CN110456291B

CN110456291B - Filter circuit and electronic device

Info

Publication number: CN110456291B
Application number: CN201910803568.XA
Authority: CN
Inventors: 张毅; 邱丰伟
Original assignee: Microport Sorin CRM Shanghai Co Ltd
Current assignee: Microport Sorin CRM Shanghai Co Ltd
Priority date: 2019-08-28
Filing date: 2019-08-28
Publication date: 2021-12-24
Anticipated expiration: 2039-08-28
Also published as: CN110456291A; WO2021037169A1

Abstract

The invention provides a filter circuit and an electronic device, which are provided with a differential-mode and common-mode filter module, a differential-mode filter module and a common-mode filter module which are connected in sequence, can provide good inhibition effect on radio frequency signals generated in the MRI process or electromagnetic interference signals in EMC test and the like, and have simple circuit structure and small occupied space; the input impedance can be balanced, the common mode and differential mode rejection performance is improved, and the sensing or output effect of actual signals is improved; in addition, the signal output by the filter circuit is completely a common mode signal, and no potential difference caused by the electromagnetic wave interference signal is generated between the anode output end and the cathode output end, and no current caused by the electromagnetic wave interference signal flows through the load of the post-stage circuit, so that the suppression and attenuation effects of the post-stage circuit connected with the output end of the filter circuit on the electromagnetic wave interference signal are favorably improved.

Description

Filter circuit and electronic device

Technical Field

The invention relates to the technical field of medical instruments, in particular to a filter circuit and an electronic device.

Background

Magnetic Resonance Imaging (MRI) is one type of medical tomography. Compared with Computed Tomography (CT), MRI has comparable CT performances such as no ionizing radiation damage and extremely high soft tissue imaging accuracy, which makes MRI have important application value in the medical diagnosis field today. However, MRI scans generate powerful electromagnetic fields, and patients with Implanted Pacemakers (IPGs), Implanted defibrillators (ICDs), and other types of active implantable medical devices are generally not allowed to perform MRI scans for safety.

Taking a cardiac pacemaker as an example, a plurality of cardiac pacemaker products are available at present, and the influence on the cardiac pacemaker and the temperature rise of MRI radio frequency generated on a pacing electrode lead are reduced by optimizing the structure design of the cardiac pacemaker and the design of the pacing electrode lead, so that a patient with the cardiac pacemaker can carry out MRI scanning under certain conditions, namely the MRI compatibility of the cardiac pacemaker is realized. But these pacemaker products must be set to an MRI safe mode before MRI scanning to turn off the pacemaker's sensing module. Under the MRI safe mode, the electrocardiosignals can not be collected, and the cardiac pacemaker can not enter the normal working state, and the main reason is that the weak electrocardiosignals under the MRI environment are submerged in the MRI electromagnetic field interference.

In summary, the MRI electromagnetic field may affect the normal use of the active implantable medical device, and induce current at the electrode lead, which may cause heat generation of the electrode lead, and these may damage the body of the patient.

Disclosure of Invention

The present invention is directed to a filter circuit and an electronic device that can suppress electromagnetic interference such as a high power Radio Frequency (RF) signal generated in a magnetic resonance imaging process.

In order to achieve the above object, the present invention provides a filter circuit including: the device comprises an anode input end, a cathode input end, an anode output end, a cathode output end, a difference-common mode filtering module, a difference-mode filtering module and a common mode filtering module; wherein the differential-common mode filter module is connected between the anode input terminal and the cathode input terminal; the differential mode filtering module is arranged between the output end of the differential mode and common mode filtering module and the input end of the common mode filtering module; the common mode filtering module is connected between the anode output end and the cathode output end; the difference common mode filter module and the common mode filter module are both provided with grounding ends.

Optionally, the differential-common mode filter module includes a first capacitor, a second capacitor and a third capacitor, the first capacitor and the second capacitor are connected in series to form a first series branch, one end of the first series branch is connected to the anode input end, the other end of the first series branch is connected to the cathode input end, the first capacitor and the pole plate connected to the second capacitor are grounded ends, one pole plate of the third capacitor is connected to the anode input end, and the other pole plate of the third capacitor is connected to the cathode input end.

Optionally, the first capacitor, the second capacitor and the third capacitor in the differential-common mode filtering module are implemented by using an X2Y capacitor filter, or, alternatively, implemented by using three mutually independent capacitors.

Optionally, the differential mode filtering module comprises a first filtering element and a second filtering element; wherein the first filter element is connected between the anode input and the anode output; the second filter element is connected between the cathode input and the cathode output.

Optionally, both the first filter element and the second filter element are inductors.

Optionally, the common mode filter module includes a fourth capacitor and a fifth capacitor, the fourth capacitor and the fifth capacitor are connected in series to form a second series branch, one end of the second series branch is connected to the anode output end, the other end of the second series branch is connected to the cathode output end, and a pole plate of the fourth capacitor connected to the fifth capacitor is a ground terminal.

Optionally, the filter circuit further includes a limiting module, the limiting module is disposed at the anode input end and/or the cathode input end, and the limiting module is configured to provide the signal with limited amplitude to the difference and common mode filter module.

Optionally, an impedance between the anode input terminal and a ground terminal of the differential-common mode filter module is equal to an impedance between the cathode input terminal and the ground terminal of the differential-common mode filter module.

Optionally, the rejection ratio of the filter circuit to the radio frequency interference signal in the range of 30MHz to 3GHz is more than 30 dB.

The invention also provides an electronic device comprising at least one filter circuit as described.

