Capacitive earplug detection in earplug charging cartridge

Abstract

An earplug having an earplug housing is provided. First and second conductive elements are formed on a surface of the earbud housing, the first and second conductive elements configured to form a first capacitive element. The first and second conductive elements, together with a third conductive element mounted to an inner surface of the charging case, are arranged in a position designed to affect a capacitance of the first and second conductive elements when the earbud is located within the charging case. An evaluation circuit of the earplug is located within the earplug housing and electrically coupled to the first and second conductive elements. In response to the first and second conductive elements having a capacitance value above a threshold, the evaluation circuit provides an indication that the earbud is within the charging box. In another embodiment, a method for detecting whether the earbud is within the charging box is provided.

Description

Technical Field

[0001] The present disclosure relates generally to electronic circuits, and more specifically, to capacitive earbud detection in an earbud charging case. Background Art

[0002] Wireless earbuds are often sold with a case that provides a place to store and charge the earbuds when not in use. The charging case may include a docking piece shaped to fit the shape of the earbuds and include contacts on the earbuds to provide spring pins for charging. Some charging cases can charge the earbuds wirelessly, eliminating the mechanical connection via the spring pins. An earbud charging case with a fully charged battery can typically charge a pair of earbuds several times. If the earbuds are inserted into a charging case with a depleted battery, communication between the charging case and the earbuds is impossible. However, the earbuds can be activated anyway via communication circuits, such as audio or Bluetooth circuits, because the earbuds do not detect that they are in a discharged charging case. This may cause the earbuds' batteries to discharge completely while in a discharged charging case. Summary of the Invention

[0003] According to an embodiment, an earbud is provided, comprising: an earbud housing; first and second conductive elements, the first and second conductive elements mounted to a surface of the earbud housing, the first and second conductive elements being configured to form a first capacitive element, wherein when the earbud is in a charging case, the first and second conductive elements, together with a third conductive element mounted to the charging case, are arranged in a position designed to affect the capacitance of the first and second conductive elements; and an evaluation circuit located in the earbud housing and electrically coupled to the first and second conductive elements, wherein in response to the first and second conductive elements having a capacitance value above a threshold, the evaluation circuit provides an indication that the earbud is in the charging case. The first, second, and third conductive elements may be metal sheets attached to a surface of the earbud housing. The first conductive element may be selectively coupled to a power supply voltage terminal, and the second conductive element may be coupled to a ground terminal. The evaluation circuit may include: a reference capacitor selectively coupled between a supply voltage terminal and a ground terminal; and a comparator having a first input coupled to a first capacitive element, a second input coupled to the reference capacitor, and an output for providing an indication that the earbud is within the charging case in response to a favorable comparison of a voltage level representing a capacitance value of the first capacitive element and a voltage level representing a capacitance value of the reference capacitor. The earbud may further include a control circuit configured to connect the first capacitive element and the reference capacitor to the supply voltage terminal during a charging phase of operation, and to disconnect the first capacitive element and the reference capacitor from the supply voltage terminal during a sensing phase of operation. A third conductive element may be formed in the charging case such that when the earbud is within the charging case, the third conductive element is parallel to the first and second conductive elements. The evaluation circuit may further include: a comparator having a first input coupled to a first capacitive element, a second input coupled to receive a reference voltage, and an output; a control circuit configured to couple the first capacitive element to a supply voltage terminal during a capacitor charging phase and to initiate a capacitive sensing phase after the capacitor charging phase, wherein a timer is started at the start of the capacitive sensing phase and the timer is stopped when the voltage of the first capacitive element drops below the reference voltage, wherein a measured time between starting the timer and stopping the timer is proportional to a capacitance value of the first capacitive element, and wherein a measured time above a threshold time provides an indication that the earbud is within the charging case. The earbud may further include a resistor connected in series with the first capacitive element. In response to detecting that the earbud is within the charging case and the battery is depleted, the circuitry of the earbud may be switched to a standby mode.

