ACTIVE IMPLANTABLE MEDICAL DEVICE

Description

FIELD OF INVENTION

[0001] The present invention relates to medical devices, more specifically active implantable medical devices (AIMDs). STATE OF THE ART

[0002] In a classic and well-established manner, an active implantable medical device (AIMD) is defined as a device whose operation depends on an energy source other than that generated by the human body, and which acts on this supplied energy by modifying its density or converting it. An AIMD may be intended to be partially or completely introduced into the human body in order to restore a vital function, compensate for a deficiency, and / or measure physiological parameters. Typically, an AIMD thus comprises at least one active component intended to be partially introduced into the human body via a clinical procedure and intended to remain in place for at least 30 days after the procedure. Broadly speaking, an AIMD is considered to allow the transfer of energy and information across the skin of an implanted patient.It is known from the state of the art that the best option, currently, for managing the transfer of energy and / or information from implants, is the WPT (. wireless power transfer based on the transfer of electromagnetic fields. Thus, most implanted devices have two coils: one located outside the body of the implanted individual and the other inside. This transfer is therefore carried out wirelessly (inductively), through the skin and in the near field, specifically via NFC technology (HF at 13.56 MHz, according to ISO 14443 or ISO 15693 standards). NFC technology allows for a reduction in the size of the coils. The acronym "NFC" stands for “Near Field Communication”NFC has its equivalent acronym in French: "CCP," for "communication en champ proche" (near-field communication). It is a short-range, high-frequency wireless communication technology. This technology, well-known in itself, allows the exchange of information between devices, generally an NFC chip and an NFC reader, up to a distance of approximately 10 cm. This technology is an extension of the ISO / IEC 14443 standard, which standardizes proximity cards using radio-frequency identification (RFID), combining a smart card and a reader within a single device. As is known from the prior art, NFC chips consist of an antenna and an integrated circuit, and have an input stage containing a protection circuit (including at least one Zener diode) designed to protect the NFC chip, thereby limiting the voltage generated in the antenna.As is known in the prior art, this intrinsic characteristic of NFC chips limits the energy that can be recovered by other functional elements of the implant. Indeed, the inherent limitation of the technology is that the NFC chip, passive in this case, returns very little of the energy it receives, resulting in a very low efficiency (approximately 15 mW recovered for every 500 mW emitted).

[0003] These observations can be extended to any type of chip with an antenna designed to receive energy and / or information.

[0004] US patent application US2018034319 describes an energy transfer / collection device comprising a first module and a second module. The first module is intended to transfer energy and data to the second module via an antenna.

[0005] French patent application FR3085551 describes passive non-contact transponders, for which a protection problem arises when they are placed in the presence of non-contact chargers.

[0006] Furthermore, in the specific context of an implantable device, the transfer of energy and / or information is significantly attenuated by the tissues of the person with the device. This attenuation leads to several constraints. On the one hand, the emitted signals must have sufficient intensity to be received correctly by the receiver. On the other hand, energy transfer must be limited to avoid damaging the tissues—in accordance with regulatory limits for specific absorption rate (SAR). This trade-off is poorly addressed in the current state of the art.

[0007] The objective of the invention is to transmit energy and data via an inductive link to a device implanted in the body, from an external device, optimizing the energy recovered while controlling the range of the implant.

[0008] The present invention achieves the aforementioned objective by proposing the addition of an electronic assembly comprising an antenna associated with an internal circuit, which may be an NFC chip, to allow the receiving antenna to reach a voltage beyond the limits imposed by the internal circuit. SUMMARY

[0009] The invention therefore relates to an active implantable medical device as defined by claim 1.

[0010] The invention enables the transmission of energy and data to a device implanted in the body via a transcutaneous link based on a technology comprising an antenna associated with an integrated circuit, such as NFC technology. The invention allows for impedance matching of the integrated circuit (and the associated antenna) to optimize the harvested energy. This impedance matching relies on adding an electronic circuit to the integrated circuit (for example, that of an NFC chip) to allow the associated antenna to reach a voltage beyond the limits imposed by the integrated circuit and to optimize the efficiency of energy transfer between the external and internal modules of the device.

[0011] The device according to the invention may comprise one or more of the following features, taken individually or in combination with each other: the report C 3 C 3 + C 4 is greater than or equal to 0.25, preferably between 0.3 and 0.6; the external module has a single external antenna, and the internal module has a single internal antenna; each antenna is connected to an impedance matching circuit, and each antenna and its associated impedance matching circuit resonate at a frequency between 12 and 14 MHz, more precisely 13.56 MHz; the external module and the internal module are intended to transfer power and data from one to the other simultaneously; the external module and the internal module are intended to transfer data from one to the other bidirectionally; the external module and the internal module are intended to transfer power and data from one to the other over a single frequency band.