Optionally, the active medical device further comprises a housing, an internal medical component located inside the housing, and an external medical component located outside the housing; the internal medical assembly is used for receiving and processing physiological signals and/or generating treatment signals; the external medical component for contacting a biological cell to sense a physiological signal and/or to perform a therapy; the filter circuit is connected between the inner medical assembly and the outer medical assembly to act as a signal transmission channel between the inner medical assembly and the outer medical assembly.

Optionally, the external medical component comprises at least one of a lead, an electrode, and a sensor; the internal medical assembly comprises a sensing module used for receiving and processing the physiological signals transmitted by the filter circuit and/or a treatment module used for generating treatment signals, wherein the sensing module and the treatment module are respectively connected with one filter circuit, or the sensing module and the treatment module share the same filter circuit.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. the differential-mode and common-mode filtering module, the differential-mode filtering module and the common-mode filtering module which are connected in sequence are adopted to filter signals in sequence, a good suppression effect can be provided for electromagnetic wave interference signals, and the circuit structure is simple and small in occupied space. The electromagnetic interference signals include, for example, radio frequency signals (300kHz-300GHz) in a broad sense, radio frequency signals generated during MRI, or high frequency electromagnetic interference signals in an EMC (Electro Magnetic Compatibility) test, and electromagnetic interference signals in other frequency bands (e.g., electromagnetic interference signals in a kHz band).

2. The input impedance can be balanced, the common mode and differential mode rejection performance is improved, and the sensing or output effect of actual signals is improved.

3. The signal output by the filter circuit is completely a common mode signal, and no potential difference caused by the electromagnetic wave interference signal is generated between the anode output end and the cathode output end, and no current caused by the electromagnetic wave interference signal flows through the load of the post-stage circuit, so that the suppression and attenuation effects of the post-stage circuit connected with the output end of the filter circuit on the electromagnetic wave interference signal are favorably improved.

4. The first capacitor and the second capacitor of the differential-common mode filter module in the filter circuit can be completely matched, so that the impedance from the anode input end to the grounding end of the differential-common mode filter module is completely the same as the impedance from the cathode input end to the grounding end of the differential-common mode filter module, the third capacitor is a differential mode interference suppression capacitor and presents low impedance in the frequency band of the electromagnetic wave interference signal, therefore, the impedance between the anode input end and the cathode input end is presented low impedance, and further the impedance of a post-stage circuit connected with the output end of the filter circuit is matched, and the anode input end and the cathode input end are presented low impedance, so that the anode input end and the cathode input end are almost conducted, further the amplitude of the electromagnetic wave interference signal on the anode input end and the cathode input end is almost the same, further, the reflection and standing wave energy is reduced, and the induced current in the post-stage circuit is reduced, the heat generation in the post-stage circuit is reduced, and the use safety of the whole circuit is ensured.

5. The filter circuit is suitable for active medical devices (such as an implantable cardiac pacemaker (IPG), an active implantable defibrillator (ICD), a cardiac resynchronization therapy defibrillator (CRT-D) and the like), and can ensure that the active medical devices are normally used in an MRI environment and can ensure the use safety of patients.

Drawings

Fig. 1 is a schematic structural diagram of a filter circuit according to an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of an X2Y capacitor according to an embodiment of the present invention.

Fig. 3 is a simulation curve of the circuit transfer characteristic S21 of the filter circuit according to the embodiment of the present invention.

Fig. 4 is a schematic diagram of an active medical device according to an embodiment of the present invention.

Fig. 5 is a schematic structural diagram of a cardiac pacemaker device according to an embodiment of the present invention.

Wherein the reference numbers are as follows:

10-filter circuit, 11-anode input terminal, 12-grounding terminal of differential mode filter module, 13-cathode input terminal, 14-differential mode filter module, 141-bypass capacitor, 142-reference plate, 15-differential mode filter module, 16-common mode filter module, 17-anode output terminal, 18-grounding terminal of common mode filter module, 19-cathode output terminal, 20-active medical device, 21-internal medical component, 211-power supply, 212-communication module, 213-memory, 214-treatment module, 214 a-pacing module, 215-sensing module, 22-external medical component.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings in order to make the objects and features of the present invention more comprehensible, however, the present invention may be realized in various forms and should not be limited to the embodiments described above. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise ratio for the purpose of facilitating and distinctly aiding in the description of the embodiments of the invention. As used herein, "and/or" means either or both.

Referring to fig. 1, the present embodiment provides a filter circuit 10, including: anode input 11, cathode input 13, anode output 17, cathode output 19, differential-mode and common-mode filtering module 14, differential-mode filtering module 15 and common-mode filtering module 16. Wherein, the difference-common mode filter module 14 is connected between the anode input terminal 11 and the cathode input terminal 13; the differential mode filtering module 15 is arranged between the output end of the differential mode and common mode filtering module 14 and the input end of the common mode filtering module 16; the differential mode filter module 16 is connected between an anode output terminal 17 and a cathode output terminal 19, and the differential mode filter module 14 and the common mode filter module 16 both have a ground terminal. Anode input 11 and cathode input 13 are for receiving signals from a preceding circuit, such as an electrode of a cardiac pacemaker, and for transmitting the signals to differential-and-common-mode filtering module 14, and anode output 17 and cathode output 19 are for outputting the filtered signals to a subsequent circuit, such as a sensing module (indicated at 215 in fig. 5) of the cardiac pacemaker.