[0004] In another embodiment, a method for detecting that an earbud is within a charging case is provided, the method comprising: inserting the earbud into the charging case, wherein when the earbud is fully within the charging case, first and second conductive elements formed on a surface of the earbud are aligned with a third conductive element formed on a surface of the charging case; detecting, by evaluation circuitry in the earbud, a capacitance value between the first, second, and third conductive elements; determining that the earbud is within the charging case when the capacitance value is above a threshold; and providing an indication that the earbud is within the charging case when the capacitance value is above the threshold. The method may further comprise switching the earbud to a standby mode in response to detecting that the earbud is within the charging case and the battery is depleted. The method may further comprise switching the earbud to the standby mode a predetermined time after determining that the earbud is within the charging case and no communication with the charging case is detected. Determining that the earbud is within the charging case may further comprise determining that the earbud is within the charging case when the capacitance value of the first capacitive element is above the capacitance value of a reference capacitor. The method may further include charging the first capacitive element during a charging phase; sensing a capacitance value of the first capacitive element during a sensing phase, the sensing phase following the charging phase; and measuring a time between starting the sensing phase and when a voltage across the first capacitive element drops below a reference voltage, wherein when the measured time is above a threshold time, providing an indication that the earbud is within the charging case.

[0005] In yet another embodiment, an integrated circuit is provided, comprising: a power supply voltage terminal coupled to receive a power supply voltage; a switch having a first terminal coupled to the power supply voltage terminal, a second terminal, and a control terminal; a comparator having a first input terminal coupled to receive a reference voltage, a second input terminal coupled to a capacitive element, the capacitive element being formed by first and second conductive elements formed on a surface of an earbud housing, and an output terminal, wherein when the earbud is inserted into a charging case, the first and second conductive elements align with a third conductive element formed on an inner side of the charging case, and wherein the first conductive element is coupled to the second terminal of the switch, and the second conductive element is coupled to ground; and a control circuit coupled to the control terminal of the switch, wherein the control circuit closes the switch and charges the capacitive element during a charging phase, wherein the control circuit closes the switch during a sensing phase following the charging phase, and wherein during the sensing phase, when a voltage level of the capacitive element is higher than a reference voltage, the output terminal of the comparator provides an indication that the earbud is within the charging case. The reference voltage may be provided by a reference capacitor formed on the integrated circuit. In response to detecting that the earbud is within the charging case, the earbud may be switched to a standby mode. The control circuit may further include a timer, wherein the timer is started at the beginning of the sensing phase and the timer is stopped when the voltage at the capacitive element drops below a reference voltage, wherein a measured time between starting the timer and stopping the timer is proportional to a capacitance value of the capacitive element, and wherein a measured time above a threshold time provides an indication that the earbud is inserted into the charging case. The first, second, and third conductive elements may be metal sheets. The integrated circuit may further include an additional capacitor connected in parallel with the capacitive element external to the integrated circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present invention is illustrated by way of example and not limitation in the accompanying figures, in which like reference numerals indicate similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale.

[0007] Figure 1 A circuit diagram illustrating an earbud detection circuit according to an embodiment is shown.

[0008] Figure 2 Shown in Figure 1 Timing diagram of the various signals during operation of the earbud detection circuit.

[0009] Figure 3 A circuit diagram illustrating an earbud detection circuit according to another embodiment is shown.

[0010] Figure 4 A circuit diagram illustrating an earbud detection circuit according to another embodiment is shown.

[0011] Figure 5Shown suitable for Figure 1 、 Figure 3 and Figure 4 The earbud detection circuit is used together with a pair of earbuds.

