Input switching circuit and method, circuit board assembly and adapter

Abstract

The embodiments of the present invention relate to the field of circuit technology, and disclose an input switching circuit and method, a circuit board assembly and an adapter. The circuit includes: a first port, a second port, a third port, an overvoltage protection circuit and a switching unit; the first port is used to connect a first power supply, the second port is used to connect a second power supply, the third port is used to connect an external load, the first port is also connected to the input end of the overvoltage protection circuit, the output end of the overvoltage protection circuit is connected to the third port, the second port is also connected to the third port, the first input end of the switching unit is connected to the first port, the second input end of the switching unit is connected to the second port, and the output end of the switching unit is connected to the enable end of the overvoltage protection circuit. The present application preferentially uses a power supply that does not require an overvoltage protection circuit to power the load, so as to reduce the frequency of use of the overvoltage protection circuit, thereby extending the maintenance cycle of the overvoltage protection circuit to save maintenance costs.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of circuit technology, and in particular to an input switching circuit and method, a circuit board assembly and an adapter. Background Art

[0002] With the rise of electronic products, there are more and more PD (Power Delivery) adapters that match them. The PD power supply in the PD adapter can usually output a voltage within a certain voltage range, but the cost of the PD power supply is usually high. Technicians usually set the PD power supply to be connected to the external load through an OVP (Over Voltage Protection) circuit with high reliability requirements to avoid the PD power supply being damaged due to overvoltage.

[0003] At present, the OVP set after the PD power supply is usually used frequently, which greatly reduces the service life of the OVP circuit. The OVP circuit is easily damaged, and the cost of the OVP circuit with high reliability requirements is usually high, so the maintenance cost is usually too high. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide an input switching circuit and method, a circuit board assembly and an adapter, which preferentially use a power supply that does not require an overvoltage protection circuit to reduce the frequency of using the overvoltage protection circuit, thereby extending the maintenance cycle of the overvoltage protection circuit and saving maintenance costs.

[0005] To solve the above technical problems, an embodiment of the present invention provides an input switching circuit, including: a first port, a second port, a third port, an overvoltage protection circuit and a switching unit; the first port is used to connect a first power supply, the second port is used to connect a second power supply, the third port is used to connect an external load, the first port is also connected to the input end of the overvoltage protection circuit, the output end of the overvoltage protection circuit is connected to the third port, the second port is also connected to the third port, the first input end of the switching unit is connected to the first port, the second input end of the switching unit is connected to the second port, and the output end of the switching unit is connected to the enable end of the overvoltage protection circuit; the switching unit is used to output an enable signal when it receives the voltage output by the first power supply and does not receive the voltage output by the second power supply; the overvoltage protection circuit is used to be in a working state when it receives the enable signal.

[0006] An embodiment of the present invention also provides an input switching method, which is applied to a switching unit in an input switching circuit, wherein the input switching circuit also includes a first port, a second port, a third port and an overvoltage protection circuit; the first port is used to connect a first power supply, the second port is used to connect a second power supply, and the third port is used to connect an external load, the first port is also connected to the input end of the overvoltage protection circuit, the output end of the overvoltage protection circuit is connected to the third port, the second port is also connected to the third port, the first input end of the switching unit is connected to the first port, the second input end of the switching unit is connected to the second port, and the output end of the switching unit is connected to the enable end of the overvoltage protection circuit; the method includes: when the voltage output by the first power supply is received and the voltage output by the second power supply is not received, an enable signal is output so that the overvoltage protection circuit is in a working state when the enable signal is received.

[0007] An embodiment of the present invention further provides a circuit board assembly, comprising the above-mentioned input switching circuit.

[0008] An embodiment of the present invention further provides an adapter, comprising the above circuit board assembly.