The differential-common mode filter module 14 is configured to suppress differential mode interference and common mode interference in signals input to the anode input terminal 11 and the cathode input terminal 13. The differential-common mode filtering module 14 includes a first capacitor Cy, a second capacitor Cy 'and a third capacitor Cx, the first capacitor Cy and the second capacitor Cy' are connected in series to form a first series branch, one end (i.e., the end where Cy and Cy 'are connected in series) a of the first series branch is connected to the anode input end 11, the other end B of the first series branch is connected to the cathode input end 13, a polar plate G connected to the first capacitor Cy and the second capacitor Cy' in the first series branch is grounded and serves as a ground end 12 of the differential-common mode filtering module 14 and is grounded, the third capacitor Cx is connected in parallel to the first series branch, i.e., one end of the third capacitor Cx is connected to the anode input end 11, and the other end of the third capacitor Cx is connected to the cathode input end 13. The first capacitor Cy, the second capacitor Cy' and the third capacitor Cx are connected to form the differential-common mode filtering module 14, the circuit structure is simple, implementation is facilitated, and the occupied space is small. Further, the first capacitor Cy and the second capacitor Cy' are completely the same, so that the impedance from the anode input terminal 11 to the ground terminal 12 of the differential-mode filter module 14 is completely the same as the impedance from the cathode input terminal 13 to the ground terminal 12 of the differential-mode filter module 14, thereby balancing the input impedance and improving the differential-mode rejection performance. The third capacitor Cx is a differential mode interference suppression capacitor and has a low impedance in a specific radio frequency band (e.g., 30MHz to 3GHz, which is a frequency band of the electromagnetic interference signal), so that the filter circuit 10 can absorb most of the energy of the electromagnetic interference signal induced in the previous stage circuit, and reduce the reflection and standing wave of the electromagnetic interference signal. In addition, since the first and second capacitances Cy and Cy' can be identical, the impedance of the anode input terminal 11 to the ground terminal 12 and the impedance of the cathode input terminal 11 to the ground terminal 12 are identical, the third capacitance Cx is a differential mode interference suppression capacitance, when the amplitudes of the electromagnetic interference signals induced from the anode input terminal 11 and the cathode input terminal 13 are different, after the electromagnetic interference signal enters the differential-common mode filter module 14, the third capacitor Cx has a low impedance at the radio frequency band of the electromagnetic interference signal, the low impedance of the third capacitor Cx makes the anode input terminal 11 and the cathode input terminal 13 have a low impedance and almost conducted, so that the electromagnetic interference signal amplitudes at the anode input terminal 11 and the cathode input terminal 13 are almost the same, this equalizes the energy of the electromagnetic interference signal, and reduces the heat generated by electromagnetic induction in the electrode or other member connected between anode input terminal 11 and cathode input terminal 13.

The first capacitance Cy, the second capacitance Cy', and the third capacitance Cx of the differential-common mode filtering module 14 can be implemented by three separate discrete capacitors, or by an X2Y capacitive filter (i.e., a capacitor integrated together). Referring to fig. 2, the X2Y capacitor filter mainly comprises a single-ended unbalanced common bypass capacitor 141 and a plurality of parallel reference plates 142. Two electrode plates G1, G2 are oppositely disposed and connect together respective sidewalls of a plurality of parallel disposed reference plates 142 to form a parallel structure. The two groups of pole plates A, B of the bypass capacitor 141 each have a vertical plate and an insertion finger plate extending from the vertical plate and perpendicular to the vertical plate, the two vertical plates are parallel and opposite to each other, the two insertion finger plates are parallel to each other and arranged between the two vertical plates, the two insertion finger plates are parallel to the reference pole plate 142, and the two vertical plates are perpendicular to the two insertion finger plates, the pole plates G1, G2 and the reference pole plate 142 respectively; the two finger-insertion plates are respectively inserted between the reference plates 142 arranged in parallel, and the electrode plates G1, G2 and the two vertical plates enclose the two finger-insertion plates and the respective reference plates 142, so that the structure of the X2Y capacitor filter as a whole resembles a faraday cage. And the reference electrode plate 142 converts the single-end unbalanced bypass capacitor 141 into a symmetrically balanced dual capacitor, the electrode plates G1, G2 and the vertical plate form four terminals of the X2Y capacitor filter, and the electrode plate G1 or G2 serves as a ground terminal of the X2Y capacitor filter and is grounded. That is, the X2Y capacitive filter is a four-terminal structure, which has the following advantages compared to the differential-common mode filtering module 14 composed of three discrete capacitors (the first capacitor Cy, the second capacitor Cy', and the third capacitor Cx): (1) the single-end unbalanced bypass capacitor 141 is converted into a symmetrical balanced double capacitor (the double capacitors respectively correspond to the first capacitor Cy and the second capacitor Cy'), the process is matched, the voltage and the temperature are the same in bias, and the aging effect of the dielectric medium is the same, so that the input impedance is the same, and the differential-common mode interference suppression performance of the differential-common mode filter module 14 is improved. (2) The dielectric stress (piezoelectric effect) in the device is opposite, the current in the structure can be forced to reverse, and mutual inductance is counteracted inside, so that the internal mutual inductance is reduced, and the differential-mode and common-mode interference suppression performance is improved. (3) The X2Y capacitive filter operates in the bypass so it is not current limited and does not add dc resistance. (4) The increase in package size of the X2Y capacitive filter reduces the inductance of the parallel structure (i.e., the parallel structure formed by the two electrode plates G1, G2 and the plurality of reference plates 142 arranged in parallel), so that the impedance of the corresponding third capacitive Cx portion of the X2Y capacitive filter in the rf frequency band is lower, which is just opposite to the common capacitance. (5) The part of the X2Y capacitor filter corresponding to the third capacitor Cx is low impedance in a specific frequency band of the electromagnetic interference signal (e.g., 30MHz to 3GHz), thereby making the anode input terminal 11 and the cathode input terminal 13 almost conductive, absorbing most of the energy of the electromagnetic interference signal induced in the preceding stage circuit, and reducing reflection and standing waves of the electromagnetic interference signal, i.e., the X2Y capacitor filter can suppress most of the energy of the electromagnetic interference signal entering the anode input terminal 11 and the cathode input terminal 13, and reduce the heat generated by the electromagnetic induction in the preceding stage circuit, so that the temperature rise in the preceding stage circuit can be controlled in a low range, and the preceding stage circuit can be protected from damage.

