Switching device

Abstract

To provide a switch device capable of performing overvoltage protection.SOLUTION: A switch device 100 comprises a first node N1, a switch unit SU1, an adjustment switch SWA, an impedance element R1, a second node N2, and a detection unit DU. A first terminal of the switch unit is coupled to the first node. A first terminal and a second terminal of the adjustment switch are coupled to a second terminal of the switch unit and a reference voltage terminal 150, respectively. A first terminal and a second terminal of the impedance element are coupled to the first terminal and the second terminal of the adjustment switch, respectively. The detection unit is coupled to the second node, a control terminal of the switch unit, and a control terminal of the adjustment switch. The detection unit detects a node signal SN of the second node, and generates a first control signal S1 and a second control signal S2 so as to control the switch unit and the adjustment switch.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a switch device, and more particularly to a switch device capable of providing overvoltage protection.

Background Art

[0002] Generally, when designing a switch device, it is necessary to consider impedance matching between a transmission end and a reception end in order to reduce the influence of impedance mismatch. For example, reflection may occur during signal transmission. This phenomenon poses a risk of damaging the switch device and / or the backend circuit coupled to the switch device due to overvoltage.

Summary of the Invention

[0003] One embodiment provides a switch device, which includes a first node, a first switch unit, an adjustment switch, an impedance element, a second node, and a detection unit. The first node is located on a first path formed between a first signal transmission / reception terminal and a second signal transmission / reception terminal. The first switch unit includes a first terminal coupled to the first node, a control terminal, and a second terminal. The adjustment switch includes a first terminal coupled to the second terminal of the first switch unit, a control terminal, and a second terminal coupled to a reference voltage terminal. The impedance element includes a first terminal coupled to the first terminal of the adjustment switch and a second terminal coupled to the second terminal of the adjustment switch. The second node is located on a second path formed between the first node and the reference voltage terminal. The detection unit is configured to detect a node signal at the second node and control the first switch unit and the adjustment switch according to the node signal, and includes a first input terminal coupled to the second node, a first output terminal coupled to the control terminal of the first switch unit, and a second output terminal coupled to the control terminal of the adjustment switch.

Brief Description of the Drawings

[0004] [Figure 1] Shows a switch device according to an embodiment. [Figure 2] Another embodiment of a switch device is shown. [Figure 3] The following describes an embodiment, showing the switch unit of the switch device shown in Figure 1 or Figure 2. [Figure 4] Another embodiment is shown, illustrating the switch unit of the switch device shown in Figure 1 or Figure 2. [Figure 5] The following describes an embodiment, showing the detection unit of the switch device shown in Figure 1 or Figure 2. [Figure 6] Another embodiment is shown, illustrating the detection unit of the switch device shown in Figure 1 or Figure 2. [Figure 7] This figure relates to an embodiment and shows the rectifier of the detection unit shown in Figure 5 or Figure 6. [Figure 8] The low-pass filter of the detection unit shown in Figure 5 or Figure 6 relates to an embodiment. [Figure 9] Another embodiment of a switch device is shown. [Figure 10] The following describes an embodiment and an application of the switch device shown in Figure 1, Figure 2, or Figure 9. [Modes for carrying out the invention]

[0005] Referring to the attached drawings, exemplary embodiments are described below in detail so as to be easily understood by a person of ordinary technical skill. The concept of the invention may be embodied in various forms, but is not limited to the exemplary embodiments described herein. Descriptions of well-known parts are omitted for clarity, and the same reference numerals refer to the same elements throughout.

