Wireless charging device for hearing instrument and hearing instrument system

Abstract

A charging device (4) for wirelessly charging a hearing instrument (2) is disclosed. The charging device (4) comprises: a first transmitter coil (12) for transmitting electromagnetic energy to a receiver coil (20) of the first hearing instrument (2); a second transmitter coil (14) for transmitting electromagnetic energy to a receiver coil (20) of a second hearing instrument (2), the second transmitter coil (14) being arranged adjacent to the first transmitter coil (12); and a barrier (22) having at least one wall (24) separating the first and second transmitter coils (12, 14) from each other. The wall (24) is made of a magnetic material, an electrically conductive material, or a laminated material made of a layer of the magnetic material and a layer of the electrically conductive material.

Description

Technical Field

[0001] The present disclosure relates to a wireless charging device for a hearing instrument and also relates to a hearing instrument system, in particular comprising the wireless charging device and two hearing instruments. Background Art

[0002] A hearing instrument (hearing device) is generally a portable device for providing sound to a person. Hearing instruments in the form of hearing aids (hearing aid devices) are used to provide care for people with difficulty in hearing or hearing loss. In order to meet many individual needs, different types of hearing aids are available, such as behind-the-ear hearing aids (BTE) and hearing aids with external receivers (RIC: receiver in the ear canal) and in-the-ear hearing aids (ITE). The hearing aids listed as examples are worn on the outer ear or in the ear canal of the hearing aid user. In addition, bone conduction hearing aids, implantable or vibrotactile hearing aids are also available on the market. These auxiliary devices stimulate the impaired hearing mechanically or electrically. However, hearing instruments generally also cover portable devices such as headphones, headsets, wearable devices, etc.

[0003] In principle, the main components of such hearing instruments are an input transducer, an amplifier and an output transducer. The input transducer is usually an acoustic-electric transducer, such as a microphone, and / or an electromagnetic receiver, such as an induction coil or a (radio frequency, RF) antenna. The output transducer is usually an electro-acoustic transducer, such as a miniature loudspeaker (receiver), or an electromechanical transducer, such as a bone conduction receiver. The amplifier is usually integrated into the signal processing device.

[0004] Hearing instruments are usually powered by batteries. Depending on the energy content of the battery and the requirements of the hearing instrument, the operating time is limited. In view of the general trend towards miniaturization, batteries with small dimensions are preferred, which additionally limits their energy content.

[0005] To avoid frequent replacement of used batteries, hearing instruments may be operated with rechargeable batteries (accumulators), such as nickel metal hydride (NiMH) or lithium ion (Li-ion) batteries.

[0006] Batteries in hearing instruments are usually charged with an electric current via metal contacts on the device. For regulatory reasons, medical devices in an increasing number of countries are not allowed to have open plug-in parts. In addition, moisture, sweat and other electrolyte-containing liquids and impurities can cause corrosion of the metal contacts.

[0007] In order to avoid galvanic metal contact, a wireless charging system can be used. This wireless charging system basically consists of two components, a transmitter and a receiver. The transmitter plays an important role in generating energy and transferring it to the receiver. The transmitter is formed by the charger circuit and the transmitter coil. The receiver coil is usually defined as the wireless charging receiver.

[0008] The transmitter coil is usually integrated into a fixed (external to the hearing instrument) charging device or hearing instrument charger, while the receiver coil is integrated into the hearing instrument and coupled to the battery. The operation of wireless charging is to induce an electromagnetic field in the (secondary) transmitter coil when the current fluctuates in the (primary) receiver coil. The receiver coil exposed to the varying electromagnetic field will capture the magnetic energy and convert it into electrical energy for the battery. Conventionally, the transmitter coil is formed using wires made of copper material, because its low ohmic resistance reduces energy losses due to heat generation.

[0009] Inductive charging systems typically require that the transmitter coil and the receiver coil be at least nearly equal in size. However, this limits the placement freedom between the receiver coil and the transmitter coil. In order to maximize the energy transfer between the coils, the receiver coil must be placed close to the transmitter coil and in the same orientation to achieve a good coupling factor. This positioning or arrangement is particularly complex for ITE hearing instruments, which are typically custom-made for the ear canal of the hearing instrument user, making ITE hearing instruments different from one device to another.

