A USB OTG power supply switching circuit

Abstract

The present invention discloses a USB OTG power supply switching circuit, comprising a first switch tube, a second switch tube, a first resistor and a power supply switching control module, wherein the input end of the first switch tube is used to connect to the VBUS port of the USB interface, the output end of the first switch tube is respectively connected to the input end of the second switch tube and the first end of the first resistor, the control end of the first switch tube is respectively connected to the control end of the second switch tube and the second end of the first resistor, the control end of the second switch tube is connected to the first end of the power supply switching control module, the output end of the second switch tube is connected to an external device, and the second end of the power supply switching control module receives a potential control signal. The present invention can control the output voltage of the first end of the power supply switching control module through the potential control signal received by the second end of the power supply switching control module, thereby controlling the conduction or cutoff of the first switch tube and the second switch tube, so that the power supply mode is switched when the USB OTG master-slave switch is performed, and the port is prevented from being burned due to power supply conflicts.

Description

Technical Field

[0001] The present invention relates to the technical field of USB bus, and in particular to a USB OTG power supply switching circuit. Background Art

[0002] Universal Serial Bus (USB) is a serial bus standard and a technical specification of an input and output interface. It is widely used in the field of electronic equipment communication. USB devices are divided into host devices (HOST) and slave devices (SLAVE). Data transmission can only be achieved when a host is connected to a slave. With the upgrading and widespread application of electronic products, there is a demand for an electronic device to have the functions of host and slave. Therefore, a new technology USB On-The-Go (USB OTG) is proposed to be applied to the connection between various electronic devices. In the prior art, USB OTG does not process the power supply. There is a power conflict caused by the power supply not being able to follow the switch when USBOTG switches between master and slave, and there is a risk of the port being burned out. Summary of the invention

[0003] The technical problem to be solved by the embodiments of the present invention is to provide a USB OTG power supply switching circuit, which can switch the power supply mode when the USB OTG master-slave switch is performed by controlling the output voltage of the power supply switching control module, thereby avoiding the port from being burned out due to power supply conflict.

[0004] In order to solve the above technical problems, an embodiment of the present invention provides a USB OTG power switching circuit, including: a power switching module and a power switching control module, wherein the power switching module includes a first switch tube, a second switch tube and a first resistor;

[0005] The input end of the first switch tube is used to connect to the VBUS port of the USB interface, the output end of the first switch tube is respectively connected to the input end of the second switch tube and the first end of the first resistor, the control end of the first switch tube is respectively connected to the control end of the second switch tube and the second end of the first resistor, the control end of the second switch tube is connected to the first end of the power supply switching control module, the output end of the second switch tube is used to connect to an external device, and the second end of the power supply switching control module is used to receive a potential control signal.

[0006] As an improvement of the above solution, the first switch tube is a MOS tube, and the second switch tube is a MOS tube.

[0007] As an improvement of the above scheme, the first switch tube is a PMOS tube, the input end of the first switch tube is a drain, the output end of the first switch tube is a source, and the control end of the first switch tube is a gate; the second switch tube is a PMOS tube, the input end of the second switch tube is a source, the control end of the second switch tube is a gate, and the output end of the second switch tube is a drain.

[0008] As an improvement of the above solution, the power supply switching control module includes: a second resistor, a third resistor, a fourth resistor and a third switch tube;

[0009] The first end of the second resistor is connected to the first end of the power supply switching control module, the second end of the second resistor is connected to the input end of the third switch tube, the output end of the third switch tube is grounded, the control end of the third switch tube is respectively connected to the first end of the third resistor and the first end of the fourth resistor, the second end of the third resistor is used to receive a potential control signal, and the second end of the fourth resistor is grounded.

[0010] As an improvement of the above scheme, it also includes: a potential control module, which specifically includes a first constant voltage power supply unit, a fifth resistor and a first switch; the first constant voltage power supply is connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the first end of the first switch for outputting a potential control signal, and the second end of the first switch is grounded.

[0011] As an improvement of the above solution, a micro control unit is further included, wherein a universal input and output port of the micro control unit is used to output the potential control signal.

[0012] As an improvement of the above solution, the third switch tube is a triode, the input end of the third switch tube is a collector, the output end of the third switch tube is an emitter, and the control end of the third switch tube is a base.

