Wireless Audio Output Device

Abstract

The present invention provides a wireless audio output device, comprising a first contact, a second contact, a third contact and a charging protection circuit. The first contact is coupled to a voltage stabilizing capacitor. The third contact is grounded. A first end of the charging protection circuit is coupled to the first contact and a charging control circuit. A second end of the charging protection circuit is coupled to the second contact and a signal receiving circuit. The charging protection circuit has a first state and a second state. In the first state, the charging protection circuit is turned on to couple the second contact to the first contact. In the second state, the charging protection circuit is not turned on to prevent the second contact from being coupled to the first contact.

Description

Technical Field

[0001] The present invention relates to an audio output device, and more particularly to a wireless audio output device. Background Art

[0002] Wireless earphones are popular among modern people due to their convenience. Generally, wireless earphones are charged through a paired charging case. In addition to the charging function, in order to meet the needs of users, the charging case usually also has a function of communicating with the wireless earphones. In response to the function configuration of the charging case, the circuit design of the wireless earphones will become an important issue. Summary of the Invention

[0003] An embodiment of the present invention provides a wireless audio output device, including a first contact, a second contact, a third contact, a charging control circuit, a signal receiving circuit, and a charging protection circuit. The first contact is coupled to a voltage stabilizing capacitor. The third contact is grounded. A first end of the charging protection circuit is coupled to the first contact and the charging control circuit. A second end of the charging protection circuit is coupled to the second contact and the signal receiving circuit. The charging protection circuit has a first state and a second state. In the first state, the charging protection circuit is turned on to couple the second contact to the first contact. In the second state, the charging protection circuit is not turned on to prevent the second contact from being coupled to the first contact. One of the first contact and the second contact is used to couple to a first output terminal of a charging device for outputting a charging voltage or a communication signal. The third contact is used to couple to a second output terminal of the charging device. When the first contact is coupled to the first output terminal and the first output terminal outputs a charging voltage, the charging protection circuit switches to the second state to transfer the charging voltage to the charging control circuit. When the second contact is coupled to the first output terminal and the charging device outputs a charging voltage, the charging protection circuit switches to the first state to transfer the charging voltage to the charging control circuit. When the second contact is coupled to the first output terminal and the charging device outputs a communication signal, the charging protection circuit switches to the second state to transfer the communication signal to the charging control circuit.

[0004] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but it is not intended to limit the present invention. Brief Description of the Drawings

[0005] Figure 1 It is a block diagram of a wireless audio output device according to an embodiment of the present invention.

[0006] Figure 2A It is a circuit block diagram of a charging protection circuit according to an embodiment of the present invention.

[0007] Figure 2B It is a circuit block diagram of a charging protection circuit according to another embodiment of the present invention.

[0008] Figure 3 It is a circuit block diagram of a charging protection circuit according to another embodiment of the present invention.

[0009] Figure 4A It is a circuit block diagram of a charging protection circuit according to another embodiment of the present invention.

[0010] Figure 4B It is a circuit block diagram of a charging protection circuit according to another embodiment of the present invention.

[0011] Figure 5A It is a circuit block diagram of a charging protection circuit according to another embodiment of the present invention.

[0012] Figure 5B It is a circuit block diagram of a charging protection circuit according to another embodiment of the present invention.

[0013] Figure 6 It is a block diagram of a control signal generation circuit according to another embodiment of the present invention.

[0014] Among them, the reference numerals:

[0015] 10: Wireless audio output device

[0016] 90: Charging device

[0017] 102: Charging control circuit

[0018] 104: Signal receiving circuit

[0019] 106, 106a to 106g: Charging protection circuit

[0020] C: Voltage stabilizing capacitor

[0021] N1: First contact

[0022] N2: Second contact

[0023] N3: Third contact

[0024] O1: First output terminal

[0025] O2: Second output terminal

[0026] Vc: Charging voltage

[0027] Sc: Communication signal

[0028] CS: Control signal

[0029] M1: First transistor

[0030] M2: Second transistor

[0031] M61, M62: Transistors

[0032] R61: Resistor

[0033] EN: Signal

[0034] D1: First diode

[0035] D2: Second diode

[0036] R1: First resistor Detailed implementation manners

[0037] The structural principle and working principle of the present invention will be specifically described below with reference to the accompanying drawings:

[0038] Figure 1 FIG. is a block diagram of a wireless audio output device 10 in accordance with an embodiment of the present invention, which is adapted to a charging device 90. Referring to Figure 1 , the wireless audio output device 10 includes a charging control circuit 102, a signal receiving circuit 104, a charging protection circuit 106, a first contact N1, a second contact N2, a third contact N3, and a voltage stabilizing capacitor C.