[0010] In order to achieve a high degree of placement freedom for the receiver coil, magnetic resonance (MR) charging can be used instead of inductive charging. MR charging can overcome the low coupling factor while maintaining high efficiency. For MR charging, a high quality factor of both the transmitter coil and the receiver coil at the resonant frequency is desired. Due to the possibility of using a low coupling factor, a loose placement of the receiver on top of the transmitter can be used. Therefore, the receiver coil size can be reduced relative to the transmitter coil size, i.e. the receiver coil can be designed to be smaller than the transmitter coil.

[0011] Since most hearing instruments are used in pairs to present sound to both ears, the corresponding charging devices are designed to charge two hearing instruments at the same time. To this end, one transmitter is implemented in the charging device for each hearing instrument. However, this leads to a problem known as "crosstalk" or "cross coupling".

[0012] Crosstalk is the interference of one charging channel in its communication with another charging channel located nearby - in the above case usually directly adjacent for space saving reasons. Therefore, when two transmitter coils are designed close to each other, one transmitter coil will shift and deviate from the resonant frequency of the other transmitter coil. Furthermore, one hearing instrument communicating with a transmitter coil in the charger may also generate crosstalk to the adjacent transmitter coil. The crosstalk effect will lead to a failure of communication between the hearing instrument and the charger, as the exact data transmitted from the respective hearing instrument cannot be identified and decoded.

[0013] The crosstalk effect of a typical charger with two transmitter coils placed next to each other can be illustrated by using an LED connected to each coil that indicates that a receiver coil is detected near that particular coil (i.e., within the charging field). The LED lights up if a receiver coil is detected and data from that receiver is captured. In many cases, placing a receiver coil over one of the transmitter coils causes the LED of the other transmitter coil to also light up. The detection of the transmitter coil by both receiver coils indicates the crosstalk effect.

[0014] Public Content

[0015] An object of the present disclosure is to provide a better way for charging two hearing instruments with the same charging device.

[0016] This object is achieved according to the present disclosure by the features of the independent claims. Advantageous or further embodiments emerge from the following description.

[0017] The basic principle of the present disclosure is to integrate a barrier between (particularly two) transmitter coils of a dual-channel transmitter in order to attenuate cross-coupling (or: "crosstalk"). The material of the barrier is one of a magnetic material, a conductive material or a laminated material (i.e., a laminated layer of the two materials mentioned above). Advantageously, a larger dimension of the barrier (such as a thicker thickness, a longer length and a higher height) results in better cross-coupling attenuation. In particular, at least one of input impedance, return loss and transmission gain is used as a measurement parameter to quantify the effectiveness of the cross-coupling attenuation.

[0018] In general, the passing criterion of the barrier is preferably based on at least one of the input impedance of the individual transmitter coils, the transmission gain and the return loss of the individual transmitter coils. Preferably, an attenuated return loss of at least -20 dB for the dual channel transmitter coils is sought.

[0019] The charging device according to the present disclosure is configured to wirelessly charge a hearing instrument. The charging device comprises a first transmitter coil for transmitting electromagnetic energy to a receiver coil of a first hearing instrument and a second transmitter coil for transmitting electromagnetic energy to a receiver coil of a second hearing instrument. The second transmitter coil is arranged adjacent to the first transmitter coil, in particular, their respective coil axes are parallel to each other. In addition, the charging device comprises a barrier (i.e., the barrier described above). The barrier has at least a wall separating the first and second transmitter coils from each other. The wall is preferably arranged parallel to the coil axis. In addition, the wall is made of one of a magnetic material, a conductive material, or a laminated material made of layers of a magnetic material and a conductive material.

[0020] Thus, each transmitter coil in the intended charging state constitutes one charging (or transmitter) channel. The barrier, in particular its walls, serves to prevent the (charging) signal from crossing from one channel to an adjacent channel, thereby preventing or at least reducing signal interference between adjacent channels. In other words, the barrier has the beneficial effect of attenuating the cross-coupling between the two transmission channels. This also improves the efficacy of the charging device due to reduced transmission losses.

[0021] To this end, the charging device according to the present disclosure advantageously exploits two characteristics of the barrier. These are, on the one hand, the material of the barrier and, on the other hand, the dimensions of the barrier, in particular the dimensions of its walls. The dimensions are height, length and thickness. The thickness is therefore measured in the direction of the distance between the first and second transmitter coils. Both length and height are measured in the plane of the wall and are therefore each perpendicular to the thickness. The object of the present disclosure is to attenuate the cross coupling so that the performance approximates that of a single-channel transmitter coil antenna.

[0022] In a preferred embodiment, the first and second transmitter coils are arranged in a common winding plane, which in turn is perpendicular to the two coil axes. In this case, the wall of the barrier is advantageously arranged perpendicular to the winding plane.