The differential mode filtering module 15 comprises a first filtering element and a second filtering element in this embodiment, the first filtering element is a first inductor L connected between the anode input terminal 11 and the anode output terminal 17. The second filter element is a second inductor L' connected between the cathode input terminal 13 and the cathode output terminal 19. The first inductor L and the second inductor L' can generate a large inductive reactance to the differential mode high frequency interference (i.e. a high impedance is embodied under a high frequency signal), and can filter the differential mode interference in the electromagnetic wave interference signal output from the differential and common mode filtering module 14, so that the differential mode interference cannot be added to the common mode filtering module 15, thereby realizing a strong differential mode filtering performance of the differential mode filtering module 15. Furthermore, the first inductor L and the second inductor L' are microstrip inductors on the printed circuit board, have a small relative occupied area, and exhibit a high impedance characteristic under a high-frequency signal, so that the high-frequency signal is prevented from flowing in the circuit, and the high-frequency signal is reflected back to the interference source, thereby exerting an inhibiting effect on the differential mode radio frequency signal and the electromagnetic interference.

The common mode filter module 16 can convert the signal output by the differential mode filter module 15 into a common mode signal, and the post-stage circuit has a considerable suppression and attenuation capability for the common mode electromagnetic wave interference signal, so that the common mode filter module 16 can be beneficial to improving the suppression and attenuation capability of the post-stage circuit for the electromagnetic wave interference signal. In this embodiment, the common mode filter module 16 includes a fourth capacitor C4 and a fifth capacitor C5, the fourth capacitor C4 and the fifth capacitor C5 are connected in series to form a second series branch, one end of the second series branch is connected to the anode output terminal 17 (which may also be connected to a circuit node where the first inductor L1 and the anode output terminal 17 are connected to each other), the other end of the second series branch is connected to the cathode output terminal 19 (which may also be connected to a circuit node where the second inductor L2 and the cathode output terminal 19 are connected to each other), and a plate of the second series branch, to which the fourth capacitor C4 and the fifth capacitor C5 are connected, is grounded and serves as a ground terminal of the common mode filter module 16. The common mode filtering module 16 formed by the fourth capacitor C4 and the fifth capacitor C5 has a simple structure and a small occupied area, and is beneficial to implementation. Further, the fourth capacitor C4 and the fifth capacitor C5 are identical to improve the common mode performance of the output signals. The fourth capacitor C4 and the fifth capacitor C5 have low impedance in the frequency band of the electromagnetic interference signal, and the energy of the electromagnetic interference signal entering the common mode filter module 16 returns to the ground terminal 18 through the fourth capacitor C4 and the fifth capacitor C5, so that the residual common mode interference after filtering by the differential mode filter module 15 at the previous stage is filtered out, and cannot be added to the circuit at the subsequent stage.

The filter circuit 10 of the present embodiment has a pi band-stop filter in its entire circuit, has a simple structure, and can effectively suppress radio frequency signals.

In addition, the selection of the types of the components in the filter circuit 10 needs to match the MRI high-power radio frequency signal or the electromagnetic wave interference signal in the EMC test. The selection of the components in this embodiment enables the filter circuit 10 to achieve an rejection ratio of more than 30dB for the radio frequency interference signals in the range of 30MHz to 3 GHz. For example, the parameters of the first inductance L and the second inductance L' include: the inductance value is 12nH +/-10%, the quality factor is 12 +/-10%, and the parasitic capacitance is 0.25pF +/-10%. The parameters of the first to fifth capacitances include: the capacitance value is 4.7nF +/-10%, the impedance is 0.21 omega +/-10%, and the parasitic inductance is 0.5nH +/-10%. Fig. 3 shows a simulation curve of the circuit transmission characteristic S21 of the filter circuit 10 having the parameters for selecting the components, and it can be seen from fig. 3 that the attenuation values of the filter circuit 10 for frequency points in the range of 30MHz to 3GHz are all more than 30dB (or less than-30 dB), for example, the attenuation value of the radio frequency interference signal corresponding to MRI 1.5T (tesla) and radio frequency RF 64MHz is-55 dB, the attenuation value of the radio frequency interference signal corresponding to MRI 3.0T, RF 128MHz is-70 dB, the MRI higher harmonic wave falls in the band and is attenuated, the attenuation value of the electromagnetic wave interference signal corresponding to RF 30MHz in the EMC test is-35 dB, and the attenuation value of the electromagnetic wave interference signal corresponding to RF 3.0GHz in the EMC test is-55 dB.