[0039] The wireless audio output device 10 is charged and communicates through connections between a first output terminal O1 and a second output terminal O2 of the charging device 90 via the first contact N1, the second contact N2, and the third contact N3. Specifically, during connection, one of the first contact N1 and the second contact N2 is coupled to the first output terminal O1 of the charging device 90, and the third contact N3 is coupled to the second output terminal O2 of the charging device 90. In addition, the third contact N3 is also coupled to a reference ground.

[0040] A first end of the charging protection circuit 106 is coupled to the first contact N1 and the charging control circuit 102. A second end of the charging protection circuit 106 is coupled to the second contact N2 and the signal receiving circuit 104. The first contact N1 is coupled to a first end of the voltage stabilizing capacitor C. The charging protection circuit 106 is controlled by a control signal CS provided by a control unit (not shown) of the wireless audio output device 10, and switches between a first state and a second state depending on the state of the control signal CS. When the charging protection circuit 106 switches to the first state, the charging protection circuit 106 couples the second contact N2 to the first contact N1 and the charging control circuit 102, that is, short-circuits between the first contact N1 and the second contact N2. When the charging protection circuit 106 switches to the second state, the charging protection circuit 106 does not couple the second contact N2 to the first contact N1 and the charging control circuit 102, that is, opens the circuit between the first contact N1 and the second contact N2.

[0041] The operating mechanism between the charging device 90 and the wireless audio output device 10 includes a first application and a second application, which are determined according to requirements. In the first application, the charging device 90 can not only charge the wireless audio output device 10, but also communicate with the wireless audio output device 10. In the second application, the charging device 90 can only charge the wireless audio output device 10 without communicating with the wireless audio output device 10. In short, whether the charging device 90 can communicate with the wireless audio output device 10 is determined by whether the first output terminal O1 of the charging device 90 is coupled to the first contact point N1 or the second contact point N2. The detailed description is as follows.

[0042] In the first application, the first output terminal O1 of the charging device 90 is used to provide a charging voltage Vc or output a communication signal Sc to the wireless audio output device 10. In this embodiment, the first output terminal O1 of the charging device 90 is coupled to the second contact point N2.

[0043] When the first output terminal O1 of the charging device 90 provides the charging voltage Vc, the charging protection circuit 106 switches to the first state in response to the enabling state of the control signal CS to short-circuit between the first contact point N1 and the second contact point N2. The charging voltage Vc provided by the charging device 90 will be transmitted to the charging control circuit 102 via the first contact point N1 and the charging protection circuit 106. The charging control circuit 102 charges one or more power storage units (not shown in the figure) of the wireless audio output device 10 according to the charging voltage Vc, and the voltage stabilizing capacitor C is used to stabilize the voltage received by the charging control circuit 102.

[0044] When the first output terminal O1 of the charging device 90 outputs the communication signal Sc, the charging protection circuit 106 switches to the second state in response to the disabling state of the control signal CS to open the circuit between the first contact point N1 and the second contact point N2. In this way, when the charging device 90 outputs the communication signal Sc, the communication signal Sc can be transmitted to the signal receiving circuit 104 for receiving the communication signal Sc. And since the circuit between the first contact point N1 and the second contact point N2 is open, the output load at the charging device 90 end will not include the voltage stabilizing capacitor C, that is to say, the load that the charging device 90 needs to drive during communication with the wireless audio output device 10 can be reduced.