[0006] Figure 1 shows a switch device 100 according to one embodiment. The switch device 100 may include a node N1, a switch unit SU1, an adjustment switch SWA, an impedance element R1, a node N2, and a detection unit DU. As shown in Figure 1, a path PTH1 may be formed between the signal transmission and reception terminals 110 and 130. According to one embodiment, path PTH1 may be a signal transmission path. The signal transmission and reception terminals 110 and 130 may be used to transmit and receive external signals. Node N1 may be located on path PTH1. The switch unit SU1 may include a first terminal coupled to node N1, a control terminal, and a second terminal. The adjustment switch SWA may include a first terminal coupled to the second terminal of the switch unit SU1, a control terminal, and a second terminal coupled to a reference voltage terminal 150. The reference voltage terminal 150 can supply a reference voltage VF. The reference voltage VF may be 0 volts or another fixed voltage. The impedance element R1 may include a first terminal coupled to the first terminal of the adjustment switch SWA and a second terminal coupled to the second terminal of the adjustment switch SWA. The impedance element R1 may include a resistor, a capacitor, an inductor, or any combination formed of at least one of the above three components. In Figure 1, the impedance element R1 includes a resistor as an example. Embodiments are not limited thereto. The path PTH2 may be formed between node N1 and the reference voltage terminal 150. According to one embodiment, the path PTH2 may be a shunt path. Node N2 may be located on the path PTH2. In Figure 1, node N2 is located between switch unit SU1 and adjustment switch SWA as an example, but embodiments are not limited thereto. The detection unit DU may include a first input terminal coupled to node N2, a first output terminal coupled to the control terminal of switch unit SU1, and a second output terminal coupled to the control terminal of adjustment switch SWA. The detection unit DU may be used to detect the node signal SN at node N2 and to control the switch unit SU1 and the adjustment switch SWA according to the node signal SN. The detection unit DU may also control the adjustment switch SWA to stop or start the use of the impedance element R1.According to one embodiment, the node signal SN may be associated with an external signal. According to one embodiment, the external signal and the node signal SN may be alternating current (AC) voltage signals such as radio frequency (RF) signals.

[0007] According to one embodiment, when the impedances corresponding to the signal transmission / reception terminals 110 and 130 are matched, an external signal can be transmitted and received between the signal transmission / reception terminals 110 and 130. In this case, the node signal SN detected by the detection unit DU may be weaker than a predetermined value, and the switch unit SU1 may be turned off to prevent the external signal from leaking into an unused path (e.g., path PTH2). Thus, energy loss can be reduced. The adjustment switch SWA may be turned on to stop the use of the impedance element R1. According to one embodiment, the predetermined value may be selected according to the actual application and design requirements. The impedance corresponding to the signal transmission / reception terminal 110 may be the equivalent impedance ZS, which is obtained by looking from node N1 along direction d1 toward the signal transmission / reception terminal 110. The impedance corresponding to the signal transmission / reception terminal 130 may be the equivalent impedance ZL1, which is obtained by looking from node N1 along direction d2 toward the signal transmission / reception terminal 130. Impedance matching may mean that the equivalent impedances ZS and ZL1 are complex conjugates of each other. Furthermore, the impedance of path PTH2 may be the equivalent impedance ZT, obtained by looking from node N1 along direction d3 toward reference voltage terminal 150. Although the impedance element R1 is not used, the equivalent impedance ZT is high because the switched-off switch unit SU1 may be equivalent to an open circuit.

[0008] According to one embodiment, during the operation of transmitting and receiving an external signal, if the signal transmission / reception terminal 130 is affected externally to increase its impedance (i.e., the equivalent impedance ZL1 is increased), it may cause an impedance mismatch between the signal transmission / reception terminals 110 and 130, and may also cause signal reflection. For example, during the process of transmitting an external signal from the signal transmission / reception terminal 110 to the signal transmission / reception terminal 130, a portion of the external signal may be reflected from the signal transmission / reception terminal 130 to the signal transmission / reception terminal 110. The reflected external signal may be added to the transmitted external signal. Since the switched-off switch unit SU1 may be considered a capacitor depending on its electrical characteristics, the externally transmitted signal, with the externally reflected signal added, may further leak through the switched-off switch unit SU1 to the path PTH2, resulting in the node signal SN detected by the detection unit DU becoming stronger than a predetermined value. As a result, the switch device 100 and / or the backend circuit coupled to the switch device 100 may be damaged by overvoltage. To avoid damage, the detection unit DU may be used to turn on the switch unit SU1 and turn off the adjustment switch SWA to begin using the impedance element R1. The impedance element R1 can provide an impedance (represented as ZR1). According to one embodiment, an impedance element R1 may be selected such that the impedance ZR1 is between 5Ω and 200Ω. Also, since the switched-on switch unit SU1 can be considered as a resistor depending on its electrical characteristics, the switched-on switch unit SU1 can provide an impedance (represented as ZSU1). In other words, the equivalent impedance ZT may be considered as the impedance generated by connecting the impedance element R1 (having impedance ZR1) and the switch unit SU1 (having impedance ZSU1) in series. Since the switched-on switch unit SU1 may be equivalent to a short circuit, and the impedance element R1 has a low impedance, the equivalent impedance ZT may be a low impedance.The impedance corresponding to the signal transmission / reception terminal 130 may be the equivalent impedance ZL2 obtained by looking from the signal transmission / reception terminal 110 toward the signal transmission / reception terminal 130 along direction d4, and can therefore be considered as the impedance generated by connecting equivalent impedances ZL1 and ZT in parallel. Accordingly, the equivalent impedance ZL2 can be lower than the equivalent impedance ZL1. In this way, the impedance corresponding to the signal transmission / reception terminal 130, which has increased due to external factors, can be reduced by connecting the equivalent impedance ZT in parallel. As a result, the impedance corresponding to the signal transmission / reception terminal 130 can be adjusted for impedance matching. Impedance matching may mean that the equivalent impedances ZS and ZL2 are complex conjugates of each other. Signal reflections caused by impedance mismatch can also be reduced. Accordingly, improving the integrity of the transmitted and received signals is useful and can provide overvoltage protection to the switch device 100 and / or the backend circuit coupled to the switch device 100. Accordingly, the node signal SN detected by the detection unit DU can be weaker than a predetermined value. Based on the node signal SN, the detection unit DU turns off the switch unit SU1 and then turns on the adjustment switch SWA again.

