METHOD, DEVICE AND CHARGER

Description

[0001] The invention relates to a method, a device and a charger.

[0002] In this context, "device" refers to a mobile device, meaning it is generally portable and has its own energy storage for power supply. The device is typically assigned to a single user and may even be customized for that user. The energy storage is usually a secondary cell (e.g., a lithium battery) that can be recharged by connecting the mobile device to a charger. For this purpose, the device is connected to the charger either via a wired connection or wirelessly to transfer energy from the charger to the device, which then uses this energy to charge the device, or more precisely, its energy storage.

[0003] A specific example of a hearing aid is a device designed to assist users with hearing loss. The hearing aid contains a microphone that picks up ambient sound and generates an electrical input signal. This signal is then processed by the hearing aid's signal processor. This processing is based on the user's individual audiogram, compensating for their specific hearing impairment. The signal processor produces an electrical output signal, which is then converted back into sound via the hearing aid's receiver and delivered to the user. Depending on the hearing aid type, other input and / or output transducers may be used instead of the microphone and receiver. The hearing aid is either binaural or monaural, meaning it is designed for use on both sides of the user's head or only one side, respectively.

[0004] Other examples of devices include headphones, headsets, wearables, smartphones and similar devices.

[0005] During charging, the device is in a charging state. After charging, and even though the device is still connected to the charger, it typically turns on and enters a discharging state, or the charger continues to supply power to prevent it from entering a discharging state. In both cases, energy is wasted.

[0006] Reference is made to US 2016 / 308386 A1.

[0007] Against this background, an object of the invention is to reduce energy consumption after charging. For this purpose, a suitable method, a device, and a charger are to be specified.

[0008] The problem is solved according to the invention by a method with the features of claim 1 and a device and a charger with the features of claim 13. Advantageous embodiments, further developments, and variants are the subject of the dependent claims. The descriptions relating to the method also apply mutatis mutandis to the device and the charger, and vice versa. Where steps of the method are described below, advantageous embodiments for the device and the charger result from the fact that they are configured to perform one or more of the steps, in particular by means of a respective control unit in the device or charger.

[0009] In this method, a device is connected to a charger, and wireless charging occurs when the device is in a charging state. This is achieved by wirelessly transferring energy from a transmitter module of the charger to a receiver module of the device. During charging, the device is switched off and in this charging state. The device has a charging port to which a charging voltage (Vcc) is applied, which is adjustable via the charger. The device also has a switching port for turning the device on and off. The charging port and the switching port are preferably connections to a power management module (PMIC) of the device. The power management module receives the charging voltage and uses it to charge an energy storage device, such as a lithium battery, within the device.

[0010] The device also has a discharge state in which energy is consumed, namely by one or more of the device's components. In the discharge state, the energy management module controls the supply of energy to the components from the device's energy storage. In the charging state, the device receives energy from the charger; in the discharge state, the device consumes energy. In the charging state, the device is necessarily connected to the charger; in the discharge state, the device is either disconnected from or connected to the charger. "The device is switched on" means that the components are being supplied with energy, particularly via the energy management module. "The device is switched off" means that the components are not being supplied with energy, although the energy management module may still consume energy. By design, the device is also switched on in the discharge state.Where the following description states that the device "will be switched off", it means firstly that if the device is switched on, it will be "switched off", and secondly, if the device is already switched off, it will "remain switched off".

[0011] The device also features a switch connected to the switching terminal, which can be activated by adjusting the charging voltage to an intermediate voltage. This switch is specifically part of the device's power-off circuit. The charger adjusts the charging voltage to the intermediate voltage, thus activating the switch and turning the device off. This means, in particular, that the device is (i.e., is or remains) switched off by the charger by adjusting the charging voltage to the intermediate voltage, thereby activating the switch and turning the device off. This adjustment of the intermediate voltage and the subsequent transition to the off state occurs primarily when charging is stopped or interrupted, but can also occur generally in the event of a fault, for example.In case of overheating or overvoltage / overcurrent of the energy storage device, the charger automatically shuts down as soon as no more energy is being transferred to the device. The charger thus initiates a change in the device's off state, in which it no longer consumes any energy – unlike in the discharge state. The charger utilizes the ability to variably adjust the charging voltage for this purpose. This automatic shutdown therefore saves energy after charging, as the device is switched off and thus does not enter the discharge state.

[0012] The device is a mobile device and therefore generally portable. It is typically assigned to a single user and may even be individually customized for that user. The energy storage device is usually a secondary cell (e.g., a lithium battery) which can be recharged by connecting the device to the charger.

[0013] Preferably, the device is a hearing aid designed to provide assistance to a user with a hearing impairment. For this purpose, the hearing aid includes a microphone that picks up ambient sound and generates an electrical input signal. This signal is then processed by the hearing aid's signal processing unit. The modification is based on the user's individual audiogram, thus compensating for their specific hearing impairment. The signal processing unit outputs an electrical signal, which is then converted back into sound via the hearing aid's receiver and delivered to the user. Depending on the hearing aid type, other input and / or output transducers may be used instead of the microphone and receiver. The hearing aid is either binaural or monaural, meaning it can be used on both sides or only one side of the user's head, respectively. Input transducers (e.g.,Microphone), output converter (e.g., headphones), and signal processing are consumers of the device.

[0014] Alternatively, the device is a headphone, headset, wearable, smartphone, or similar.

[0015] To charge, the device is connected to the charger and is appropriately placed into, inserted into, or placed on top of it. For example, the charger may be designed as a charging cradle with a recess into which the device can be placed. Optionally, the charger may have a lid to close it and cover the recess, thus completely enclosing the device inside the charger. The recess is advantageously shaped to hold the device in a well-defined position relative to the charging cradle.

[0016] Depending on the charge level of the energy storage device, i.e., how fully charged it is, it provides a voltage Vbat to one or more consumers. This voltage may be transformed beforehand by a transformation unit, for example, in the energy management module, so that it then outputs a voltage Vout to the consumers. The greater the charge, the higher this voltage typically is. The device is charged by the charger with a charging input voltage Vcc, where the charging voltage is the voltage present in the device for charging the energy storage device. The energy storage device is then charged until the desired charge or voltage is reached. For this purpose, a suitable charging threshold voltage Vchg,thres is specified, which is compared with the charging voltage to determine when charging begins and when it does not.Preferably, charging is terminated when the charging voltage falls below the charging threshold voltage. The charging threshold voltage is, for example, a fixed, predefined voltage.

[0017] To switch off the device (i.e., the device is switched off or remains switched off) after it has been fully charged, an automatic switch-off is advantageous. In this case, the automatic switch-off is performed by the device itself, but not initiated by the device; rather, it is initiated by the charger. Therefore, the automatic switch-off is more accurately described as an "externally initiated automatic switch-off." The charger determines when the device should be switched off and then sends a switch-off signal to the device, causing it to switch off. In this case, the switch-off signal results in the device being at intermediate voltage. Without an automatic switch-off, the device would remain switched on and consume energy continuously, even after charging, particularly at least by the energy management module for its operation.Even if the current used is typically low, the device still consumes energy. This energy may also be drawn from the charger while it remains connected to the device after charging is complete. Specifically, with a portable charger that has its own energy storage, this storage would continuously discharge from the device, primarily to prevent the device from switching on and entering a discharge state. Furthermore, there are often specifications designed to ensure compatibility between devices. One such specification is "Made for iPhone / iPod / iPad," or MFi for short.For example, one specification requires that the device's BLE (Bluetooth Low Energy) function be switched off, meaning the device is not in pairing or offer mode while connected to the charger and unless explicitly enabled by the user. Regarding pairing mode, the specification stipulates that the device should not be able to pair with another device while connected to the charger. Regarding offer mode, the specification further requires that the device should not transmit a ready signal (indicating its readiness to pair) to other devices while connected to the charger.

[0018] However, some scenarios may cause the device to switch on after charging, but while still connected to the charger, and thus operate in a discharge state, in which the BLE function is also enabled contrary to the specification. One such scenario is a power outage, which interrupts the charger's power supply. A second scenario is the removal of the charger's power cable, where the cable connects the charger to a power source, such as a household outlet. This second scenario is essentially similar to the first. A third scenario is that the portable charger's energy storage is completely discharged, so the charger can no longer supply power to charge the device. In all these scenarios, no more power is transferred to the device, and therefore the device typically enters a discharge state.As a result, the device is switched on instead of off. Consequently, energy-consuming functions, such as the BLE function, are also enabled.

[0019] Generally, but especially due to the specifications as described, it is therefore desirable to switch off the device after charging, as long as it is still connected to the charger. The device should ideally not be put into discharge mode and switched on when charging is complete; instead, it should be switched off.