[0009] Compared with the related art, in the embodiment of the present invention, the first power supply can be connected to the third port through the first port and the overvoltage protection circuit. When the second power supply is not yet connected to the second port, if the switching unit receives the voltage output by the first power supply, the switching unit will output an enable signal to the overvoltage protection circuit to enable the overvoltage protection circuit to be in a working state, and the first power supply will supply power to the load. After the second power supply is connected to the second port, the switching unit will receive the voltage output by the second power supply, and will no longer output an enable signal to the overvoltage protection circuit, and the overvoltage protection circuit will no longer be in a working state, which is equivalent to cutting off the power supply circuit of the first power supply, and only the second power supply will supply power to the load. The present application can choose to use the first power supply to power the load according to demand, but will give priority to using the second power supply that does not require an overvoltage protection circuit to power the load, so as to reduce the frequency of use of the overvoltage protection circuit, thereby extending the maintenance cycle of the overvoltage protection circuit to save maintenance costs.

[0010] In addition, the switching unit includes a first switch and a second switch, and the enable signal is a low level; the first end of the first switch serves as the first input end of the switching unit, the second end of the first switch serves as the output end of the switching unit, the third end of the first switch is grounded, the first end of the second switch serves as the second input end of the switching unit, the second end of the second switch is connected to the first end of the first switch, and the third end of the second switch is grounded; the first switch is used to connect the second end of the first switch and the third end of the first switch when the first end of the first switch is at a high level; the second switch is used to connect the second end of the second switch and the third end of the second switch when the first end of the second switch is at a high level. In this embodiment, a specific circuit implementation form of the switching unit is provided. When the switching unit only receives the voltage output by the first power supply, it means that the second power supply has not yet been connected to the second port. At this time, the first end of the first switch is at a high level, the first end of the second switch is at a low level, the first switch is turned on, and the second switch is turned off. At this time, the second end of the first switch is grounded, that is, it is considered that the switching unit outputs a low-level enable signal to the overvoltage protection circuit, and the first switch now supplies power to the load; when the switching unit receives the voltage output by the second power supply, the first end of the second switch is at a high level, and the second switch will lower the level of the first end of the first switch. At this time, the first switch is no longer grounded, that is, it is considered that the switching unit no longer outputs an enable signal to the overvoltage protection circuit, and the first switch no longer supplies power to the load, and only the second power supply supplies power to the load.

[0011] In addition, the first switch is a first MOS tube, and the second switch is a second MOS tube; the gate of the first MOS tube serves as the first end of the first switch, the drain / source of the first MOS tube serves as the second end of the first switch, and the source / drain of the first MOS tube serves as the third end of the first switch; the gate of the second MOS tube serves as the first end of the second switch, the drain / source of the second MOS tube serves as the second end of the second switch, and the source / drain of the second MOS tube serves as the third end of the second switch. In this embodiment, a specific implementation form of the first switch and the second switch is provided.

[0012] In addition, the input switching circuit also includes a fourth port; the fourth port is connected to the embedded controller, and the enable end of the overvoltage protection circuit is connected to the fourth port; the embedded controller is used to output an enable signal to the overvoltage protection circuit when the first power supply is connected to the first port, and after a preset time, the enable signal is prohibited from being output. In this embodiment, when the first power supply is just connected to the first port, it cannot stably output voltage to the switching unit, and it cannot effectively control the overvoltage protection circuit to start working. At this time, the embedded controller (EC) first outputs an enable signal to the overvoltage protection circuit so that the overvoltage protection circuit is in a working state first, which can reduce the time difference between the first power supply being connected to the circuit and finally supplying power to the load. After the preset time, the EC no longer outputs the enable signal. At this time, if the first power supply is still connected to the first port and the second power supply is not yet connected to the second port, the switching unit will output an enable signal to the overvoltage protection circuit so that the first power supply supplies power to the load.

[0013] In addition, the input switching circuit further includes a diode; the second input end of the input switching circuit is connected to the output end of the input switching circuit through a diode, wherein the second input end of the input switching circuit is connected to the positive electrode of the diode, and the negative electrode of the diode is connected to the output end of the input switching circuit. In this embodiment, a diode can be set on the line where the second power supply supplies power to the load to prevent backflow, which ensures that the second power supply is not damaged to a certain extent, improves the reliability of the entire power supply system, and further reduces the maintenance cost.