[0023] In a further preferred embodiment, the dimensions of the wall, in particular at least one of the height, thickness and length, are selected depending on the material of the wall.

[0024] Advantageously, these dimensions of the wall are also selected (in addition to or instead of the wall material dependency) according to the targeted effect of reducing cross-coupling effects between the transmissions of the first and second transmitter coils (channels), which in turn are characterized by input impedance and scattering parameters such as return loss and transmission gain as described above. Thus, as described above, the dimensions of the wall are preferably selected so that the input impedance of the transmitter coil is similar to that of a single transmitter coil and / or a transmission gain of at least -17 dB, more preferably -20 dB is achieved (particularly when both transmitter coils are "active"). Such reductions in input impedance and / or transmission gain are each similar to the criteria used to design the wall. Another cumulative or alternative criterion for wall design is another scattering parameter, namely return loss. As described above, the two criteria of input impedance and return loss are preferably selected to approximate the corresponding measurements of independent transmitter coils.

[0025] In yet another preferred embodiment, a material with high magnetic permeability is selected as the magnetic material of the wall. In this case, a ferrite material is conveniently selected. Such magnetic materials, in particular ferrites, are often used in the cores of power transformers or inductors due to their high magnetic permeability and low losses at high frequencies. High magnetic permeability is understood to mean that the material is more conductive to magnetic fields and the material can easily absorb the generated magnetic field. Lossy magnetic materials dissipate magnetic fields. Good ferrite materials will redirect the propagation of magnetic fields. Therefore, neither lossy magnetic materials nor ferrite magnetic materials allow the magnetic field to penetrate, so that the other channel transmitter coil cannot pick up the magnetic field. In addition, the high magnetic permeability of the barrier leads to an increase in the inductance of the transmitter coil. This will also cause the resonant frequency of the transmitter coil to shift to a lower frequency.

[0026] In an advantageous embodiment, copper, aluminum or silver is selected as the conductive material. Materials such as copper, silver or aluminum have low magnetic permeability (especially compared to magnetic materials) in addition to their electrical conductivity. Therefore, the conductive material can absorb the electric field and disperse it on the conductive material. It can also block the magnetic field by attenuating the magnetic field. This in turn leads to a reduction in the magnetic energy picked up by other channels. Mumetal is a composite material containing nickel, iron and other materials. Typically, it has a high magnetic permeability, but is only effective at frequencies up to 100kHz. This is not effective for magnetic fields of high (i.e., above 100kHz) frequencies. However, due to its main alloying components nickel and iron, Mumetal has similar properties to conductive materials. It has conductive properties and can also absorb electric fields and attenuate magnetic fields. Due to the low magnetic permeability and high electrical conductivity of the conductive material, a barrier made of it will reduce the inductance of the transmitter coil and therefore cause the resonant frequency of the transmitter coil to shift to a higher frequency.

[0027] The laminated material is made of two layers of magnetic material sandwiching a layer of conductive material. This stacking of magnetic and conductive materials will further improve the cross-coupling attenuation. Therefore, the laminated material can effectively shield the cross-coupling of the two transmitter coils because it combines the two above-mentioned properties, namely redirecting the electromagnetic field and attenuating the magnetic field. The magnetic material usually dominates the conductive material in inductance changes. Therefore, a laminated material with equal thickness will have a slightly increased inductance compared to a wall made of a single material. Again, this will cause the resonant frequency of the transmitter coil to be shifted to only a slightly lower frequency (compared to a wall made of ferrite alone).

[0028] In an advantageous embodiment, the height of the wall measured in the direction of the coil axis of at least one of the transmitter coils is selected between at least 5 mm and 40 mm, preferably between 15 mm and 35 mm. Most preferably, the height is selected to be 30 mm. Preferably, the height of the wall is (advantageously by a multiple) greater than the coil thickness (also described as height or length, i.e. in the direction of the respective coil axis).

[0029] In a further advantageous embodiment, the thickness of the wall is selected between 0.25 and 2.5 mm, preferably 2 mm.

[0030] In the case of a laminated material, the thickness of each magnetic material layer is preferably in the range between 0.1 mm and 0.8 mm, and the thickness of the conductive material layer is in particular in the range from 0.4 mm to 1 mm.

[0031] In a further advantageous embodiment, the length of the wall is selected to be between 40% and 110% of the maximum diameter of one of the transmitter coils measured in the length direction of the wall. In particular, the length is selected between 5 and 15 mm, preferably 10 mm (in the preferred case the width measured parallel to the wall or coil diameter is 10 mm).