[0009] According to one embodiment, when the signal transmission / reception terminals 110 and 130 stop transmitting and receiving external signals, the detection unit DU can be used to turn on the switch unit SU1 and the adjustment switch SWA, and the external signals on the signal transmission / reception terminals 110 and 130 can be shunted to the reference voltage terminal 150. In this way, undesirable operation of the transmitted and received signals can be prevented from occurring between the signal transmission / reception terminals 110 and 130, and the isolation between the signal transmission / reception terminals 110 and 130 can be greatly increased.

[0010] According to one embodiment, as shown in Figure 1, the detection unit DU may further include a second input terminal for receiving a base voltage VTH. The base voltage VTH may be a fixed voltage and may be equal to the predetermined value described above. The detection unit DU may generate a first control signal S1 and a second control signal S2 in response to the node signal SN and the base voltage VTH. The first control signal S1 may be output via a first output terminal of the detection unit DU to control a switch unit SU1. The second control signal S2 may be output via a second output terminal of the detection unit DU to control an adjustment switch SWA.

[0011] According to one embodiment, the first control signal S1 may have an enable level higher than the threshold voltage of the switch unit SU1 and a disable level lower than the threshold voltage of the switch unit SU1 in order to switch the switch unit SU1 on and off. The second control signal S2 may have an enable level higher than the threshold voltage of the regulating switch SWA and a disable level lower than the threshold voltage of the regulating switch SWA in order to switch the regulating switch SWA on and off. However, if the reference voltage VF approaches the disable level of the first control signal S1 excessively during operation to send and receive an external signal, the switch unit SU1 may not be effectively turned off.

[0012] Figure 2 shows a switch device 200 according to another embodiment. Figure 2 may be the same as Figure 1. However, the switch device 200 shown in Figure 2 may further include a DC blocking capacitor CB. The DC blocking capacitor CB is coupled between the second terminal of the switch unit SU1 and the first terminal of the adjustment switch SWA to block the reference voltage VF, thereby reducing the influence of the reference voltage VF on the switch unit SU1. According to one embodiment, the bias voltage applied to the second terminal of the switch unit SU1 may be further increased to effectively turn off the switch unit SU1. Furthermore, the DC blocking capacitor CB can provide an impedance (denoted as ZCB). In other words, when the switch unit SU1 is turned on and the adjustment switch SWA is turned off using the detection unit DU, the equivalent impedance ZT may be considered to be the impedance generated by coupling the switch unit SU1 (having impedance ZSU1), the DC blocking capacitor CB (having impedance ZCB), and the impedance element R1 (having impedance ZR1) in series. Thus, the impedance corresponding to the signal transmission / reception terminal 130, which has increased due to an external factor (i.e., an increased equivalent impedance ZL1), can be reduced by coupling equivalent impedance ZT in parallel (i.e., equivalent impedances ZT and ZL1 coupled in parallel). Therefore, the circuit structure of the switch device 200 can provide the same effect as the switch device 100 shown in Figure 1. In yet another embodiment, the DC blocking capacitor CB may be omitted when the disable level of the first control signal S1 is a negative voltage level.

