Input / output common port circuit and mobile terminal device

Abstract

The application provides an input-output shared port circuit and a mobile terminal device. The input-output shared port circuit comprises a switching circuit, which comprises a signal output end, a signal input end, a signal input or output end and a conduction path control end. The signal output end is used for connecting a main control circuit. The signal input end is used for connecting the main control circuit. The signal input or output end is used for connecting an external device. The conduction path control end is used for connecting the main control circuit. When the control signal input by the conduction path control end is a first level signal, the signal output end and the signal input or output end are conducted. When the control signal input by the conduction path control end is a second level signal, the signal input end and the signal input or output end are conducted. Since the external device and the mobile terminal device can share the signal input or output end, the number of contacts is reduced, the size of the printed circuit board is reduced, the cost is reduced, the structure space of the mobile terminal device is reduced, and the difficulty of interference protection is reduced.

Description

Technical Field

[0001] This utility model relates to the field of mobile terminal equipment technology, specifically to an input / output shared port circuit and a mobile terminal equipment. Background Technology

[0002] As mobile terminal devices become more and more functional, they also need to connect to more external devices. Among these connections, external devices are often connected via external contacts.

[0003] In related technologies, when a mobile terminal device supports multiple functions, each function requires corresponding contact points to communicate with external devices in order to support multiple functions. However, the contact points for each function are not shared. This results in an excessive number of contact points in the mobile terminal device, leading to a larger printed circuit board size, increased cost, larger internal structural space, and increased difficulty in interference protection. Summary of the Invention

[0004] The main technical problem this invention addresses is that when a mobile terminal device supports multiple functions, the method of setting up a contact point for each function to communicate with external devices results in too many contact points in the mobile terminal device. This leads to an increase in the size of the printed circuit board inside the mobile terminal device, increasing costs, increasing the structural space inside the mobile terminal device, and correspondingly increasing the difficulty of interference protection.

[0005] According to the first aspect, one embodiment of this application provides an input / output shared port circuit, applied to a mobile terminal device, the mobile terminal device including a printed circuit board, on which a main control circuit is disposed; The input / output shared port circuit includes a switching circuit disposed on the printed circuit board. The switching circuit includes a signal output terminal, a signal input terminal, a signal input or output terminal, and a conduction path control terminal. The signal output terminal is used to connect to the main control circuit to output a signal to the main control circuit. The signal input terminal is used to connect to the main control circuit to receive a signal output by the main control circuit. The signal input or output terminal is used to connect to an external device to output a signal to the external device or receive a signal output by the external device. The conduction path control terminal is used to connect to the main control circuit for inputting control signals. When the control signal input to the control terminal of the conduction path is a first level signal, the switching circuit is used to respond to the first level signal and conduct the signal output terminal and the signal input or output terminal, so that the output signal of the external device is output to the main control circuit through the signal input or output terminal and the signal output terminal; When the control signal input to the control terminal of the conduction path is a second level signal, the switching circuit is used to respond to the second level signal and conduct the signal input terminal and the signal input or output terminal, so that the output signal of the main control circuit is output to the external device through the signal input terminal and the signal input or output terminal; The first level signal and the second level signal are at different levels.

[0006] In one embodiment, the switching circuit includes: a first resistor, a second resistor, a third resistor, a first field-effect transistor, a second field-effect transistor, a first contact, a second contact, a third contact, a fourth contact, a first diode, and a second diode; One end of the first resistor is connected to the first contact, and the other end of the first resistor is connected to the second contact; The first terminal of the first field-effect transistor is connected to the other end of the first resistor, the second terminal of the first field-effect transistor is grounded, and the control terminal of the first field-effect transistor is connected to the third contact. The first end of the second field-effect transistor is connected to the fourth contact, the second end of the second field-effect transistor is connected to the second contact, and the control end of the second field-effect transistor is connected to the third contact. The third contact is connected to the first power supply through the second resistor; The fourth contact is connected to the first power supply via the third resistor; The first diode is connected in series in the connection path between the other end of the first resistor and the second contact, and the other end of the first resistor is connected to the positive terminal of the first diode; The second diode is connected in series on the connection path between the second terminal of the second field-effect transistor and the second contact, and the second terminal of the second field-effect transistor is connected to the positive terminal of the second diode; Wherein, the first contact is the signal output terminal; the second contact is the signal input or output terminal; the third contact is the conduction path control terminal; and the fourth contact is the signal input terminal.