[0032] The above exemplary dimensions of the wall are selected for a transmitter coil having a circular length (or diameter) of approximately 10 millimeters. For such a transmitter coil, the above values ​​of the passing criteria for input impedance, transmission gain and / or return loss can be met by these exemplary measurements. By scaling up or down the size of the transmitter coil, the dimensions of the wall will have to be changed accordingly based on the respective criteria.

[0033] In a preferred embodiment, both transmitter coils are configured for magnetic resonance charging. In particular, the two transmitter coils are individually tuned to a magnetic resonance charging frequency of approximately 13.56 MHz. As described above, this frequency may be affected by the barrier. However, this effect on the resonant charging frequency is reduced to a maximum deviation of approximately 0.2 MHz.

[0034] A hearing instrument system according to the present disclosure comprises a charging device as described above and two hearing instruments arranged for wireless charging. The hearing instrument system shows the same features and corresponding resulting benefits as the charging device.

[0035] Here and hereinafter, the conjunction “and / or” is to be understood in particular in such a way that the features connected by this conjunction can be realized together and as alternatives to one another. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In the following, the present disclosure is described with the aid of the accompanying drawings.

[0037] Figure 1 A hearing instrument system comprising two hearing instruments and a wireless charging device is schematically shown in a side view,

[0038] Figure 2 A transmitter system of a wireless charging device is schematically shown in a perspective view,

[0039] Figure 3The transmitter system is schematically shown in a side view,

[0040] Figure 4 The transmitter system is shown in cross-section.

[0041] Figure 5 The individual transmitter coils and the corresponding electromagnetic measurements are shown in tables and perspective diagrams.

[0042] Figure 6 In such Figure 5 The diagram of shows two adjacent transmitter coils showing the cross-coupling effect,

[0043] Figure 7 In such Figure 5 The chart shows Figure 2 transmitter systems and their associated electromagnetic measurements,

[0044] Figure 8 The graph shows the transmission gain versus thickness of the barrier between the two transmitter coils of the transmitter system.

[0045] Fig. 9 In such Figure 1 The figure shows a transmitter system with an external receiver, and

[0046] Fig.10 In such Figure 2 The view shows the Fig. 9 Simulation of the magnetic field caused by the situation.

[0047] The same reference numerals are used for the same parts throughout the drawings. DETAILED DESCRIPTION

[0048] Figure 1 A hearing instrument system 1 is shown. The hearing instrument system 1 comprises: two hearing instruments, referred to as hearing aids 2 for short; and a wireless charging device 4 which is configured to wirelessly charge the hearing aids 2. To this end, the charging device 4 comprises a housing 6 having two recesses 8 for placing the hearing aids 2. In addition, the charging device 4 comprises a transmitter system 10, which in turn comprises a first transmitter coil 12 and a second transmitter coil 14, which are arranged adjacent to each other below the respective recesses 8 (see also Figure 2 ).

[0049] The respective coil axes 16 of the two coils 12 and 14 are arranged parallel to one another. In addition, the two coils 12 and 14 are arranged in a common winding plane 18. The transmitter coils 12 and 14 are arranged to transfer energy to a receiver coil 20 of the hearing aid 2 by inductive energy transfer. In particular, the transmitter coils 12 and 14 and the receiver coil 20 are arranged for so-called magnetic resonance charging. This means that the transmitter coils 12 and 14 transmit energy in a very narrow frequency band, the so-called resonance frequency, which is set to 13.56 MHz.

[0050] In one example, but not by way of limitation, the length of transmitter coils 12 and 14 is 10 millimeters.

[0051] In order to reduce the cross coupling between the transmitter coils 12 and 14 and thus reduce energy losses during the charging process of the hearing aid 2, the transmitter system 10 comprises a barrier 22 comprising a (shielding) wall 24. In the specific embodiment shown in the figures, the barrier 22 consists practically only of the wall 24. The wall 24 is positioned between the first and second transmitter coils 12 and 14, its (wall) plane being arranged parallel to the coil axis 16 and thus perpendicular to the winding plane 18. The dimensions of the wall 24 are a thickness t (measured in the direction of the distance between the two transmitter coils 12 and 14), a length l (measured on the winding plane 18) and a height h (measured in the direction of the coil axis 16, cf. Figure 3 and Figure 4 ).