[0014] In addition, the input switching circuit further includes at least one voltage stabilizing capacitor; the first end of the voltage stabilizing capacitor is connected to the first port and / or the second port, and the second end of the voltage stabilizing capacitor is grounded. In this embodiment, the voltage of the first port and / or the second port can be stabilized by setting the voltage stabilizing capacitor.

[0015] In addition, the input switching circuit also includes a first inductor and a second inductor; the first port is connected to the input end of the overvoltage protection circuit through the first inductor, and the second port is connected to the third port through the second inductor. In this embodiment, the current in the circuit can be stabilized by setting the inductor so that it will not change suddenly. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0017] Figure 1 is a structural schematic diagram of an input switching circuit according to an embodiment of the present application;

[0018] Figure 2is a structural diagram of an input switching circuit according to another embodiment of the present application. DETAILED DESCRIPTION

[0019] To make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. However, it will be appreciated by those skilled in the art that in the embodiments of the present invention, many technical details are proposed in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can be implemented. The division of the following embodiments is for the convenience of description, and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined and referenced with each other under the premise of no contradiction.

[0020] An embodiment of the present invention relates to an input switching circuit for switching the power supply for powering an external load, specifically for preferentially using a power supply that does not require an overvoltage protection circuit to power the external load, so as to reduce the frequency of use of the overvoltage protection circuit, thereby extending the maintenance cycle of the overvoltage protection circuit and saving maintenance costs.

[0021] Please refer to Figure 1 The input switching circuit 100 includes: a first port 1, a second port 2, a third port 3, an overvoltage protection circuit 4 and a switching unit 5. The first port 1 is used to connect to a first power source 6, the second port 2 is used to connect to a second power source 7, and the third port 3 is used to connect to an external load. The first port 1 is also connected to the input end of the overvoltage protection circuit 4, and the output end of the overvoltage protection circuit 4 is connected to the third port 3. The second port 2 is also connected to the third port 3. The first input end of the switching unit 5 is connected to the first port 1, the second input end of the switching unit 5 is connected to the second port 2, and the output end of the switching unit 5 is connected to the enable end EN of the overvoltage protection circuit 4. Figure 1 In the figure, it is taken as an example that the first power source 6 is connected to the first port 1 and the second power source 7 is connected to the second port 2 .

[0022] The switching unit 5 will output an enable signal when receiving the voltage output by the first power supply 6 and not receiving the voltage output by the second power supply 7; the overvoltage protection circuit 4 will be in a working state when receiving the enable signal.

[0023] In this embodiment, the first power supply can be connected to the third port through the first port and the overvoltage protection circuit. When the second power supply is not yet connected to the second port, if the switching unit receives the voltage output by the first power supply, the switching unit will output an enable signal to the overvoltage protection circuit to enable the overvoltage protection circuit to be in a working state. At this time, the first power supply supplies power to the load. After the second power supply is connected to the second port, the switching unit will receive the voltage output by the second power supply. At this time, the enable signal will no longer be output to the overvoltage protection circuit, and the overvoltage protection circuit will no longer be in a working state, which is equivalent to cutting off the power supply circuit of the first power supply, and only the second power supply supplies power to the load. The present application can choose to use the first power supply to power the load according to demand, but preferentially use the second power supply that does not require an overvoltage protection circuit to power the load, so as to reduce the frequency of use of the overvoltage protection circuit, thereby extending the maintenance cycle of the overvoltage protection circuit to save maintenance costs.

[0024] The implementation details of the input switching circuit of this embodiment are described in detail below. The following content is only provided for easy understanding of the implementation details and is not necessary for implementing this solution.