[0007] In one embodiment, the switching circuit further includes a bidirectional Zener diode, the second contact being connected to one end of the bidirectional Zener diode, and the other end of the bidirectional Zener diode being grounded.

[0008] In one embodiment, the first field-effect transistor is an N-MOS transistor; and / or, the second field-effect transistor is an N-MOS transistor.

[0009] In one embodiment, the switching circuit includes: a switching chip, a pull-up resistor, a resistor, and a current-limiting resistor; The first pin of the switching chip is the signal output terminal, the second pin of the switching chip is grounded, the third pin of the switching chip is the signal input terminal, the fourth pin of the switching chip is the signal input or output terminal, the fifth pin of the switching chip is connected to the first power supply through a current limiting resistor, and the sixth pin of the switching chip is the conduction path control terminal. One end of the pull-up resistor is connected to the first pin of the switching chip, and the other end of the pull-up resistor is connected to the second power supply. One end of the pull-down resistor is connected to pin 6 of the switching chip, and the other end of the pull-down resistor is grounded.

[0010] In one embodiment, the switching circuit further includes a filtering circuit connected to the connection between the current-limiting resistor and the fifth pin of the switching chip.

[0011] In one embodiment, the filtering circuit includes a filter capacitor connected to the connection line between the current-limiting resistor and the fifth pin of the switching chip.

[0012] According to a second aspect, this application provides a mobile terminal device in one embodiment, including: a printed circuit board, on which a main control circuit is disposed, and on which an input / output shared port circuit as described above is also disposed.

[0013] In one embodiment, the main control circuit is a central processing unit built into the mobile terminal device.

[0014] According to the input / output shared port circuit and mobile terminal device of the above embodiments, when the signal output terminal and the signal input or output terminal are connected, the output signal of the external device can be output to the main control circuit through the signal input or output terminal and the signal output terminal; when the signal input terminal and the signal input or output terminal are connected, the output signal of the main control circuit can be output to the external device through the signal input terminal and the signal input or output terminal; this allows the external device and the mobile terminal device to share the signal input or output terminal for signal transmission, reduces the number of contacts in the mobile terminal device, reduces the size of the printed circuit board in the mobile terminal device, reduces costs, and at the same time reduces the structural space of the mobile terminal device, making interference protection easier. Attached Figure Description

[0015] Figure 1 This is a block diagram of a circuit with a shared input / output port. Figure 2 A circuit diagram of a switching circuit according to one embodiment; Figure 3 A circuit diagram of a switching circuit according to another embodiment; Figure 4 This is a schematic diagram of the structure of a switching chip in one embodiment.

[0016] Reference numerals: 100, Switching circuit; 101, Signal output terminal; 102, Signal input terminal; 103, Conduction path control terminal; 104, Signal input or output terminal; 105, First contact; 106, Second contact; 107, Third contact; 108, Fourth contact; 200, Main control circuit; 300, External device; R1, First resistor; R2, Second resistor; R3, Third resistor; R4, Pull-up resistor; R5, Pull-down resistor; R6, Current limiting resistor; C1, Filter capacitor; Q1, First field-effect transistor; Q2, Second field-effect transistor; D1, First diode; D2, Second diode; T1, Bidirectional Zener diode; U1, Switching chip; VCC1, First power supply; VCC2, Second power supply. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0018] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0019] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages). As mobile terminal devices become more and more functional, the number of external devices that need to be connected also increases.