[0052] The material and dimensions of the wall 24 are selected in relation to one another with the goal of achieving suppression of cross coupling during energy propagation of the transmitter coils 12 and 14. In particular, for the transmission system 10, the goal is to be as close as possible to the independent transmitter coil 30 ( Figure 5 ) performance. One of the criteria for low cross coupling is a so-called transmission gain between the two transmitter coils 12 and 14 of a value of -20 dB. Other measurements or characteristics considered as corresponding criteria during the design process of the wall 24 are return loss and input impedance. In the following, several embodiments of the wall 24 and the influence on the electromagnetic characteristics of the transmitter system 10, in particular the measurements of the above criteria, are described.

[0053] Input impedance refers to the impedance seen from the corresponding transmitter coil 12, 14 or 30. The input impedance is measured in ohms. For an independent transmitter coil 30, the input impedance has a single peak at the resonant frequency, here at 13.56 MHz (see Figure 5 ). The input impedance decreases exponentially at both higher and lower frequencies. Figure 6As can be seen in FIG. 1 , two adjacent independent (ie, unshielded) transmitter coils 30 cause the input impedance to be split into two local peaks at different frequencies due to cross coupling ("crosstalk").

[0054] Return loss is the reflected wave of the transmitter coil 12, 14 or 30. The unit measurement of the return loss parameter is decibel. Reduced return loss indicates weaker cross-coupling between two adjacent transmitter coils 12, 14 or 30. A single independent transmitter coil has a minimum peak return loss at the resonant frequency and has a higher return loss at both higher and lower frequencies.

[0055] The transmission gain is a decibel parameter indicating the ratio of the output of adjacent transmitter coils 12, 14 or 30 to the transmitter coil input. In other words, the transmission gain means the attenuation of the transmission power from one transmitter coil 12, 14 or 30 to the adjacent transmitter coil 12, 14 or 30, respectively. A lower gain indicates a weaker cross-coupling between the two transmitter coils 12, 14 or 30. For example, a transmission gain of 0 dB at the resonant frequency means that the two adjacent transmitter coils 12, 14 or 30 are 100% coupled. A transmission gain value of -20 dB, which is equivalent to 0.01, means that only 1% of the transmission power crosses from one transmitter coil 12, 14 or 30 to the corresponding other coil. A low transmission gain means a low cross-coupling between adjacent transmitter coils 12, 14 or 30.

[0056] As for the material of the wall 24, three variations are described below, specifically: a magnetic material with high magnetic permeability, here ferrite; a conductive material, here aluminum; and a stack of two layers of ferrite sandwiching an aluminum layer.

[0057] For ferrites, the thickness of the barrier 22 (and, respectively, the wall 24) determines the absorptivity of the magnetic field. Thicker ferrite materials absorb magnetic fields more effectively.

[0058] For aluminum, a thicker wall 24 may reduce the penetration of the magnetic field.

[0059] In general, thicker walls 24 having magnetic and / or conductive material may reduce cross coupling of the two transmitter coils 12 and 14 .

[0060] In order to understand the influence of the material of the wall 24 on the cross coupling, several simulations have been performed. Input impedance, return loss and transmission gain have been used to quantify the cross coupling effect. Simulations were performed without the barrier 22 (i.e., for two unshielded adjacent transmitter coils 30) and for the transmitter system 10. To simulate the transmitter system 10, different materials for the wall 24 have been selected, such as ferrite, aluminum and stacked materials. The wall 24 was always modeled to have a thickness t of 2 mm, a height h of 30 mm and a length l of 10 mm.

[0061] The (single) independent transmitter coil 30 has only a single maximum peak of input impedance at about 25 ohms and a very small minimum peak return loss at -175 dB at the resonant frequency. The very small minimum peak return loss of the single independent transmitter coil 30 is only an ideal case, but it will not happen because there is always reflected wave loss.

[0062] When two unshielded transmitter coils 30 are placed close together and cross-coupled, the input impedance is split into two local maxima (values ​​of approximately 14 to 16 ohms) at two different frequencies. For these cross-coupled transmitter coils 30 (without any barriers), the minimum return loss value is -11 dB and the maximum transmission gain is -7 dB.

[0063] The simulation results also show that ferrite, aluminum and laminated materials can effectively converge the input impedance to a single peak again at the resonant frequency and reduce the return loss and transmission gain. For ferrite, the maximum input impedance is at about 24.5 ohms, the minimum return loss is at about -40dB, and the maximum transmission gain is at about -20dB. Aluminum shows a maximum input impedance at about 20 ohms, a minimum return loss at about -25dB, and a maximum transmission gain at -12dB. The simulation results also show that the laminated material (with 0.5mm of ferrite on each side of the 1mm aluminum layer) has the highest maximum input impedance at about 24.8 ohms, the lowest minimum return loss at about -43dB, and the lowest maximum transmission gain at about -22dB. The above values ​​are measured at a resonant frequency of 13.56MHz.