[0012] Figure 6 A method for detecting an earbud in a discharged earbud cartridge according to an embodiment is shown. DETAILED DESCRIPTION

[0013] Generally, an earbud detection circuit is provided for detecting when an earbud is inserted into its charging case or cradle. The earbud detection circuit monitors the capacitance of a sensing capacitor to detect when the earbud is inside the charging case. This sensing capacitor is formed by a conductive element mounted on or in the earbud housing, casing, or outer shell. The conductive element can be formed from metal or other conductive materials. In one embodiment, the conductive element can be formed from a metal sheet. A first conductive element of the sensing capacitor is conformally mounted on a surface of the earbud housing and coupled to a power supply voltage. A second conductive element is also mounted on the earbud housing near the first conductive element to form a sensing capacitor. A third conductive element can be formed on the inside of the charging case and aligned with the first and second conductive plates on the earbud when the earbud is fully inserted into the charging case. The third conductive element is used to contribute to the capacitance generated between the first and second conductive elements. The sensing capacitor thus formed is sensitive to the proximity of the third conductive plate. Subsequently, in one embodiment, this capacitance, or the charge state of the capacitor represented by a voltage level, can be compared to a reference value, and the comparison result can be used to distinguish between two different sensing states to indicate whether the earbud is inside or outside the charging case. In another embodiment, a reference capacitor is not required, and instead the discharge time of a sensing capacitor is measured to detect whether the earbud is in the charging case. If it is determined that the earbud is in the charging case, circuits such as communication circuits, audio circuits, or other circuits of the earbud are switched to standby mode to avoid discharging the battery of the earbud. In the described embodiments, the earbud includes the detection circuitry instead of the charging case. In one embodiment, both earbuds in a pair of earbuds include a sensing capacitor and a detection circuit. These embodiments for sensing the earbud charging case enable low power and low cost sensing operations, which are useful for battery powered systems. In other embodiments, the capacitive sensing described may be applicable to other applications, such as pen applications, hearing aids, and devices that do not need to be activated in the charging case.

[0014] Figure 1 FIG1 shows a circuit diagram of an earbud detection circuit 10 according to an embodiment. The earbud detection circuit 10 includes a switch 12, a voltage source 13, resistors 14 and 15, a reference capacitor 16, a comparator 17, and a sensing capacitor 18. The sensing capacitor 18 is formed on the surface of the earbud using first and second conductive elements corresponding to capacitor plates (see FIG10 ). Figure 5In one embodiment, the first and second conductive elements may be metal sheets. One plate of the sensing capacitor 18 is connected to a first terminal of the switch 12 via a resistor 15, and the other plate is coupled to ground. Furthermore, a third conductive element is formed in the charging case and is positioned to influence and increase the capacitance generated between the first and second conductive elements. In one embodiment, except for the sensing capacitor 18 of the earbud detection circuit 10, the other components are implemented in hardware on an integrated circuit (IC) inside the earbud housing.

[0015] The earbud positioning process can be divided into two phases: the capacitor charging phase (Phase 1) and the capacitor sensing phase (Phase 2). During Phase 1, the switch 12 is closed and the integrated circuit (IC) internal voltage source 13 provides a voltage labeled “V pulse ” to fully charge capacitors 16 and 18 to the same voltage via charging resistors 14 and 15. The resistance of resistors 14 and 15 is marked as R. In another embodiment, resistors 14 and 15 may have different resistances. In this embodiment, resistance R also defines the leakage current. During the sensing phase (phase 2), switch 12 is opened, and both capacitors 16 and 18 are charged according to their time constants R·C sense and R.C. ref Therefore, the comparator 17 is used to discharge the capacitance C of the capacitor 18. sense and the capacitance C of capacitor 16 ref The corresponding voltage level of the capacitor 18 is indirectly compared with the capacitance C sense and the capacitance C of capacitor 16 ref . Then, if the voltage V sense The value is greater than the voltage V ref , the comparator output V comp Indicates that the earbuds are inside the charging case, and if the voltage V sense The value is less than the voltage V ref , the comparator output V comp Indicates that the earbuds are outside the charging case.

[0016] If the earbud is determined to be in the charging case, the earbud's communication circuit (e.g., Bluetooth or audio circuit) can be switched to standby mode to avoid discharging the earbud's battery. If the charging case's battery is not discharged, the charging case can activate the earbud's battery charging circuit to charge the battery.