[0020] In related technologies, when a mobile terminal device supports multiple functions, each function needs to be configured with corresponding touch points to communicate with external devices in order to support multiple functions. However, the touch points between each function are not shared.

[0021] For example, when the mobile terminal device is a mobile phone, as the functions of the mobile phone increase, the size of the corresponding electronic components and circuit boards also increases. To accommodate the increased functions, each function is equipped with a contact point to connect to external devices. Taking unconventional explosion-proof mobile phones as an example, explosion-proof mobile phones have multiple functions, each with a corresponding contact point for communication with external devices. This results in larger explosion-proof mobile phones, more complex structures, increased costs, and a corresponding increase in the difficulty of interference protection.

[0022] It is evident that setting up contact points for each function in mobile terminal devices results in an excessive number of contact points, which in turn increases the size of the printed circuit boards inside the mobile terminal devices, increases costs, increases the structural space inside the mobile terminal devices, and correspondingly increases the difficulty of interference protection.

[0023] To address the aforementioned technical issues, this application provides an input / output shared port circuit and a mobile terminal device. When the external device 300 and the mobile terminal device transmit signals, they can share the signal input or output terminal 104, reducing the number of contacts in the mobile terminal device, making the printed circuit board inside the mobile terminal device smaller, reducing costs, and simultaneously reducing the structural space of the mobile terminal device, thus lowering the difficulty of interference protection.

[0024] like Figure 1 The diagram illustrates an input / output shared port circuit according to this application, applied to a mobile terminal device. The mobile terminal device includes a printed circuit board (PCB) on which a main control circuit 200 is disposed. The mobile terminal device can be a mobile phone, and the main control circuit 200 can be a CPU (Central Processing Unit). The input / output shared port circuit may include a switching circuit 100 disposed on the PCB.

[0025] In some embodiments, the switching circuit 100 may include a signal output terminal 101, a signal input terminal 102, a signal input or output terminal 104, and a conduction path control terminal 103.

[0026] Signal output terminal 101 is used to connect to the main control circuit 200 to output a signal to the main control circuit 200; signal input terminal 102 is used to connect to the main control circuit 200 to receive the signal output by the main control circuit 200; signal input or output terminal 104 is used to connect to an external device 300 to output a signal to the external device 300 or receive the signal output by the external device 300; conduction path control terminal 103 is used to connect to the main control circuit 200 to input a control signal; when the control signal input to the conduction path control terminal 103 is a first-level signal, the switching circuit 100 is used to respond to the first-level signal and The signal output terminal 101 and the signal input or output terminal 104 are turned on so that the output signal of the external device 300 is output to the main control circuit 200 through the signal input or output terminal 104 and the signal output terminal 101; when the control signal input to the control terminal 103 is a second level signal, the switching circuit 100 is used to respond to the second level signal and turn on the signal input terminal 102 and the signal input or output terminal 104 so that the output signal of the main control circuit 200 is output to the external device 300 through the signal input terminal 102 and the signal input or output terminal 104; wherein, the first level signal and the second level signal are different levels.

[0027] In one embodiment, the first level signal can be a high level signal, and correspondingly, the second level signal is a low level signal. Of course, the first level signal can also be a low level signal, and correspondingly, the second level signal is a high level signal.

[0028] When signal output terminal 101 and signal input or output terminal 104 are connected, the output signal of external device 300 can be output to main control circuit 200 through signal input or output terminal 104 and signal output terminal 101; when signal input terminal 102 and signal input or output terminal 104 are connected, the output signal of main control circuit 200 can be output to external device 300 through signal input terminal 102 and signal input or output terminal 104.

[0029] Therefore, when the mobile terminal device and the external device 300 transmit signals, they can share the signal input or output terminal 104, which reduces the number of contacts in the mobile terminal device, makes the printed circuit board inside the mobile terminal device smaller, reduces costs, and reduces the structural space of the mobile terminal device, making interference protection easier.