[0064] In order to understand the effect of increasing the thickness t of the wall 24, further simulations have been performed. For this simulation, similar materials, similar heights h and similar lengths l have been used. The thickness t of the wall 24 varies from 0 mm (no shielding) to 2.0 mm. Ferrite is used as the material for the wall 24 in this simulation. The height h of the wall 24 is 30 mm and its length l is 10 mm. The thickness t increases in steps of 0.5 mm. The maximum transmission gain decreases stepwise from about -7.5 dB (0 mm) to -15 dB (0.5 mm), -17.4 dB (1 mm), -18.7 dB (1.5 mm) and -19.8 dB (2 mm) - see Figure 8 The above values ​​are measured at a resonant frequency of 13.56 MHz.

[0065] The above simulation results show that a thicker wall 24 results in a lower transmission gain and, therefore, a reduction in the cross coupling between the two transmitter coils 12 and 14 . Figure 8 The effect of the thickness t on the transmission gain of a wall 24 made of ferrite is schematically shown. For a better understanding, the transmission gain is also shown as a percentage. It can be seen from the figure that for a wall 24 made of ferrite, the effect on the transmission gain decreases (i.e. the gradient of the curve becomes smaller) when the thickness t is greater than 0.7 mm. However, the goal of the barrier is to have a transmission gain below 1.5%. Therefore, the value of the thickness t of the wall 24 must be greater than 1.3 mm.

[0066] Another simulation was performed to show the influence of the height h of the wall 24. The simulation was performed with the same material, the same thickness t and the same length l but different heights h. As material for the wall 24, aluminum was chosen, the length l was 10 mm and the thickness t was 0.4 mm. The height t was chosen to be 20 mm, 25 mm and 30 mm.

[0067] For a height h from 20 mm to 30 mm, the input impedance of the wall 24 gradually converges from multiple peaks to a single peak. At the same time, the minimum return loss decreases from -15 dB (h = 20 mm) to -17.5 dB (h = 25 mm) and -18 dB (h = 30 mm). The maximum transmission gain also decreases from -8.5 dB (h = 20 mm) to -10.5 dB (h = 25 mm) and -13.5 dB (h = 30 mm). The above values ​​are measured at a resonant frequency of 13.56 MHz, respectively.

[0068] Compared to the above simulations, further simulations were performed on the effect of the length l of the wall 24. The length l was varied from 5 mm to 7.5 mm and 10 mm (50%, 75% and 100% of the diameter of the transmitter coils 12, 14 in the direction of the wall 24). The thickness t was set to 2 mm and the height h was set to 30 mm. Ferrite was selected as the material of the wall 24.

[0069] For the shortest length, the maximum input impedance was found to be 22 ohms, the minimum return loss was -29 dB, and the maximum transmission gain was -14.5 dB. For a length l of 7.5 mm, the maximum input impedance was found to be 23.5 ohms, the minimum return loss was -34.5 dB, and the maximum transmission gain was -17 dB. For a length l of 10 mm, the maximum input impedance was found to be 24.5 ohms, the minimum return loss was -40 dB, and the maximum transmission gain was -20 dB. The above values ​​were measured at a resonant frequency of 13.56 MHz.

[0070] The simulation results imply that a greater length of the wall 24 results in better cross-coupling attenuation. This is due to more magnetic field absorption or better magnetic field attenuation. Figure 2 In the case of the coil design shown, the magnetic field of the transmitter coil 12, 14 propagates from the center and returns through the two arms of the transmitter coil 12, 14. However, the magnetic field does not propagate further out of the transmitter coil contour. For effective electromagnetic field shielding, the length l of the wall 24 is set to a value at least the same as or greater than the diameter of the transmitter coil 12 or 14 (measured parallel to the wall 24), respectively.

[0071] To attenuate the vertically downward pointing component of the magnetic field, a copper layer of the circuit board carrying the respective transmission coil 12, 14 is placed at the bottom (i.e., below) of the transmitter coil 12, 14. Thus, the walls 24 of the barrier 22 extending downward to the circuit board are sufficient to prevent the generated vertically downward magnetic field from crossing. On the other hand, the magnetic field can freely propagate upward.