[0020] To meet the specifications, it is advantageous to use the charging port of the device's energy management module to implement automatic shutdown, thereby switching off the device after charging. The charging port is an electrical contact, such as a contact pin, through which the device is connected to the charger for charging and is thus galvanically coupled in the case of contact-based charging. The charging voltage is present at the charging port, which is therefore generally a power contact. The switching port is also designed, for example, as a contact pin. The switching port is typically pulled up with a pull-up resistor. A manually operable switch is conveniently connected between the switching port and ground for manually switching off the device.For automatic shutdown via the charger, the device features the aforementioned shutdown circuit with a switch, which utilizes the charging port and the switching port. The switch is preferably a transistor with a gate, source, and drain, i.e., with corresponding terminals. The terms gate, drain, and source are used here and subsequently to denote the three terminals of the transistor. However, these descriptions apply generally to any three-terminal switch, where the gate, source, and drain of a transistor are functionally equivalent. The gate of the transistor is pulled up to the charging voltage via the charging port and a resistor in the shutdown circuit. The resistor connects the gate to the source and to ground. The drain and source of the transistor are connected to the switching port and to ground, respectively.

[0021] In general, and specifically using the shutdown circuit described above, the automatic shutdown advantageously provides an additional operating state for the device: the "off" state. In this state, the device is connected to the charger but switched off, meaning it neither consumes energy nor receives energy from the charger. In contrast, the device is switched off in the charging state but still receives energy (particularly for operating the energy management module), and switched on and consumes energy in the discharging state. To switch between the charging and discharging states (in both directions), the device also features a standby state (i.e., "idle state"), resulting in a total of four possible operating states, which are mutually exclusive.

[0022] The device preferably switches from the discharge state, the off state, or the standby state to the charging state when the charging voltage is at least equal to the charging threshold voltage. The charging state remains active as long as the charging voltage is at least equal to the charging threshold voltage. The device switches from the charging state to the standby state when the charging voltage is lower than the charging threshold voltage. The device switches from the standby state to the discharge state when the charging voltage is lower than a reset voltage Vrst and, in particular, when a time has elapsed that is longer than a discharge time tdisc. The reset voltage is, for example, a fixed, predefined voltage and, in particular, a parameter of the energy management module.The reset voltage serves primarily to stop the operation of the energy management module and initialize it to a predefined standard state by applying a voltage to the energy management module that is at least equal to the reset voltage. This initialization then enables subsequent proper operation. The reset voltage is also used, in particular, to determine when the device switches from standby to discharge mode. The discharge time, for example, is a fixed, predefined period of a few seconds. Conversely, the device switches from discharge to standby mode when the charging voltage is lower than the charging threshold voltage and higher than the reset voltage, and from standby to charging mode when the charging voltage is at least equal to the charging threshold voltage. As long as the charging voltage is lower than the charging threshold voltage, the standby mode remains active.

[0023] Automatic shutdown, i.e., switching to the off state, is achieved by adjusting the charging voltage at the charging terminal to an intermediate voltage. This intermediate voltage is the gate-source threshold voltage (Vgs-thres) of the transistor and is conveniently located between the reset voltage and a minimum gate-source threshold voltage. The gate-source threshold voltage is the voltage required to switch (especially turn on) the transistor and lies, in particular, in a range between the minimum gate-source threshold voltage (the voltage required at least to switch the transistor) and a maximum gate-source threshold voltage (the maximum voltage possible to switch the transistor).The reset voltage is, in particular, higher than the actual gate-source threshold voltage, but the maximum gate-source threshold voltage can be higher than the reset voltage. Advantageously, the transistor should have the largest possible difference between the minimum gate-source threshold voltage and the maximum gate-source threshold voltage. The maximum gate-source threshold voltage is, for example, 20 V.

[0024] The gate-source minimum threshold voltage on the one hand and the reset voltage on the other define a voltage range for the intermediate voltage, which is used to switch to the off state. If the charging voltage is lower than the reset voltage, the device switches to the discharge state. The discharge state is initially active as long as the charging voltage is lower than the gate-source minimum threshold voltage. The device then switches to the off state when the charging voltage is lower than the reset voltage and higher than the charging threshold voltage, and additionally, if a time (during which the intermediate voltage is maintained) has elapsed that is longer than the switching terminal active time tsca. Accordingly, as soon as the intermediate voltage is reached at the transistor's gate, the transistor is switched on and the switching terminal is pulled to ground.The device briefly switches to a discharge state and from there to the off state, particularly after the switching-initiated active time. The switching-initiated active time is, for example, a fixed, predefined period of a few seconds. A switch to the off state is preferably only possible from a discharge state.

[0025] Switching the device on, and specifically changing it from the off state to the discharge state, is initially possible via the charging state. In a suitable design, the device switches from the off state to the charging state when the charging voltage corresponds to at least the charging threshold voltage. Alternatively or additionally, switching the device on from the off state is possible by manual activation. For this purpose, the device has a switch, such as a button, push button, slide switch, or similar device.

[0026] The described solution for automatically switching off the device is easily possible with contact-based charging, as a galvanic connection exists through which the intermediate voltage can be easily adjusted. Since the charging voltage is supplied directly by the charger, the intermediate voltage is correspondingly easy to adjust. However, this is not so easily possible with a wireless charger, as the charging voltage is not supplied directly by the charger, but rather induced in the device by the transmitter module and therefore is not necessarily present in the charger itself.Without an automatic shut-off, the charger must continuously supply energy to the device to prevent it from entering the discharge state. If the power supply is interrupted, the device would regularly and automatically enter the discharge state, possibly with an interim standby state as described above. A key aspect of the present invention is to implement the off state as described specifically for a wireless charger, i.e., not via a physical connection, but wirelessly. The preceding explanations apply to both physical and wireless charging. In a wireless charger, energy transfer from the charger to the device occurs via a transmitter module in the charger and a receiver module in the device.

[0027] During charging, energy transfer preferably occurs via a magnetic field, which is generated by a transmitting coil of the transmitter module and received by a receiving coil of the receiver module. To then adjust the charging voltage to the intermediate voltage in a wireless charger, the transmitter module is controlled in such a way that the intermediate voltage is induced in the device. A significant advantage of the present invention is that the charger can be used to wirelessly switch off the device. For this purpose, the magnetic field of the charger adjusts the charging voltage to the intermediate voltage, causing the device to switch off. This achieves wireless automatic shutdown using a magnetic field. The magnetic field otherwise used for charging thus simultaneously constitutes the switch-off signal, which is sent from the charger to the device when appropriately controlled.For this purpose, the device and charger are appropriately designed. In particular, the magnetic field in the charger, which generally induces the charging voltage in the device, is modified in such a way as to generate the intermediate voltage. The off state is automatically activated, especially when the device is fully charged or the charger no longer supplies power (see the various scenarios above), so that the device is then switched off and consumes no energy. Wireless automatic switching is also advantageous because, compared to contact-based automatic switching, it allows for a more flexible spatial arrangement of the device and charger relative to each other, at least within the limits where energy transfer for charging is still possible.

[0028] The charger and the wireless charging device together form a wireless charging system. In addition to the energy management module and the energy storage unit, the device also includes the aforementioned receiver module and one or more loads. These loads are powered by energy from the energy storage unit when the device is discharged. Examples of loads include a Bluetooth Low Energy (BLE) module providing BLE functionality, a signal processing unit, or electroacoustic devices such as headphones or a microphone. The receiver module provides the charging voltage and outputs it to the energy management module. The receiver module is designed to receive energy from the charger, which, correspondingly, has the aforementioned transmitter module for transmitting energy. The transmitter module ideally has a transmitting coil for sending energy, and the receiver module has a receiving coil for receiving energy.The transmitting coil is generally powered by a current source from the charger. The receiving module conveniently includes a circuit for the receiving coil to generate the charging voltage. This circuit includes, for example, a tuning capacitor, a smoothing capacitor, and a Schottky diode.

[0029] The charging voltage Vcc typically depends on a variety of parameters, in particular the current Itx to the transmitting coil, the respective inductances of the transmitting coil Ltx and the receiving coil Lrx, a transmission frequency f, which is used to transfer the energy via the magnetic field, and a coupling factor k. The coupling factor, in turn, depends primarily on the distance and the angle of inclination between the transmitting coil and the receiving coil, i.e., generally on the spatial arrangement of the charger and the device during charging. The smaller the distance and the smaller the angle of inclination, the greater the coupling factor. The general formula for the charging voltage is: Vcc ∝ 2π · f · k · √(Ltx · Lrx) · Itx.This makes it especially clear that the charging voltage actually present in the device depends on several parameters (transmission frequency, inductance of the transmitting coil, current for operating the transmitting coil) of the charger and can therefore be manipulated by it.

[0030] The shutdown circuit for wireless automatic shutdown is fundamentally designed the same as for contact-based automatic shutdown. In other words, the shutdown circuit includes a switch, preferably a transistor, which is switched (in particular, turned on) by the intermediate voltage. The transistor in the shutdown circuit is preferably a MOSFET. The resistor connecting the gate and source of the transistor is suitably of a high value, e.g., 100 kΩ, and generally preferably between 10 kΩ and 1 MΩ. The gate is pulled high to the charging voltage from the receiver module. The drain is connected to the switching terminal of the power management module, and the source to ground. In this way, as already described, four operating states are enabled, including the off state.