[0013] Figure 3 shows a switch unit SU1 of the switch device 100 in Figure 1 or the switch device 200 in Figure 2, relating to one embodiment. As shown in Figure 3, the switch unit SU1 may include a switch SW1. The switch SW1 may include a first terminal connected to the first terminal of the switch unit SU1, a control terminal connected to the control terminal of the switch unit SU1, and a second terminal connected to the second terminal of the switch unit SU1.

[0014] FIG. 4 relates to another embodiment and shows the switch unit SU1 of the switch device 100 in FIG. 1 or the switch device 200 in FIG. 2. As shown in FIG. 4, the switch unit SU1 may include n switches SW11 to SW1n, and each of the switches SW11 to SW1n may include a first terminal, a control terminal, and a second terminal. The control terminals of each of the switches SW11 to SW1n are connected to the control terminal of the switch unit SU1. The first terminal of the i-th switch SW1i is coupled to the second terminal of the (i - 1)-th switch SW1(i - 1), and the second terminal of the i-th switch SW1i is coupled to the first terminal of the (i + 1)-th switch SW1(i + 1). The first terminal of the first switch SW11 is coupled to the first terminal of the switch unit SU1. The second terminal of the n-th switch SW1n is coupled to the second terminal of the switch unit SU1. In other words, the n switches SW11 to SW1n may form a stack structure. Here, n and i are positive integers, and 1 < i < n. According to another embodiment, the switch unit SU1 may include a plurality of control terminals, and the number of the first output terminals of the detection unit DU may correspond to the number of the control terminals of the switch unit SU1. In this state, the control terminals of the switches SW11 to SW1n may be respectively coupled to the corresponding control terminals of the plurality of control terminals of the switch unit SU1.

[0015] According to one embodiment, each of the above-described adjustment switch SWA, switch SW1, and switches SW11 to SW1n may be a field effect transistor (FET). Therefore, for each of the adjustment switch SWA, switch SW1, and switches SW11 to SW1n, the first terminal may be a drain terminal, the second terminal may be a source terminal, and the control terminal may be a gate terminal.

[0016] Figure 5 shows a detection unit DU shown in the switch device 100 of Figure 1 or the switch device 200 of Figure 2, relating to one embodiment. As shown in Figure 5, the detection unit DU may include a comparator 510. The comparator 510 may include a first terminal connected to the first input terminal of the detection unit DU and receiving a detection voltage Vdet, a second terminal connected to the second input terminal of the detection unit DU and receiving a base voltage VTH, and an output terminal that outputs a comparison signal Sc. According to one embodiment, the detection voltage Vdet may be positively correlated with the node signal SN. The comparison signal Sc may be at a high level when the detection voltage Vdet is higher than the base voltage VTH (i.e., when the node signal SN is greater than a predetermined value). The comparison signal Sc may be at a low level when the detection voltage Vdet is lower than the base voltage VTH (i.e., when the node signal SN is less than a predetermined value).

[0017] As shown in Figure 5, the detection unit DU may further include a rectifier 520. The rectifier 520 may include a first terminal connected to the first input terminal of the detection unit DU and receiving a node signal SN, and a second terminal outputting a rectified signal SR. The rectifier 520 can rectify the node signal SN to generate a rectified signal SR.

[0018] As shown in Figure 5, the detection unit DU may further include a low-pass filter 530. The low-pass filter 530 may include a first terminal coupled to the second terminal of the rectifier 520 for receiving a rectified signal SR, and a second terminal for outputting a detection voltage Vdet. The low-pass filter 530 can perform low-pass filtering on the rectified signal SR to generate the detection voltage Vdet.

[0019] As shown in Figure 5, the detection unit DU may further include a logic element 540. The logic element 540 may include an input terminal connected to the output terminal of the comparator 510 for receiving a comparison signal Sc, a first output terminal connected to the first output terminal of the detection unit DU for outputting a first control signal S1, and a second output terminal connected to the second output terminal of the detection unit DU for outputting a second control signal S2. According to one embodiment, the logic element 540 may be a decoder. The logic element 540 can generate a first control signal S1 and a second control signal S2 in response to the comparison signal Sc. Furthermore, when the comparison signal Sc is at a high level, the first control signal S1 is at an enable level and the second control signal S2 is at a disabled level. When the comparison signal Sc is at a low level, the first control signal S1 is at a disabled level and the second control signal S2 is at an enable level.