[0072] In conclusion, a large-sized barrier 2 has a more effective cross-coupling attenuation result. However, increasing the size of the barrier 2 will add more cost, weight, and simultaneously enlarge the size of the charger device 1.

[0073] When an (unshielded) transmitter coil 30 is coupled with another (unshielded) transmitter coil 30 having almost the same resonant frequency, the input impedance will be split into two peaks at two different frequencies (as already shown above). With the known coupling factors in the two transmitter coils 30, the split frequency of the transmitter coils can be obtained using equation (1), where f0 is the resonant frequency and k is the coupling factor. When two channel transmitter coils 30 are cross-coupled, the phase angle of one transmitter coil 30 is split into multiple zero crossings, where one zero crossing is at a higher frequency than the resonant frequency and one zero crossing is at a lower frequency than the resonant frequency. Stronger cross coupling of the two transmitter coils 30 will split the two peaks of the input impedance further away from the resonant frequency. Stronger cross coupling of the two transmitter coils 30 also generates multiple zero crossing phase angles further away from higher and lower frequencies. Figure 6The input impedance of two cross-coupled transmitter coils 30 is shown versus frequency for various coupling factors (at Figure 6 The relationship in the table is called "Coup").

[0074]

[0075] Fig. 9 and Fig.10 Simulation results for a model (i.e., a transmitter system 10) having a 2 mm thick wall 24 and a receiver coil 20 placed above a transmitter coil 12 are described. The model is used to examine the effect of the magnetic field generated from the transmitter coil 12 crossing over to the adjacent side in the presence of the wall 24. The simulations were performed under the condition that both the transmitter coils 12, 14 and the receiver coil 20 were well tuned to the same resonant frequency. The simulations were performed under the assumption that the wall 24 can shield the cross coupling between the two transmitter coils 12, 14.

[0076] Fig.10 The scattering of the magnetic field is shown, where the transmitted power is given to the transmitter coil 12 on the right. The transmitted magnetic field is scattered with high density at the upper right space of the transmitter coil 12, and with low density at the upper left space. The simulation results indicate that the wall 24 can attenuate the cross coupling between the two transmitter coils 12 and 14.

[0077] In order to investigate the influence of the wall 24 on the resonant frequency, additional simulation-based tests have been performed. Four scenarios have been simulated:

[0078] First (again) independent transmitter coil,

[0079] Second, the independent transmitter coil also has a 2mm thick ferrite wall.

[0080] Third, the independent transmitter coil also has a 2mm thick aluminum wall, and

[0081] Fourth, an independent transmitter coil also has a wall of laminated material, including a 0.18 mm ferrite layer, a 0.4 mm aluminum layer and a 0.18 mm ferrite layer.

[0082] In these tests, the frequencies of maximum input impedance and minimum return loss are evaluated. For the standalone transmitter coil, the frequency is 13.63 MHz. For the ferrite wall, the frequency is 13.57 MHz, and for the aluminum wall, the frequency is 13.71 MHz. For the laminate material, the frequency is 13.61 MHz. Therefore, the ferrite wall shifts the resonant frequency of the transmitter coil to a lower frequency, and the aluminum wall shifts the resonant frequency of the transmitter coil to a higher frequency. The laminate material wall causes the resonant frequency to shift to a lower frequency, but not as low as the pure ferrite wall.

[0083] Another measurement test was conducted by simulation to investigate the effectiveness of ferrite material on cross-coupling attenuation. The test model was two cross-coupled transmitter coils with and without a barrier between them. The ferrite material was used as a representative of the wall, with a thickness of 2 mm, a length of 10 mm (100% coverage), and a height of 30 mm. For the unshielded cross-coupled transmitter coil, the maximum input impedance was detected at 13.57 MHz, showing 17.4 ohms, the minimum return loss was detected at 13.59 MHz, showing -5.8 dB, and the maximum transmission gain was detected at 13.64 MHz, showing -10 dB. For the shielded coil, the corresponding values ​​at 13.57 MHz were 25.23 ohms, the minimum return loss at 13.56 MHz was -9.53 dB, and the maximum transmission gain at 13.57 MHz was -20.73 dB. Based on the results, the wall 24 made of ferrite with a thickness of 2 mm, a length of 10 mm and a height of 30 mm can effectively attenuate the return loss and the transmission gain. The ferrite wall 24 can also restore a certain amount of maximum input impedance and minimum return loss.

[0084] The subject matter of the present disclosure is not limited to the above-described embodiments. On the contrary, those skilled in the art can derive other embodiments of the present disclosure from the above description. In particular, the various features of the present disclosure described based on various embodiment examples and embodiment variations thereof can also be combined with each other in other ways.

