A direct current motor electromagnetic interference suppression circuit and dental X-ray machine

Abstract

The application provides a direct current motor electromagnetic interference suppression circuit, which comprises a first filter circuit, a second filter circuit and a third filter circuit; the first filter circuit is connected in parallel to both ends of the direct current motor and is used for absorbing low-frequency high-order harmonics generated during commutation of the direct current motor; the second filter circuit is connected in cascade with the first filter circuit and is used for filtering out medium-frequency noise signals generated during operation of the direct current motor; and the third filter circuit is connected in cascade with the second filter circuit and is used for filtering out high-frequency common-mode interference signals. The direct current motor electromagnetic interference suppression circuit adopts a three-stage composite filter architecture and can precisely and efficiently suppress wide-frequency electromagnetic interference generated by the direct current motor.

Description

Technical Field

[0001] This utility model relates to the field of medical imaging equipment technology, and in particular to a DC motor electromagnetic interference suppression circuit and a dental X-ray machine. Background Technology

[0002] Dental X-ray machines, especially CBCT (cone-beam computed tomography), contain sophisticated X-ray tubes, flat panel detectors, and sensitive electronic control systems. These devices are extremely sensitive to electromagnetic interference. However, the DC brushed motors used in CBCTs to drive the patient positioning system, light field indicator, or collimator generate strong broadband electromagnetic interference during brush commutation. This interference spectrum can extend from tens of MHz to the GHz band, severely contaminating the weak signals acquired by the X-ray detector. This results in noise and streaking artifacts in the reconstructed two-dimensional or three-dimensional images, reducing image quality and affecting diagnostic accuracy.

[0003] In existing technologies, single-stage LC filtering or metal shielding methods are commonly used (which are costly, accounting for 15%-20% of the total cost of the motor). However, single suppression methods often fail to cover the entire interference spectrum from low to high frequencies, resulting in limited effectiveness. Therefore, there is an urgent need for a comprehensive solution that can effectively and hierarchically suppress broadband electromagnetic interference. Utility Model Content

[0004] This application proposes a DC motor electromagnetic interference suppression circuit and a dental X-ray machine, which precisely and efficiently suppresses the wideband electromagnetic interference signals generated by the DC motor during operation in different frequency bands, thereby ensuring the imaging quality of the dental X-ray machine.

[0005] In a first aspect, this application provides a DC motor electromagnetic interference suppression circuit, the circuit comprising:

[0006] The first filter circuit is connected in parallel to both ends of the DC motor to absorb the low-frequency high-order harmonics generated when the DC motor is commutated.

[0007] A second filter circuit, cascaded with the first filter circuit, is used to filter out the intermediate frequency noise signal generated when the DC motor is operating; and

[0008] The third filter circuit, cascaded with the second filter circuit, is used to filter out high-frequency common-mode interference signals.

[0009] Secondly, this application provides a dental X-ray machine, comprising:

[0010] PC, used to issue commands according to user needs;

[0011] The motherboard is used to issue control signals according to the instructions issued by the PC;

[0012] The X-ray tube emits X-rays according to the control signal from the main board.

[0013] The detector is used to receive and image X-rays that have passed through the irradiated object according to the control signals of the main board;

[0014] A DC motor driver is used to provide intermittently adjustable power signals based on control signals from the main board.

[0015] A DC motor, the speed of which is adjusted according to the intermittently adjustable power supply signal; and

[0016] The DC motor electromagnetic interference suppression circuit described above is connected between the DC motor driver and the DC motor.

[0017] Compared with existing technologies, the electromagnetic interference suppression circuit of DC motor in this invention adopts a three-level composite filter architecture to suppress low-frequency high-order harmonics, intermediate-frequency noise signals and high-frequency common-mode signals generated when DC motor is working. This achieves "full coverage" precise and efficient suppression of wideband electromagnetic interference signals, with suppression efficiency far exceeding that of single methods. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the modules of the dental X-ray machine in the embodiments of this application;

[0020] Figure 2 This is a specific circuit diagram of a DC motor electromagnetic interference suppression circuit in an embodiment of this application.