[0030] The following explanation uses a mobile phone as an example, with the main control circuit 200 being the CPU. Example 1

[0031] like Figure 2As shown, the switching circuit 100 may include a first resistor R1, a second resistor R2, a third resistor R3, a first field-effect transistor Q1, a second field-effect transistor Q2, a first contact 105, a second contact 106, a third contact 107, a fourth contact 108, a first diode D1, and a second diode D2.

[0032] One end of the first resistor R1 is connected to the first contact 105, and the other end of the first resistor R1 is connected to the second contact 106; the first end of the first field-effect transistor Q1 is connected to the other end of the first resistor R1, the second end of the first field-effect transistor Q1 is grounded, and the control terminal of the first field-effect transistor Q1 is connected to the third contact 107; the first end of the second field-effect transistor Q2 is connected to the fourth contact 108, the second end of the second field-effect transistor Q2 is connected to the second contact 106, and the control terminal of the second field-effect transistor Q2 is connected to the third contact 107; the third contact 107 is connected to the first power supply VCC1 through the second resistor R2; the fourth contact 108 is connected to the first power supply VCC1 through the third resistor R3; the first diode D1 is connected in series in the connection path between the other end of the first resistor R1 and the second contact 106, and the other end of the first resistor R1 is connected to the positive terminal of the first diode D1; the second diode D2 is connected in series in the connection path between the second end of the second field-effect transistor Q2 and the second contact 106, and the second end of the second field-effect transistor Q2 is connected to the positive terminal of the second diode D2. Among them, the first contact 105 is the signal output terminal 101 ( Figure 2 ENIT_IN); the second contact 106 is the signal input or output terminal 104 (in the context of ENIT_IN); Figure 2 IN_OUT); the third contact 107 is the conduction path control terminal 103 ( Figure 2 In the EN_IN&OUT); the fourth contact 108 is the signal input terminal 102 ( Figure 2 (GPIO_OUT in the middle).

[0033] The first field-effect transistor Q1 is an N-MOS transistor (N-Metal-Oxide-Semiconductor). The second field-effect transistor Q2 is also an N-MOS transistor. When the conduction path control terminal 103 is high, the signal output terminal 101 ( Figure 2 The ENIT_IN signal and signal input or output terminal 104 are turned on ( Figure 2 In the IN_OUT section, when the conduction control terminal 103 is low, the signal input terminal 102 ( Figure 2 GPIO_OUT and signal input or output terminal 104 ( Figure 2 IN_OUT in the middle is turned on.

[0034] Specifically, in the initial state, the signal output terminal 101 of the switching circuit 100 is unstable. When there is no control state, the conduction path control terminal 103 is pulled high through the second resistor R2, and the control terminals of the first field-effect transistor Q1 and the second field-effect transistor Q2 are at high levels. Similarly, when the conduction path control terminal 103 has a control state and the control signal is high, the control terminals of the first field-effect transistor Q1 and the second field-effect transistor Q2 are at high levels.

[0035] When the control terminal 103 is high and the external device 300 and the mobile phone are assembled together, the signal input or output terminal 104 is pulled low. At this time, the first field-effect transistor Q1 and the second diode D2 are turned on, and the signal output terminal 101 connected to the CPU ( Figure 2 The ENIT_IN signal is pulled low. In one embodiment, the external device 300 can be detected by the phone's CPU as to whether it is in a contact state or a triggered state, where the third resistor R3 is a pull-up current-limiting resistor R6. Furthermore, when the conduction control terminal 103 is high, the second field-effect transistor Q2 is in the conducting state, and the unstable voltage of the first resistor R1 is pulled low. Therefore, at the signal input terminal 102 (… Figure 2 When GPIO_OUT is high, it will not affect the conduction path formed by signal output terminal 101 and signal input or output terminal 104; wherein, the first resistor R1 is the current limiting resistor R6.