[0017] Figure 2 Shown in Figure 1 A timing diagram of various signals during operation of the earplug detection circuit 10. Figure 2 , plot V over time sense 、V ref and V comp The voltage level of Figure 2 In the voltage V sense As shown by curve 17, the voltage V ref As shown by curve 19, and the voltage V comp This is shown by curve 18. At time t=0, the earbud is outside the charging case, which means that the capacitance C sense Smaller than the capacitance C ref . Figure 2 Two detection cycles are shown. The first detection cycle includes time periods T1 and T2, and the second detection cycle includes time periods T3 and T4. Time periods T1 and T3 are charging time periods, and time periods T2 and T4 are sensing time periods. Figure 1 and Figure 2 In both cases, during the time period T1, the voltage V pulse is high and capacitors 16 and 18 are charged to 3 volts through similar resistors 14 and 15 having resistance R. During time period T2, the voltage V pulse The connection is disconnected, and both capacitors 16 and 18 discharge to ground via leakage current. In time period T2, the voltage V sense 17 Keep below voltage V ref 19, therefore, the voltage V from comparator 17 comp 18 also remains low, indicating that the earbuds are not in the charging case. Time period T3 begins another detection cycle. During the charging time period T3, switch 12 is closed again and capacitors 16 and 18 are charged to 3V. In time period T3, starting at time t=0.8ms, capacitor C sense Increase to a value higher than the capacitance C ref , and the corresponding voltage increase indicates that the earbuds are in the charging box. Next, during the sensing period T4, the switch 12 is turned off and the capacitors 16 and 18 begin to discharge. The voltage V sense 17 Maintain voltage higher than V ref 18, and the voltage V provided by the comparator 17 comp 18 goes high, which indicates that the earbuds are in the charging case. In this example, V comp becomes high because the voltage V sense The value is greater than the voltage V ref It should be noted that in one embodiment, a safety margin (eg, 0.2 volts) may be added to the voltage V ref .

[0018] Figure 3A circuit diagram of an earbud detection circuit 20 according to another embodiment is shown. As with the earbud detection circuit 10, the earbud detection circuit 20 is implemented in the earbud, rather than in the charging case. The earbud detection circuit 20 includes an evaluation circuit 21 and a sensing capacitive element 31. The evaluation circuit 21 includes a reference capacitor 22, switches 23-25, resistors 26 and 27, a comparator 28, and a control circuit 29. The sensing capacitive element 31 includes conductive elements 32-34. In one embodiment, the conductive elements 32 and 33 are metal sheets. The metal sheets are formed very close to each other around a portion of the earbud housing so that the capacitance value between them can be measured. In one embodiment, the conductive elements 32 and 33 are attached with an adhesive and coated with an insulating material. Figure 5 An example is shown in . The earbud housing is typically made of plastic and encloses the earbud's electronics and battery. In one embodiment, conductive element 34 is the same type of material as conductive elements 32 and 33 and is mounted to the inner surface of the charging case in a position that aligns with conductive elements 32 and 33 when the earbud is inserted into the charging case. In another embodiment, conductive element 34 can be a different type of conductive material. Evaluation circuit 21 is connected to sensing capacitor conductive element 32 via terminal 37. Conductive element 33 is connected to ground. Conductive element 34 is used to enhance the capacitance generated by conductive elements 32 and 33 and has no electrical connection to evaluation circuit 21. In some embodiments, an external capacitor 35 can be included to increase the capacitance seen at terminal 37. Current sources 30 and 36 are included to illustrate the inherent leakage current that will cause the stored capacitance of capacitors 22 and 31 to decrease over time.

