switching device

Abstract

This invention relates to a switching device including a first circuit. The first circuit has a first terminal coupled between a first terminal and a second terminal, and a second terminal coupled between the first and second terminals, or coupled to a third terminal. The first circuit includes a first switch and a second switch. The first switch is coupled between the first and second terminals of the first circuit and is turned on or off according to a first control signal. The second switch is connected in parallel with the first switch and is turned on or off according to a second control signal. The first and second switches contain transistors of the same type. In surge protection mode, the second switch is turned on to discharge surge current.

Description

Technical Field

[0001] This invention relates to a switching device, and more particularly to a switching device that can improve switching speed. Background Technology

[0002] In the prior art, in order to ensure that the switching device has a certain degree of electrostatic discharge protection capability, a large-sized transistor is often set in the shunt circuit to effectively dissipate the electrostatic discharge current.

[0003] However, the large-size transistors placed in the shunt circuit provide large parasitic capacitances during the switching process, which reduces the switching speed of the switching device and affects the performance of signal switching speed. Summary of the Invention

[0004] The present invention provides a switching device that can improve the switching speed of the switching device and / or enhance the surge current discharge capability in surge protection mode.

[0005] The switching device of the present invention includes a first circuit. The first circuit has a first terminal coupled between a first terminal and a second terminal, and a second terminal coupled between the first and second terminals, or coupled to a third terminal. The first circuit includes a first switch and a second switch. The first switch is coupled between the first and second terminals of the first circuit and is turned on or off according to a first control signal. The second switch is connected in parallel with the first switch and is turned on or off according to a second control signal. The first and second switches contain transistors of the same type. In surge protection mode, the second switch is turned on to discharge surge current.

[0006] Based on the above, the present invention provides a first switch and a second switch in the switching device. In normal mode, the first switch can be used for switching signal transmission, and the second switch can be used to improve the switching speed of the first switch. In surge protection mode, the second switch can be used to assist in dissipating surge current. The switching device of the present invention can improve the switching speed of the switching device and / or enhance the surge current dissipation capability. Attached Figure Description

[0007] Figure 1 A schematic diagram of a switching device according to an embodiment of the present invention is shown. Figure 2 A schematic diagram of a switching device according to another embodiment of the present invention is shown. Figure 3 A schematic diagram of a switching device according to another embodiment of the present invention is shown. Figure 4 A schematic diagram of a switching device according to another embodiment of the present invention is shown. Figure 5AA waveform diagram illustrating one embodiment of the control signal of the shunt circuit in the switching device of the present invention is shown. Figure 5B A waveform diagram illustrating another embodiment of the control signal of the shunt circuit in the switching device of the present invention is shown. Figure 6A A schematic diagram illustrating an embodiment of the shunt circuit in the switching device of the present invention is shown. Figure 6B as well as Figure 6C Schematic diagrams illustrating other embodiments of the shunt circuit in the switching device according to embodiments of the present invention are shown respectively. Figure 7A Draw Figure 6A The waveform diagram of one embodiment of the shunt circuit. Figure 7B Draw Figure 6A The waveform diagram of another embodiment of the shunt circuit of the implementation method. Figure 8A as well as Figure 8B Schematic diagrams illustrating other embodiments of the shunt circuit in the switching device according to embodiments of the present invention are shown respectively. Figure 9 A schematic diagram of a switching device according to another embodiment of the present invention is shown. [Symbol Explanation] 101, 102, 301, 302, 900: Switching devices Δt1, Δt2: During constant potential A1, A2, B1, B2: Ends E1~E4, EC: Terminal R1~R4, RB: Resistors SH1, SH2, 600, 601, 602: Circuits SW1~SW4, 810-1, 820-1, 810-2, 820-2, SW1A, SW1B: Switches T1~T3, T21~T2N, T31~T3M, T1A, T1B: Transistors TA: Multigate transistor tP1, tP2: Period VB: Base voltage VC1~VC4: Control signals Detailed Implementation

[0008] Please refer to Figure 1 and Figure 2 , Figure 1 and Figure 2 A schematic diagram illustrating switching devices 101 and 102 according to an embodiment of the present invention is shown.