[0020] Figure 6 relates to another embodiment and shows a detection unit DU of the switch device 100 of Figure 1 or the switch device 200 of Figure 2. Figure 6 may be the same as Figure 5, but the detection unit DU may further include a hold unit 650 as shown in Figure 6. The hold unit 650 may include an input terminal connected to the output terminal of the comparator 510 to receive a comparison signal Sc, and an output terminal that outputs a hold signal Sd. The logic element 540 may include an input terminal connected to the output terminal of the hold unit 650 to receive a hold signal Sd, a first output terminal connected to the first output terminal of the detection unit DU to output a first control signal S1, and a second output terminal connected to the second output terminal of the detection unit DU to output a second control signal S2. The logic element 540 may generate the first control signal S1 and the second control signal S2 in response to the hold signal Sd. Furthermore, if the comparison signal Sc is at a high level, the hold unit 650 may hold the comparison signal Sc at a high level for a predetermined time interval (e.g., 200 microseconds), thereby generating a hold signal Sd. In this way, the logic element 540 can increase the time it turns on the switch unit SU1 and turns off the adjustment switch SWA depending on the duration that the hold signal Sd is at a high level, and thus the overvoltage protection time is extended.

[0021] FIG. 7 relates to an embodiment and shows the rectifier 520 of the detection unit DU of FIG. 5 or FIG. 6. The rectifier 520 may include an impedance element R2 and a diode 527. The impedance element R2 may include a first terminal coupled to the first terminal of the rectifier 520 and a second terminal coupled to the second terminal of the rectifier 520. The impedance element R2 may be used to divide the node signal SN in order to generate a divided voltage signal SDV. According to an embodiment, the impedance element R2 may have an impedance of 50 to 2000 Ω in order to avoid affecting the operation on the path PTH2. The impedance element R2 may include a resistor, a capacitor, an inductor, or any combination formed by at least one of the above three components. In FIG. 7, the impedance element R2 including a resistor is merely an example and does not limit the scope of the embodiment. The diode 527 may include a first terminal coupled to the second terminal of the impedance element R2 and a second terminal coupled to the reference voltage terminal 150. The diode 527 can rectify the divided voltage signal SDV to generate a rectified signal SR. According to an embodiment, the first terminal of the diode 527 may be an anode and the second terminal of the diode 527 may be a cathode. FIG. 7 is an example, and the structure of the rectifier 520 is not limited thereto.

[0022] FIG. 8 shows a low-pass filter 530 of the detection unit DU in FIG. 5 or FIG. 6 according to one embodiment. The low-pass filter 530 may include an impedance element R3 and a capacitor 538. The impedance element R3 may include a first terminal coupled to the first terminal of the low-pass filter 530 and a second terminal coupled to the second terminal of the low-pass filter 530. According to an embodiment, the impedance element R3 may include a resistor, a capacitor, an inductor, or any combination formed by at least one of the three components. In FIG. 8, the impedance element R3 including a resistor is merely an example and does not limit the scope of the embodiment. The capacitor 538 may include a first terminal coupled to the second terminal of the impedance element R3 and a second terminal coupled to the reference voltage terminal 150.

[0023] FIG. 9 shows a switch device 900 according to another embodiment. FIG. 9 may be the same as FIG. 2, but as shown in FIG. 9, the switch device 900 may further include a switch unit SU2. The switch unit SU2 may be disposed in the path PTH1. The switch unit SU2 may include a first terminal coupled to the signal transceiver terminal 110, a control terminal for receiving a third control signal S3, and a second terminal coupled to the signal transceiver terminal 130. In FIG. 9, as an example, the switch unit SU2 is disposed between the node N1 and the signal transceiver terminal 130. The embodiment is not limited thereto. According to yet another embodiment, the second terminal of the switch unit SU2 may be coupled to the node N1. In other words, the switch unit SU2 may be coupled between the signal transceiver terminal 110 and the node N1. The circuit structure of the switch unit SU2 may be the same as the circuit structure of the aforementioned switch unit SU1 and will not be described repeatedly. Note that the number and size (if any) of the switch(es) of the switch unit SU2 may be different from those of the switch unit SU1.