[0045] In the second application, the first output terminal O1 of the charging device 90 is used to output the charging voltage Vc but not the communication signal Sc. In this embodiment, the first output terminal O1 of the charging device 90 is coupled to the first contact point N1. The charging protection circuit 106 maintains the second state in response to the disabling state of the control signal CS. That is to say, in the second application, since there is no signal communication between the charging device 90 and the wireless audio output device 10, the circuit between the first contact point N1 and the second contact point N2 can be maintained open.

[0046] In addition, in one embodiment, when the wireless audio output device 10 is not connected to the charging device 90, the charging protection circuit 106 can be maintained in the second state.

[0047] During the charging operation under the first application or the second application, the charging control circuit 102 is used to receive the charging voltage Vc, and based on the charging voltage Vc, charge the power storage unit of the wireless audio output device 10 with an appropriate voltage and current. During the communication operation, the signal receiving circuit 104 is used to receive the communication signal Sc and transmit the communication signal Sc to one or more processing units (not shown in the figure) of the wireless audio output device 10.

[0048] In a practical example, the wireless audio output device 10 is a wireless earphone, and the charging device 90 is a charging case for the wireless earphone. In this example, the connection manner between the charging device 90 and the wireless audio output device 10 at the contact points can be non-fixed. That is to say, during the design stage of the wireless audio output device 10, it is necessary to consider that the charging voltage Vc may be input from the first contact point N1 or may be input from the second contact point N2. Whether the charging voltage Vc is input from the first contact point N1 or from the second contact point N2, it is necessary to consider how to avoid the generation of leakage current when the charging protection circuit 106 is in the second state, and to ensure that the charging protection circuit 106 is in the correct state (the first state or the second state) at the correct time.

[0049] Figure 2A FIG. is a circuit block diagram of a charging protection circuit 106a according to an embodiment of the present invention. For a clearer understanding, please also refer to Figure 2A and Figure 1 , the charging protection circuit 106a can be used to implement Figure 1 the charging protection circuit 106 in . The charging protection circuit 106a includes a first transistor M1. A first end of the first transistor M1 is coupled to the second contact point N2. A second end of the first transistor M1 is coupled to the first contact point N1 (and the charging control circuit 102). A control end of the first transistor M1 is coupled to the control unit. A base of the first transistor M1 is floating. When the first transistor M1 is turned on, the charging protection circuit 106a is in the first state. When the first transistor M1 is turned off, the charging protection circuit 106a is in the second state.

[0050] By floating the base of the first transistor M1, it is possible to allow current to flow from the second contact N2 to the first contact N1 and also from the first contact N1 to the second contact N2. Specifically, since the charging protection circuit 106a cannot know whether the charging voltage Vc will be input from the first contact N1 or the second contact N2 before connecting the charging device 90, that is, which end of the first transistor M1 will have a higher voltage, floating the base of the first transistor M1 can pull up the voltage of the base to be close to the voltage of the higher voltage end among the first end and the second end of the first transistor M1 (i.e., the voltage of the higher voltage end among the first end and the second end of the first transistor M1 minus the threshold voltage of the parasitic diode PD1 or PD2) through the parasitic diode PD1 or PD2 between the higher voltage end and the base among the first end and the second end. As the base voltage increases, the voltage difference between the lower voltage end and the base among the first end and the second end cannot reach the threshold voltage of the parasitic diode and thus it does not conduct. In this way, the voltage of the base of the first transistor M1 can be dynamically determined. When the voltage of the first end of the first transistor M1 is higher than the voltage of the second end of the first transistor M1, the base voltage of the first transistor M1 will be equal to the voltage of the first end of the first transistor M1 minus the threshold voltage of the parasitic diode PD1; conversely, when the voltage of the first end of the first transistor M1 is lower than the voltage of the second end of the first transistor M1, the base voltage of the first transistor M1 will be equal to the voltage of the second end of the first transistor M1 minus the threshold voltage of the parasitic diode PD2. To clearly illustrate the beneficial effects of floating the base of the first transistor M1 compared to coupling the base of the first transistor M1 to the first end or the second end of the first transistor M1 (i.e., the first contact N1 or the second contact N2), the following will give two cases for illustration.