[0012] The invention also relates to a method of transferring energy and data, the method being implemented by means of a device according to one of the characteristics stated above, the voltage supplied to the internal integrated circuit being between 100mV and 5V, the voltage supplied to the electronic energy harvesting assembly being between 100mV and 50V. DETAILED DESCRIPTION

[0013] The present invention therefore relates to an active implantable medical device (AIMD) 10, more particularly an inductive link for AIMD 10, suitable for implantation in a subject, as schematically illustrated in figure 1. In particular, the device 10 comprises two communication and energy transfer modules 12, 14 complementary to each other (an external module 12 and an internal module 14) and a stimulator 15. In place of a stimulator, some embodiments may, for example, present a device for measuring physiological or physical signals internal to the human body, including EMG (electromyogram), EEG (electroencephalogram), ECG (electrocardiogram), or ENG (electroneurogram) or temperature measurement.

[0014] When the device 10 is used on the subject, the external module 12 is positioned outside the subject, for example, fixed to the subject's skin, and the internal module 14 is implanted inside the subject, for example, under the subject's skin. The stimulator 15 is connected to the internal module 14 and is therefore, after implantation, also positioned inside the subject. In the embodiment including a stimulator 15, this stimulator 15 can be used to stimulate tissues, nerves, or muscles, for example, in order to control organs or limb movements.

[0015] The external module 12 and the internal module 14 are designed to transfer energy and data from one to the other. The energy is then transferred to the stimulator 15. More specifically, the energy transfer is unidirectional from the external module 12 to the internal module 14, and the data transfer can be bidirectional, from the external module 12 to the internal module 14 and vice versa.

[0016] According to the embodiment illustrated in figure 1 The external module 12 is an NFC reader 16 comprising: a modeled generator 18, on the figure 1, by a sinusoidal generator G of frequency 13.56MHz and the associated resistance RG, an external antenna 20 (and the associated resistance R 20) connected to the generator 18, an external impedance matching network 22 located between the generator 18 of the NFC reader 16 and the external antenna 20, the external impedance matching network 22 comprising a first capacitor of capacitance C 1 and a second capacitor of capacitance C 2 connected so as to form a capacitive divider bridge.

[0017] As illustrated on the figure 2 The generator 18, the external antenna 20 and the external impedance matching network 22 form the analog part 16b of the NFC reader 16. In addition, the NFC reader 16 may include a digital part 16a linked to the analog part 16b by a digital / analog converter.

[0018] Using an NFC reader allows for two-way data exchange. The data exchanged includes: commands and stimulation parameters from external module 12 to internal module 14, responses, error notifications and measured data returned from internal module 14 to external module 12.

[0019] Impedance matching, as is well known in itself, is a technique for optimizing the transfer of electrical power between an electrical transmitter and receiver to optimize the exchange of data and / or energy between the receiver and the transmitter, particularly the exchange of telecommunications signals.

[0020] Internal module 14 includes: an internal antenna 24 (and the associated resistor R24) defining two terminals (241, 242), a chip 26 intended to cooperate with the NFC reader 16 of the external module 12, the chip 26 being connected to the internal antenna 24, the chip 26 also comprising the series connection between terminals 241 and 242 of the internal antenna 24: o of a third capacitor of capacitance C3 and o of an internal integrated circuit 28 having an equivalent input impedance Z whose capacitive part is modeled by a fourth capacitor of capacitance C4, and, the ratio C 3 C 3 + C 4 being greater than or equal to 0.1, C3 and C4 forming a capacitive voltage divider, an electronic circuit for harvesting electrical energy (not referenced) connected to the internal antenna 24 and intended to supply the simulator 15 with electrical energy, the electronic circuit for harvesting being external to the internal integrated circuit 28 of the chip 26, the electronic circuit for harvesting energy comprising a rectifier circuit 30 located upstream of an electronic energy storage circuit and a voltage regulation circuit (not shown), the rectifier circuit 30 comprising several diodes D1, D2, D3, D4 intended to generate a DC voltage source intended to power the electronic circuit for harvesting energy, an internal impedance matching network 32 located between the internal antenna 24 and the rectifier circuit 30,This internal impedance matching network 32 comprises a fifth and a sixth capacitor with capacitances C5 and C6 respectively, connected to form an L-shaped network, allowing impedance matching.

[0021] The internal integrated circuit 28 is preferably an NFC type circuit.

[0022] Furthermore, as illustrated on the figure 2 , a microstorage module 31a and a voltage regulation module 31b can be arranged between the rectifier circuit 30 and the stimulator 15.