[0031] For wireless power transfer, the charger ideally includes a converter and an oscillator. The oscillator generates a current to operate the transmitting coil and is therefore a current source. The transmitting coil and the oscillator together form the transmitter module. The oscillator is, for example, an inverter or power amplifier and generally generates a current (i.e., alternating current) to create the magnetic field for the transmitting module. The converter, on the other hand, generates a converter voltage to operate the oscillator. The converter thus influences the current with which the transmitting coil is operated. The charging voltage, and therefore specifically the intermediate voltage, is set by means of the converter voltage. Preferably, the converter is a buck converter (also known as a step-down converter or "buck converter"), which is designed to convert an input voltage into a reduced output voltage, namely the converter voltage.The converter is specifically connected or connectable to an energy source for the charger, e.g. to an energy storage device of the charger or to a power grid outside the charger.

[0032] For fixed values ​​of the inductances of the transmitting and receiving coils and the transmission frequency, the charging voltage increases linearly with both an increasing coupling factor and an increasing current to the transmitting coil. These two relationships—between charging voltage and coupling factor on the one hand, and between charging voltage and current on the other—are advantageously utilized here to control the charging voltage in the device by adjusting the current to the transmitting coil in the charger, given a known coupling factor. This allows for targeted activation of the off state. The converter voltage of the charger's transducer controls the oscillator, which in turn controls the current to the transmitting coil. Thus, the current to the transmitting coil can be adjusted first using the converter and its converter voltage, and ultimately, the charging voltage in the device can also be adjusted, including to the intermediate voltage.The device's off state is then activated externally by the charger through suitable control of the converter and adjustment of its converter voltage. The relationship between converter voltage Vdd and charging voltage Vcc is, as described above, given by Vcc ∝ 2π · f · k · √(Ltx · Lrx) · Itx, where the current Itx, as described, is a function of the converter voltage Vdd; suitably, the current is proportional to the converter voltage.

[0033] The converter voltage, which must be set to generate a specific charging voltage and, in particular, the intermediate voltage, depends—as described above—on the coupling factor between the transmitting module and the receiving module and can, in principle, vary. The inductances and the transmission frequency, on the other hand, are known for a given charging system by design. The transmission frequency preferably lies between 3 MHz and 30 MHz and is, for example, 13.56 MHz. In a preferred embodiment, the converter voltage, and thus also the current, is set to generate the intermediate voltage by first determining the coupling factor and then using this factor to determine the converter voltage required to generate the intermediate voltage. This is done based on the relationship between charging voltage and converter voltage, namely Vcc ∝ 2π · f · k · √(Ltx · Lrx) · Itx (Vdd).To automatically switch off, the converter voltage determined in this way is then set, so that the intermediate voltage is induced in the device and the device switches to the off state.

[0034] The coupling factor is also suitably determined via the relationship between charging voltage and current / converter voltage, but now with a known pair of values ​​for the charging voltage Vcc and the current Itx. Since the charging voltage is unknown to the charger, communication between the charger and the device is advantageous for determining the coupling factor. At the end of charging, when no more energy is transferred to the device, the device sends the last charging voltage applied during charging (more precisely: its value) to the charger. This last charging voltage is also referred to as the "final charging voltage." The final charging voltage is, in particular, higher than the reset voltage and the gate-source threshold voltage. Furthermore, the charger stores the current (more precisely: its value) that is used to operate the transmitting coil at the time of the final charging voltage.The final current applied during charging is referred to as the final charging current. This final charging voltage is transmitted via a data connection between the device and the charger. For this purpose, both the device and the charger have a communication unit, such as an antenna and a suitable antenna circuit, for sending and / or receiving data, specifically the final charging voltage. The charger receives the final charging voltage, and the coupling factor is then determined in combination with the final current, particularly using the aforementioned relationship.

[0035] The converter voltage is then determined using the intended intermediate voltage and the coupling factor. Since the intermediate voltage lies within a voltage range between the reset voltage and the minimum gate-source threshold voltage, a suitable voltage range is also derived for the converter voltage, from which the converter voltage is then selected, e.g., simply the average of the voltage range.

[0036] In summary, setting the converter voltage preferably comprises the following four steps: First, a final current and a final charging voltage are determined. Second, the coupling factor is determined based on the final current and charging voltage. Third, the required converter voltage is determined using the coupling factor and the intended intermediate voltage. Finally, this converter voltage is set in a fourth step.

[0037] The relationship used to determine the coupling factor and the converter voltage is stored, for example, as a function or as a table in the charger's memory. Conveniently, the relationship Vcc ∝ 2π · f · k · √(Ltx · Lrx) · Itx (Vdd) is stored as a parameterized function set. To determine the coupling factor, the charging voltage is stored as a function of the coupling factor and parameterized with the current, resulting in a corresponding function set. Similarly, to determine the converter voltage, the charging voltage is stored as a function of the converter voltage and parameterized with the coupling factor, resulting in a corresponding function set.

[0038] The following are typical numerical examples for illustration purposes, which are not to be understood as limiting, but in any case indicate suitable orders of magnitude.

[0039] The final charging voltage is, for example, 7.6 V, and the corresponding final current is, for example, 0.5 A. Based on these values, and in combination with the inductances and the transmission frequency, the coupling factor is determined, for example, as k = 0.07. If the reset voltage is, for example, 2 V and the gate-source minimum threshold voltage is 1 V, then the intended intermediate voltage range is between 1 V and 2 V. For this intermediate voltage, a converter voltage in the range of 0.125 V to 0.275 V is then determined, for example, using the coupling factor k = 0.07. The converter voltage is then set, for example, to 0.2 V, so that the corresponding intermediate voltage is present in the device, and the device switches to the off state, initiated wirelessly by the charger.

[0040] A given transistor is only suitable if its gate-source threshold voltage is at least partially lower than the reset voltage; other transistors are unsuitable for the turn-off circuit. For the example reset voltage of 2 V mentioned above, this means that a suitable transistor must have a minimum gate-source threshold voltage of less than 2 V, for example, 1.4 V or 0.7 V.

[0041] The reset voltage defines an upper limit for the converter voltage at all distances, as this must not exceed the value that would cause the reset voltage to be exceeded in the device (for simplicity, we refer to this as the distance, but the explanations generally apply to the coupling constant). For example, with the reset voltage of 2 V, the upper limit for the converter voltage is 0.69 V. If this limit cannot be maintained, automatic shutdown may not be possible at some distances. The distance between the transmitting coil and the receiving coil is suitable for charging between 1 mm and 10 mm. To enable automatic shutdown at all distances, the charging voltage must be above the gate-source threshold voltage at every distance. Automatic shutdown is not possible at those distances where this condition is not met.This makes it clear that a transistor with the lowest possible gate-source minimum threshold voltage enables automatic turn-off over a significantly wider range of distances. In the example above, with a transistor having a gate-source minimum threshold voltage of 0.685 V, the voltage range available for the converter voltage to generate a suitable intermediate voltage for automatic turn-off at all distances is only 0.005 V. A lower converter voltage might then no longer be sufficient for automatic turn-off at a distance of 5 mm or more. With a different transistor, having a gate-source minimum threshold voltage of 0.5 V, the voltage range available for the converter voltage to generate a suitable intermediate voltage for automatic turn-off at all distances is approximately 0.2 V.This allows for automatic switching off across the entire range from 1 mm to 10 mm without any problems. A wide voltage range for the converter voltage is also advantageous in order to compensate for any potential tolerances.

[0042] In an example application, the distance between the transmitting coil and the receiving coil is 4 mm. The device first enters the charging state and is charged. For automatic shutdown, the converter voltage is then set to 0.6 V. This sets the charging voltage in the device to an intermediate voltage of 1.5 V. The device then enters the discharging state and begins consuming energy a few seconds later, for which the energy management module provides a voltage of, for example, 1.3 V to the loads. The device then switches to the off state. After a few seconds (e.g., ≥ 6 s), the converter voltage is set to 0 V to switch off the converter. The charger can now be switched off completely and disconnected from the device, which then remains in the off state without returning to the discharging state, even though the charging voltage is now 0 V.

[0043] By determining the coupling factor for automatic device shutdown, the actual spatial arrangement of the device and charger is automatically taken into account, making shutdown advantageously largely independent of this arrangement. This allows for a high degree of freedom in the arrangement without compromising the automatic shutdown function. The automatic shutdown is initiated by the charger via its magnetic field. In contrast to contact-based (i.e., with a galvanic connection between the device and charger) automatic shutdown, wireless (i.e., without a galvanic connection between the device and charger) automatic shutdown is initially more complex, because the intermediate voltage cannot simply be set by the charger, as it is only indirectly generated via the magnetic field and is also dependent on the coupling constant.Accordingly, suitable data, namely the final charging voltage, is transmitted from the device to the charger. The solution for wireless automatic shutdown described here therefore differs from the solution for contact-based automatic shutdown, particularly in the design of the charger, specifically its hardware in general and its converter and communication unit in particular, and in the design of the device, specifically its switch for the shutdown circuit.