Further, the filter circuit 10 of the present embodiment further includes a limiting module (which may be a transient suppression diode Array TVS Array, not shown), disposed at the anode input terminal 11 and/or the cathode input terminal 13, for providing the rf signal with limited amplitude to the differential-common mode filter module 14. For example, a 64MHz radio frequency signal is emitted during 1.5T MRI scanning, the 64MHz radio frequency signal is induced by a preceding stage circuit, and a 64MHz radio frequency interference signal with a voltage as high as tens of volts is generated after being transmitted to the anode input terminal 11 and the cathode input terminal 13, and the amplitude of the radio frequency interference signal is clamped to 10Vp-p (namely, the peak voltage is 10V) after entering the amplitude limiting module of the filter circuit 10; then, the amplitude of the radio frequency interference signal of 64MHz is reduced from 10Vp-p to 20mVp-p (namely the peak voltage is 20mV) through the sequential filtering of the difference-common mode filtering module 14, the difference-mode filtering module 15 and the common mode filtering module 16; the radio frequency interference signal can be further attenuated by a post-stage circuit to finally obtain a required interference-free 64MHz radio frequency signal, for example, the amplitude of the radio frequency interference signal output by the filter circuit 10 is reduced from 20mVp-p to 0.02mVp-p to 0.2mVp-p (namely, the peak voltage is 0.02mV to 0.2mV) by a signal filter with out-of-band attenuation of at least 40dB in the post-stage circuit; and then the amplitude of the radio frequency interference signal is reduced to 0.2 mu Vp-p-2 mu Vp-p (namely the peak voltage is 0.2 mu V-2 mu V) through a sense amplifier with the common mode rejection ratio of 40 dB-60 dB in the post-stage circuit, so that the sense amplifier in the post-stage circuit can sense and acquire electrocardiosignals and the like in an MRI environment.

In addition, it should be noted that the filter circuit 10 of the present embodiment may be similar to a mirror-symmetrical structure, i.e., when the anode input terminal 11 and the cathode input terminal 13 are used as signal input terminals, the anode output terminal 17 and the cathode output terminal 19 are used as signal output terminals, and when the anode input terminal 11 and the cathode input terminal 13 are used as signal output terminals, the anode output terminal 17 and the cathode output terminal 19 are used as signal input terminals. Thus, the filter circuit 10 can be switched into the circuit in the forward direction or in the reverse direction. The filter circuit 10 can perform corresponding filtering effects. In addition, although the working principle and effect of the filter circuit 10 of the present embodiment are mainly described in the above embodiment by using MRI radio frequency signals in the range of 30MHz to 3GHz as the electromagnetic interference signals, the filter circuit of the present invention is not limited to applying some scenarios that require filtering electromagnetic interference signals in the range of 30MHz to 3GHz, but also can be applied to scenarios that require filtering electromagnetic interference signals in other frequency bands by changing the values of capacitance, impedance, and other parameters of corresponding components in the common mode filter module 14, the differential mode filter module 15, and the common mode filter module 16 according to requirements, so that the common mode filter module 14, the differential mode filter module 15, and the common mode filter module 16 are all resonated in the frequency band of the electromagnetic interference signals, wherein the electromagnetic interference signals may be radio frequency signals in a broad sense (300kHz to 300GHz), radio frequency signals generated in the MRI process, or EMC (Electro Magnetic Compatibility) signals, Electromagnetic compatibility) and electromagnetic interference signals of other frequency bands (for example, electromagnetic interference signals of a frequency band in kilohertz (kHz), and the like.

In summary, the filter circuit of the present invention has a simple structure, can match the impedance of the front stage circuit, reduce the reflection and standing wave energy, reduce the induced current of the front stage circuit, and reduce the heat generation, and meanwhile, can balance the input impedance through the differential-common mode filter module, and improve the common-mode and differential-mode rejection performance, and can have a considerable signal attenuation effect on the electromagnetic interference signals of the corresponding frequency band, for example, when the common-mode filter module 14, the differential-mode filter module 15, and the common-mode filter module 16 all resonate at the frequency band of 30MHz to 3GHz, the rejection performance of the filter circuit of the present invention on the radio frequency signals of 30MHz to 3GHz frequency band can reach more than-30 dB. In addition, when the difference-common mode filter module in the filter circuit is realized by adopting the X2Y capacitor, the material cost of the product can be reduced, and the manufacturing process can be simplified. The filter circuit of the invention can be suitable for the requirements of various electronic devices for filtering electromagnetic wave interference signals, for example, the filter circuit can be suitable for the requirements of MRI radio frequency interference signals of active medical devices in an MRI radio frequency signal environment which needs to work in the range of 30MHz to 3 GHz. Accordingly, an embodiment of the present invention further provides an electronic device, please refer to fig. 4 and fig. 5, which includes at least one filter circuit 10 as described above. The electronic device may be a connector or a filter comprising only the filter circuit 10; it may be an electronic apparatus including a preceding stage circuit, a filter circuit 10, and a succeeding stage circuit connected in this order, which has functions other than the filter function and the connector function (e.g., a calculation function, a sensing function, a medical function, a biological signal detection function, and the like). For example, the electronic device is a sensor that detects a corresponding signal. As another example, the electronic device is an active medical device having the functions of sensing physiological signals and performing biological therapy, which may be, by way of example, an active contact bio-device including an implantable electrical stimulator, an energy therapy device, a diagnostic monitoring device, a fluid delivery device, or an ionizing radiation device. The implantable electrical stimulator can be divided into a cardiac pacemaker, a deep brain stimulator, a spinal cord stimulator, a peripheral nerve stimulator, a muscle stimulator, a bone stimulator, a stomach stimulator, an ear stimulator and the like according to different stimulation parts; energy treatment instruments such as laser treatment instruments, ultrasonic treatment instruments, magnetic treatment instruments, and the like; diagnostic monitoring devices such as electrocardiography monitors, pH probes, implantable sensors, pill cameras, external nerve stimulators, etc., fluid delivery devices such as drug pumps, external insulin pumps, external drug pumps, external catheters, etc.; ionizing radiation instruments such as X-ray machines and the like.