[0023] In the embodiment illustrated in figure 1The value of resistor RG is 50Ω, and resistors R20 and R24 are 5Ω. Furthermore, the value of the first capacitor C1 is 38pF, that of the second capacitor C2 is 62pF, and that of capacitor C3 is 36pF. The value of the fourth capacitor C4 is 35pF, that of the fifth capacitor C5 is 6.8pF, and the value of the sixth capacitor C6 is 8.2pF. In other embodiments, the values ​​of the various capacitors may vary slightly, but remain of the same order of magnitude. In this embodiment, the ratio C 3 C 3 + C 4 is approximately 0.5, which leads to a good distribution of the signal received by the internal antenna 24 between the chip 26 on the one hand and the electronic energy harvesting assembly on the other.

[0024] In the case of the present invention, the external module 12 comprises a single external antenna 20, and the internal module 14 comprises a single internal antenna 24. Each antenna 20, 24 is both a receiving and a transmitting antenna. More particularly, the external antenna 20 is a transmitting antenna for power and data, and potentially a receiving antenna for data, and the internal antenna 24 is a receiving antenna for data and power and potentially a transmitting antenna for data. The external and internal antennas 20, 24 are designed to achieve an inductance value that allows them to resonate at a frequency between 12 and 14 MHz, more precisely at a frequency of 13.56 MHz ( ISM frequency ) , taking into account the equivalent input impedance Z of the internal integrated circuit 28 of the chip 26.

[0025] Thanks to these two antennas 20 and 24, the external module 12 and the internal module 14 transfer power and data from one to the other simultaneously, and on a single frequency band. Furthermore, as already mentioned, the external module 12 and the internal module 14 can transfer data bidirectionally between them.

[0026] As mentioned in the introduction, the internal integrated circuit 28 of chip 26 has an input stage containing a protection circuit (including at least one Zener diode) that limits the voltage across the internal antenna 24. In an alternative embodiment, this protection can be achieved using a cascade of conventional diodes. This limits the energy harvestable by the electrical energy harvesting circuit used to power the stimulator 15. The addition of capacitor C3 connected in series limits the voltage supplied to the internal integrated circuit 28 of chip 26 while maintaining a high voltage at the input of the electrical energy harvesting circuit, thus ensuring a good power supply to the stimulator 15.

[0027] The report C 3 C 3 + C 4 expresses the energy distribution between the electrical energy harvesting electronic circuit and the internal integrated circuit 28 of chip 26. In the absence of capacitor C3, the ratio is zero and energy transfers are very limited. It has been observed that for a ratio C 3 C 3 + C 4 greater than 0.1, energy transfer is significantly improved. Preferably, the ratio C 3 C 3 + C 4 is greater than 0.25, or even greater than 0.3. The ratio C 3 C 3 + C 4 is less than 0.7. If the ratio tends towards 0 (C3 is small compared to C4), everything behaves as if there were no longer a capacitive voltage divider, and the Zener diode of the internal integrated circuit 28 of chip 26 resumes limiting the input voltage of the electrical energy harvesting circuit. Conversely, for a ratio tending towards 1 (C3 is large compared to C4), the internal integrated circuit 28 of chip 26 no longer receives a signal, and everything is transferred to the energy harvesting circuit, according to: V nfc = C 3 C 3 + C 4 ∗ V antenne

[0028] The search for maximum energy transfer is typically sought in inductive chargers, but is not desirable in the context of an implantable device for which the transferable energy is limited due to tissue sensitivity and for which the intensity of the signal - transmitted at the same time as the energy - must be sufficient to be received correctly.

[0029] In one embodiment, the report C 3 C 3 + C 4 is between 0.3 and 0.6.

[0030] In this configuration, from the point of view of the electrical energy harvesting electronic circuit, the internal integrated circuit 28 of the chip 26 is considered as a capacitor in parallel with a variable resistor whose value depends on the input voltage, so as to model the Zener effect of a real NFC circuit for example, forming part of the impedance matching network between the internal antenna 24 and the electrical energy harvesting electronic circuit.

[0031] Thus, in the present invention, the assembly formed by the third capacitor C3, the internal integrated circuit 28 of the chip 26, and the internal impedance matching network 32 ensures both: the impedance matching to optimize the coupling between the internal antenna 24 and the electrical energy harvesting electronic assembly, the deflection of part of the received energy, so as to ensure a stable and sufficient power supply for the electrical energy harvesting electronic assembly without affecting the operation of the chip 26.

[0032] The particularity of the transcutaneous link of the present invention is thus to simultaneously transfer energy and data (the data being transferred bidirectionally) by a single near-field link, and therefore a single antenna on each side of the subject's skin, recovering an optimized amount of energy at the level of the internal module 14.