[0009] In one embodiment, such as Figure 1 As shown, the switching device 101 includes a first circuit SH1 and a switch SW3. The first terminal A1 and the second terminal A2 of the first circuit SH1 are coupled to the current path formed between the first terminal E1 and the second terminal E2. In this embodiment, the first terminal A1 of the first circuit SH1 is coupled to the first terminal E1, and the second terminal A2 is coupled to the second terminal E2. In this embodiment, the first terminal B1 of the switch SW3 is coupled to the first terminal E1 and the first terminal A1 of the first circuit SH1, and the second terminal B2 of the switch SW3 is coupled to the third terminal E3. In another embodiment, as... Figure 2 As shown, the first terminal B1 of switch SW3 can also be coupled to the second terminal A2 and the second terminal E2 of the first circuit SH1. In the above embodiment, switch SW3 is turned on or off according to control signal VC3. In a further embodiment, switch SW3 may include transistor T3, and the control terminal of transistor T3 is used to receive control signal VC3.

[0010] In the above description, the first circuit SH1 can be used to switch signals between the first terminal E1 and the second terminal E2, and the switch SW3 can be used for shunt operation. For example, when the first circuit SH1 is turned off so that the signal is not transmitted between the first terminal E1 and the second terminal E2, the switch SW3 is turned on. However, the present invention is not limited to this. In other embodiments, the switch SW3 can be used to switch signals between the first terminal E1 and the second terminal E2, and the first circuit SH1 can be a shunt circuit, which can be used to perform shunt operation when it is turned on.

[0011] Please refer to the following: Figure 3 and Figure 4 The diagram illustrates a switching device according to another embodiment of the present invention. The switching device 301 includes a first shunt circuit SH1 and a switch SW3. A first terminal B1 of the switch SW3 is coupled to a first terminal E1, and a second terminal B2 is coupled to a second terminal E2. In this embodiment, the first terminal A1 of the shunt circuit SH1 is coupled to both the first terminal E1 and the first terminal B1 of the switch SW3 (e.g., ...). Figure 3 As shown), or coupled to the second terminal E2 and the second terminal B2 of switch SW3 (as shown). Figure 4 (As shown).

[0012] In one embodiment, the first terminal E1 and the second terminal E2 can be signal transceivers used to receive or send signals. The third terminal E3 can be a reference voltage terminal used to receive a reference voltage, such as ground.

[0013] In one embodiment, please refer to Figure 1-4The first circuit SH1 includes switches SW1 and SW2. The first terminal of switch SW1 is coupled to the first terminal A1 of the first circuit SH1, and the second terminal of switch SW1 is coupled to the second terminal A2 of the first circuit SH1. Switch SW2 is connected in parallel with switch SW1. Switches SW1 and SW2 are turned on or off according to control signals VC1 and VC2, respectively. Further, switches SW1 and SW2 may each include transistors T1 and T2. The first terminals of transistors T1 and T2 are coupled to each other, and the second terminals of transistors T1 and T2 are coupled to each other. The control terminals of transistors T1 and T2 receive control signals VC1 and VC2, respectively. In one embodiment, transistors T1 and T2 are of the same type. For example, transistors T1 and T2 may both be N-type transistors or both may be P-type transistors. For example, in the case of N-type transistors, the first terminal of transistors T1 and T2 is the drain, the second terminal is the source, and the control terminal is the gate. In this embodiment, using transistors T1 and T2 of the same type can improve switching speed without significantly increasing the manufacturing process and cost.

[0014] In one embodiment, during normal signal transmission, the on / off states of switches SW1 and SW3 can be different. For example, when switch SW1 is on, switch SW3 can be off, and when switch SW1 is off, switch SW3 can be on. Furthermore, in normal mode, switches SW1 and SW3 can switch between on and off states respectively according to control signals VC1 and VC3. Figure 1-2 As shown, when switch SW1 is on, the signal can be transmitted between the first terminal E1 and the second terminal E2. When switch SW1 is off, switch SW3 can be on to perform shunt. Or, as... Figure 3-4 As shown, when switch SW3 is on, the signal can be transmitted between the first terminal E1 and the third terminal E3. When switch SW3 is off, switch SW1 is on, so that the shunt circuit SH1 can be turned on to perform shunt.