[0044] Regarding the hardware in general, the charger is primarily designed for wireless charging and preferably not for contact-based charging. A contact module with corresponding electrical contacts, e.g., contact pins or pogo pins, for energy transfer is not necessary and is preferably omitted. However, as described, the charger includes a transmitter module for energy transfer and a communication unit for data exchange with the device. The antenna of the communication unit is, for example, spiral and / or helical in shape and designed as a wire or conductor.

[0045] The device and the charger each preferably have a communication unit for exchanging data. The communication unit of the charger and the communication unit of the device form a communication system for data exchange. In this case, the communication system serves, in particular, at least to transmit data, especially concerning the charging voltage, from the device to the charger. Accordingly, the communication system can be bidirectional or only unidirectional, from the device to the charger. The communication system is preferably wireless and uses a suitable communication protocol, for example, magnetic induction in a communication frequency band in the MHz range, for data transmission. Data transmission takes place either within (i.e., "in-band") the communication frequency band, e.g., by means of amplitude modulation, or outside (i.e., "out-of-band") the communication frequency band, e.g.,by means of frequency modulation or phase-shift keying. Accordingly, the data from the device is modulated for transmission (also referred to as load modulation). The data transmitted from the device to the charger includes, in particular, data relating to the device's energy storage and preferably its state of charge (SOC), current voltage, current charging current, temperature, the charging voltage already described, or a combination thereof. The charger receives the data and demodulates it (also referred to as load demodulation). For demodulation, the charger suitably includes a demodulator circuit. In an advantageous embodiment, the current in the transmitting module is also determined by the demodulator circuit, more precisely, the current through the transmitting coil, which is integrated into the demodulator circuit for this purpose.For this purpose, the demodulator circuit suitably includes a capacitor, across which the current is determined as the ratio of a maximum object detection voltage of the demodulator circuit and its impedance at the transmission frequency of the transmitting coil.

[0046] In the case of a contact-based automatic power-off, the converter is preferably a low-dropout voltage regulator (LDO) or a buck converter, and outputs a voltage between the reset voltage and the minimum gate-source threshold voltage to power off the device. However, this voltage range for the converter is not necessarily applicable to wireless automatic power-off, as a lower converter voltage is typically required for power-off in this case. With wireless automatic power-off, the converter's output voltage is an input voltage for the oscillator. The oscillator is specifically a power amplifier. The converter voltage is preferably a DC voltage, and the oscillator then converts the converter voltage to an AC voltage to generate the corresponding AC current for the transmit coil.The oscillator also amplifies the converter voltage, resulting in a correspondingly higher charging voltage within the device, especially if the receiving coil has more turns than the transmitting coil. If the charging voltage is too high, particularly higher than the reset voltage, the device switches to the charging or standby state, but not to the off state, which is then no longer accessible. Therefore, the converter voltage is significantly lower in the case of wireless automatic shutdown than in the case of contact-based automatic shutdown and is preferably in the millivolt range, i.e., at least 1 mV and certainly less than 0.6 V.The converter, especially in its buck converter configuration, is typically unable to generate a converter voltage below its internal feedback reference voltage, which is regularly at least 0.6 V. Therefore, in a preferred embodiment, the charger includes a voltage reference circuit in addition to the converter to generate a converter voltage below the converter's feedback reference voltage. This voltage reference circuit provides an external reference voltage, connected to a feedback terminal of the converter. The external reference voltage is higher than the internal feedback reference voltage.The voltage reference circuit is then configured and connected to the converter such that the converter voltage Vdd is the difference between the internal feedback reference voltage Vfb and the difference between the external reference voltage Vref and the internal feedback reference voltage Vfb, weighted by a suitable resistance ratio R1 / R2 of two resistors. In other words: Vdd = Vfb - R1 · (Vref - Vfb) / R2. The two resistors form a voltage divider with two endpoints: one connected to an output of the converter and the other to the external reference voltage. The feedback connection is located at a midpoint between the two resistors.

[0047] The switch of the device's off circuit is—as described above—preferably a transistor, specifically a MOSFET. With respect to the voltages involved, this transistor is preferably configured as described below. The gate-source maximum threshold voltage is advantageously as high as possible to prevent damage if the charging voltage is unintentionally too high or in the event of a fault. For example, the charging voltage may fluctuate at the start of charging and not yet be stable, or it may overshoot due to external interference. The gate-source maximum threshold voltage is suitably at least equal to the maximum possible charging voltage. Also of importance is the gate-source threshold voltage, which is also referred to as the turn-on voltage.The gate-source threshold voltage is advantageously lower than the reset voltage, allowing the device to switch to the discharge state and from there to the off state. The larger the voltage range between the minimum gate-source threshold voltage and the reset voltage, the more different spatial arrangements (distance and angle of inclination) of the device and charger relative to each other automatic shutdown is possible. Therefore, the lowest possible gate-source threshold voltage is preferred. For automatic shutdown, the charging voltage must drop to an intermediate voltage in the voltage range between the minimum gate-source threshold voltage and the reset voltage. The voltage range between the minimum gate-source threshold voltage and the reset voltage preferably has a width of at least 1 V.In summary, the following are therefore preferably true: 1) Gate-source minimum threshold voltage Vgs-thres < charging voltage Vcc < reset voltage Vrst and 2) Reset voltage Vrst - Gate-source maximum threshold voltage Vgs,max_thres ≥ 1 V.

[0048] Ideally, the charger has a control unit to which the communication unit and the converter are connected. The control unit is used to configure the converter, based on the data received by the communication unit.

[0049] The charger should ideally have an emergency energy storage system to maintain the intermediate voltage even if the power supply to the charger is interrupted (see the scenarios above). This system is particularly useful for generating the shutdown signal and thus causing the device to switch to the off state. If the power supply to the charger is interrupted, no energy is immediately available to operate the charger, preventing it from generating a shutdown signal. However, the emergency energy storage system provides an alternative energy source, separate from the regular power supply via cable or energy storage, that can at least temporarily generate the shutdown signal. This emergency energy storage system is designed to be separate from any energy storage that may be present in the charger for charging the device.The emergency energy storage device is correspondingly small in size. A suitable emergency energy storage device is either a battery or a supercapacitor.

[0050] Overall, the shutdown circuit, in combination with the communication system, implements an advantageous method in which the device is wirelessly and automatically switched off by the charger, particularly at the end of charging the device's energy storage and generally when the energy transfer from the charger to the device is interrupted. The method preferably comprises one or more of the following steps, preferably in the order mentioned. In a first step, the device sends data to the charger, preferably repeatedly. In a second step, the data is analyzed, e.g., by the control unit. If the data is modulated, it is demodulated beforehand in the second step, e.g., using the described demodulator circuit. In a third step, the converter is adjusted based on the data, particularly by the control unit.The control unit sets the converter, for example, with a DAC signal (digital-to-analog converter) or a PWM signal (pulse width modulation). In a fourth step, the converter then outputs a converter voltage to the oscillator, thereby controlling it. Also in a fourth step, the oscillator outputs a current, which then powers the transmitting coil. The current is thus indirectly set by the converter in the fourth step. In a fifth step, the transmitting coil generates a magnetic field depending on the current. In a sixth step, the magnetic field is received by the receiving coil, which, depending on this, generates a charging voltage in the device, so that the charger induces a charging voltage in the device.In a seventh step, the device is switched off if the charging voltage is within the voltage range between the reset voltage and the minimum gate-source threshold voltage, i.e., if the charging voltage is an intermediate voltage as described. Therefore, if an intermediate voltage is present, the device switches to the off state in the seventh step and is then switched off. Preferably, in the seventh step, the device only switches to the off state after a time has elapsed that is longer than the switching terminal active time, as described. Ultimately, the automatic switch-off depends on the data that the device sends to the charger. In a convenient eighth step, the converter is then switched off, preferably after a specific time, e.g., 10 seconds, after the device has switched to the off state. This prevents the converter from consuming any further energy.

[0051] It has been described so far that the device switches off when charging is complete. The data then contains at least the final charging voltage, which is determined in conjunction with the final current and is also used in combination with this, particularly by the control unit, to determine a suitable converter voltage and then adjust the converter accordingly. However, events other than the end of charging are also suitable for initiating automatic shutdown, for example, if the temperature of the energy storage device exceeds a limit (overheating), if the voltage or current at the energy storage device exceeds a corresponding limit (overvoltage / overcurrent), generally in the event of a fault in the energy storage device (fault case), or similar events.The control unit then infers one or more of these events when analyzing the data and then controls the converter accordingly to initiate the automatic shutdown.