[0085] Reference numerals list

[0086] 1 Hearing Instrument System

[0087] 2 Hearing instruments

[0088] 4 Charging equipment

[0089] 6 Housing

[0090] 8. Pit

[0091] 10 Transmitter System

[0092] 12 Transmitter Coil

[0093] 14 Transmitter Coil

[0094] 16 Coil axis

[0095] 18 Winding plane

[0096] 20 Receiver Coil

[0097] 22 Barrier

[0098] 24 wall

[0099] 30 Transmitter Coil

[0100] h Height

[0101] Length

[0102] t Thickness

Claims

1. A charging device (4) for wirelessly charging a hearing instrument (2), characterized in that include: - a first transmitter coil (12) for transmitting electromagnetic energy to a receiver coil (20) of the first hearing instrument (2), a second transmitter coil (14) for transmitting electromagnetic energy to a receiver coil (20) of a second hearing instrument (2), said second transmitter coil (14) being arranged adjacent to said first transmitter coil (12), as well as - a barrier (22) having at least one wall (24) separating the first transmitter coil (12) and the second transmitter coil (14) from each other, Wherein, the wall (24) is made of the following materials: * A laminated material, the laminated material being made of a layer of the magnetic material and a layer of the conductive material, wherein the laminated material is made of two layers of the magnetic material sandwiching a layer of the conductive material.

2. The charging device (4) according to claim 1, It is characterized in that The first transmitter coil (12) and the second transmitter coil (14) are arranged in a common winding plane (18).

3. The charging device (4) according to claim 1, It is characterized in that As the magnetic material of the wall (24), a material with high magnetic permeability is selected.

4. The charging device (4) according to claim 3, It is characterized in that The material with high magnetic permeability is ferrite.

5. The charging device (4) according to claim 1, It is characterized in that Copper, aluminum or silver are selected as the conductive material of the wall (24).

6. The charging device (4) according to claim 1, It is characterized in that The thickness of each magnetic material layer ranges between 0.1 mm and 0.8 mm, and the thickness of each conductive material layer ranges between 0.4 mm and 1 mm.

7. The charging device (4) according to claim 1, It is characterized in that The dimensions (h, l, t) of the wall (24) are selected according to the material of the wall (24).

8. The charging device (4) according to claim 1, It is characterized in that The dimensions of the wall (24) are selected based on at least one of the criteria of input impedance and scattering parameters.

9. The charging device (4) according to claim 8, It is characterized in that The scattering parameters are return loss and transmission gain.

10. The charging device (4) according to claim 8, It is characterized in that The dimensions are selected such that the input impedance of the transmitter coil (12, 14) is similar to that of a single transmitter coil and / or the transmission gain of the transmitter coil (12, 14) is less than -17 dB.

11. The charging device (4) according to claim 10, It is characterized in that At least one of the height (h) of the wall (24) measured in the direction of the coil axis (16) of at least one of the transmitter coils (12, 14), the thickness (t) of the wall (24) measured in the direction of the distance between the first and second transmitter coils (12, 14), and the length (l) of the wall (24) is selected such that the input impedance of the transmitter coils (12, 14) is similar to that of a single transmitter coil and / or the transmission gain of the transmitter coils (12, 14) is less than -17 dB.

12. The charging device (4) according to any one of claims 7 to 10, It is characterized in that The transmitter coils (12, 14) have a length of 10 mm and the wall (24) has a height (h) selected between at least 5 mm and 40 mm.

13. The charging device (4) according to claim 12, characterized in that The height (h) of the wall (24) is selected between 15 mm and 35 mm.

14. The charging device (4) according to claim 10, It is characterized in that The transmitter coil (12, 14) has a length of 10 mm and the wall (24) has a thickness (t) selected between 0.25 mm and 2.5 mm.

15. The charging device (4) according to claim 7, It is characterized in that The length (l) of the wall (24) is selected between 40% and 110% of the maximum diameter of one of the transmitter coils (12, 14) measured in the length direction of the wall (24).

16. The charging device (4) according to claim 1, It is characterized in that Two transmitter coils (12, 14) are configured for magnetic resonance charging.

17. The charging device (4) according to claim 16, It is characterized in that The two transmitter coils (12, 14) are each tuned to a magnetic resonance charging frequency of approximately 13.56 MHz.

18. A hearing instrument system (1), characterized in that The invention comprises a charging device (4) according to claim 1 and two hearing instruments (2) arranged for wireless charging.

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