[0025] In one embodiment, the first power supply 6 can be specifically set as a PD adapter, and the second power supply 7 can be specifically set as an ordinary adapter, such as a DIN adapter. The price of the PD adapter is higher than that of the ordinary adapter, so an overvoltage protection circuit 4 is usually used to protect it to avoid damage to the PD adapter, saving maintenance costs, and in the input switching circuit 100, a lower-priced ordinary adapter is preferentially used to power the external load to reduce the frequency of use of the PD adapter, which can further save maintenance costs. In addition, setting two power supply circuits to power the load can play a double insurance role. When one power supply has no output power, the other power supply can power the external load. Moreover, compared with setting both power supplies as PD adapters, setting one power supply as a PD adapter and the other power supply as an ordinary adapter can also save costs to a certain extent.

[0026] In one embodiment, the overvoltage protection circuit 4 may include: Figure 2 For any chip of the chip structure shown, such as chip KTS1677, the input end of the overvoltage protection circuit 4 may include 5 input ends VIN, the input end of the overvoltage protection circuit 4 may include 5 input ends VOUT, and the overvoltage protection circuit 4 also includes 3 ground ends GND and 1 enable end EN.

[0027] In one embodiment, a specific circuit implementation form of the switching unit 5 is provided, please refer to Figure 2The switching unit 5 includes a first switch Q1 and a second switch Q2, and the enable signal is at a low level; the first switch Q1 and the second switch Q2 can both be MOS tubes, or both can be triodes, or one can be a MOS tube and the other can be a triode, Figure 2 In the figure, it is taken as an example that both the first switch Q1 and the second switch Q2 are MOS tubes. The model of the MOS tube may be 2SK3541, and the MOS tube may also be selected according to needs, which is not limited here.

[0028] Specifically, the first switch Q1 is a first MOS tube, the second switch Q2 is a second MOS tube, the gate of the first MOS tube serves as the first end of the first switch Q1, the drain / source of the first MOS tube serves as the second end of the first switch Q1, and the source / drain of the first MOS tube serves as the third end of the first switch Q1; the gate of the second MOS tube serves as the first end of the second switch Q2, the drain / source of the second MOS tube serves as the second end of the second switch Q2, and the source / drain of the second MOS tube serves as the third end of the second switch Q2.

[0029] The first end of the first switch Q1 serves as the first input end of the switching unit 5, the second end of the first switch Q1 serves as the output end of the switching unit 5, the third end of the first switch Q1 is grounded, the first end of the second switch Q2 serves as the second input end of the switching unit 5, the second end of the second switch Q2 is connected to the first end of the first switch Q1, and the third end of the second switch Q2 is grounded.

[0030] The first switch Q1 connects the second end of the first switch Q1 and the third end of the first switch Q1 when the first end of the first switch Q1 is at a high level, and the second switch Q2 connects the second end of the second switch Q2 and the third end of the second switch Q2 when the first end of the second switch Q2 is at a high level.

[0031] Specifically, when the first power supply 6 is connected to the first port 1 and the second power supply 7 is not yet connected to the second port 2, the first power supply 6 will output a signal PD_SINK_EN to the first end of the first switch Q1, the first end of the first switch Q1 will be at a high level, and the first end of the second switch Q2 will be at a low level. At this time, the second switch Q2 is disconnected, and the first switch Q1 is turned on, and the second end of the first switch Q1 is grounded, so as to simulate the output of a low-level enable signal to the enable end EN of the overvoltage protection circuit 4 by lowering the voltage of the enable end EN of the overvoltage protection circuit 4. At this time, the overvoltage protection circuit 4 is in a working state, and the first power supply 6 can output electrical energy to the third port 3 through the overvoltage protection circuit 4 to power the external load.

[0032] Once the second power supply 7 is connected to the second port 2, the first end of the second switch Q2 will be at a high level. At this time, the second end of the second switch Q2 is grounded, which will pull down the voltage of the first end of the first switch Q1 and disconnect the first switch Q1. At this time, the second end of the first switch Q1 is not grounded, and it can no longer pull down the voltage of the enable terminal EN of the overvoltage protection circuit 4. At this time, the overvoltage protection circuit 4 is no longer in a working state, which is equivalent to cutting off the power supply line of the first power supply 6 to the external load. At this time, the second power supply 7 will be connected to the external load through the second port 2, so that the second power supply 7 can power the external load.