[0036] When the control terminal 103 of the conduction path is at a low level, the control terminals of the first field-effect transistor Q1 and the second field-effect transistor Q2 are both at a low level. The first field-effect transistor Q1 and the second field-effect transistor Q2 are both in the off state. Therefore, the high level of the signal input terminal 102 to the external device 300 through the first resistor R1, the first diode D1 and the signal input or output terminal 104 is not affected.

[0037] When the control terminal 103 is at a low level, if the signal input terminal 102 is at a low level through the first resistor R1, the first diode D1, and the signal input or output terminal 104 to the external device 300, the cathode of the first diode D1 is at a low level, and the first diode D1 is in an open state. At this time, the signal input terminal 102 is at a low level. It can be seen that when the signal input terminal 102 is at a low level, the low level of the signal input terminal 102 to the external device 300 through the first resistor R1, the first diode D1, and the signal input or output terminal 104 is not affected.

[0038] In this embodiment, the conduction control terminal 103 in the switching circuit 100 can respond to a high level or a low level. The mobile phone can output a high level or a low level through the signal input or output terminal 104 and the signal input terminal 102, and can also detect the high level or low level input of the external device 300 through the signal input or output terminal 104 and the signal output terminal 101. It can be seen that when the mobile phone and the external device 300 transmit signals, they can share the signal input or output terminal 104, which reduces the number of contacts in the mobile phone, makes the printed circuit board inside the mobile phone smaller, reduces the cost, and makes the structural space of the mobile phone smaller, reducing the difficulty of interference protection.

[0039] In this embodiment, operating software can be installed on the mobile phone to control whether the level of the conduction path control terminal 103 is high or low. For example, the level type of the conduction path control terminal 103 can be triggered by a specific mode.

[0040] Furthermore, such as Figure 2 As shown, the switching circuit 100 also includes a bidirectional Zener diode T1, and the second contact 106 is connected to one end of the bidirectional Zener diode T1, while the other end of the bidirectional Zener diode T1 is grounded. The bidirectional Zener diode T1 is an electrostatic discharge (ESD) protection device when a level signal is connected to the signal input or output terminal 104, preventing static electricity from damaging the internal circuitry of the mobile terminal device through the signal input or output terminal 104. Example 2

[0041] like Figure 3 As shown, the switching circuit 100 may include a switching chip U1, a pull-up resistor R4, a pull-down resistor R5, and a current-limiting resistor R6; the first pin of the switching chip U1 is the signal output terminal 101. Figure 3 In the ENIT_IN, pin 2 of the switch chip U1 is grounded, and pin 3 of the switch chip U1 is the signal input terminal 102 ( Figure 3 In the GPIO_OUT, pin 4 of the switching chip U1 is the signal input or output terminal 104 ( Figure 3 In the IN_OUT section, pin 5 of the switching chip U1 is connected to the first power supply VCC1 through the current limiting resistor R6, and pin 6 of the switching chip U1 is the conduction control terminal 103. Figure 3 (EN_IN&OUT); one end of the pull-up resistor R4 is connected to pin 1 of the switching chip U1, and the other end of the pull-up resistor R4 is connected to the second power supply VCC2, which can be 1.8V DC; one end of the pull-down resistor R5 is connected to pin 6 of the switching chip U1, and the other end of the pull-down resistor R5 is grounded.

[0042] In this embodiment, when the level signal received by the conduction path control terminal 103 is high, pins 4 and 1 of the switching chip U1 are turned on to form a conduction path; when the level signal received by the conduction path control terminal 103 is low, pins 4 and 3 of the switching chip U1 form a conduction path.

[0043] When the mobile phone and the external device 300 are assembled together, if the mobile phone needs to detect whether the level signal output by the external device 300 is high or low, the mobile phone can output a high level to the conduction path control terminal 103 through its internal CPU, so that the signal input or output terminal 104 and the signal output terminal 101 are connected; if the mobile phone needs to control the external device 300, the mobile phone can output a low level to the conduction path control terminal 103 through its internal CPU, so that the signal input or output terminal 104 and the signal input terminal 102 are connected.