[0033] The advantages of the present invention compared to the prior art are: Energy transfer occurs simultaneously with communication, without mutual constraints. Device 10 has only one set of antennas 20, 24, namely one antenna on each side of the subject's skin, avoiding the use of multiple antennas and thus greatly reducing steric bulk. Energy and data are transmitted on the same frequency band. Device 10 is compatible with a standard NFC reading system. The data transfer range is reduced, helping to limit the risks of listening and intrusion and thus ensuring better transmission security.

[0034] In particular, using only a single set of antennas 20, 24 makes it possible to combine information and energy exchange, which breaks with the prior art: indeed, conventional devices comprise two separate systems (one for information, the other for energy), whereas the approach of the present invention allows the two to be merged, thereby reducing the size. This result is achieved without complicating the device, since it only involves the addition of a few passive components.

[0035] Several prior art implants have only one antenna; however, these antennas do not operate in this frequency band and do not support NFC (HF at 13.56 MHz, according to ISO 14443 or ISO 15693 standards) with energy harvesting. The device 10 according to the invention enables the implementation of a transcutaneous energy and data transfer method in which the voltage supplied to the internal integrated circuit 28 is between 100 mV and 5 V, and the voltage supplied to the energy harvesting electronic assembly is between 100 mV and 50 V. The energy transfer efficiency between the external module 12 and the internal module 14 is thus between 10% and 70%. The transfer rate between the external module 12 and the internal module 14 is also between 6 kbit / s and 900 kbit / s, preferably between 106 kbit / s and 847 kbit / s or between 6.62 kbit / s and 26.48 kbit / s, so as to also cover the standard ISO / IEC 15693.

[0036] The essential point of the present invention therefore lies in increasing the efficiency of transcutaneous energy transfer by combining an integrated circuit, for example a standard NFC chip, with an electronic energy harvesting assembly external to the integrated circuit, so as to obtain a device 10 which combines good energy transfer efficiency with a reliable wireless communication link. DESCRIPTION OF THE FIGURES

[0037] [ Fig. 1] Figure 1 is an electronic schematic of a device according to the present invention, [ Fig. 2] Figure 2 is a functional diagram of a device according to the present invention.

Claims

1. An active implantable medical device (10) able to be partially implanted in a subject, the device comprising, once implanted, an external module (12) to the subject and an internal module (14) to the subject, the external module (12) and the internal module (14) being intended to transfer data from one to the other and energy from the external module (12) to the internal module (14), - the external module (12) comprising an external antenna (20), - the internal module (14) comprising: ▪ an internal antenna (24) defining two terminals (241, 242); ▪ an internal integrated circuit (28) associated with the internal antenna (24) having an equivalent input impedance with a capacitive part C4, said internal integrated circuit (28) being connected to the first terminal (242) and being connected to a capacitor with a capacitance C3, said capacitor with a capacitance C3 being connected to the second terminal (241) thereby forming an association in series of the internal integrated circuit (28) and of the capacitor C3 between said terminals (241, 242), with the ratio C 3 C 3 + C 4 greater than or equal to 0.1 and lower than 0.7, and ▪ an electrical energy recovery electronic assembly connected to said terminals (241, 242), the recovery electronic assembly being external to the internal integrated circuit (28).

2. The device (10) according to the preceding claim, characterised in that the ratio C 3 C 3 + C 4 is greater than or equal to 0.25, preferably comprised between 0.3 and 0.6.

3. The device (10) according to any one of the preceding claims, characterised in that the external module (12) includes a unique external antenna (20), and in that the internal module (14) includes a unique internal antenna (24).

4. The device (10) according to any one of the preceding claims, characterised in that each antenna (20, 24) is connected to an impedance matching circuit (22, 32) and that each antenna (20, 24) and its associated impedance matching circuit (22, 32) resonate at a frequency comprised between 12 and 14 MHz, more specifically 13.56 MHz.

5. The device (10) according to any one of the preceding claims, characterised in that the external module (12) and the internal module (14) are intended to transfer energy and data from one to the other simultaneously.

6. The device (10) according to any one of the preceding claims, characterised in that the external module (12) and the internal module (14) are intended to transfer data from one to the other in a bidirectional manner.

7. The device (10) according to any one of the preceding claims, characterised in that the external module (12) and the internal module (14) are intended to transfer energy and data from one to the other over a unique frequency band.

8. A method for transferring energy and data, the method being implemented by means of a device (10) according to any one of the preceding claims, the voltage supplied to the internal integrated circuit (28) being comprised between 100 mV and 5 V, the voltage supplied to the energy recovery electronic assembly being comprised between 100 mV and 50 V.