[0052] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Each drawing schematically shows: Fig. 1 a device and a charger, Fig. 2 an equivalent circuit diagram of the device and the charger made of Fig. 1 , Fig. 3 another representation of the device and the charger made of Fig. 1 , Fig. 4 another representation of the device from Fig. 1 , Fig. 5 four operating states of the device from Fig. 1 , Fig. 6 another representation of the charger made of Fig. 1 Fig. 7 the charging voltage as a function of the coupling factor, Fig. 8 the charging voltage as a function of the converter voltage, Fig. 9 four steps of a procedure, Fig. 10 the charging voltage as a function of the converter voltage for two different transistors, Fig. 11 the charging voltage and the voltage for consumers of the device as a function of time, Fig. 12 the voltages from Fig. 11 At a later time, Fig. 13 shows a demodulator circuit of the charger. Fig. 1 , Fig. 14A voltage reference circuit of the charger made of Fig. 1 , Fig. 15 eight steps of a process.

[0053] In Fig. 1 A device 2 and a charger 4 are shown, which are suitable for carrying out the procedure described here. The device 2 is connected to the charger 4 and, in a charging state LZ, wireless charging takes place by wirelessly transferring energy from a transmitter module 6 of the charger 4 to a receiver module 8 of the device 2. The device 2 is in Fig. 1 An example is a binaural hearing aid with two individual units, so that there are two receiver modules 8, which are supplied by the transmitter module 6 of the charger. Fig. 2 An equivalent circuit diagram for device 2 and charger 4 is shown in Fig. 3 Then another representation of device 2 and charger 4. In Fig. 4 Only device 2 is shown. Fig. 2 , 3 und 4 are compared to Fig. 1 The diagram is simplified in that only one receiver module 8 and one transmitter module 6 are shown, i.e., only one of the individual devices. However, the following explanations apply generally regardless of the number of transmitter modules 6 and receiver modules 8; that is, depending on the configuration of the device 2 and the charger 4, one or more receiver modules 8 may be present, and regardless of this, one or more transmitter modules 6 may also be present.

[0054] During charging, device 2 is switched off and in the charging state LZ. Device 2 has a charging port 10, to which a charging voltage Vcc is applied, which can be adjusted using the charger 4. Device 2 also has a switching port 12 for switching on and off. The charging port 10 and the switching port 12 are connections of an energy management module 14 (also referred to as PMIC), which receives the charging voltage Vcc and uses it to charge an energy storage device 16 of device 2.

[0055] Device 2 also has a discharge state EZ, in which energy is consumed by one or more consumers 18. In the discharge state EZ, the energy management module 14 controls the provision of energy to the consumers 18 from the energy storage unit 16. In the charging state LZ, device 2 thus receives energy from the charger 4, while in the discharge state EZ, device 2 consumes energy.

[0056] "Device 2 is switched on" means that the consumers 18 are supplied with energy by means of the energy management module 14. "Device 2 is switched off" means that the consumers 18 are not supplied with energy, although the energy management module 14 may still consume energy. In the discharge state EZ, Device 2 is also switched on by design. When it is subsequently described that Device 2 is "switched off," this means, firstly, that Device 2 is "switched off" if it is switched on, and secondly, that if Device 2 is already switched off, it "remains switched off."

[0057] Device 2 also has a switch 20, which is connected to the switching terminal 12 and can be switched by adjusting the charging voltage Vcc to an intermediate voltage. Switch 20 is part of a shutdown circuit 22. Device 2 is switched off by the charger 4, which adjusts the charging voltage Vcc to the intermediate voltage, thus switching the switch 20 and causing Device 2 to enter an off state AZ. The charger 4 therefore sets the intermediate voltage, whereupon Device 2 switches to the off state AZ. This occurs, for example, when charging is stopped or interrupted, but can also generally occur in the event of a fault, such as overheating or overvoltage / overcurrent of the energy storage device 16. Thus, the charger 4 provides automatic shutdown as soon as no more energy is transferred to Device 2.The charger 4 thus initiates a change of device 2 to the off state AZ, in which device 2 then consumes no energy – unlike in the discharge state EZ. Here, the charger 4 utilizes the ability to variably adjust the charging voltage Vcc.

[0058] Device 2, shown here as an example, is a hearing aid designed to provide assistance to a user with a hearing impairment. The hearing aid features a microphone 24 (two microphones 24 per device) that picks up ambient sound and generates an electrical input signal. This signal is then processed by a signal processor (not explicitly shown), which produces an electrical output signal. This output signal is then converted back into sound via a receiver 26 of the hearing aid and delivered to the user. Depending on the hearing aid type, other input and / or output transducers may be used instead of the microphone 24 and receiver 26. The hearing aid is configured binaurally here, or alternatively, monaurally. The microphones 24, the receivers 26, and the signal processor are each considered consumers 18 of Device 2. Alternatively, Device 2 could be a headphone, headset, wearable device, smartphone, or similar device.

[0059] To charge, device 2 is connected to charger 4, for example as shown in... Fig. 1 shown inserted into this. The charger 4 shown here is designed as a charging cradle, with a recess 28 into which the device 2 can be inserted. Optionally, the charger 4 has a lid 30. The recess is advantageously shaped such that the device is held in it in a defined position relative to the charging cradle.

[0060] Depending on the charge level of the energy storage device 16, it provides a voltage Vbat to the consumers 18, which may be transformed beforehand by a transformation unit 32. The greater the charge, the higher this voltage Vbat typically is. The device 2 is charged by the charger 4 with a charging voltage Vcc, which is the voltage present in the device 2 for charging the energy storage device 16. The energy storage device 16 is then charged until the desired charge or voltage Vbat is reached. For this purpose, a charging threshold voltage Vchg,thres is specified, which is compared with the charging voltage Vcc to determine when charging begins and when it does not. Charging is then terminated when the charging voltage Vcc falls below the charging threshold voltage Vchg,thres. The charging threshold voltage Vchg,thres is, for example, a fixed, predefined voltage.

[0061] Although the automatic shutdown is performed by device 2 itself, it is not initiated by device 2, but rather by the charger 4, which determines when device 2 should be switched off and then sends a shutdown signal to device 2, causing it to switch off. This shutdown signal results in the intermediate voltage being present in device 2.

[0062] Generally, it is desirable to switch off device 2 after charging, as long as it is still connected to charger 4. When charging (LZ) is complete, device 2 should ideally not be put into discharge (EZ) and thus remain switched on; instead, device 2 should be switched off.

[0063] To implement automatic shutdown and thus switch off the device 2 after charging, the charging port 10 of the energy management module 14 is used. The charging voltage Vcc is applied to charging port 10. In one embodiment (not explicitly shown), the switching port 12 is pulled high with a pull-up resistor, and a manually operable switch is connected between the switching port and ground 34 for manually switching off the device 2. Independently of this, or suitablely combined with it, the device 2 has the aforementioned shutdown circuit 22 with switch 20 for automatic shutdown using the charger 4, which uses the charging port 10 and the switching port 12 in an analogous manner. Here, the switch 20 is a transistor, specifically a MOSFET, with gate 36, source 38, and drain 40, i.e., with corresponding connections. The gate 36 is pulled high to the charging voltage Vcc via charging port 10 and a resistor 42.Resistor 42 connects gate 36 to source 38 and ground 34. Drain 40 and source 38 are connected to switch terminal 12 and ground 34, respectively.

[0064] In the now implemented off state AZ, device 2 is connected to charger 4 but switched off and neither consumes energy itself nor receives energy from charger 4. In contrast, in the charging state LZ, device 2 is switched off but still receives energy to operate the energy management module 14, and in the discharging state EZ, it is switched on and consumes energy accordingly. To switch between the charging state LZ and the discharging state EZ (in both directions), device 2 in the illustrated example also has a standby state WZ, so that a total of four operating states AZ, EZ, LZ, WZ are possible, which are also mutually exclusive.

[0065] An exemplary dependency of the operating states AZ, EZ, LZ, WZ is shown in Fig. 5 The device 2 switches from the discharge state EZ, the off state AZ, or the standby state WZ to the charge state LZ when the charging voltage Vcc is at least equal to the charge threshold voltage Vchg,thres. The charge state LZ remains active as long as the charging voltage Vcc is at least equal to the charge threshold voltage Vchg,thres. The device 2 switches from the charge state LZ to the standby state WZ when the charging voltage Vcc is lower than the charge threshold voltage Vchg,thres. The device 2 switches from the standby state WZ to the discharge state EZ when the charging voltage Vcc is lower than a reset voltage Vrst, and additionally when a time t has elapsed that is longer than a discharge time tdisc. The reset voltage Vrst is a fixed voltage and a parameter of the energy management module 14, and serves to stop its operation and initialize it to a predefined standard state.The reset voltage Vrst is also used here to determine when the device switches from the standby state WZ to the discharge state EZ. The discharge time tdisc, for example, is a fixed, predetermined time of a few seconds. Conversely, device 2 switches from the discharge state EZ to the standby state WZ when the charging voltage Vcc is lower than the charging threshold voltage Vchg,thres and higher than the reset voltage Vrst, and from the standby state WZ to the charging state LZ when the charging voltage Vcc is at least equal to the charging threshold voltage Vchg,thres. As long as the charging voltage Vcc is lower than the charging threshold voltage Vchg,thres, the standby state WZ remains active.