[0015] In one embodiment, when switching device 101 or 102 receives a surge voltage or surge current (also referred to as: surge voltage or surge current), such as during electrostatic discharge, switching device 101 or 102 can enter a surge protection mode. In surge protection mode, switch SW2 can be turned on according to control signal VC2 to assist in dissipating surge current. Furthermore, in surge protection mode, switches SW1 and SW3 can also be turned on to dissipate surge current. Further, in surge protection mode, transistor T1 of switch SW1, transistor T2 of switch SW2, and transistor T3 of switch SW3 can all be turned on to dissipate surge current. In this embodiment, compared to a circuit that only includes switches SW1 and SW3, transistor T2 of switch SW2 can increase the ability to dissipate surge current in surge protection mode.

[0016] Specifically, in the first embodiment, transistor T2 of switch SW2 remains off in normal mode (not shown), while transistors T1 and T3 can switch between on and off to switch signal transmission. In this embodiment, the size of transistor T2 can be greater than, less than, or equal to the size of transistor T1 to assist in dissipating surge current. Alternatively, in the second embodiment, transistor T2 switches between on and off in normal mode, and the size of transistor T2 can be smaller than the size of transistor T1 to improve the switching speed of transistor T1. Note that in the first and second embodiments, as described above, transistor T2 is turned on when, for example, electrostatic discharge occurs and surge protection mode is entered.

[0017] The following is Figure 3 The operation of transistor T2 in the second embodiment will be further explained using an example.

[0018] You can refer to this simultaneously. Figure 3 , Figure 5A and Figure 5B ,in Figure 5A and Figure 5B The diagram illustrates a waveform of one embodiment of the control signals VC1 and VC2 of the shunt circuit SH1 in the switching device of the present invention.

[0019] exist Figure 5A In the first period tP1, transistor T1 is kept on by a control signal VC1 with a relatively high level, and in the second period tP2, transistor T1 is kept off by a control signal VC1 with a relatively low level. At the beginning of the first period tP1, transistor T1 changes from off to on, and transistor T2 is turned on during a constant potential period Δt1 by a high voltage pulse on the control signal VC2. At the beginning of the second period tP2, transistor T1 changes from on to off, and transistor T2 is turned on during a constant potential period Δt2 by another high voltage pulse on the control signal VC2. During the constant potential periods Δt1 and Δt2, transistor T2 is turned on, thereby setting the voltage across transistor T1 to the same value. In this embodiment, since the size of transistor T2 is smaller than that of transistor T1, transistor T2 can have a faster switching speed than transistor T1. By rapidly turning on transistor T2, the voltage across transistor T1 is set to the same value, allowing the gate-source and gate-drain voltages of transistor T1 to quickly reach the desired values, thus enabling transistor T1 to quickly enter the on or off state. Therefore, transistor T2 can improve the switching speed of transistor T1 between on and off states.

[0020] exist Figure 5B In the middle, the operation of transistor T1 is related to Figure 5AThe illustration is similar and will not be repeated here. The difference lies in the potential difference: before the start of the first period tP1 (before the start), during a certain potential period Δt1, the control signal VC2 can be pulled high to turn on transistor T2, maintaining this constant potential for the duration of Δt1. Then, during the first period tP1, the voltage value of the control signal VC2 remains high, keeping transistor T2 continuously on. From the start of the second period tP2, transistor T1 changes from on to off, and during a certain potential period Δt2, the voltage value of the control signal VC2 remains high, keeping transistor T2 on until the end of the constant potential period Δt2, at which point the voltage value of the control signal VC2 is pulled low, turning off transistor T2. During the constant potential periods Δt1 and Δt2, transistor T2 is on, thus setting the same voltage value across transistor T1. Please refer to [reference needed]. Figure 3 During the first period tP1, transistors T1 and T2 can be turned on simultaneously and can synchronously perform shunt operations. In the embodiment shown in 5B, the starting point of the constant potential period Δt1 is earlier than the starting point of the first period tP1, and the starting point of the constant potential period Δt2 overlaps with the starting point of the second period tP2.

[0021] Figure 5A and Figure 5B The diagram illustrates the states of transistors T1 and T2 in normal mode in the second embodiment. During the first period tP1 and / or the second period tP2, electrostatic discharge may occur, and the switching device may enter the surge protection mode. Transistors T1, T2, and T3 may be turned on simultaneously to dissipate surge current.