[0021] Figure label:

[0022] 10. Dental X-ray machine; 101. PC; 102. AC power supply; 103. AC / DC conversion module; 104. Switch; 105. Motherboard; 106. X-ray tube; 107. First detector; 108. Second detector; 109. DC motor driver; 110. DC motor electromagnetic interference suppression circuit; 1101. First filter circuit; 1102. Second filter circuit; 1103. Third filter circuit; 111. DC motor; C1. First capacitor; L1. First ferrite bead; L2. Second ferrite bead; C2. Second capacitor; C3. Third capacitor; L3. Common mode inductor. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0026] Please see Figure 1 This application provides a schematic diagram of a dental X-ray machine 10, including a PC (Personal Computer) 101, an AC power supply 102, an AC / DC conversion module 103, a switch 104, a motherboard 105, an X-ray tube 106, a first detector 107, a second detector 108, a DC motor driver 109, a DC motor electromagnetic interference suppression circuit 110, and a DC motor 111.

[0027] The AC power supply 102 is connected to the PC 101, the AC / DC conversion module 103, and the X-ray tube 106 to provide AC power. The AC / DC conversion module 103 is connected between the AC power supply 102 and the switch 104, the motherboard 105, the first detector 107, and the second detector 108 to convert the received AC power into DC power for power supply. The switch 104 is connected between the PC 101 and the first detector 107 and the second detector 108, and the switch 104 is connected to the PC 101 via a local area network. The motherboard 105 is connected to the PC 101, the X-ray tube 106, the first detector 107, the second detector 108, and the DC motor driver 109. The DC motor driver 109 is connected to the DC motor 111 via a wire. The longer the wire, the more severe the electromagnetic interference. Therefore, the DC motor electromagnetic interference suppression circuit 110 is connected between the DC motor driver 109 and the DC motor 111 to suppress the broadband electromagnetic radiation generated when the brush head commutates. In this embodiment, the DC motor driver 109 is used to provide an intermittently adjustable power signal, and then the DC motor 111 adjusts its speed according to the intermittently adjustable power signal.

[0028] In this embodiment, PC 101 sends a command to motherboard 105 according to user needs. Specifically, when the doctor begins acquiring patient images, motherboard 105 sends a control signal based on the PC 101's command, controlling the DC motor driver 109, X-ray tube 106, and first detector 107 and second detector 108 to begin operation. That is, motherboard 105 drives DC motor 111 via DC motor driver 109 to control the motion mechanism, controlling X-ray tube 106 to emit X-rays. First detector 107 and second detector 108 receive the X-rays passing through the irradiated object and form an image according to the control signal from motherboard 105. Simultaneously, PC 101 can read the images from first detector 107 and second detector 108 via switch 104 and reconstruct three-dimensional or two-dimensional images using algorithms to provide fluoroscopic information to the doctor. In this embodiment, PC 101 and motherboard 105 are connected via a serial data communication interface RS232.

[0029] In this embodiment, the dental X-ray machine 10 employs two detectors to expand the scanning field of view and acquire the entire skull image in a single scan. This effectively expands the coverage area along the Z-axis (vertical direction), eliminating the need for stitching two scans to obtain a three-dimensional image. In other embodiments of this invention, for optimal cost optimization, the dental X-ray machine 10 may also use only one detector to achieve three-dimensional imaging.