As an example, referring to fig. 4 and 5, the active medical device includes, in addition to the filter circuit 10, a housing 23, an internal medical component 21 located inside the housing 23, and an external medical component 22 located outside the housing 10. The filter circuit 10 may be a connector, which is connected between the internal medical component 21 and the external medical component 22 to provide a signal transmission path between the internal medical component 21 and the external medical component 22, in which case a part of the filter circuit 10 may be located inside the housing 23 and another part may be located outside the housing 23, or a through hole may be formed on a sidewall of the housing 23, and the filter circuit 10 as a connector is inserted into the through hole and does not protrude from an outer sidewall of the housing 23. In other embodiments of the invention, the filter circuit 10 may also be integrated with the internal medical assembly 21 on the same printed circuit board, which is disposed inside the housing 23.

The internal medical assembly 21 is configured to receive and process physiological signals and/or to generate therapeutic signals, and in this embodiment, the internal medical assembly 21 includes a controller 210, a power source 211, a communication module 212, a memory 213, a therapy module 214, and a sensing module 215. The power source 211 provides power for the filtering circuits 10 and the internal medical components 21, the communication module 212 can communicate with the outside in a wired or wireless manner to receive data such as external system control parameters (for example, information parameters for a doctor to set an active medical device for treating and monitoring the condition of a patient), and transmit data such as biological sign information obtained by the internal medical components 21 to the outside, the memory 213 is used for storing corresponding data and parameters, the treatment module 214 is used for generating treatment signals, the sensing module 215 is used for receiving and processing physiological signals transmitted by the filtering circuits 10, and the controller 210 is used for controlling and coordinating the operations of the filtering circuits 10 and the internal medical components 21. In this embodiment, the sensing module 215 and the therapy module 214 share the same filter circuit 10, at this time, one input end of the sensing module 215 and one output end of the therapy module 214 are commonly connected to the anode input end 11 of the filter circuit 10, and the other input end of the sensing module 215 and the other output end of the therapy module 214 are commonly connected to the cathode input end 13 of the filter circuit 10, so that the filter circuit 10 can filter the signal received by the sensing module 215, can allow the signal sent by the therapy module 214 to be transmitted to the external medical component 22, and even can filter the signal sent by the therapy module 214, thereby avoiding the occupied area of one more filter circuit, and facilitating the miniaturization of the active medical device. In other embodiments of the present invention, each of sensing module 215 and treatment module 214 may be connected to a filtering circuit 10, so that a signal transmission channel is established between each of treatment module 214 and sensing module 215 and external medical component 22, and crosstalk between signals transmitted by treatment module 214 and signals received by sensing module 215 is avoided.

The external medical assembly 22 is for contacting biological cells to sense physiological signals and/or perform therapy and may include at least one of leads, electrodes, and sensors.

The following describes in detail the filtering effect of the filter circuit of the present embodiment on MRI high-power radio frequency signals and electromagnetic interference signals in EMC test entering the active medical device in the range of 30MHz to 3GHz by taking a cardiac pacemaker as an example.

When the active medical device is a cardiac pacemaker, please refer to fig. 1 and 5, the sensing module 215 in the internal medical assembly 21 is used to sense an electrocardiographic signal, the therapy module 214 is a pacing module (also called a pulse output circuit, and hereinafter referred to as a pacing module 214a) used to generate a cardiac pacing signal, the communication module 212 may be a wireless communication module and may communicate with an external program controller through bluetooth or infrared, all the internal medical assemblies 21 are also referred to as pulse generators, the communication module 212 wirelessly realizes data exchange between the program controller and the pulse generators, for example, realizes that the program controller sends or modifies control parameters to the pulse generators and receives operating state signals and detected physiological signals from the pulse generators, the external medical assembly 22 includes at least one electrode (also referred to as an electrode lead, and hereinafter referred to as an electrode 22), sensing module 215 and pacing module 214a share a filter circuit 10, at this time, one input terminal of sensing module 215 and one output terminal of pacing module 214a are connected to anode input terminal 11 of filter circuit 10, the other input terminal of sensing module 215 and the other output terminal of pacing module 214a are connected to cathode input terminal 13 of filter circuit 10, and electrode 22 is connected to anode output terminal 17 and cathode output terminal 19 of filter circuit 10.

The housing 23 may be selectively connected to the ground terminal 12 of the differential-and-common mode filter module 14 of the filter circuit 10 for grounding, or alternatively, to the anode input terminal 11 of the differential-and-common mode filter module 14 of the filter circuit 10.

The sensing module 215 includes a sensing amplifier (not shown) and a sensing filter (not shown), wherein the respective input terminals of the sensing filter are connected to the anode output terminal 17 and the cathode output terminal 19 of the filter circuit 10, the output terminal of the sensing filter is connected to the input terminal of the sensing amplifier, and the sensing filter and the sensing amplifier can sequentially perform further filtering suppression on the signal output by the common mode filtering module 16 of the filter circuit 10, so as to obtain a higher-performance required signal.