[0022] In the above embodiments, the duration of the constant potential period Δt1 is less than the duration of the first period tP1, and the duration of the constant potential period Δt2 is less than the duration of the second period tP2. In a further embodiment, transistor T2 may be turned on only during either Δt1 or Δt2, and the present invention does not limit this.

[0023] Please refer to the following: Figures 6A-6C , Figures 6A-6CA schematic diagram illustrating an embodiment of the shunt circuit 600 in the switching device of the present invention is shown. The shunt circuit 600 includes switches SW1, SW2, and SW4. Switches SW1, SW2, and SW4 are connected in parallel between a first terminal A1 and a second terminal A2 of the shunt circuit 600. Switches SW1, SW2, and SW4 may each include transistors T1, T2, and T4. The first terminals of transistors T1, T2, and T4 are commonly coupled to the first terminal A1 of the shunt circuit 600, and the second terminals of transistors T1, T2, and T4 are commonly coupled to the second terminal A2 of the shunt circuit 600. The control terminals of transistors T1, T2, and T4 respectively receive control signals VC1, VC2, and VC4. Transistors T1, T2, and T4 are turned on or off according to the control signals VC1, VC2, and VC4, respectively.

[0024] Specifically, in the third embodiment, in normal mode, transistor T1 can switch between on and off to switch signal transmission, transistor T2 switches between on and off to improve the switching speed of transistor T1, and transistor T4 can remain off (not shown). When, for example, electrostatic discharge occurs and the surge protection mode is entered, transistor T4 turns on to dissipate surge current. Furthermore, in surge protection mode, transistors T1-T4 can all be turned on to dissipate surge current. In this embodiment, the size of transistor T2 can be smaller than the size of transistor T1.

[0025] For details regarding the operation of this embodiment, please refer to [link / reference]. Figure 6A , Figure 7A ,and Figure 7B ,in Figure 7A and 7B Draw Figure 6A The waveform diagram shows the operation of one embodiment of the shunt circuit 600. In this embodiment, in normal mode, the timing operation of transistors T1 and T2 is similar to... Figure 5A and 5B That will not be elaborated upon here. The difference lies in the fact that, compared to... Figure 5A and 5B It also includes a switch SW4, which contains a transistor T4, in such a way... Figure 7A and 7B In the normal mode shown, whether in the first period tP1 or the second period tP2, transistor T4 remains in the off state according to the control signal VC4 which is always low voltage. On the other hand, electrostatic discharge may occur in the first period tP1 and / or the second period tP2, and the switching device enters the surge protection mode. Transistors T1, T2 and T4 can be turned on simultaneously to discharge surge current.

[0026] In some embodiments, transistor T2 may be smaller than transistor T1, thus allowing for a faster switching speed. The rapid turn-on of transistor T2 enables transistor T1 to quickly enter either the on or off state. Therefore, transistor T2 improves the switching speed of transistor T1 between on and off states. In a further embodiment, transistor T4 may be larger than transistor T1, thus providing greater current discharge capability in surge protection mode, thereby improving the reliability of the switching device. However, this invention is not limited to this; in other embodiments, the size of transistor T4 may be equal to or smaller than that of transistor T1, depending on factors such as space availability. In this case, since transistors T1, T2, and T4 can all be turned on in surge protection mode, T4 can provide auxiliary current discharge capability without significantly increasing cost.

[0027] Please refer to Figure 6B as well as Figure 6C , Figure 6B as well as Figure 6C Schematic diagrams illustrating other embodiments of the shunt circuit 600 in the switching device of this invention are shown respectively.

[0028] exist Figure 6B In this circuit, the shunt circuit 601 includes transistors T1, T2, and T4, and resistors R1, R2, and R4. The first terminals of transistors T1, T2, and T4 are mutually coupled to the first terminal A1 of the shunt circuit, and the second terminals of transistors T1, T2, and T4 are mutually coupled to the second terminal A2 of the shunt circuit. The control terminals of transistors T1, T2, and T4 are respectively coupled to one end of resistors R1, R2, and R4, and the other ends of resistors R1, R2, and R4 receive control signals VC1, VC2, and VC4, respectively. Furthermore, transistors T1, T2, and T4 each have their own substrate, and these substrates are mutually coupled via wires. Each substrate of transistors T1, T2, and T4 can receive a substrate voltage VB through a common resistor RB.