[0030] In this invention, the DC motor electromagnetic interference suppression circuit 110 adopts a three-stage composite filter architecture, the specific circuit structure of which is as follows: Figure 2As shown, the DC motor electromagnetic interference suppression circuit 110 includes a first filter circuit 1101, a second filter circuit 1102, and a third filter circuit 1103. The first filter circuit 1101 is connected in parallel across the DC motor 111 and includes a first capacitor C1 for absorbing high-order harmonics generated during commutation of the DC motor 111. In this embodiment, the first capacitor C1 is a ceramic capacitor, positioned as close as possible to the DC motor 111, and has a capacitance of 100nF. When the DC motor 111 commutates, it generates high-order harmonics in the 10MHz-30MHz frequency band. The first filter circuit 1101 provides a local discharge loop with extremely low impedance, effectively attenuating low-frequency harmonic emission energy from the source by absorbing the harmonic energy in this frequency band and greatly reducing the loop area of ​​the high-frequency noise current.

[0031] The second filter circuit 1102 is cascaded with the first filter circuit 1101 to filter the intermediate frequency noise generated when the DC motor 111 is working. It includes a first ferrite bead L1, a second ferrite bead L2, a second capacitor C2, and a third capacitor C3. One end of the first ferrite bead L1 is connected to one end of the first capacitor C1, and the second capacitor C2 is connected in parallel with the first ferrite bead L1, forming a first energy-dissipating filter circuit. The end of the first ferrite bead L1 connected to the first capacitor C1 serves as the input terminal of the first energy-dissipating filter circuit. One end of the second ferrite bead L2 is connected to the other end of the first capacitor C1, and the third capacitor C3 is connected in parallel with the second ferrite bead L2, forming a second energy-dissipating filter circuit. The end of the second ferrite bead L2 connected to the first capacitor C1 serves as the input terminal of the second energy-dissipating filter circuit. The other end of the first ferrite bead L1 serves as the output terminal of the first energy-dissipating filter circuit, and the other end of the second ferrite bead L2 serves as the output terminal of the second energy-dissipating filter circuit. In this embodiment, the first magnetic bead L1 and the second magnetic bead L2 are both ferrite beads with an equivalent inductance of 10uH each; the second capacitor C2 and the third capacitor C3 are film capacitors with a capacitance of 10nF each. The second filter circuit 1102 utilizes the high resistance characteristics of the first magnetic bead L1 and the second magnetic bead L2 at high frequencies to prevent the conduction of intermediate frequency harmonic energy in the 50MHz-200MHz frequency band along the conductor to the downstream circuit, and converts this energy into heat for dissipation. Simultaneously, the first and second energy-dissipating filter circuits can further filter out intermediate frequency noise at specific frequency points. In this embodiment, the second filter circuit 1102 is positioned as close as possible to the DC motor 111.

[0032] The third filter circuit 1103 is cascaded with the second filter circuit 1102 to filter out common-mode interference signals. It includes a common-mode inductor L3, which has a first terminal, a second terminal, a third terminal, and a fourth terminal. In this embodiment, the first terminal of the common-mode inductor L3 is connected to the output terminal of the first energy-dissipating filter circuit, its second terminal is connected to the output terminal of the second energy-dissipating filter circuit, and its third and fourth terminals are connected to the DC motor driver 109 to receive intermittent power signals output by the DC motor driver 109. In other embodiments of this invention, when the wires of the DC motor 111 are long, the third filter circuit 1103 may include multiple common-mode inductors L3, spaced apart and arranged in series, to enhance and suppress noise in specific high-frequency bands. In this invention, the common-mode inductor L3 exhibits extremely high impedance to common-mode interference with frequencies above 200MHz, thereby effectively suppressing high-frequency common-mode noise signals generated by the long motor wires.

[0033] In summary, the DC motor electromagnetic suppression circuit 10 with a three-stage filtering architecture in the dental X-ray machine of this invention has the following advantages:

[0034] First, it employs tiered precision suppression, targeting the interference characteristics of low-frequency (10-30MHz), mid-frequency (50-200MHz), and high-frequency (>200MHz) frequencies respectively. By selecting the most suitable components and topologies, it achieves a "full-coverage" precision strike against broadband electromagnetic interference, with suppression efficiency far exceeding that of a single method.