[0066] Automatic switch-off, i.e., a change to the off state AZ, is achieved by adjusting the charging voltage Vcc at charging terminal 10 to an intermediate voltage. This intermediate voltage is the gate-source threshold voltage Vgs-thres of the transistor and lies between the reset voltage Vrst and a minimum gate-source threshold voltage Vgs-thres,min, i.e., a minimum value for the gate-source threshold voltage Vgs-thres. The gate-source threshold voltage Vgs-thres is the voltage required to switch the transistor and lies within a range between the minimum gate-source threshold voltage Vgs-thres,min and a maximum gate-source threshold voltage Vgs-thres,max. The reset voltage V rst is greater than the actually used gate-source threshold voltage V gs-thres, but the gate-source maximum threshold voltage V gs-thres,max can be greater than the reset voltage V rst.

[0067] The gate-source minimum threshold voltage Vgs-thres,min on the one hand and the reset voltage Vrst on the other define a voltage range for the intermediate voltage, which is used to switch to the off state AZ. If the charging voltage Vcc is lower than the reset voltage Vrst, the device 2 switches to the discharge state EZ. The discharge state EZ is initially active as long as the charging voltage Vcc is lower than the gate-source minimum threshold voltage Vgs-thres,min. The device 2 then switches to the off state AZ when the charging voltage Vcc is lower than the reset voltage Vrst and higher than the charging threshold voltage Vchg,thres, and additionally if a time (during which the intermediate voltage is maintained) has elapsed that is longer than a switching terminal active time tsca.Accordingly, as soon as the intermediate voltage is reached at gate 36, the transistor is switched on and the switching terminal 12 is pulled to ground 34. Device 2 briefly switches to the discharge state EZ and from there, after the switching terminal active time t sca, to the off state AZ. The switching terminal active time t sca is, for example, a fixed time of a few seconds. In this case, a transition to the off state AZ is only possible starting from the discharge state EZ.

[0068] Switching on the device 2, and specifically changing it from the off state AZ to the discharge state EZ, is initially possible via the charge state LZ. In the configuration shown here, the device 2 switches from the off state AZ to the charge state LZ when the charging voltage V cc corresponds to at least the charge threshold voltage V chg,thres. Alternatively or additionally, switching from the off state AZ to the device 2 can be done manually by the user. For this purpose, the device 2 has a switch (not explicitly shown) (e.g., as described above).

[0069] The described solution for automatically switching off device 2 is readily possible with contact-based charging, as a galvanic connection exists through which the intermediate voltage can be easily adjusted. However, this is not readily possible with a wireless charging charger 4 as described here, since the charging voltage Vcc is not directly supplied by the charger 4, but is merely induced in device 2 by the transmitter module 6 and is therefore not necessarily present in the charger 4 itself.

[0070] As in Fig. 2 As can be seen, during charging, energy is transferred by means of a magnetic field M, which is generated by a transmitting coil 44 of the transmitting module 6 and received by a receiving coil 46 of the receiving module 8. To then adjust the charging voltage Vcc of a wireless charger 4 to the intermediate voltage, the transmitting module 6 is controlled accordingly, such that the intermediate voltage is induced in the device 2. The magnetic field M, otherwise used for charging, thus simultaneously represents the switch-off signal, which is sent from the charger 4 to the device 2, when appropriately controlled.

[0071] The charger 4 and the wireless charging device 2 together form a wireless charging system. The receiver module 8 provides the charging voltage Vcc and outputs it to the power management module 14. The transmitting coil 44 in the transmitting module 6 is generally powered by a current source from the charger 4. The receiver module 8 also includes a circuit for the receiving coil 46 to generate the charging voltage Vcc. This circuit includes a tuning capacitor 48, a smoothing capacitor 50, and a Schottky diode 52.

[0072] The charging voltage Vcc depends on a multitude of parameters, in particular the current Itx to the transmitting coil 44, the respective inductances of the transmitting coil Ltx and the receiving coil Lrx, a transmission frequency f, which is used to transfer the energy via the magnetic field M, and a coupling factor k. The coupling factor k, in turn, depends in particular on the distance A and the angle of inclination between the transmitting coil 44 and the receiving coil 46, i.e., generally on the spatial arrangement of the charger 4 and the device 2 during charging. The smaller the distance A and the smaller the angle of inclination, the larger the coupling factor k. The general equation for the charging voltage Vcc is: Vcc ∝ 2π · f · k · √(Ltx · Lrx) · Itx.

[0073] The charger 4 also includes a converter 54 and an oscillator 56 for wireless power transfer. This is described in detail in Fig. 6 The oscillator 56 generates the current Itx to operate the transmitting coil 44 and is therefore a current source. The transmitting coil 44 and the oscillator 56 then form the transmitting module 6. The converter 54 generates a converter voltage Vdd to operate the oscillator 56. The converter 54 thus influences the current Itx with which the transmitting coil 44 is operated. The charging voltage Vcc, and therefore also the intermediate voltage, is thus set by means of the converter voltage Vdd.

[0074] For fixed values ​​of the inductances Ltx and Lrx of transmitting coil 44 and receiving coil 46, and the transmission frequency f, the charging voltage Vcc increases with increasing coupling factor k and, conversely, with increasing current Itx to the transmitting coil 44. These two relationships—namely, between charging voltage Vcc and coupling factor k on the one hand, and between charging voltage Vcc and current Itx on the other—are used here to control the charging voltage Vcc by means of the current Itx, given a known coupling factor k, and thus to selectively activate the off-state AZ. The off-state AZ of the device 2 is then activated externally by the charger 4 through suitable control of the converter 54 and adjustment of its converter voltage Vdd. The relationship between converter voltage V dd and charging voltage V cc is as described above by V cc ∝ 2π · f · k · √(L tx · L rx ) · I tx , where the current I tx is as described a function of the converter voltage V dd.

[0075] The converter voltage Vdd, which must be set to generate a specific charging voltage Vcc and the intermediate voltage, depends on the coupling factor K and can therefore vary. The inductances Ltx, Lrx, and the transmission frequency f, on the other hand, are known for a given combination of device 2 and charger 4. Here, the converter voltage Vdd, and thus also the current Itx, are set to generate the intermediate voltage by first determining the coupling factor K and then using this factor to determine the converter voltage Vdd required to generate the intermediate voltage. This is described in the Fig. 7 and 8 illustrated and is based on the relationship between charging voltage V cc and converter voltage V dd , namely V cc ∝ 2π · f · k · √(L tx · L rx ) · I tx (Vdd).

[0076] As in Fig. 7 As shown, the coupling factor k is determined via the relationship between charging voltage Vcc and current Itx / converter voltage Vdd, using a known pair of values ​​for the charging voltage Vcc and the current Itx. Since the charging voltage Vcc is unknown to the charger 4, communication takes place between the charger 4 and the device 2 to determine the coupling factor k. At the end of the charging process, the device 2 sends the last charging voltage Vcc (more precisely: its value) to the charger 4. This last charging voltage Vcc is also referred to as the "final charging voltage" Vcc. Additionally, the charger 4 stores the current Itx (more precisely: its value) that is used to operate the transmitting coil 44 at the time of the final charging voltage Vcc, i.e., the last current Itx present during charging, which is analogously referred to as the final current Itx.The final charging voltage Vcc is transmitted via a data connection between device 2 and charger 4. For this purpose, device 2 and charger 4 each have a communication unit 58, 60, e.g., an antenna and a suitable circuit for the antenna, for sending and / or receiving data, specifically the final charging voltage Vcc. Charger 4 receives the final charging voltage Vcc, whereupon the coupling factor k is determined in combination with the final current Itx, namely via the aforementioned relationship and, e.g., as in [reference]. Fig. 7 shown.

[0077] The converter voltage V dd of converter 54 is then determined using the intended intermediate voltage and the coupling factor k. Since the intermediate voltage lies in a voltage range between the reset voltage V rst and the gate-source minimum threshold voltage V gs-thres,min, the result is as shown in Fig. 8 A suitable voltage range 62 for the converter voltage V dd is also shown, from which this is then selected, e.g. simply the mean value of the voltage range 62.

[0078] In summary, the adjustment of the converter voltage Vdd described here thus includes the following: Fig. 9 The four steps shown, S101-S104, are as follows: In the first step, S101, a final current Itx and a final charging voltage Vcc are determined. Subsequently, in the second step, S102, the coupling factor k is determined based on the final current Ist and the final charging voltage Vcc. Following this, in the third step, S103, the necessary converter voltage Vdd is determined using the coupling factor k and the intended intermediate voltage, and finally, in the fourth step, S104, this voltage is set.