[0024] According to one embodiment, the detection unit DU can control the switch unit SU2 depending on whether the signal transmission / reception terminals 110 and 130 transmit or receive an external signal. As shown in Figure 9, the detection unit DU can further generate a third control signal S3. The detection unit DU includes a third output terminal, which is connected to a control terminal of the switch unit SU2 and outputs a third control signal S3 for controlling the switch unit SU2. According to another embodiment, the switch unit SU2 may include a plurality of control terminals, and the number of third output terminals of the detection unit DU may correspond to the number of control terminals of the switch unit SU2. According to one embodiment, the third control signal S3 may have an enable level higher than the threshold voltage of the switch unit SU2 and a disable level lower than the threshold voltage of the switch unit SU2 for turning the switch unit SU2 on or off. According to yet another embodiment, the third control signal S3 may be supplied by another circuit instead of the detection unit DU.

[0025] According to one embodiment, when the impedances corresponding to the signal transmission / reception terminals 110 and 130 are matched, the third control signal S3 may be set to an enable level to turn on the switch unit SU2, and external signals may be transmitted and received between the signal transmission / reception terminals 110 and 130. If the impedances corresponding to the signal transmission / reception terminals 110 and 130 are mismatched during the operation of transmitting and receiving external signals, the third control signal S3 can be maintained at an enable level to keep the switch unit SU2 on. When the operation of transmitting and receiving external signals between the signal transmission / reception terminals 110 and 130 is stopped, the third control signal S3 may be set to a disable level to turn off the switch unit SU2. The operation of the switch unit SU1 and the adjustment switch SWA can be as described above and will not be described again. According to one embodiment, when the size(s) of the switches(s) included in the switch unit SU2 is larger than the size(s) of the switches(s) included in the switch unit SU1, the impedance of the turned-on switch unit SU2 can be smaller than the impedance of the turned-on switch unit SU1. Here, the switched-on switch units SU1 and SU2 may be considered as resistors according to their electrical characteristics. In this state, with respect to the equivalent impedance ZL2 obtained by looking from the signal transmission / reception terminal 110 along direction d4 toward the signal transmission / reception terminal 130, the impedance of the switched-on switch unit SU2 when the detection unit DU turns on switch units SU1 and SU2 and turns off adjustment switch SWA may be arbitrarily omitted.

[0026] Figure 10 relates to one embodiment and shows an application of the switch device 100, 200, or 900 shown in Figure 1, Figure 2, or Figure 9. According to one embodiment, the signal transmitting / receiving terminal 110 may be coupled to the amplifier 1060. The signal transmitting / receiving terminal 130 may be coupled to the antenna 1070. The amplifier 1060 may be a power amplifier or a low-noise amplifier. For example, if the impedances of the signal transmitting / receiving terminals 110 and 130 are matched, (i) if the amplifier 1060 is a power amplifier, the external signal may be a signal amplified by the amplifier 1060, and the external signal can be transmitted to the antenna 1070 via the switch device 100, 200, or 900. (ii) If the amplifier 1060 is a low-noise amplifier, the external signal may be a signal received by the antenna 1070, and the external signal can be transmitted to the amplifier 1060 via the switch device 100, 200, or 900.

[0027] In summary, each of the switch devices 100, 200, and 900 can dynamically control the switch unit SU1 and the regulating switch SWA in order to provide overvoltage protection for the switch devices and / or the backend circuits coupled to the switch devices. Thus, each of the switch devices 100, 200, and 900 and / or the backend circuits coupled to the switch devices are prevented from being damaged by overvoltage.

[0028] Those skilled in the art will readily understand that many modifications and changes to the apparatus and method may be made while retaining the teachings of the present invention. Accordingly, the above disclosure should be construed as being limited only to the scope of the claims appended herein.