[0013] As an improvement of the above scheme, the circuit also includes a mode switching control module, which includes a sixth resistor, a seventh resistor, an eighth resistor, a fourth switch tube and a second constant voltage power supply unit; the first end of the sixth resistor is used to receive the potential control signal, the second end of the sixth resistor is respectively connected to the first end of the seventh resistor and the control end of the fourth switch tube, the second end of the seventh resistor is grounded, the output end of the fourth switch tube is grounded, the input end of the fourth switch tube is connected to the first end of the eighth resistor, the input end of the fourth switch tube is also used to connect to the USB ID port of the USB interface, and the second end of the eighth resistor is connected to the second constant voltage power supply unit.

[0014] As an improvement of the above solution, the fourth switch tube is a triode, the control end of the fourth switch tube is the base, the output end of the fourth switch tube is the collector, and the input end of the fourth switch tube is the emitter.

[0015] Compared with the prior art, an embodiment of the present invention provides a USB OTG power switching circuit, including a power switching module and a power switching control module, wherein the power switching module includes a first switch tube, a second switch tube and a first resistor; the input end of the first switch tube is used to connect to the VBUS port of the USB interface, the output end of the first switch tube is respectively connected to the input end of the second switch tube and the first end of the first resistor, the control end of the first switch tube is respectively connected to the control end of the second switch tube and the second end of the first resistor, the control end of the second switch tube is connected to the first end of the power switching control module, the output end of the second switch tube is used to connect to an external device, and the second end of the power switching control module is used to receive a potential control signal; the switching circuit can control the output voltage of the first end of the power switching control module by receiving the potential control signal, thereby controlling the conduction or cutoff of the two switch tubes in the power switching module, so that the power supply can switch the power supply mode following the master-slave switching of the USBOTG, thereby avoiding the port from being burned out due to power supply conflict. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a preferred embodiment of a USB OTG power supply switching circuit provided by the present invention;

[0017] Figure 2 It is a structural schematic diagram of another preferred embodiment of a USB OTG power supply switching circuit provided by the present invention;

[0018] Figure 3 It is a structural schematic diagram of another preferred embodiment of a USB OTG power supply switching circuit provided by the present invention;

[0019] Figure 4 It is a structural schematic diagram of another preferred embodiment of a USB OTG power supply switching circuit provided by the present invention;

[0020] Figure 5 The present invention provides a circuit schematic diagram of a USB OTG power supply switching circuit. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this technical field without creative work are within the scope of protection of the present invention.

[0022] The embodiment of the present invention provides a USB OTG power supply switching circuit, see Figure 1 , which is a structural schematic diagram of a preferred embodiment of a USB OTG power switching circuit provided by the present invention, wherein the USB OTG power switching circuit comprises a power switching module 1 and a power switching control module 2, wherein the power switching module 1 comprises a first switch tube, a second switch tube and a first resistor;

[0023] The input end of the first switch tube is used to connect to the VBUS port of the USB interface, the output end of the first switch tube is respectively connected to the input end of the second switch tube and the first end of the first resistor, the control end of the first switch tube is respectively connected to the control end of the second switch tube and the second end of the first resistor, the control end of the second switch tube is connected to the first end of the power supply switching control module 2, the output end of the second switch tube is used to connect to an external device, and the second end of the power supply switching control module 2 is used to receive a potential control signal (V EN ).

[0024] Specifically, the switching circuit mainly consists of a power supply switching module 1 and a power supply switching control module 2. In actual applications, when the device where the USB interface is located acts as a host device (HOST), it supplies power to the external device. When the device where the USB interface is located acts as a slave device (Device), it stops supplying power to the external device, so as to realize power switching while switching between master and slave device modes. The external device can be a USB flash drive or other electronic products, which can be selected according to actual conditions.

[0025] The power supply switching module 1 mainly includes a first switch tube, a second switch tube and a first resistor. The input end of the first switch tube is used to connect to the VBUS port of the USB interface. The VBUS port is used for power output. Generally, the output voltage of the VBUS port is 5V. The output end of the first switch tube is respectively connected to the input end of the second switch tube and the first end of the first resistor. The control end of the first switch tube is respectively connected to the control end of the second switch tube and the second end of the first resistor. The output end of the second switch tube is used to connect to an external device. It can be understood that when the first switch tube and the second switch tube are turned on, the output voltage of the VBUS port passes through the turned-on first switch tube and the second switch tube to supply power to the connected external device. When the first switch tube or the second switch tube is turned off, the output voltage of the VBUS port cannot be transmitted to the connected external device.