[0044] In this embodiment, the purpose of the pull-down resistor R5 is to pull pin 6 of the switching chip U1 low when the switching chip U1 is not operated. That is, in the default state of the switching chip, pins 4 and 3 of the switching chip U1 are connected. In other words, when the mobile phone is in the initialization state and the signal input terminal 102 (GPIO_OUT) is not controlled, pin 6 of the switching chip U1 is pulled low, and pins 4 and 3 of the switching chip U1 are connected.

[0045] In this embodiment, pin 6 of the switching chip U1 can be controlled according to the usage scenario. For example, if the mobile phone is equipped with operating software, the level signal type of pin 6 of the switching chip U1 can be changed through the operating software so that the signal input or output terminal 104 is in the state of transmitting signal or receiving signal.

[0046] Therefore, when the mobile phone and external device 300 transmit signals, they can share the signal input or output terminal 104, which reduces the number of contacts in the mobile phone, makes the printed circuit board inside the mobile phone smaller, reduces costs, and makes the structural space of the mobile phone smaller, thus reducing the difficulty of interference protection.

[0047] When setting the switch chip U1, the switch chip U1 can be an SGM3157 chip, such as... Figure 4 The diagram shown is a structural schematic of the SGM3157 chip. Of course, the switching chip U1 can also be an SGM3799, BCT4223, RS2227, or other switching chips. Those skilled in the art can determine the specific model of the switching chip U1 based on the actual situation; no further limitations are imposed here.

[0048] Furthermore, such as Figure 3As shown, the switching circuit 100 also includes a filter circuit, which is connected to the connection between the current-limiting resistor R6 and the fifth pin of the switching chip.

[0049] Specifically, the filtering circuit may include a filter capacitor C1, which is connected to the connection between the current limiting resistor R6 and the fifth pin of the switching chip. The filter capacitor C1 reduces interference signals in the power supply voltage.

[0050] In some embodiments, this application also provides a mobile terminal device, which may include a printed circuit board. The printed circuit board has a main control circuit 200 and an input / output shared port circuit as described above. The mobile terminal device may be, but is not limited to, a mobile phone. Specific details are as described in the above embodiment of an input / output shared port circuit, and will not be elaborated further here.

[0051] In some embodiments, the main control circuit 200 is a central processing unit built into the mobile terminal device. Specific details are as described in the above embodiment of an input / output shared port circuit, and will not be elaborated further here.

[0052] In summary, this application provides an input / output shared port circuit and a mobile terminal device, which have the following beneficial effects: When signal output terminal 101 and signal input or output terminal 104 are connected, the output signal of external device 300 can be output to main control circuit 200 through signal input or output terminal 104 and signal output terminal 101; when signal input terminal 102 and signal input or output terminal 104 are connected, the output signal of main control circuit 200 can be output to external device 300 through signal input terminal 102 and signal input or output terminal 104; this allows external device 300 and mobile terminal device to share signal input or output terminal 104 for signal transmission, reduces the number of contacts in mobile terminal device, reduces the size of printed circuit board in mobile terminal device, reduces cost, and reduces the structural space of mobile terminal device, thus reducing the difficulty of interference protection.

[0053] The above-described specific examples are for illustrative purposes only and are not intended to limit the scope of this invention. Those skilled in the art to which this invention pertains can make various simple deductions, modifications, or substitutions based on the concept of this invention.