[0035] Secondly, the combination of source suppression and path blocking, with the first-stage filter circuit absorbing noise at its source (the DC motor end), is the most direct and effective measure. The second and third-stage filter circuits then block the noise propagation path, preventing interference energy from contaminating the overall power supply and signal system. This combined design fundamentally suppresses interference.

[0036] Furthermore, to ensure image quality, by effectively suppressing electromagnetic interference generated by the DC motor, the possibility of image artifacts and noise is greatly reduced, ensuring the clarity and reliability of dental X-ray machine (especially CBCT) output images, thereby guaranteeing the quality of dental X-ray imaging.

[0037] Finally, it has a simple structure and low cost, using common passive components. The circuit structure is simple and easy to integrate and implement on existing motor drive circuits, giving it a high cost-performance ratio and promising industrialization prospects.

[0038] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0039] Unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0041] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0042] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0043] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A DC motor electromagnetic interference suppression circuit, characterized in that, The circuit includes: The first filter circuit is connected in parallel to both ends of the DC motor to absorb the low-frequency high-order harmonics generated when the DC motor is commutated. A second filter circuit, cascaded with the first filter circuit, is used to filter out the intermediate frequency noise signal generated when the DC motor is operating; and The third filter circuit, cascaded with the second filter circuit, is used to filter out high-frequency common-mode interference signals; The first filter circuit includes a first capacitor, which is connected in parallel across the two ends of the DC motor and is positioned close to the DC motor; The second filter circuit includes: A first magnetic bead, one end of which is connected to one end of the first capacitor; and The second magnetic bead has one end connected to the other end of the first capacitor; The second filter circuit includes; The second capacitor is connected in parallel with the first ferrite bead to form the first energy-consuming filter circuit, wherein the end of the first ferrite bead connected to the first capacitor serves as the input terminal of the first energy-consuming filter circuit. The third capacitor is connected in parallel with the second ferrite bead to form the second energy-consuming filter circuit, wherein the end of the second ferrite bead connected to the first capacitor serves as the input terminal of the second energy-consuming filter circuit. Wherein, the other end of the first magnetic bead serves as the output terminal of the first energy-consuming filter circuit, and the other end of the second magnetic bead serves as the output terminal of the second energy-consuming filter circuit; The third filter circuit includes a common-mode inductor for suppressing common-mode interference signals. It has a first terminal, a second terminal, a third terminal, and a fourth terminal. The first terminal of the common-mode inductor is connected to the output terminal of the first energy-consuming filter circuit, the second terminal is connected to the output terminal of the second energy-consuming filter circuit, and the third and fourth terminals are used to receive intermittently adjustable power signals.

2. The DC motor electromagnetic interference suppression circuit as described in claim 1, characterized in that, The first capacitor is a ceramic capacitor with a capacitance of 100nF.

3. The DC motor electromagnetic interference suppression circuit as described in claim 1, characterized in that, The first and second magnetic beads are both ferrite beads with an equivalent inductance of 10uH. The second and third capacitors are film capacitors with a capacitance of 10nF.

4. The DC motor electromagnetic interference suppression circuit as described in claim 1, characterized in that, The third filter circuit includes multiple common-mode inductors, which are arranged in series.

5. A dental X-ray machine, characterized in that, include: PC, used to issue commands according to user needs; The motherboard is used to issue control signals according to the instructions issued by the PC; The X-ray tube emits X-rays according to the control signal from the main board. The detector is used to receive and image X-rays that have passed through the irradiated object according to the control signals of the main board; A DC motor driver is used to provide intermittently adjustable power signals based on control signals from the main board. A DC motor, the speed of which is adjusted according to the intermittently adjustable power supply signal; as well as The DC motor electromagnetic interference suppression circuit as described in any one of claims 1-4 is connected between the DC motor driver and the DC motor.

6. A dental X-ray machine as described in claim 5, characterized in that, The number of detectors is one or two.

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