[0029] exist Figure 6C In this circuit, transistors T1, T2, and T4 can share the same substrate. For example, the shunt circuit 602 may include a multi-gate transistor TA. The multiple gates of the multi-gate transistor TA are respectively coupled to resistors R1, R2, and R4, and receive control signals VC1, VC2, and VC4 through resistors R1, R2, and R4 respectively. The first terminal of the multi-gate transistor TA is coupled to the first terminal A1 of the shunt circuit 602, and the second terminal of the multi-gate transistor TA is coupled to the second terminal A2 of the shunt circuit 602. The substrate of the multi-gate transistor TA receives the substrate voltage VB through resistor RB.

[0030] In some implementations, transistors T1, T2, and T4 can all be N-type transistors, or they can all be P-type transistors. For example, in the case of N-type transistors, the first terminals of transistors T1, T2, and T4 can be drains, the second terminals can be sources, and the control terminals can be gates. Please refer to... Figure 8A as well as Figure 8B , Figure 8A as well as Figure 8B Schematic diagrams of other embodiments of the shunt circuits 801 and 802 in the switching device of the present invention are shown respectively.

[0031] exist Figure 8A In the circuit, the shunt circuit 801 includes switches 810-1 and 820-1, which are connected in parallel and coupled to each other. Further, switch 810-1 includes multiple transistors T11 to T1N, and switch 820-1 includes multiple transistors T21 to T2M, where N and M are integers greater than 1. In switch 810-1, transistors T11 to T1N are sequentially connected in series between the first terminal A1 and the second terminal A2. In switch 820-1, transistors T21 to T2M are sequentially connected in series between the first terminal A1 and the second terminal A2. In this embodiment, the number of transistors T11 to T1N can be equal to the number of transistors T21 to T2M, i.e., N = M. However, the invention is not limited to this; in other embodiments, N may be different from M. For example, in... Figure 8B In the circuit, switch 810-2 includes transistors T11 to T13, and switch 820-2 includes transistors T21 and T22. That is, N = 3 and M = 2.

[0032] In some embodiments, the control terminals of transistors T11 to T1N can receive the same control signal VC1, so that they can be turned on or off simultaneously. The control terminals of transistors T21 to T2M can receive the same other control signal VC2, so that they can be turned on or off simultaneously. In this embodiment, the on / off action of switch 810-1 is the same as... Figures 1 to 4 The on and off actions of switch SW1 in the embodiment are similar, and the on and off actions of switch 820-1 are similar. Figures 1 to 4 The conduction and cutoff operations of switch SW2 in this embodiment are similar and will not be described in detail here. In this embodiment, transistors T11 to T1N can be the same type of transistor, for example, N-type transistors. Transistors T21 to T2M can be the same type of transistor, for example, N-type transistors.

[0033] Please refer to Figure 9 , Figure 9A schematic diagram of a switching device according to another embodiment of the present invention is shown. The switching device 900 includes shunt circuits SH1 and SH2, switches SW1A and SW1B. One end of shunt circuit SH1 is coupled to a first terminal E1, and the other end is coupled to a third terminal E3. One end of switch SW1A is coupled to the first terminal E1, and the other end is coupled to a common terminal EC. One end of switch SW1B is coupled to the common terminal EC, and the other end is coupled to a second terminal E2. One end of shunt circuit SH2 is coupled to the second terminal E2, and the other end is coupled to a fourth terminal E4. Shunt circuits SH1 and SH2 can be implemented using any of the shunt circuits from the foregoing embodiments. The circuit architectures of shunt circuits SH1 and SH2 can be the same or different, and the present invention does not limit this.

[0034] In this embodiment, the first terminal E1, the second terminal E2, and the shared terminal EC are signal transceivers, while the third terminal E3 and the fourth terminal E4 are reference voltage terminals, such as grounded terminals. Furthermore, switch SW1A may include transistor T1A, and switch SW1B may include transistor T1B. Switches SW1A and SW1B are turned on or off according to control signals VC1A and VC1B, respectively.