[0079] The relationship used to determine the coupling factor k and the converter voltage V dd is, for example, as in the Fig. 7 and 8 Each function shown is stored as a parameterized function bundle. To determine the coupling factor k, for example, as shown in... Fig. 7 The charging voltage Vcc is shown as a function of the coupling factor k and parameterized with the current Itx, resulting in a corresponding set of functions. To determine the converter voltage Vdd, for example, as shown in... Fig. 8 The charging voltage V cc is shown as a function of the converter voltage V dd and parameterized with the coupling factor k, resulting in a corresponding function bundle.

[0080] In the example of the Fig. 7 The final charging voltage Vcc is 7.6 V, and the corresponding final current Itx is 0.5 A. Based on these values, and in combination with the inductances Ltx and Lrx, and the transmission frequency f, the coupling factor k is determined to be k = 0.07. The reset voltage Vrst is 2 V, and the gate-source minimum threshold voltage Vgs-thres,min is 1 V. Therefore, the intended intermediate voltage range is between 1 V and 2 V. For this intermediate voltage, the following is then determined according to the example in [reference missing]. Fig. 8 With a coupling factor k = 0.07, a converter voltage V dd in the range of 0.125 V and 0.275 V is determined. The converter voltage V dd is then, for example, set to 0.2 V, so that the corresponding intermediate voltage results in device 2 and device 2 switches to the off state AZ.

[0081] The gate-source threshold voltage Vgs-thres must be at least partially lower than the reset voltage Vrst. For the aforementioned reset voltage Vrst of 2 V, this means that a suitable transistor must have a minimum gate-source threshold voltage Vgs-thres,min of less than 2 V, e.g., 1.4 V or 0.7 V.

[0082] The reset voltage Vrst defines an upper limit for the converter voltage Vdd for all distances A (for simplicity, we refer to the distance A here, but the explanations apply generally to the coupling constant k). For example, with the aforementioned reset voltage Vrst of 2 V, the upper limit for the converter voltage Vdd is 0.69 V. If this limit cannot be maintained, automatic switch-off may not be possible for some distances A. This is explained in Fig. 10 illustrated. The distance A for loading is, for example, between 1 mm and 10 mm (in Fig. 10 The charging voltage Vcc is shown as a function of the converter voltage Vdd for various distances A from 1 mm to 7 mm in 1 mm increments. To enable automatic turn-off for all distances A, the charging voltage Vcc must be above the gate-source threshold voltage Vgs-thres at every distance A. For those distances A where this condition is not met, automatic turn-off is not possible. This makes it clear that a transistor with the lowest possible minimum gate-source threshold voltage Vgs-thres,min enables automatic turn-off for a significantly larger range of distances A. In the example above, with a transistor having a minimum gate-source threshold voltage Vgs-thres,min of 0.685 V, the voltage range 64 available for the converter voltage Vdd to generate a suitable intermediate voltage for automatic turn-off at all distances A is only 0.005 V.A lower converter voltage Vdd may no longer be sufficient for automatic switch-off at a distance A of 5 mm or more. With a different transistor, having a minimum gate-source threshold voltage Vgs-thres,min of 0.5 V, the voltage range available for the converter voltage Vdd to generate a suitable intermediate voltage for automatic switch-off at all distances A is approximately 0.2 V. This then makes automatic switch-off possible without any problems across the entire range from 1 mm to 10 mm.

[0083] The Fig. 11 and 12Each figure shows an oscilloscope measurement in an exemplary application. The charging voltage Vcc and the voltage Vout, which is output by the energy management module 14 to the consumers 18, are shown as a function of time t. The distance A between the transmitting coil 44 and the receiving coil 46 is 4 mm. The device 2 first switches to the charging state LZ and is charged. For automatic shutdown, the following procedure is then followed: Fig. 11 The converter voltage V dd of converter 54 is shown set to 0.6 V. The charging voltage V cc in device 2 is thus set to an intermediate voltage of 1.5 V. Device 2 first switches to the discharge state EZ and begins to consume energy a few seconds later, for which the energy management module 14 provides a voltage V out of, for example, 1.3 V to the consumers 18. Then device 2 switches to the off state AZ, which then Fig. 12 is active. After a few seconds (e.g., ≥ 6 s), the converter voltage V dd is then set to 0 V to switch off the converter 54, so that then as in Fig. 12 The charging voltage Vcc is shown to be 0 V. Charger 4 can now be switched off completely and disconnected from device 2, whereby device 2 then remains in the off state AZ without switching back to the discharge state EZ, even though the charging voltage Vcc is then 0 V.

[0084] As previously described, device 2 and charger 4 each have a communication unit (58, 60) for data exchange. The communication unit (60) of charger 4, together with the communication unit (58) of device 2, forms a communication system for data exchange. This communication system serves to transmit data concerning the charging voltage (Vcc) from device 2 to charger 4. Accordingly, the communication system can be bidirectional or unidirectional, from device 2 to charger 4. The communication system is wireless and uses a suitable communication protocol, such as magnetic induction. In this case, the data from device 2 is modulated for transmission. The data transmitted includes, for example, the state of charge (SOC), current voltage, current charging current, temperature, the previously described charging voltage (Vcc) of the energy storage device (16), or a combination thereof.The charger 4 receives the data and demodulates it. For this purpose, the charger 4 has a demodulator circuit 68, e.g. as shown in . Fig. 13 The demodulator circuit 68 shown there also determines the current I tx in the transmitter module 6, more precisely the current I tx through the transmitter coil 44, which is integrated into the demodulator circuit 68 for this purpose. The demodulator circuit 68 includes a capacitor 70, across which the current I tx is the ratio of the maximum object detection voltage V OD of the demodulator circuit 68 to its impedance at the transmission frequency f of the transmitter coil 44.

[0085] In the case of contact-based automatic shutdown, the converter 54 outputs a voltage Vdd between the reset voltage Vrst and the gate-source minimum threshold voltage Vgs-thres,min to switch off the device 2. However, this voltage range for the converter voltage Vdd is not necessarily applicable to wireless automatic shutdown, as a lower converter voltage Vdd is required for shutdown in this case. During wireless automatic shutdown, the converter voltage Vdd of the converter 54 is an input voltage for the oscillator 56, which amplifies the converter voltage Vdd, resulting in a correspondingly higher charging voltage Vcc in the device 2, especially if the receiving coil 46 has more turns than the transmitting coil 44.The converter voltage Vdd is therefore significantly lower in the case of wireless automatic switch-off than in the case of contact-based automatic switch-off and is, for example, in the millivolt range. The converter 54 is typically unable to generate a converter voltage Vdd below its internal feedback reference voltage Vfb, which is regularly at least 0.6 V. Therefore, the charger 4 shown here includes a voltage reference circuit 72 in addition to the converter 54 in order to generate a converter voltage Vdd below the feedback reference voltage Vfb of the converter 54. An embodiment of such a voltage reference circuit 72 is shown in [reference missing]. Fig. 14 The circuit is shown and features an external reference voltage Vref with respect to the converter 54, which is connected to a feedback terminal 74 of the converter 54. The external reference voltage Vref is greater than the internal feedback reference voltage Vfb. The voltage reference circuit 72 is then configured and connected to the converter 54 such that the converter voltage Vdd is the difference between the internal feedback reference voltage Vfb on the one hand and the difference between the external reference voltage Vref and the internal feedback reference voltage Vfb, weighted by a suitable resistance ratio R1 / R2 of two resistors 76, 78, on the other hand, i.e., Vdd = Vfb - R1 · (Vref - Vfb) / R2.The two resistors 76, 78 form a voltage divider, with two endpoints 80, to which an output 82 of the converter 54 on one side and the external reference voltage V ref on the other are connected, and with a midpoint 84 between the two resistors 76, 78, to which the feedback connection 74 is connected.

[0086] The charger 4 also includes a control unit 86, to which the communication unit 58 and the converter 54 are connected. The control unit 86 is used to configure the converter 54 based on the data received by the communication unit 58. Optionally, the charger 4 also includes an emergency energy storage device 88 to maintain the intermediate voltage and generate the shutdown signal in the event of a power supply interruption to the charger 4.

[0087] The control unit 86 is configured to perform one or more of the steps of the procedure described herein. Device 2 also has a control unit 90, which is configured to perform one or more of the steps of the procedure described herein.