The filter circuit 10 can absorb the MRI high-power radio frequency signal and the electromagnetic wave interference signal in EMC test within the range of 30 MHz-3 GHz entering the cardiac pacemaker, so that the cardiac pacemaker can normally sense the electrocardiosignal in the heart chamber in the electromagnetic wave interference environment such as the MRI high-power radio frequency signal and the like, and simultaneously match the impedance of the electrode 22 of the cardiac pacemaker, so as to reduce the reflection and standing wave energy, thereby reducing the heat generated on the electrode 22 and enabling the patient implanted with the cardiac pacemaker to carry out MRI scanning. The cardiac pacemaker with the filter circuit 10 can also dispense with EMC testing according to national standards.

Taking an example that a 64MHz radio frequency signal is emitted during 1.5T MRI scanning and the filter circuit 10 is designed to resonate at 64MHz, referring to fig. 1 and 5, the filter circuit 10 can suppress the 64MHz MRI radio frequency signal, so that a patient implanted with the cardiac pacemaker can perform MRI scanning, and the specific principle is as follows:

firstly, the spectrum of the electrocardiosignal is concentrated in a low frequency band (0.5 Hz-150 Hz), the amplitude is about 0.4mV, the cardiac pacemaker needs to collect the electrocardiosignal to ensure the normal work in the body of a patient, therefore, other interference signals such as myoelectricity and the like need to be suppressed, namely, signals except the electrocardiosignal in the heart cavity are not needed, the electrode 22 implanted into the human body of the cardiac pacemaker can be interfered by the induction of various electromagnetic wave signals, wherein the radio frequency signal emitted during MRI scanning is a strong interference for the cardiac pacemaker.

The electrode 22 senses a 64MHz radio frequency signal emitted during MRI scanning, the cardiac pacemaker uses the metal titanium housing 23 to shield the signal, the unshielded 64MHz radio frequency signal is transmitted to the feed-through port of the cardiac pacemaker (i.e. the anode input terminal 11 and the cathode input terminal 13 of the filter circuit 10) through the electrode 22 to generate a 64MHz radio frequency interference signal, the voltage generated between the anode input terminal 11 and the cathode input terminal 13 by the 64MHz radio frequency interference signal is up to tens of volts, the amplitude limiting module in the filter circuit 10 clamps the amplitude of the 64MHz radio frequency interference signal to 10Vp-p, and the amplitude limited 64MHz radio frequency interference signal continues to enter the differential-common mode filter module 14 in the filter circuit 10.

Since the connected electrode plates of the first capacitor Cy and the second capacitor Cy in the differential-common mode filtering module 14 are connected to the housing 23 and grounded, most of the interference signal energy can be transmitted to the housing 23 again, so that most of the energy of the 64MHz radio frequency interference signal induced by the electrode 22 can be absorbed, and the reflection and standing wave of the 64MHz radio frequency interference signal are reduced, further, since the first capacitor Cy and the second capacitor Cy are completely the same, the impedance from the anode input end 11 to the housing 23 is completely the same as the impedance from the cathode input end 13 to the housing 23, and the third capacitor Cx in the differential-common mode filtering module 14 is low impedance in the 64MHz radio frequency band, so that the impedance between the anode input end 11 and the cathode input end 13 is low and almost conductive, the amplitudes of the radio frequency interference signals at the anode input end 11 and the cathode input end 13 are almost the same, and the radio frequency interference energy is equally divided, reducing the amount of heat generated by radio frequency induction (i.e., electromagnetic induction) of the electrode 22.

The energy of the remaining part of the 64MHz radio frequency interference signal passes through the differential mode filtering module 15 (for example, a microstrip inductor on a printed circuit board), is further filtered and suppressed, and then enters the common mode filtering module 16, and because the resonance of the fourth capacitor C4 and the fifth capacitor C5 in the common mode filtering module 16 is near 64MHz, the low impedance can be presented to the 64MHz radio frequency interference signal, and the remaining energy of the 64MHz radio frequency interference signal is further absorbed, and the 64MHz radio frequency interference signal is converted into a common mode signal to be output. In this embodiment, the filter circuit 10 has a suppression capability of 55dB for the 64MHz radio frequency interference signal, that is, the attenuation is greater than 500 times, and after the 64MHz radio frequency interference signal is filtered by the differential-common mode filter module 14, the differential-mode filter module 15, and the common mode filter module 16, the amplitude of the 64MHz radio frequency interference signal can be reduced from the amplitude of 10Vp-p to 20 mVp-p.

At this time, the input of the sensing module 215 of the cardiac pacemaker does not enter a saturation state, the sensing filter is a band-pass filter, and the out-of-band attenuation of the sensing filter is at least 40dB, so that the amplitude of the 64MHz radio frequency interference signal can be reduced from 20mVp-p to 0.02-0.2 mVp-p after the signal is further filtered by the sensing filter, and in addition, the signal output by the common-mode filtering module 16 is a common-mode signal, and the sensing filter is a band-pass filter, so that the common-mode characteristic of the signal cannot be changed; therefore, the 64MHz radio frequency interference signal is still a common mode interference signal when transmitted to the sense amplifier, and the sense amplifier has a common mode rejection ratio of 40-60 dB, so that the amplitude of the 64MHz radio frequency interference signal is reduced from 0.02-0.2 mVp-p to 0.2 μ Vp-p-2 μ Vp-p (namely, the peak voltage is 0.2 μ V-2 μ V) after the 64MHz radio frequency interference signal is further rejected by the sense amplifier. That is to say, after the 64MHz radio frequency interference signal generated by the 64MHz MRI scan is filtered by the filter circuit 10 and suppressed by the sensing module 215, the amplitude is as much as three orders of magnitude lower than the electrocardiographic signal (with an amplitude of about 0.4mV) in the heart chamber sensed by the sensing module 215, which does not affect the detection of the electrocardiographic signal.