[0033] In this embodiment, a specific circuit implementation form of a switching unit is provided. When the switching unit receives only the voltage output by the first power supply, it indicates that the second power supply has not yet been connected to the second port. At this time, the first end of the first switch is at a high level, the first end of the second switch is at a low level, the first switch is turned on, and the second switch is turned off. At this time, the second end of the first switch is grounded, that is, it is considered that the switching unit outputs a low-level enable signal to the overvoltage protection circuit, and the first switch supplies power to the load at this time; when the switching unit receives the voltage output by the second power supply, the first end of the second switch is at a high level, and the second switch will pull down the level of the first end of the first switch, and the first switch is no longer grounded, that is, it is considered that the switching unit no longer outputs an enable signal to the overvoltage protection circuit, and the first switch no longer supplies power to the load, and only the second power supply supplies power to the load.

[0034] In one embodiment, please refer to Figure 2 The input switching circuit 100 further includes a fourth port 8. The fourth port 8 is connected to the embedded controller 9, and the enable terminal of the overvoltage protection circuit 4 is connected to the fourth port 8. When the first power source 6 is connected to the first port 1, the embedded controller 9 outputs a signal PWR_EC_DELAY as an enable signal to the overvoltage protection circuit 4, and prohibits outputting the enable signal after a preset time.

[0035] Specifically, when the first power supply 6 is just connected to the first port 1, it cannot stably output the signal PD_SINK_EN to the switching unit 5, that is, the first end of the first switch Q1 in the switching unit 5 cannot be stably at a high level at the beginning. At this time, the second end of the first switch Q1 is not grounded, which is equivalent to the switching unit 5 not outputting an enable signal to the overvoltage protection circuit 4 at this time. It takes a period of time until the first power supply 6 can stably output the signal PD_SINK_EN to the switching unit 5, the overvoltage protection circuit 4 can be in a working state, and the first power supply 6 can supply power to the external load.

[0036] In this embodiment, an embedded controller 9 is provided, which is connected to the fourth port 8 of the input switching circuit 100. When the first power supply 6 cannot stably output the signal PD_SINK_EN to the switching unit 5, the embedded controller 9 first outputs an enable signal to the overvoltage protection circuit 4 for a short time, so that the overvoltage protection circuit 4 is in a working state, so that the first power supply 6 can supply power to the external load. After a preset period of time, it is considered that the first power supply 6 can stably output the signal PD_SINK_EN to the switching unit 5, and the embedded controller 9 is prohibited from outputting the enable signal. When the first power supply 6 is no longer connected to the fourth port 8, the enable end of the overvoltage protection circuit 4 will restore the high level, and the overvoltage protection circuit 4 will no longer be in a working state.

[0037] In this embodiment, when the first power source is just connected to the first port, it cannot stably output voltage to the switching unit, and cannot effectively control the overvoltage protection circuit to start working. At this time, the embedded controller first outputs an enable signal to the overvoltage protection circuit to put the overvoltage protection circuit into a working state first, which can reduce the time difference between the first power source being connected to the circuit and finally supplying power to the load. After a preset time, the embedded controller no longer outputs the enable signal. At this time, if the first power source is still connected to the first port and the second power source is not yet connected to the second port, the switching unit will output an enable signal to the overvoltage protection circuit so that the first power source supplies power to the load.

[0038] In one embodiment, please refer to Figure 2 The input switching circuit 100 also includes a diode D1, and the second port 2 is connected to the third port 3 through the diode D1, wherein the second port 2 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the third port 3, wherein the diode D1 can be a RBR3LAM40C model diode or a common diode.

[0039] In this embodiment, a diode can be set on the line where the second power supply supplies power to the load to prevent backflow, which ensures that the second power supply is not damaged to a certain extent, improves the reliability of the entire power supply system, and further reduces maintenance costs.