[0019] In one embodiment, the evaluation circuit 21 is implemented in hardware on an integrated circuit (IC) mounted inside the earbud housing. PULSE The evaluation circuit 21 operates in detection cycles, each detection cycle having the same Figure 1 and Figure 2 During the charging phase, control circuit 29 closes switches 23 and 24 and opens switch 25. Capacitors 22 and 31 are both charged to a high voltage through resistors 23 and 27, reaching a voltage equal to approximately V PULSE During the sensing phase, switches 23 and 24 are open and switch 25 is closed. Comparator circuit 28 is activated during the sensing phase. The voltage V REF and the voltage V of the sensing capacitive element 31 SENSE Provided to the input of comparator 28. If the voltage V SENSE Greater than voltage V REF , then the output voltage V from the comparator 28 COMP Indicates that the earbuds are in the charging case. Similarly, if the voltage V REF Greater than voltage VSENSE , then the output voltage V from the comparator 28 COMP Indicates that the earbuds are outside the charging case.

[0020] The capacitive element 31 may be sized so that when the earbud is outside the charging case, the capacitance C of the reference capacitor 22 is ref Greater than the capacitance C of the sensing capacitive element 31 sense , and when the earbuds are in the charging box, the capacitor C ref Lower than the capacitance C sense Therefore, the metal piece installed in the charging box is positioned to sense The value of has an appropriate effect. For example, the conductive element 34 can be located inside the charging case so that when the earbud is completely inside the charging case, it is parallel to the conductive elements 32 and 33. In addition, the capacitance C can be adjusted by adding another external parallel capacitor 35. sense Alternatively, for efficiency reasons, the capacitive elements 22 and 31 may be sized differently, and the charging time of the capacitive elements may be tailored by using different resistance values ​​for the resistors 26 and 27 .

[0021] As discussed above, in response to the comparator 28 indicating that the earbud is in the charging case, the communication circuit of the earbud is then placed in standby mode to reduce power consumption. In another embodiment, the earbud is switched to standby mode a predetermined time after determining that the earbud is in the charging case and no communication with the charging case is detected.

[0022] The earbud detection circuit 20 provides a cost-effective and easy-to-implement way to detect whether an earbud is in the charging case. The earbud detection circuit 20 can be added to existing devices with minimal effort. No additional dedicated sensor system, such as a Hall sensor system, is required. The earbud detection circuit provides low current consumption, for example, 2.5 nanoamperes (nA) root mean square (rms) with a 10 Hz detection cycle rate in one embodiment. It should be noted that the time between the capacitor charging phase and the sensing phase can be adjusted to optimize power consumption.

[0023] As an example current consumption calculation, assume that C ref =1.5 pico Farad (pF), C sense =2pF, V pulse =3 volts (V), and the charging resistors 26 and 27 have a resistance R = 50 megohms (MΩ). Also, assuming a 10 Hz sensing cycle, then

[0024]

[0025] I rms (C sense )=1.34nA,

[0026] I rms (C ref ) = 1.16nA, and

[0027] I rms =2.5nA.

[0028] Other embodiments may produce different results.

[0029] Figure 4 A conceptual circuit diagram of an earbud detection circuit 40 according to another embodiment is shown. Earbud detection circuit 40 detects earbuds in the charging case by measuring the time it takes for the voltage across a sensing capacitor to drop below a specific voltage threshold. This embodiment eliminates the use of a reference capacitor but may require more complex evaluation circuitry. Earbud detection circuit 40 includes a voltage source 41, a resistor 42, a sensing capacitor 43, a reference voltage source 44, a comparator 45, a control circuit 46, and switches 48 and 49. Control circuit 46 includes a timer 47. Earbud detection circuit 40 is implemented similarly to capacitive element 31 of earbud detection circuit 40, with sensing capacitor 43 formed from two conductive elements mounted on the surface of the earbud and a third conductive element formed on the inside of the charging case. As discussed above, the detection cycle has a charging phase and a sensing phase. The charging phase begins by closing switch 48 and opening switch 49 to charge sensing capacitor 43 from voltage source 41 through resistor 42. The sensing phase begins when switch 48 is opened and switch 49 is closed to provide the START TIMER signal to the control circuit 46 to start the discharge timing using timer 47. The measured time period between starting the timer and stopping the timer is proportional to the capacitance value of the sensing capacitor 43. When the voltage V SENSE drops below the reference voltage V REF When the time period is greater than the threshold, the comparator 45 provides a STOPTIMER signal to stop the timer 47. If the measured time period is higher than the threshold, the earbud is inside the charging case.