Claims

1. An input / output shared port circuit, characterized in that, Applied to mobile terminal devices, the mobile terminal devices include printed circuit boards, and the printed circuit boards are provided with main control circuits; The input / output shared port circuit includes a switching circuit disposed on the printed circuit board. The switching circuit includes a signal output terminal, a signal input terminal, a signal input or output terminal, and a conduction path control terminal. The signal output terminal is used to connect to the main control circuit to output a signal to the main control circuit. The signal input terminal is used to connect to the main control circuit to receive a signal output by the main control circuit. The signal input or output terminal is used to connect to an external device to output a signal to the external device or receive a signal output by the external device. The control terminal of the conductive path is used to connect to the main control circuit for inputting control signals; When the control signal input to the control terminal of the conduction path is a first level signal, the switching circuit is used to respond to the first level signal and conduct the signal output terminal and the signal input or output terminal, so that the output signal of the external device is output to the main control circuit through the signal input or output terminal and the signal output terminal; When the control signal input to the control terminal of the conduction path is a second level signal, the switching circuit is used to respond to the second level signal and conduct the signal input terminal and the signal input or output terminal, so that the output signal of the main control circuit is output to the external device through the signal input terminal and the signal input or output terminal; The first level signal and the second level signal are at different levels.

2. The input / output shared port circuit as described in claim 1, characterized in that, The switching circuit includes: a first resistor, a second resistor, a third resistor, a first field-effect transistor, a second field-effect transistor, a first contact, a second contact, a third contact, a fourth contact, a first diode, and a second diode; One end of the first resistor is connected to the first contact, and the other end of the first resistor is connected to the second contact; The first terminal of the first field-effect transistor is connected to the other end of the first resistor, the second terminal of the first field-effect transistor is grounded, and the control terminal of the first field-effect transistor is connected to the third contact. The first end of the second field-effect transistor is connected to the fourth contact, the second end of the second field-effect transistor is connected to the second contact, and the control end of the second field-effect transistor is connected to the third contact. The third contact is connected to the first power supply through the second resistor; The fourth contact is connected to the first power supply via the third resistor; The first diode is connected in series in the connection path between the other end of the first resistor and the second contact, and the other end of the first resistor is connected to the positive terminal of the first diode; The second diode is connected in series on the connection line between the second terminal of the second field-effect transistor and the second contact, and the second terminal of the second field-effect transistor is connected to the positive terminal of the second diode; Wherein, the first contact is the signal output terminal; the second contact is the signal input or output terminal; the third contact is the conduction path control terminal; and the fourth contact is the signal input terminal.

3. The input / output shared port circuit as described in claim 2, characterized in that, The switching circuit further includes a bidirectional Zener diode, the second contact being connected to one end of the bidirectional Zener diode, and the other end of the bidirectional Zener diode being grounded.

4. The input / output shared port circuit as described in claim 2 or 3, characterized in that, The first field-effect transistor is an N-MOS transistor; and / or, the second field-effect transistor is an N-MOS transistor.

5. The input / output shared port circuit as described in claim 1, characterized in that, The switching circuit includes: a switching chip, a pull-up resistor, a pull-down resistor, and a current-limiting resistor; The first pin of the switching chip is the signal output terminal, the second pin of the switching chip is grounded, the third pin of the switching chip is the signal input terminal, the fourth pin of the switching chip is the signal input or output terminal, the fifth pin of the switching chip is connected to the first power supply through a current limiting resistor, and the sixth pin of the switching chip is the conduction path control terminal. One end of the pull-up resistor is connected to the first pin of the switching chip, and the other end of the pull-up resistor is connected to the second power supply. One end of the pull-down resistor is connected to pin 6 of the switching chip, and the other end of the pull-down resistor is grounded.

6. The input / output shared port circuit as described in claim 5, characterized in that, The switching circuit also includes a filtering circuit, which is connected to the connection between the current-limiting resistor and pin 5 of the switching chip.

7. The input / output shared port circuit as described in claim 6, characterized in that, The filtering circuit includes a filter capacitor, which is connected to the connection line between the current limiting resistor and the fifth pin of the switching chip.

8. A mobile terminal device, characterized in that, include: A printed circuit board, wherein a main control circuit is provided on the printed circuit board, and the printed circuit board is further provided with an input / output common port circuit as described in any one of claims 1-7.

9. The mobile terminal device as described in claim 8, characterized in that, The main control circuit is the central processing unit built into the mobile terminal device.

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