[0040] In one embodiment, please refer to Figure 2 , the input switching circuit 100 further includes at least one voltage stabilizing capacitor C, the first end of the voltage stabilizing capacitor C is connected to the first port 1 and / or the second port 2, and the second end of the voltage stabilizing capacitor C is grounded. In one embodiment, the input switching circuit 100 further includes a first inductor L1 and a second inductor L2, the first port 1 is connected to the input end of the overvoltage protection circuit 4 through the first inductor L1, and the second port 2 is connected to the third port 3 through the second inductor L2. Figure 2In the figure, the input switching circuit 100 includes a first inductor L1 and a second inductor L2, and the input switching circuit 100 includes 8 voltage-stabilizing capacitors C. As an example, the input switching circuit 100 includes a first inductor L1 and a second inductor L2.

[0041] In this embodiment, the voltage of the first port and / or the second port may be stabilized by setting a voltage stabilizing capacitor, and the current in the circuit may be stabilized so as not to change suddenly by setting an inductor.

[0042] In one embodiment, in order to ensure the normal operation of the input switching circuit 100, technicians can set the resistors R1, R2, R3, R4 and R5 on the input switching circuit 100 as needed. The specific setting positions are as follows: Figure 2 As shown. And the resistance value of each resistor is obtained by debugging. For example, the resistance value of resistor R1 can be set to 100KΩ, the resistance value of resistor R2 can be set to 1KΩ, the resistance value of resistor R3 can be set to 220KΩ, the resistance value of resistor R4 can be set to 100KΩ, and the resistance value of resistor R5 can be set to 10KΩ. In addition, the input switching circuit 100 can also be set to include 8 voltage-stabilizing capacitors C1, C2, C3, C4, C5, C6, C7 and C8, and the capacitance values ​​can be set to 100PF, 1000PF, 1000PF, 100PF, 100PF, 100PF, 100PF, 100PF and 100PF respectively. The first inductor L1 is set to be located on the line between capacitor C2 and capacitor C3, and the second inductor L2 is set to be located on the line between capacitor C6 and capacitor C7. The inductive reactances of the first inductor L1 and the second inductor L2 are both set to 120Ω.

[0043] In one embodiment, the overvoltage protection circuit 4 also includes an overvoltage lockout (OVLO) pin, which is used to control the overvoltage protection circuit 4 to disconnect the connection line between the first power supply 6 and the external load when the voltage input to the first power supply 6 exceeds the preset value, or when the voltage at the output terminal connected to the load terminal exceeds the preset value, so as to protect the first power supply 6 and the external load from being damaged due to overvoltage. The technician adjusts the preset value by setting resistors R6 and R7 and adjusting the resistance values ​​of R6 and R7. In one embodiment, the resistance value of R6 is set to 1MΩ and the resistance value of R7 is set to 82KΩ.

[0044] One embodiment of the present invention relates to a circuit board assembly, comprising the input switching circuit in any one of the above embodiments.

[0045] One embodiment of the present invention relates to an adapter, comprising the circuit board assembly in any one of the above embodiments.

[0046] An embodiment of the present invention relates to an input switching method, which is applied to the switching unit 5 in the input switching circuit 100. For details, please refer to Figure 1The input switching circuit 100 also includes a first port 1, a second port 2, a third port 3 and an overvoltage protection circuit 4; the first port 1 is used to connect to a first power supply 6, the second port 2 is used to connect to a second power supply 7, the third port 3 is used to connect to an external load, the first port 1 is also connected to the input end of the overvoltage protection circuit 4, the output end of the overvoltage protection circuit 4 is connected to the third port 3, the second port 2 is also connected to the third port 3, the first input end of the switching unit 5 is connected to the first port 1, the second input end of the switching unit 5 is connected to the second port 2, and the output end of the switching unit 5 is connected to the enable end EN of the overvoltage protection circuit 4.

[0047] The switching unit 5 will output an enable signal when receiving the voltage output by the first power supply and not receiving the voltage output by the second power supply, so that the overvoltage protection circuit is in a working state when receiving the enable signal.