[0030] Figure 5 Shown suitable for Figure 1 、 Figure 3 and Figure 4 The pair of earbuds 50 is used together with the earbud detection circuit. The pair of earbuds 50 includes an earbud 51 and an earbud 52. The conductive element 53 of the sensing capacitor is as shown in FIG. Figure 3The conductive element is provided as shown and can be mounted to the plastic housing of the earbud 50 in a variety of ways. For example, a suitably sized piece of metal can be shaped to fit the curved surface of the earbud and attached, for example with an adhesive, in a position that can be aligned with a corresponding conductive element located in the earbud docking piece of the charging case, which is shaped to fit the shape of the earbud (charging case not shown). It should be noted that even though a rectangular conductive element is shown, the conductive element can have any shape and size to fit the specific shape and size of the earbud.

[0031] Figure 6 A method 60 for detecting an earbud in a charging case according to an embodiment is shown. Method 60 begins at block 61. At block 61, the earbud is inserted into the charging case such that, when the earbud is fully within the charging case, first and second conductive elements formed on a surface of the earbud are aligned with a third conductive element formed on a surface of the charging case. At block 62, an evaluation circuit in the earbud detects a capacitance value between the first, second, and third conductive elements. At block 63, when the capacitance value is above a threshold, it is determined that the earbud is in the charging case. It should be noted that in one embodiment, a voltage level is used to indicate the charge state of the first and second conductive elements. At block 64, when the capacitance value is above a threshold, an indication that the earbud is in the charging case is provided.

[0032] Various embodiments or portions of embodiments may be implemented in hardware or as instructions on a non-transitory machine-readable storage medium, including any mechanism for storing information in a form readable by a machine, such as a personal computer, laptop computer, file server, smartphone, or other computing device. Non-transitory machine-readable storage media may include volatile and non-volatile memory, such as read-only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory, etc. Non-transitory machine-readable storage media do not include transitory signals.

[0033] Although the present invention has been described herein with reference to specific embodiments, various modifications and changes may be made without departing from the scope of the present invention as set forth in the appended claims. The specification and drawings are therefore to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. It is not intended that any benefits, advantages, or solutions to problems described herein with respect to specific embodiments be construed as key, required, or essential features or elements of any or all the claims.

[0034] In addition, as used herein, the terms "a" or "an" are defined as one or more than one. Moreover, the use of introductory phrases such as "at least one" and "one or more" in the claims should not be interpreted as implying that another claim element introduced by the indefinite article "a" or "an" limits any particular claim containing the introduced claim element to inventions containing only one of the element, even when the same claim includes the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "an". The same applies to the use of definite articles.

[0035] Unless otherwise stated, terms such as "first" and "second" are used to arbitrarily distinguish between the elements such terms describe. Therefore, these terms are not necessarily intended to indicate a temporal or other prioritization of such elements. As used herein, the term "coupled" is not intended to be limited to a direct coupling or a mechanical coupling.

Claims

1. An earplug, characterized in that: include: earbud housing; first and second conductive elements mounted to a surface of the earbud housing, the first and second conductive elements configured to form a first capacitive element, wherein when the earbud is within a charging case, the first and second conductive elements, along with a third conductive element mounted to the charging case, are arranged in a position designed to affect the capacitance of the first and second conductive elements; as well as An evaluation circuit is located within the earbud housing and electrically coupled to the first and second conductive elements, wherein in response to the first and second conductive elements having a capacitance value above a threshold, the evaluation circuit provides an indication that the earbud is within the charging case.