[0051] Case 1: The voltage of the first contact N1 is higher than the voltage of the second contact N2, and the first transistor M1 is not conducting. When floating the base of the first transistor M1 using the above embodiment, current will flow from the first contact N1 to the base through the parasitic diode PD2 and determine the voltage of the base to make the parasitic diode PD1 cut off. Since the parasitic diode PD1 is cut off, there will be no leakage current flowing from the base to the second contact N2 through the parasitic diode PD1. In contrast, if the base of the first transistor M1 is fixedly coupled to the first contact N1, current will flow from the first contact N1 to the base and determine the voltage of the base to make the parasitic diode PD1 cut off, and there will also be no leakage current flowing from the base to the second contact N2. However, if the base of the first transistor M1 is fixedly coupled to the second contact N2, current will flow from the first contact N1 to the base through the parasitic diode PD2 and then flow from the base to the second contact N2 through the path established by the fixed coupling, resulting in leakage current.

[0052] Case 2: The voltage of the second contact N2 is higher than that of the first contact N1, and the first transistor M1 is not conducting. When the base of the first transistor M1 is floating-connected according to the above embodiment, the current will flow from the second contact N2 to the base through the parasitic diode PD1 and determine the voltage of the base to cut off the parasitic diode PD2. Since the parasitic diode PD2 is cut off, there will be no leakage current flowing from the base to the first contact N1 through the parasitic diode PD2. On the contrary, if the base of the first transistor M1 is fixedly coupled to the second contact N2, the current will flow from the second contact N2 to the base and determine the voltage of the base to cut off the parasitic diode PD2, and there will also be no leakage current flowing from the base to the first contact N1. However, if the base of the first transistor M1 is fixedly coupled to the first contact N1, the current will flow from the second contact N2 to the base through the parasitic diode PD1 and then flow from the base to the first contact N1 through the path established by the fixed coupling, resulting in leakage current.

[0053] From the above description, it can be seen that when it is impossible to determine which of the first contact N1 and the second contact N2 will be the one with the higher voltage, fixedly coupling the base of the first transistor M1 to the first contact N1 or the second contact N2 may generate leakage current in specific situations, increasing unnecessary power consumption. The above embodiment effectively avoids the generation of leakage current by floating-connecting the base of the first transistor M1, thereby reducing unnecessary power consumption.

[0054] Please refer to Figure 2B , Figure 2B FIG. [FIGURE NUMBER] is a circuit block diagram of a charging protection circuit 106b according to another embodiment of the present invention. The charging protection circuit 106b is connected to Figure 2AThe charging protection circuit 106a is similar, with the difference that the charging protection circuit 106b further includes a first diode D1 and a second diode D2, and the base of the first transistor M1 in the charging protection circuit 106b is not floating. In this embodiment, a first end of the first diode D1 is coupled to the first end of the first transistor M1, a second end of the first diode D1 is coupled to the base of the first transistor M1, a first end of the second diode D2 is coupled to the second end of the first transistor M1, and a second end of the second diode D2 is coupled to the base of the first transistor M1. In this embodiment, the voltage of the base of the first transistor M1 can be determined by the actually provided first diode D1 or second diode D2, rather than by the parasitic diode PD1 between the first end and the base of the first transistor M1 or the parasitic diode PD2 between the second end and the base of the first transistor M1. However, the charging protection circuit 106b and the charging protection circuit 106a are still similar in operation. That is, when the voltage at the first end of the first transistor M1 is higher than the voltage at the second end of the first transistor M1, the base voltage of the first transistor M1 will be equal to the voltage at the first end of the first transistor M1 minus the threshold voltage of the first diode D1; conversely, when the voltage at the first end of the first transistor M1 is lower than the voltage at the second end of the first transistor M1, the base voltage of the first transistor M1 will be equal to the voltage at the second end of the first transistor M1 minus the threshold voltage of the second diode D2. In this way, regardless of which of the voltages at the first end and the second end of the first transistor M1 is higher, leakage current can be avoided under specific circumstances.