[0026] The second end of the power supply switching control module 2 is used to receive the potential control signal, and the first end of the power supply switching control module 2 is connected to the control end of the second switch tube, which is used to control the conduction and cutoff of the first switch tube and the second switch tube, thereby controlling the power supply state of the power supply switching module 1 to the external device. When the device where the USB interface is located is in the HOST state, it is necessary to power the connected external device. The second end of the power supply switching control module 2 generates a corresponding control signal by receiving the potential signal (potential control signal) and outputs it from the first end of the power supply switching control module 2 to the power supply switching module 1, so that the first switch tube and the second switch tube are turned on, and the device where the USB interface is located supplies power to the external device; when the device where the USB interface is located is in the Device state, it is necessary to stop supplying power to the connected external device. The power supply switching control module 2 generates a corresponding control signal by receiving the potential signal and outputs it from the first end of the power supply switching control module 2 to the power supply switching module 1, so that the device where the USB interface is located stops supplying power to the external device. By receiving the corresponding potential signal according to the state of the device where the USB interface is located, the output voltage of the first end of the power supply switching control module 2 is controlled, so that the power supply follows the master-slave switching of the USBOTG and switches the power supply mode, avoiding the port from being burned due to power supply conflicts.

[0027] In a preferred embodiment, the first switch tube is a MOS tube, and the second switch tube is a MOS tube.

[0028] It is worth mentioning that MOS tube is a metal-oxide semiconductor field effect tube, which is divided into PMOS tube and NMOS tube.

[0029] In another preferred embodiment, the first switch tube is a PMOS tube, the input end of the first switch tube is a drain, the output end of the first switch tube is a source, and the control end of the first switch tube is a gate; the second switch tube is a PMOS tube, the input end of the second switch tube is a source, the control end of the second switch tube is a gate, and the output end of the second switch tube is a drain.

[0030] It is worth noting that in this preferred embodiment, the two MOS tubes are PMOS tubes, but in practical applications, NMOS tubes can also be used. Accordingly, the connection relationship between the three pins of the NMOS tube and other devices in the power supply switching module 1 can be adjusted according to actual conditions.

[0031] See also Figure 2 As shown, it is a circuit schematic diagram of a preferred embodiment of a USB OTG power supply switching circuit provided by the present invention, wherein the power supply switching control module 2 comprises: a second resistor, a third resistor, a fourth resistor and a third switch tube;

[0032] The first end of the second resistor is connected to the first end of the power supply switching control module 2, the second end of the second resistor is connected to the input end of the third switch tube, the output end of the third switch tube is grounded, the control end of the third switch tube is respectively connected to the first end of the third resistor and the first end of the fourth resistor, the second end of the third resistor is used to receive a potential control signal, and the second end of the fourth resistor is grounded.

[0033] Specifically, in actual applications, the potential control signal is received by the second end of the third resistor to control the conduction and cutoff of the third switch tube, and then the voltage of the first end of the power supply switching control module 2 is controlled to achieve the purpose of controlling the conduction and cutoff of the first switch tube and the second switch tube, thereby realizing power switching control.

[0034] See also Figure 3 As shown, in a preferred embodiment, the switching circuit also includes a potential control module 3, and the potential control module 3 specifically includes a first constant voltage power supply unit, a fifth resistor and a first switch; the first constant voltage power supply is connected to the first end of the fifth resistor, and the second end of the fifth resistor is connected to the first end of the first switch for outputting the potential control signal, and the second end of the first switch is grounded.

[0035] Specifically, the potential control module 3 mainly includes a first constant voltage power supply, a fifth resistor and a first switch, the first constant voltage power supply is connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the first end of the first switch, the second end of the fifth resistor is used to output a potential control signal, and the second end of the first switch is grounded; the first constant voltage power supply provides a constant voltage, and controls the level of the potential signal input to the control end of the third switch tube by controlling the opening and closing of the first switch, so as to control the conduction and cutoff of the third switch tube, and then control the voltage of the first end of the power supply switching control module 2, so as to achieve the purpose of controlling the conduction and cutoff of the first switch tube and the second switch tube, and realize power switching control. Optionally, the first switch can be a dial switch or a key switch, which is not limited here.