2. The earplug according to claim 1, wherein The first conductive element is selectively coupled to a power supply voltage terminal, and the second conductive element is coupled to a ground terminal.

3. The earplug according to claim 2, wherein: The evaluation circuit comprises: a reference capacitor selectively coupled between the power supply voltage terminal and the ground terminal; and a comparator having a first input coupled to the first capacitive element, a second input coupled to the reference capacitor, and an output for providing the indication that the earbud is within the charging case in response to a favorable comparison of a voltage level representing the capacitance value of the first capacitive element and a voltage level representing the capacitance value of the reference capacitor.

4. The earplug according to claim 3, wherein Also included is a control circuit configured to connect the first capacitive element and the reference capacitor to the supply voltage terminal during a charging phase of operation, and the control circuit configured to disconnect the first capacitive element and the reference capacitor from the supply voltage terminal during a sensing phase of operation.

5. The earplug according to claim 1, wherein The evaluation circuit further comprises: a comparator having a first input coupled to the first capacitive element, a second input coupled to receive a reference voltage, and an output; A control circuit is configured to couple the first capacitive element to a supply voltage terminal during a capacitor charging phase and to start a capacitive sensing phase after the capacitor charging phase, wherein a timer is started when the capacitive sensing phase starts and the timer is stopped when the voltage of the first capacitive element drops below the reference voltage, wherein a measured time between starting the timer and stopping the timer is proportional to a capacitance value of the first capacitive element, and wherein the measured time being above a threshold time provides an indication that the earbud is within the charging case.

6. A method for detecting whether an earbud is in a charging box, characterized in that: The method comprises: Inserting the earbud into the charging case, wherein when the earbud is fully inside the charging case, first and second conductive elements formed on a surface of the earbud are aligned with a third conductive element formed on a surface of the charging case; detecting capacitance values ​​between the first, second, and third conductive elements by an evaluation circuit in the earplug; When the capacitance value is higher than a threshold, determining that the earbud is in the charging box; and When the capacitance value is higher than the threshold, an indication is provided that the earbud is in the charging case.

7. The method according to claim 6, characterized in that Determining that the earbud is in the charging box further includes: when the capacitance value of the first capacitive element is higher than the capacitance value of the reference capacitor, determining that the earbud is in the charging box.

8. The method according to claim 6, characterized in that Also includes: charging the first capacitive element during a charging phase; sensing a capacitance value of the first capacitive element during a sensing phase, the sensing phase subsequent to the charging phase; as well as A time is measured between starting the sensing phase and when the voltage across the first capacitive element drops below a reference voltage, wherein when the measured time is above a threshold time, an indication that the earbud is within the charging case is provided.

9. An integrated circuit, characterized in that: include: a power supply voltage terminal coupled to receive a power supply voltage; a switch having a first terminal coupled to the power supply voltage terminal, a second terminal, and a control terminal; a comparator having a first input coupled to receive a reference voltage, a second input coupled to a capacitive element formed by first and second conductive elements formed on a surface of the earbud housing, and an output, wherein when the earbud is inserted into the charging case, the first and second conductive elements align with a third conductive element formed on an interior side of the charging case, and wherein the first conductive element is coupled to the second end of the switch and the second conductive element is coupled to ground; as well as a control circuit coupled to the control terminal of the switch, wherein the control circuit closes the switch and charges the capacitive element during a charging phase, wherein the control circuit closes the switch during a sensing phase following the charging phase, and wherein during the sensing phase, when the voltage level of the capacitive element is higher than the reference voltage, the output terminal of the comparator provides an indication that the earbud is within the charging case.

10. The integrated circuit according to claim 9, wherein: The control circuit further includes a timer, wherein the timer is started when the sensing phase begins and the timer is stopped when the voltage at the capacitive element drops below the reference voltage, wherein a measured time between starting the timer and stopping the timer is proportional to a capacitance value of the capacitive element, and wherein the measured time being above a threshold time provides an indication that the earbud is inserted into the charging case.

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