.

[0076] For example, when the input voltage is 48V, the primary voltage can be increased to about 70V through the resonant circuit, and each secondary voltage can reach about 140V after passing through the voltage doubler rectifier circuit. Since N=4, after 4 secondary sides are connected in series, the output voltage can reach about 550V.

[0077] In the embodiment of the present application, the isolated resonant power supply circuit is sealed in a shielding box. Filters are provided on both the input and output terminals to suppress noise from entering the sampling window of the magnetic resonance system.

[0078] The present application also provides a magnetic resonance imaging system. The magnetic resonance imaging system is composed of Figure 8 As shown, Figure 1 The repetitive parts will not be repeated.

[0079] In some embodiments, Figure 1The 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 a radio frequency switch in the scanning room, and the radio frequency switch can be a diode (such as a PIN tube), and the radio frequency switch can be used to switch the state of the transmit / receive chain module, such as Figure 8 The transmit / receive conversion switch 62 in the embodiment of the present application is not limited thereto.

[0080] In some embodiments, the isolated resonant power supply circuit 200 can be arranged in the scanner housing, for example, in the space between the main magnet and the housing, and connected to the RF switch through a cable to power the RF switch, but the embodiment of the present application is not limited thereto. The isolated resonant power supply circuit 200 can also be arranged in the scanning room, but outside the scanner housing, and connected to the RF switch through a cable to power the RF switch, which will not be exemplified one by one here.

[0081] Fig. 9 is an example diagram of an isolated resonant power supply circuit according to an embodiment of the present application, such as Fig. 9 As shown, the isolated resonant power supply circuit includes a voltage-frequency converter 91, an isolated drive circuit 92, a half-bridge circuit 93, an LCC resonant circuit 94, an air-core transformer 95, four voltage-doubling rectifier circuits 96, an output capacitor 97, and a voltage stabilizing circuit 98. The composition of the above-mentioned circuits and the connection relationship of the devices are as described above and will not be repeated here. The values ​​of each resistor, capacitor, inductor, and voltage device can be designed as needed, and the embodiments of the present application are not limited to this.

[0082] The above embodiments are merely exemplary of the embodiments of the present application, but the present application is not limited thereto, and appropriate modifications may be made based on the above embodiments. For example, the above embodiments may be used alone, or one or more of the above embodiments may be combined.

[0083] The embodiments of the present application are 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 embodiments of the present application. Those skilled in the art can make various modifications and variations to the embodiments of the present application based on the spirit and principles of the embodiments of the present application, and these modifications and variations are also within the scope of the embodiments of the present application.

[0084] The preferred embodiments of the present application are described above with reference to the accompanying drawings. Many features and advantages of these embodiments are clear from this detailed description, and therefore the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. In addition, since many modifications and changes are easily conceivable to those skilled in the art, it is not intended to limit the embodiments of the present application to the precise structures and operations illustrated and described, but all suitable modifications and equivalents that fall within its scope may be covered.

Claims

1. An isolated resonant power supply circuit, which is arranged in a scanning room of a magnetic resonance imaging system, characterized in that: The isolated resonant power supply circuit comprises: an inverter circuit, a resonant transformer circuit, and a 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; and 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 transformer circuit includes an air-core transformer, a first capacitor, a second capacitor and an inductor, the first capacitor, the second capacitor and the inductor are connected in series, and the second capacitor is connected in parallel with the primary winding of the air-core transformer.

2. The isolated resonant power supply circuit according to claim 1, characterized in that: The air-core transformer includes a plurality of secondary windings connected in series.

3. The isolated resonant power supply circuit according to claim 2, characterized in that: The air-core transformer further includes a frame, on which the primary winding and the plurality of secondary windings are wound in the same manner, and the number of turns of the primary winding and each of the plurality of secondary windings is the same.

4. The isolated resonant power supply circuit according to claim 2, characterized in that: The rectifier circuit includes a voltage doubler rectifier circuit connected to each secondary winding.

5. The isolated resonant power supply circuit according to claim 1, characterized in that: The inverter circuit at least includes a voltage-frequency converter for generating a square wave voltage with a duty cycle of 50%; wherein the frequency of the square wave voltage generated by the voltage-frequency converter is adjusted according to the output voltage feedback of the isolated resonant power supply circuit.

6. The isolated resonant power supply circuit according to claim 1, characterized in that: The isolated resonant power supply circuit is sealed in a shielding box.

7. The isolated resonant power supply circuit according to claim 6, characterized in that: The input terminal and the output terminal of the isolated resonant power supply circuit are respectively connected to the EMI filter.

8. The isolated resonant power supply circuit according to claim 6, characterized in that: Some components in the isolated resonant power supply circuit are in contact with the shell of the shielding box via a thermal pad.

9. A magnetic resonance imaging system, characterized in that: include: 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; as well as, The isolated resonant power supply circuit according to any one of claims 1 to 8 is arranged in a scanning room of the magnetic resonance imaging system and supplies power to devices in the scanning room.

10. The magnetic resonance imaging system according to claim 9, characterized in that: The devices in the scanning room include: a radio frequency switch; In addition, the isolated resonant power supply circuit is connected to the radio frequency switch to supply power to the radio frequency switch.

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