[0055] Please refer to Figure 3 , Figure 3 FIG. is a circuit block diagram of a charging protection circuit 106c according to another embodiment of the present invention. The charging protection circuit 106c is similar to Figure 2B the charging protection circuit 106b, with the difference that the charging protection circuit 106c further includes one or more first resistors R1. If there are multiple first resistors R1, the multiple first resistors R1 can be formed into a resistor circuit based on the multiple first resistors R1 by series connection, parallel connection, or a combination of series and parallel connections. Here, the example of connecting multiple first resistors R1 in series is taken. In this embodiment, the series-connected multiple first resistors R1 are connected between the first end and the second end of the first transistor M1 and are in parallel with the first transistor M1.

[0056] In some applications, it is necessary to identify whether the charging device 90 is connected to one of the first contact N1 and the second contact N2. For this purpose, a detection circuit (not shown) is provided to detect whether the charging device 90 is connected to one of the first contact N1 and the second contact N2. Benefiting from the setting of the first transistor M1, the minimum number of detection circuits required to achieve the above purpose is relatively small, and the details are described as follows.

[0057] In a case where a detection circuit is directly coupled to the second contact N2, if the charging device 90 is connected to the second contact N2, since the detection circuit is also coupled to the second contact N2, it can detect that the charging device 90 is connected to the second contact N2; if the charging device 90 is connected to the first contact N1, the voltage provided by the charging device 90 at the first contact N1 is coupled to the second contact N2 through the first resistor R1. Accordingly, the detection circuit directly coupled to the second contact N2 can also detect that the charging device 90 is connected to the first contact N1. Therefore, to achieve the above object, the minimum number of detection circuits required is only one. Similarly, in a case where a detection circuit is directly coupled to the first contact N1, only one detection circuit is also required to achieve the above object, which will not be elaborated herein.

[0058] Please refer to Figure 4A , Figure 4A FIG. 143 is a circuit block diagram of a charging protection circuit 106d according to another embodiment of the present invention. The charging protection circuit 106d is similar to Figure 3 the charging protection circuit 106c, except that the charging protection circuit 106d further includes a second transistor M2. A first end and a base of the second transistor M2 are coupled to the base of the first transistor M1. A second end of the second transistor M2 is coupled to the second end of the first transistor M1. A control end of the second transistor M2 is coupled to the first end of the first transistor M1.

[0059] In the second application, as described above, when the charging device 90 is connected from the first contact N1, there should be no current flowing from the first contact N1 to the second contact N2. However, in some embodiments, the determination of the control signal CS includes the voltage of the second contact N2. In the above case, when the second contact N2 is accidentally grounded, the first transistor M1 may be turned on unexpectedly due to the voltage of the control signal CS depending on the voltage of the second contact N2, such that the voltage difference between the control end and the second end (the first contact N1) of the first transistor M1 is greater than the threshold voltage of the first transistor M1, causing current to pass through. By providing the second transistor M2 to increase the threshold voltage of the first transistor M1, the possibility of a large current passing through the first transistor M1 when the second contact N2 is accidentally grounded in the second application can be effectively reduced or even avoided.

[0060] Specifically, in one embodiment, the following is adopted as Figure 6The control signal generation circuit 60 shown. The control signal generation circuit 60 includes transistors M61 and M62 and resistor R61, and the control signal CS is generated according to the signal EN, where the signal EN is an enable signal used to determine whether the transistor M62 is turned on or off. In the second application, when the enable signal EN turns off the transistor M62 (the transistor M62 is an NMOS in this example), the second contact N2 is grounded as a reference (the second contact N2 should be floating under normal conditions of the second application), and when the transistor M61 (the transistor M61 is a PMOS in this example) is turned on because the voltage of the first contact N1 is much greater than the voltage of the second contact N2, the drain voltage of the transistor M61 (i.e., the gate voltage of the first transistor M1) is the voltage division result of the on-resistance of the transistor M61 (non-ideal transistor) and the resistor R61, and its effect is to turn off the first transistor M1 to achieve the purpose of short-circuit protection. However, when the voltage difference between this voltage division result and the voltage of the first contact N1 is greater than the threshold voltage of the first transistor M1, the first transistor M1 will still be turned on, and then a large current will flow through the first transistor M1, which may still cause damage to the first transistor M1. Increasing the threshold voltage of the first transistor M1 can increase the gate-source voltage difference required to turn on the first transistor M1, thereby reducing the chance of the first transistor M1 being accidentally turned on in the above situation. Specifically, arranging the second transistor M2 between the base and the drain of the first transistor M1 can increase the threshold voltage of the first transistor M1 to solve the above problem. It should be noted that the source and drain of a transistor are determined by the voltage applied to it. In the above scenario, although Figure 6 one end of the transistor M61 that provides the control signal CS is labeled as the source, but since the voltage of the first contact N1 is greater than the voltage of the second contact N2, this end is actually the drain.