[0088] Overall, the switching-off circuit 22, in combination with the communication system, implements a method in which the device 2 is wirelessly and automatically switched off at the initiation of the charger 4, specifically at the end of charging the energy storage device 16 of the device 2 and generally when the energy transfer from the charger 4 to the device 2 is interrupted. For this purpose, the method uses, for example, one or more of the components described in Fig. 15The steps shown are carried out, preferably in the order mentioned. In a first step S201, the device sends 2 data to the charger 4, e.g., repeatedly. In a second step S202, the data is analyzed, e.g., by the control unit 86. If the data is modulated, it is demodulated beforehand in the second step S202, e.g., using the described demodulator circuit 68. In a third step S203, the converter 54 is set based on the data, e.g., by the control unit 86. The control unit 86 sets the converter 54, for example, with a DAC signal or a PWM signal. In a fourth step S204, the converter 54 then outputs a converter voltage V dd to the oscillator 56 and thereby controls it. Also in the fourth step S204, the oscillator 56 outputs a current I tx, which is then used to operate the transmitting coil 44. The current I tx is thus indirectly set by converter 54 in the fourth step S204.In a fifth step S205, the transmitting coil 44 generates a magnetic field M depending on the current I tx. In a sixth step S206, the magnetic field M is received by the receiving coil 46, which generates a charging voltage V cc in the device 2, so that the charger 4 induces a total charging voltage V cc in the device 2. In a seventh step S207, the device 2 is then switched off if the charging voltage V cc lies within the voltage range between the reset voltage V rst and the gate-source minimum threshold voltage V gs-thres,min, i.e., if the charging voltage V cc is an intermediate voltage as described. Therefore, if an intermediate voltage is present, the device 2 switches to the off state AZ in the seventh step S207 and is then switched off. In the seventh step S207, the device 2 optionally only switches to the off state AZ if, in addition, a time t has elapsed as described, which is longer than a switching connection active time t sca .Ultimately, the automatic shutdown occurs depending on the data that device 2 sends to the charger 4. In an optional eighth step S208, the converter 54 is also switched off, preferably after a specific time t, e.g., 10 s, after device 2 has switched to the off state AZ.

[0089] It has been described so far that device 2 is switched off when charging is complete. The data then contains at least the final charging voltage Vcc, which is determined in conjunction with the final current Itx and is also used in combination with this, in particular by the control unit 88, to determine a converter voltage Vdd and to adjust the converter. However, events other than the end of charging are also suitable for initiating automatic shutdown, e.g., if the temperature of the energy storage device 16 exceeds a limit temperature (overheating), if the voltage or current at the energy storage device 16 exceeds a corresponding limit (overvoltage / overcurrent), generally in the event of a fault in the energy storage device 16 (fault case), or similar events.The control unit 86 then infers one or more of these events when the control unit 86 analyzes the data, and then controls the converter 54 accordingly to initiate the automatic shutdown. Reference symbol list

[0090] 2 Device 4 Charger 6 Transmitter module 8 Receiver module 10 Charging port 12 Switching port 14 Energy management module 16 Energy storage 18 Consumer 20 Switch 22 Off circuit 24 Microphone 26 Earpiece 28 Recess 30 Cover 32 Transformation unit 34 Ground 36 Gate 38 Source 40 Drain 42 Resistor 44 Transmitting coil 46 Receiving coil 48 Tuning capacitor 50 Smoothing capacitor 52 Schottky diode 54 Converter 56 Oscillator 58 Communication unit (of the device) 60 Communication unit (of the charger) 62 Voltage range (for converter voltage) 64 Voltage range 66 Voltage range 68 Demodulator circuit 70 Capacitor 72 Voltage reference circuit 74 Feedback port 76 Resistor 78 Resistor 80 Endpoint 82 Output 84 Center point 86 Control unit (of the charger) 88 Emergency power storage 90 Control unit (of the device) A Distance AZ Off-state EZ Discharge state I tx Current k Coupling factor L rx Inductance of the receiving coil L tx Inductance of the transmitting coil LZ Charging state M Magnetic field S101 - S104 Step S201 - S208 Step t disc Discharge time t sca Switching terminal active time V bat Voltage V cc Charging voltage V chg,thres Charging threshold voltage V dd Converter voltage V fb Feedback reference voltage V gs-thres Gate-source threshold voltage V gs-thres,max Gate-source maximum threshold voltage V gs-thres,min Gate-source minimum threshold voltage V OD Object detection voltage V out Voltage (from the energy management module to the load) V ref Reference voltage V rst Reset voltage WZ Waiting state t Time

Claims

1. Method, - wherein a device (2) is connected to a charger (4), - wherein the device assumes a charging state (LZ), in state which wireless charging is executed, wherein, by means of a transmitter module (6) of the charger (4), energy is transmitted to a receiver module (8) of the device (2), in a wireless arrangement, - wherein the device (2) assumes a discharging state (EZ), in which state energy is consumed, characterized in that - the device (2) comprises a charging terminal (10) to which, for the purposes of charging, a charging voltage (Vcc) is applied, which voltage is adjustable by means of the charger (4), - the device (2) comprises a switching terminal (12) for the switch-on and switch-off of the device (2), - the charging terminal (10) and the switching terminal (12) are terminals of an energy management module (14) of the device (2), - the device (2) comprises a switch (20), which switch is connected to the switching terminal (12) and is switchable by means of the charging voltage (Vcc), wherein the charging voltage (Vcc) is adjusted to an intermediate voltage, - the charger (4) adjusts the charging voltage (Vcc) to the intermediate voltage, such that the switch (20) is switched and the device (2) executes a switchover to an OFF state (AZ), in which the device (2) is switched off.

2. Method according to Claim 1, wherein charging is terminated, in the event that the charging voltage (Vcc) undershoots a charging threshold voltage (Vchg,thres).

3. Method according to Claim 2, wherein the device (2) executes a switchover from the discharging state (EZ), or from the OFF state (AZ), to the charging state (LZ), if the charging voltage (Vcc) at least corresponds to the charging threshold voltage (Vchg,thres) .

4. Method according to Claim 2 or 3, wherein the device (2) executes a switchover from charging state (LZ) to an idle state (WZ), if the charging voltage (Vcc) is lower than the charging threshold voltage (Vchg,thres), and from the idle state (WZ) to the discharging state (EZ), if the charging voltage (Vcc) is lower than a reset voltage (Vrst).

5. Method according to one of Claims 1 to 4, wherein the switch (20) is a transistor, having a gate (36), a source (38) and a drain (40), wherein the gate (36) is connected to the charging terminal (10) and is pulled up to the charging voltage (Vcc) by means of a resistor (42), wherein the resistor (42) connects the gate (36) to the source (38) and to ground (34), wherein the drain (40) is connected to the switching terminal (12), and the source (38) is connected to ground (34).

6. Method according to one of Claims 1 to 5, wherein, during charging, an energy transfer is executed by means of a magnetic field (M), which field is generated using a transmitter coil (44) of the transmitter module (6) and is received by a receiver coil (46) of the receiver module (8), and wherein, in order to execute the adjustment of the charging voltage (Vcc) to the intermediate voltage, the transmitter module (6) is correspondingly actuated, such that the intermediate voltage is induced in the device (2).

7. Method according to Claim 6, wherein the charger (4) comprises a converter (54) and an oscillator (56), wherein the oscillator (56) generates a current (Itx) for the generation of the magnetic field (M) by means of the transmitter module (6), wherein the converter (54) generates a converter voltage (Vdd) for the operation of the oscillator (56), wherein the charging voltage (Vcc) is adjusted by means of the converter voltage (Vdd).

8. Method according to Claim 7, wherein the converter voltage (Vdd) is dependent upon a coupling factor (k) between the transmitter module (6) and the receiver module (8), wherein, for the generation of the intermediate voltage, the converter voltage (Vdd) is adjusted, wherein the coupling factor (k) is initially determined and then, by means thereof, that converter voltage (Vdd) is determined which is required for the generation of the intermediate voltage.

9. Method according to Claim 8, wherein the device (2) transmits the ultimate charging voltage (Vcc) applied during charging to the charger (4), by way of the final charging voltage (Vcc), wherein the charger (4) saves that current (Itx) which is employed at the time of the final charging voltage (Vcc) for operating the transmitter coil (44), by way of the final current (Itx), wherein the charger (4) receives the final charging voltage (Vcc), whereafter, in combination with the final current (Itx), the coupling factor (k) is then determined.

10. Method according to one of Claims 1 to 9, wherein the device (2) and the charger (4) respectively comprise a communications unit (58, 60) for the exchange of data, wherein data are modulated by the device (2) for transmission, wherein the charger (4) receives and demodulates data, wherein the charger (4), for the purposes of demodulation, incorporates a demodulator circuit (69), by means of which the current (Itx) in the transmitter module (6) is also determined.

11. Method according to one of Claims 1 to 10, wherein the charger (4), additionally to the converter (54), comprises a voltage reference circuit (72), in order to a generate a converter voltage (Vdd) which, overall, lies below a feedback reference voltage (Vfb) of the converter (54).

12. Method according to one of Claims 1 to 11, wherein the charger (4) comprises a back-up energy store (88), in order to enable the adjustment of the intermediate voltage notwithstanding an interruption of the energy supply to the charger (4).

13. Device (2) and charger (4) for executing a method according to one of Claims 1 to 12.

14. Device (2) and charger (4) according to Claim 13, wherein the device (2) is configured in the form of a hearing aid.