In addition, through reasonable setting of parameters of electronic components in each module in the filter circuit 10, the upper limit of the frequency of the radio frequency interference signal that can be suppressed by the filter circuit 10 can be up to 3GHz, and the non-detection level that the anti-interference capability required by EMC test of 30MHz to 3GHz in the national standard is greater than 30dB attenuation can be achieved, and further, the cardiac pacemaker with the filter circuit 10 can also work in other MRI scanning environments such as 3.0T MRI, radio frequency 128MHz and the like. Wherein, EMC test includes the requirement in two aspects: on one hand, the electromagnetic interference generated to the environment by the equipment in the normal operation process cannot exceed a certain limit value; another aspect is that the appliance has a degree of immunity to electromagnetic interference present in the environment, i.e., electromagnetic susceptibility.

In summary, the cardiac pacemaker of the present embodiment adopts the filter circuit of the present embodiment, and performs considerable signal attenuation on the MRI radio frequency signal entering the cardiac pacemaker through the filter circuit, so that the cardiac pacemaker can normally sense and acquire the electrocardiosignal in the MRI environment, and the heat generated by the electrode lead during MRI scanning can be reduced, thereby ensuring the safety of the patient. Meanwhile, in the aspect of EMC test, the cardiac pacemaker can inhibit electromagnetic interference signals within the radio frequency range of 30 MHz-3 GHz by the filtering action of the filter circuit by more than 30dB, and the EMC test can be omitted according to the national standard.

The other electronic devices having the filter circuit of the present embodiment can be used in an interference environment of MRI high-power radio frequency signals of 30MHz to 3GHz, as in the cardiac pacemaker having the filter circuit of the present embodiment.

It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A filter circuit for an active medical device, comprising: the device comprises an anode input end, a cathode input end, an anode output end, a cathode output end, a difference-common mode filtering module, a difference-mode filtering module and a common mode filtering module; wherein the differential-common mode filter module is connected between the anode input terminal and the cathode input terminal; the differential mode filtering module is arranged between the output end of the differential mode and common mode filtering module and the input end of the common mode filtering module; the common mode filtering module is connected between the anode output end and the cathode output end; the difference common-mode filtering module and the common-mode filtering module respectively comprise grounding ends; the anode input end and the cathode input end are used for being connected with a preceding stage circuit of the active medical device so as to receive signals collected by the preceding stage circuit, and the anode output end and the cathode output end are used for being connected with a subsequent stage circuit of the active medical device so as to provide filtered signals for the subsequent stage circuit; and a low impedance is formed between the anode input end and the cathode input end, and the low impedance is matched with the impedance of the post-stage circuit.

2. The filter circuit according to claim 1, wherein the differential-mode and common-mode filter module includes a first capacitor, a second capacitor and a third capacitor, the first capacitor and the second capacitor are connected in series to form a first series branch, one end of the first series branch is connected to the anode input end, the other end of the first series branch is connected to the cathode input end, a plate of the first capacitor connected to the second capacitor is a ground terminal, a plate of the third capacitor is connected to the anode input end, and another plate of the third capacitor is connected to the cathode input end.

3. The filter circuit of claim 2, wherein the first capacitor, the second capacitor and the third capacitor in the differential-and-common mode filter module are implemented by an X2Y capacitor filter, or implemented by three capacitors independent of each other.

4. The filter circuit of claim 1, wherein the differential mode filtering module comprises a first filtering element and a second filtering element; wherein the first filter element is connected between the anode input and the anode output; the second filter element is connected between the cathode input and the cathode output.

5. The filter circuit of claim 4, wherein the first filter element and the second filter element are both inductors.

6. The filter circuit according to claim 1, wherein the common mode filter module includes a fourth capacitor and a fifth capacitor, the fourth capacitor and the fifth capacitor are connected in series to form a second series branch, one end of the second series branch is connected to the anode output terminal, the other end of the second series branch is connected to the cathode output terminal, and a plate of the fourth capacitor connected to the fifth capacitor is a ground terminal.

7. The filter circuit according to any one of claims 1 to 6, further comprising a limiting module, wherein the limiting module is disposed at the anode input terminal and/or the cathode input terminal, and the limiting module is configured to provide a signal with limited amplitude to the differential-common mode filter module.

8. The filter circuit of claim 1, wherein an impedance between the anode input and a ground of the differential-and-common mode filter module is equal to an impedance between the cathode input and the ground of the differential-and-common mode filter module.

9. The filter circuit of claim 1, wherein the filter circuit has a rejection ratio of 30dB or more for radio frequency interference signals in a range of 30MHz to 3 GHz.

10. An electronic device, characterized in that it comprises at least one filter circuit according to any one of claims 1 to 9.

11. The electronic device of claim 10, wherein the electronic device is an active medical device further comprising a housing, an internal medical component located inside the housing, and an external medical component located outside the housing; the internal medical assembly is used for receiving and processing physiological signals and/or generating treatment signals; the external medical component for contacting a biological cell to sense a physiological signal and/or to perform a therapy; the filter circuit is connected between the inner medical assembly and the outer medical assembly to act as a signal transmission channel between the inner medical assembly and the outer medical assembly.

12. The electronic device of claim 11, wherein the external medical component comprises at least one of a lead, an electrode, and a sensor; the internal medical assembly comprises a sensing module used for receiving and processing the physiological signals transmitted by the filter circuit and/or a treatment module used for generating treatment signals, wherein the sensing module and the treatment module are respectively connected with one filter circuit, or the sensing module and the treatment module share the same filter circuit.