[0036] In a preferred embodiment, a micro control unit (not shown) is further included, and a universal input and output port of the micro control unit is used to output a potential control signal.

[0037] Specifically, the potential signal generated by the microcontroller unit (MCU) is sent to the second end of the power supply switching control module through a general-purpose input / output port (GPIO).

[0038] It is worth noting that the source of the potential signal received by the second end of the power supply switching control module 2 is not limited to the above-mentioned potential control module 3 and the micro control unit, and the source of the potential signal can be set according to actual conditions.

[0039] In a preferred embodiment, the third switch tube is a triode, the input end of the third switch tube is a collector, the output end of the third switch tube is an emitter, and the control end of the third switch tube is a base.

[0040] It is worth noting that when the third switch tube is a transistor, the potential signal received by the second end of the power supply switching control module 2 controls the conduction and cutoff of the third switch tube. The third switch tube can be an NPN transistor or a PNP transistor, which can be selected according to actual conditions.

[0041] See also Figure 4As shown, in a preferred embodiment, the switching circuit also includes a mode switching control module 4, which includes a sixth resistor, a seventh resistor, an eighth resistor, a fourth switch tube and a second constant voltage power supply unit; the first end of the sixth resistor is used to receive the potential control signal, the second end of the sixth resistor is respectively connected to the first end of the seventh resistor and the control end of the fourth switch tube, the second end of the seventh resistor is grounded, the output end of the fourth switch tube is grounded, the input end of the fourth switch tube is connected to the first end of the eighth resistor, the input end of the fourth switch tube is also used to connect to the USB ID port of the USB interface, and the second end of the eighth resistor is connected to the second constant voltage power supply unit.

[0042] Specifically, in actual applications, the mode switching control module 4 is used to control the switching of the HOST state and the Device state of the device where the USB interface is located, and mainly includes a sixth resistor, a seventh resistor, an eighth resistor, a fourth switch tube and a second constant voltage power supply unit. The first end of the sixth resistor is used to receive a potential control signal, and the second end of the sixth resistor is respectively connected to the first end of the seventh resistor and the control end of the fourth switch tube, the second end of the seventh resistor is grounded, the output end of the fourth switch tube is grounded, the input end of the fourth switch tube is connected to the first end of the eighth resistor, and the input end of the fourth switch tube is also used to connect to the USB ID port of the USB interface, and the second end of the eighth resistor is connected to the second constant voltage power supply unit; by controlling the potential control signal received by the first end of the sixth resistor, the conduction and cutoff of the fourth switch tube are controlled, and then the potential output to the USB ID port of the USB interface by the mode switching control module 4 is controlled. When the USB ID port receives a high potential, the device where the USB interface is located acts as a master device, and when the USB ID port receives a low potential, the device where the USB interface is located acts as a slave device.

[0043] In a preferred embodiment, the fourth switch tube is a triode, the control end of the fourth switch tube is a base, the output end of the fourth switch tube is a collector, and the input end of the fourth switch tube is an emitter.

[0044] It is worth noting that when the fourth switch tube is a transistor, the potential signal received by the first end of the sixth resistor controls the conduction and cutoff of the fourth switch tube. The fourth switch tube can be an NPN transistor or a PNP transistor, which can be selected according to actual conditions.

[0045] It is understandable that the types of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube can be set according to the actual application, but it is necessary to ensure that the four switch tubes can be turned on at the same time under a certain potential signal. This is to achieve accurate power switching when the device where the USB interface is located switches the master-slave device mode, and avoid the port being burned out due to power conflicts.

[0046] In order to make the specific working process of the present invention clearer, a specific example is used below to illustrate. Figure 5 As shown, it is a specific circuit schematic diagram of a USB OTG power supply switching circuit provided by the present invention. The USB OTG power supply switching circuit includes a power supply switching module 1, a power supply switching control module 2, a mode switching control module 4 and a potential control module 3; the power supply switching module 1 includes a PMOS tube Q1 (a first switch tube), a PMOS tube Q2 (a second switch tube) and a first resistor R1; the power supply switching control module 2 includes a second resistor R2, a third resistor R3, a fourth resistor R4 and an NPN-type transistor Q3 (a third switch tube); the mode switching control module 4 includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, an NPN-type transistor Q4 (a fourth switch tube) and a second constant voltage power supply (VCC); the potential control module 3 includes a first constant voltage unit (VCC), a fifth resistor R5 and a first switch S1.