[0035] In normal mode, the on / off states of switches SW1A and SW1B can be reversed. For example, in normal mode, when switch SW1A is on, shunt circuit SH1 does not perform current shunt operation. At this time, switch SW1B can be off, and shunt circuit SH2 is activated to perform current shunt operation. When switch SW1A is off, shunt circuit SH1 is activated to perform current shunt operation. At this time, switch SW1B can be on, and shunt circuit SH2 does not perform current shunt operation.

[0036] In surge protection mode, at least one of the shunt circuits SH1 and SH2 can be activated to discharge surge current. Furthermore, at least one of the switches SW1A and SW1B can be activated to discharge surge current.

[0037] In summary, this invention provides a first switch and a second switch in a switching device. In normal mode, the first switch can be used for switching signal transmission, and the second switch can be used to improve the switching speed of the first switch. In surge protection mode, the second switch can be used to assist in dissipating surge current. Further, this invention provides a first switch, a second switch, and a fourth switch in a switching device. In normal mode, the first switch can be used for switching signal transmission, the second switch can be used to improve the switching speed of the first switch, and the fourth switch is off. In surge protection mode, the second and fourth switches can be used to assist in dissipating surge current. The switching device of this invention can improve the switching speed of the switching device and / or enhance the surge current dissipation capability.

Claims

1. A switching device, comprising: A first circuit, wherein a first terminal of the first circuit is coupled between a first terminal and a second terminal, and a second terminal of the first circuit is coupled between the first terminal and the second terminal, or coupled to a third terminal, the first circuit comprising: A first switch, wherein a first terminal of the first switch is coupled to a first terminal of the first circuit, and a second terminal of the first switch is coupled to a second terminal of the first circuit; and A second switch, connected in parallel with the first switch. The first switch and the second switch contain the same type of transistor. In a normal mode, the first switch switches between on and off according to a first control signal to transmit an RF signal when on, and the second switch switches between on and off according to a second control signal to adjust the switching speed of the first switch. In one surge protection mode, the second switch is turned on to discharge a surge current.

2. The switching device as claimed in claim 1, wherein, The first terminal of the first circuit is coupled to the first terminal, and the second terminal of the first circuit is coupled to the second terminal. The switching device further includes: A third switch, wherein a first terminal of the third switch is coupled to the first terminal or the second terminal, a second terminal of the third switch is coupled to the third terminal, and the third switch is turned on or off according to a third control signal. The first terminal and the second terminal are signal transceivers, and the third terminal is a reference voltage terminal. In the normal mode, the conduction state of the third switch is different from that of the first switch.

3. The switching device as claimed in claim 1, wherein, The first terminal of the first circuit is coupled between the first terminal and the second terminal, and the second terminal of the first circuit is coupled to the third terminal. The switching device further includes: A third switch, wherein a first terminal of the third switch is coupled to the first terminal, a second terminal of the third switch is coupled to the second terminal, and the third switch is turned on or off according to a third control signal. The first terminal and the second terminal are signal transceivers, and the third terminal is a reference voltage terminal. In the normal mode, the conduction state of the third switch is different from that of the first switch.

4. The switching device as claimed in claim 2 or 3, wherein in the normal mode, when the first switch is on, the third switch is off, and when the first switch is off, the third switch is on.

5. The switching device as claimed in claim 2 or 3, wherein the first switch includes a first transistor, the second switch includes a second transistor, the first transistor and the second transistor are coupled to each other at a first terminal and a second terminal, the control terminals of the first transistor and the second transistor respectively receive the first control signal and the second control signal, and the first transistor and the second transistor are of the same type. The third switch includes a third transistor. The first circuit is a first shunt circuit.

6. The switching device of claim 5, wherein when the first transistor switches between on and off, the second transistor is turned on to set the voltage at the first terminal and the second terminal of the first transistor, wherein the size of the second transistor is smaller than the size of the first transistor.

7. The switching device of claim 6, wherein in the normal mode, the first transistor remains on during a first period and remains off during a second period, and the second transistor is turned on during at least a certain potential period at the beginning of the first period and / or the second period, the duration of the at least certain potential period being shorter than the duration of the first period and / or the second period.