[0061] Please refer to Figure 4B , Figure 4B FIG. is a circuit block diagram of a charging protection circuit 106e according to another embodiment of the present invention. The charging protection circuit 106e is similar to the Figure 4A charging protection circuit 106d, except that the charging protection circuit 106e includes a plurality of first resistors R1, and the control terminal of the second transistor M2 is coupled between two of the serially connected first resistors R1 (i.e., the control terminal of the second transistor M2 is coupled to the series connection point between two first resistors R1), rather than being coupled to the first end of the first transistor M1. The control terminal of the second transistor M2 is coupled to the second contact N2 through one or more of the first resistors R1.

[0062] The control terminal of the second transistor M2 is coupled to the first terminal of the first transistor M1. This embodiment is applicable to the case where the withstand voltage of the second transistor M2 is relatively low. For example, when the charging voltage Vc is 5.5V and this charging voltage Vc is provided to the second contact N2, and the withstand voltage between the first terminal and the second terminal of the second transistor M2 is 5V, by making the voltage at the control terminal of the second transistor M2 equal to the voltage division between the first contact N1 and the second contact N2 to reduce the cross voltage between the source and the drain of the second transistor M2, it is possible to effectively avoid damage to the second transistor M2 due to insufficient withstand voltage, thereby improving the durability of the second transistor M2.

[0063] Please refer to Figure 5A , Figure 5A FIG. is a circuit block diagram of a charging protection circuit 106f according to another embodiment of the present invention. The charging protection circuit 106f is similar to Figure 4A the charging protection circuit 106d, except that the charging protection circuit 106f further includes a third transistor M3. A first terminal and a base of the third transistor M3 are coupled to the base of the first transistor M1. A second terminal of the third transistor M3 is coupled to the first terminal of the first transistor M1. A control terminal of the third transistor M3 is coupled to the second terminal of the first transistor M1. The function of the third transistor M3 is similar to that of the second transistor M2, which can increase the threshold voltage of the first transistor M1, thereby solving the problem that when the first contact N1 is accidentally referenced to ground in the first application, the first transistor M1 conducts and a large current passes through.

[0064] Please refer to Figure 5B , Figure 5B FIG. is a circuit block diagram of a charging protection circuit 106g according to another embodiment of the present invention. The charging protection circuit 106g is similar to Figure 5A the charging protection circuit 106f, except that the control terminal of the second transistor M2 in the charging protection circuit 106g is coupled between two of the first resistors R1 connected in series, rather than being coupled to the first terminal of the first transistor M1, and the control terminal of the third transistor M3 is coupled between two of the first resistors R1 connected in series, rather than being coupled to the second terminal of the first transistor M1. Compared with the charging protection circuit 106f, the cross voltage between the source and the drain of the second transistor M2 and the cross voltage between the source and the drain of the third transistor M3 can be reduced, thereby improving the durability of the second transistor M2 and the third transistor M3.

[0065] It should be noted that the above embodiments can be appropriately mixed and used according to requirements. For example, in the charging protection circuits 106d to 106g, the first diode D1 and the second diode D2 can be replaced with Figure 2AThe parasitic diodes PD1 and PD2 of the charging protection circuit 106a. For another example, in the charging protection circuits 106c, 106d, and 106f, one or more first resistors R1 connected in series between the first end and the second end of the first transistor M1 can be removed, and a detection circuit can be connected to the first contact point N1 and the second contact point N2 respectively to determine whether there is an access of the charging device 90.