Claims

1. A first node located in a first path formed between a first signal transmission / reception terminal and a second signal transmission / reception terminal, which are configured to transmit and receive external signals, A first switch unit including a first terminal connected to the first node, a control terminal, and a second terminal, An adjustment switch including a first terminal connected to the second terminal of the first switch unit, a control terminal, and a second terminal connected to the reference voltage terminal, An impedance element including a first terminal coupled to the first terminal of the adjustment switch and a second terminal coupled to the second terminal of the adjustment switch, A second node located in a second path formed between the first node and the reference voltage terminal, The detection unit is configured to detect a node signal, which is an alternating current (AC) voltage signal associated with the external signal, at the second node, and to control the first switch unit and the adjustment switch according to the node signal, and includes a first input terminal connected to the second node, a first output terminal connected to the control terminal of the first switch unit, and a second output terminal connected to the control terminal of the adjustment switch. A DC blocking capacitor is provided, which includes a first terminal connected to the second terminal of the first switch unit and a second terminal connected to the first terminal of the adjustment switch. The detection unit further includes a second input terminal configured to receive a base voltage, The detection unit generates a first control signal and a second control signal in accordance with the node signal and the base voltage, the first control signal is output via the first output terminal of the detection unit to control the first switch unit, and the second control signal is output via the second output terminal of the detection unit to control the adjustment switch. The detection unit further, A comparator comprising: a first terminal connected to the first input terminal of the detection unit and configured to receive a detection voltage positively correlated with the node signal; a second terminal connected to the second input terminal of the detection unit and configured to receive the base voltage; and an output terminal configured to output a comparison signal, The comparison signal is at a high level when the detected voltage is higher than the base voltage. A switch device in which, when the node signal is stronger than a predetermined value, the detection unit is configured to turn on the first switch unit and turn off the adjustment switch.

2. The switch device according to claim 1, wherein the second node is located between the first switch unit and the adjustment switch.

3. The switch device according to claim 1, wherein the detection unit is configured to turn off the first switch unit and turn on the adjustment switch when the node signal is weaker than a predetermined value.

4. The switch device according to claim 1, wherein the detection unit is configured to turn on the first switch unit and the adjustment switch when the transmission and reception operation of the external signal is stopped.

5. The switch device according to claim 1, wherein the detection unit controls the adjustment switch to stop or start using the impedance element, and the equivalent impedance of the second path is a first value when the impedance element is not used, and the equivalent impedance of the second path is a second value lower than the first value when the impedance element is used.

6. The detection unit further, The switch device according to claim 1, comprising a rectifier configured to rectify the node signal in order to generate a rectified signal, the rectifier having a first terminal connected to the first input terminal of the detection unit and configured to receive the node signal, and a second terminal configured to output the rectified signal.

7. The detection unit further, The switch device according to claim 6, comprising a low-pass filter configured to perform low-pass filtering on the rectified signal to generate the detection voltage, the low-pass filter having a first terminal connected to the second terminal of the rectifier and configured to receive the rectified signal, and a second terminal configured to output the detection voltage.

8. The detection unit further, The switch device according to claim 7, comprising a logic element configured to generate a first control signal and a second control signal in accordance with the comparison signal, the logic element having an input terminal connected to the output terminal of the comparator and configured to receive the comparison signal, a first output terminal connected to the first output terminal of the detection unit and configured to output the first control signal, and a second output terminal connected to the second output terminal of the detection unit and configured to output the second control signal.

9. The detection unit further, A hold unit configured to generate a hold signal by holding the comparison signal at the high level for a predetermined time interval when the comparison signal is at the high level, the hold unit having an input terminal connected to the output terminal of the comparator and configured to receive the comparison signal, and an output terminal configured to output the hold signal, The switch device according to claim 7, comprising a logic element configured to generate a first control signal and a second control signal in response to the hold signal, the logic element having an input terminal connected to the output terminal of the hold unit and configured to receive the hold signal, a first output terminal connected to the first output terminal of the detection unit and configured to output the first control signal, and a second output terminal connected to the second output terminal of the detection unit and configured to output the second control signal.

10. The switch device according to claim 1, further comprising a second switch unit including a first terminal connected to the first signal transmitting / receiving terminal, a control terminal configured to receive a third control signal, and a second terminal connected to the second signal transmitting / receiving terminal.

11. When the impedances corresponding to the first signal transmission / reception terminal and the second signal transmission / reception terminal are matched, the third control signal is at the enable level, thereby turning on the second switch unit to transmit and receive external signals between the first signal transmission / reception terminal and the second signal transmission / reception terminal. The switch device according to claim 10, wherein, during the operation of transmitting and receiving the external signal, if the impedances corresponding to the first signal transmitting / receiving terminal and the second signal transmitting / receiving terminal become mismatched with each other, the third control signal is maintained at the enable level that keeps the second switch unit on.

12. The switch device according to claim 11, wherein the third control signal is at a disabled level so as to turn off the second switch unit when the transmission and reception operation of the external signal between the first signal transmission / reception terminal and the second signal transmission / reception terminal is stopped.

13. The switch device according to claim 1, wherein the impedance element has an impedance between 5Ω and 200Ω.

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