8. The switching device of claim 7, wherein the start point of the at least certain potential period of the second transistor is earlier than the start point of the corresponding first period and / or the second period, or the start point of the at least certain potential period overlaps with the start point of the corresponding first period and / or the second period.

9. The switching device of claim 6, wherein the first shunt circuit further comprises: A fourth switch, comprising a fourth transistor, wherein a first terminal of the fourth transistor is coupled to a first terminal of the first transistor, and a second terminal of the fourth transistor is coupled to a second terminal of the first transistor, and a control terminal of the fourth transistor receives a fourth control signal, and the fourth transistor is turned on or off according to the fourth control signal. In this normal mode, when the first transistor switches between on and off, the third transistor remains off.

10. The switching device of claim 9, wherein in the normal mode, the first transistor remains on during a first period and remains off during a second period. The second transistor is turned on during at least a certain potential period at the beginning of the first period and / or the second period, wherein the duration of the at least certain potential period is shorter than the duration of the first period and / or the second period. The starting point of the at least certain potential period is earlier than the starting point of the corresponding first period and / or the second period, or the starting point of the at least certain potential period overlaps with the starting point of the corresponding first period and / or the second period.

11. The switching device of claim 9, wherein, The fourth transistor is the same type of transistor as the first transistor.

12. The switching device of claim 11, wherein the first transistor, the second transistor, and the fourth transistor are P-type transistors or N-type transistors, wherein... The first terminal of the first transistor, the second transistor, and the fourth transistor are drains, the second terminals of the first transistor, the second transistor, and the fourth transistor are sources, and the control terminals of the first transistor, the second transistor, and the fourth transistor are gates.

13. The switching device of claim 12, wherein the substrates of the first transistor, the second transistor, and the fourth transistor are coupled to each other, or the first transistor, the second transistor, and the fourth transistor share the same substrate.

14. The switching device as claimed in claim 1, wherein in the surge protection mode, both the first switch and the second switch are turned on to jointly discharge the surge current.

15. The switching device of claim 5, wherein the first transistor receives the first control signal through a first resistor, and the second transistor receives the second control signal through a second resistor.

16. The switching device of claim 9, wherein the fourth switch receives the fourth control signal through a resistor.

17. The switching device of claim 3, wherein the first switch includes a plurality of first transistors connected in series, and the second switch includes a plurality of second transistors connected in series, the number of the second transistors being less than or equal to the number of the first transistors.

18. The switching device of claim 17, wherein each of the plurality of first transistors is coupled in parallel to one of the plurality of second transistors and is aligned with each other.

19. The switching device of claim 9, further comprising: A fifth switch is coupled between a common terminal and the second terminal, wherein the common terminal is coupled between the first terminal and the second terminal; as well as A second shunt circuit, wherein a first end of the second shunt circuit is coupled to the second terminal, and a second end of the second shunt circuit is coupled to a fourth terminal, wherein the fourth terminal is a second reference voltage terminal.

20. A switching device, comprising: A first circuit, wherein a first terminal of the first circuit is coupled between a first terminal and a second terminal, and a second terminal of the first circuit is coupled to a third terminal, wherein the first terminal and the second terminal are signal transceiver terminals, and the third terminal is a reference voltage terminal, the first circuit is a first shunt circuit, the first circuit comprising: A first switch, wherein a first terminal of the first switch is coupled to a first terminal of the first circuit, and a second terminal of the first switch is coupled to a second terminal of the first circuit, the first switch being turned on or off according to a first control signal; and A second switch, connected in parallel with the first switch, is turned on or off according to a second control signal. The first switch includes a first transistor, and the second switch includes a second transistor. The first transistor and the second transistor are coupled to each other at their first and second terminals. The control terminals of the first transistor and the second transistor respectively receive the first control signal and the second control signal. The first transistor and the second transistor are of the same type. The switching device further includes a third switch, a first terminal of which is coupled to the first terminal, a second terminal of which is coupled to the second terminal, and the third switch is turned on or off according to a third control signal, wherein the third switch includes a third transistor. In a normal mode, the third switch is in a different on state than the first switch, and the second switch remains off. In one surge protection mode, the second switch is turned on to discharge a surge current.

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