[0066] In addition to the effect of avoiding the generation of leakage current, the charging protection circuit of the present invention further has a short-circuit protection function when the second contact point is accidentally referenced to ground in the second application. In addition, by coupling one or more first resistors connected in series between the first end and the second end of the first transistor, the need for separately designing a set of detection circuits for the first contact point and the second contact point can be eliminated.

[0067] Of course, the present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention. However, these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A wireless audio output device, characterized in that, comprising: a first contact coupled to a voltage stabilizing capacitor; a second contact; a third contact coupled to a reference ground; a charging control circuit coupled to the first contact; a signal receiving circuit coupled to the second contact; and a charging protection circuit, a first end of the charging protection circuit is coupled to the first contact and the charging control circuit, a second end of the charging protection circuit is coupled to the second contact and the signal receiving circuit, the charging protection circuit has a first state and a second state, in the first state, the charging protection circuit is turned on to couple the second contact to the first contact, in the second state, the charging protection circuit is not turned on to prevent the second contact from being coupled to the first contact, wherein one of the first contact and the second contact is used to be coupled to a first output end of a charging device for outputting a charging voltage or a communication signal, the third contact is used to be coupled to a second output end of the charging device, when the first contact is coupled to the first output end and the charging device outputs the charging voltage, the charging protection circuit switches to the second state to transfer the charging voltage to the charging control circuit, when the second contact is coupled to the first output end and the charging device outputs the charging voltage, the charging protection circuit switches to the first state to transfer the charging voltage to the charging control circuit, when the second contact is coupled to the first output end and the charging device outputs the communication signal, the charging protection circuit switches to the second state to transfer the communication signal to the signal receiving circuit.

2. The wireless audio output device according to claim 1, characterized in that, the charging protection circuit comprises: a first transistor, a first end of the first transistor is coupled to the second contact, a second end of the first transistor is coupled to the first contact, a control end of the first transistor receives a control signal, a base of the first transistor is floating, when the charging protection circuit is in the first state, the first transistor is turned on under the control of the control signal, when the charging protection circuit is in the second state, the first transistor is not turned on under the control of the control signal.

3. The wireless audio output device according to claim 1, characterized in that, the charging protection circuit comprises: a first transistor, a first end of the first transistor is coupled to the second contact, a second end of the first transistor is coupled to the first contact, a control end of the first transistor receives a control signal, when the charging protection circuit is in the first state, the first transistor is turned on under the control of the control signal, when the charging protection circuit is in the second state, the first transistor is not turned on under the control of the control signal; a first diode, a first end of the first diode is coupled to a base of the first transistor, a second end of the first diode is coupled to the first end of the first transistor; and a second diode, a first end of the second diode is coupled to the base of the first transistor, a second end of the second diode is coupled to the second end of the first transistor.

4. The wireless audio output device according to claim 3, wherein, the charging protection circuit further includes: one or more first resistors, connected in series between the first end and the second end of the first transistor.

5. The wireless audio output device according to claim 4, wherein, the charging protection circuit further includes: a second transistor, a first end and a base of the second transistor are coupled to the base of the first transistor, a second end of the second transistor is coupled to the second end of the first transistor, and a control end of the second transistor is coupled to the first end of the first transistor.

6. The wireless audio output device according to claim 4, wherein, the charging protection circuit further includes: a second transistor, a first end and a base of the second transistor are coupled to the base of the first transistor, a second end of the second transistor is coupled to the second end of the first transistor, there are a plurality of the first resistors, and a control end of the second transistor is coupled between two of the plurality of first resistors.

7. The wireless audio output device according to claim 5, wherein, the charging protection circuit further includes: a third transistor, a first end and a base of the third transistor are coupled to the base of the first transistor, a second end of the third transistor is coupled to the first end of the first transistor, and a control end of the third transistor is coupled to the second end of the first transistor.

8. The wireless audio output device according to claim 6, wherein, the charging protection circuit further includes: a third transistor, a first end and a base of the third transistor are coupled to the base of the first transistor, a second end of the third transistor is coupled to the first end of the first transistor, and a control end of the third transistor is coupled between two of the plurality of first resistors.

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