[0048] It is not difficult to find that this embodiment is Figure 1 The corresponding embodiment or Figure 2 Corresponding embodiments and corresponding method embodiments, this embodiment can be used with Figure 1 The corresponding embodiment or Figure 2 The corresponding embodiments are implemented in coordination with each other. Figure 1 The corresponding embodiment or Figure 2 The relevant technical details mentioned in the corresponding embodiment are still valid in this embodiment, and will not be repeated here to reduce repetition. Figure 1 The corresponding embodiment or Figure 2 In the corresponding embodiment.

[0049] Those skilled in the art will appreciate that the above embodiments are specific embodiments for implementing the present invention, and that in actual applications, various changes may be made in form and detail without departing from the spirit and scope of the present invention.

Claims

1. An input switching circuit, characterized in that: include: A first port, a second port, a third port, an overvoltage protection circuit and a switching unit; The first port is used to connect a first power source, the second port is used to connect a second power source, the third port is used to connect an external load, the first port is also connected to an input end of the overvoltage protection circuit, the output end of the overvoltage protection circuit is connected to the third port, the second port is also connected to the third port, the first input end of the switching unit is connected to the first port, the second input end of the switching unit is connected to the second port, and the output end of the switching unit is connected to an enable end of the overvoltage protection circuit; The switching unit is configured to output an enable signal when receiving the voltage output by the first power supply and not receiving the voltage output by the second power supply; The overvoltage protection circuit is used to be in a working state when receiving the enable signal; The first power source is set as a PD adapter, and the second power source is set as an adapter that is not a PD adapter; The switching unit includes a first switch and a second switch, the enable signal is at a low level; the first end of the first switch serves as the first input end of the switching unit, the second end of the first switch serves as the output end of the switching unit, the third end of the first switch is grounded, the first end of the second switch serves as the second input end of the switching unit, the second end of the second switch is connected to the first end of the first switch, and the third end of the second switch is grounded; the first switch is used to connect the second end of the first switch and the third end of the first switch when the first end of the first switch is at a high level; the second switch is used to connect the second end of the second switch and the third end of the second switch when the first end of the second switch is at a high level; The first switch is a first MOS tube, and the second switch is a second MOS tube; the gate of the first MOS tube serves as the first end of the first switch, one of the drain and the source of the first MOS tube serves as the second end of the first switch, and the other serves as the third end of the first switch; the gate of the second MOS tube serves as the first end of the second switch, one of the drain and the source of the second MOS tube serves as the second end of the second switch, and the other serves as the third end of the second switch; The input switching circuit further includes a fourth port; the fourth port is connected to the embedded controller, and the enable terminal of the overvoltage protection circuit is connected to the fourth port; The embedded controller is used for outputting the enable signal to the overvoltage protection circuit when the first power source is connected to the first port, and prohibiting the output of the enable signal after a preset time period.

2. The input switching circuit according to claim 1, characterized in that: Also includes diodes; The second port is connected to the third port through the diode, wherein the second port is connected to the anode of the diode, and the cathode of the diode is connected to the third port.

3. The input switching circuit according to claim 1, characterized in that: Also includes at least one voltage stabilizing capacitor; A first end of the voltage-stabilizing capacitor is connected to the first port and / or the second port, and a second end of the voltage-stabilizing capacitor is grounded.

4. The input switching circuit according to claim 3, characterized in that: Also includes a first inductor and a second inductor; The first port is connected to the input end of the overvoltage protection circuit through the first inductor, and the second port is connected to the third port through the second inductor.

5. An input switching method, characterized in that: A switching unit applied to an input switching circuit as claimed in any one of claims 1 to 4, the method comprising: When the voltage output by the first power supply is received and the voltage output by the second power supply is not received, an enable signal is output so that the overvoltage protection circuit in the input switching circuit is in a working state when the enable signal is received.

6. A circuit board assembly, characterized in that: The invention comprises the input switching circuit as claimed in any one of claims 1 to 4.

7. An adapter, characterized in that: Comprising the circuit board assembly as claimed in claim 6.

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