[0047] The drain of the PMOS tube Q1 is used to connect to the VBUS port (VBUS_IN) of the USB interface, the source of the PMOS tube Q1 is respectively connected to the source of the PMOS tube Q2 and the first end of the first resistor R1, the gate of the PMOS tube Q1 is respectively connected to the gate of the PMOS tube Q2 and the second end of the first resistor R1, the gate of the PMOS tube Q2 is connected to the first end of the second resistor R2, and the drain of the PMOS tube Q2 is used to connect to an external device; the second end of the second resistor R2 is connected to the collector of the NPN type transistor Q3, the emitter of the NPN type transistor Q3 is grounded, and the base of the NPN type transistor Q3 is respectively connected to the third resistor R3 The first end of the sixth resistor R6 is connected to the first end of the fourth resistor R4, the second end of the third resistor R3 is connected to the VBUS_EN port (the input port of the potential control signal, used to receive the potential control signal), and the second end of the fourth resistor R4 is grounded; the first end of the sixth resistor R6 is used to connect to the VBUS_EN port, the second end of the sixth resistor R6 is respectively connected to the first end of the seventh resistor R7 and the base of the NPN transistor Q4, the second end of the seventh resistor R7 is grounded, the emitter of the NPN transistor Q4 is grounded, the collector of the NPN transistor Q4 is connected to the first end of the eighth resistor R8, the collector of the NPN transistor Q4 is also used to connect to the USB ID port (SOC_USB_OTG_ID port) of the USB interface, and the second end of the eighth resistor R8 is connected to the second constant voltage power supply; the first constant voltage power supply is connected to the first end of the fifth resistor R5, the second end of the fifth resistor R5 is respectively connected to the first end of the first switch and the VBUS_EN port, and the second end of the first switch is grounded; the VBUS_EN port is also used to connect an external potential control unit (such as a general input and output port of a micro control unit).

[0048] When the device where the USB interface is located is working normally, USB OTG is in HOST state, the USB interface is connected to an external device such as a U disk and provides power to the outside, and the USB ID needs to be input as low. At this time, the first switch S1 remains in the disconnected state, and the first constant voltage power supply can provide a high potential for the VBUS_EN port or the GPIO port of the external potential control unit can provide a high potential for the VBUS_EN port. The voltage division of the sixth resistor R6 and the seventh resistor R7 makes the base of the NPN transistor Q4 high, and the NPN transistor Q4 is in the on state. The SOC_USB_OTG_ID port is connected to GND (ground) through the CE end (collector and emitter) of the NPN transistor Q4, so that the USB ID interface is at a low potential, and the USB OTG is in HOST state, so that the mode of the device where the USB interface is located is the master device mode; because the signal sources of the control of the master-slave mode and the control of the power supply switching are both input from the VBUS_EN port, when the mode of the device where the USB interface is located is the master device mode, the third resistor R3 and the fourth resistor R4 divide the voltage so that the NPN transistor Q3 is in the on state, the G poles (gates) of the PMOS tubes Q1 and Q2 are at a low potential, VBUS_IN is turned on through the parasitic diode of the PMOS tube Q1 (the manufacturing process of the MOS tube makes the MOS tube have a parasitic diode), the voltage of the G pole and the S pole (source) of the PMOS tube Q1 reaches the turn-on voltage, the conductive channel of the PMOS tube Q1 is formed, and the current passes through the D pole (drain) and S pole of the PMOS tube Q1. Since the PMOS tube Q1 and the PMOS tube Q2 are connected to the same G pole, similarly, the GS voltage of the PMOS tube Q2 also meets the turn-on voltage, Q2 is also in the on state, and the current flows from the S pole to the D pole of Q2; at this time, Q1-Q4 are all in the on state, the device where the USB interface is located is in the master device state, and the current flows from VBUS_IN to VBUS_OUT to power the external device.

[0049] When the device where the USB interface is located is in the debugging stage, the USB OTG is in the Device state, the potential of the USB ID of the USB interface needs to be high or floating, and the external device provides power to the USB port. At this time, VBUS_IN and VBUS_OUT need to be disconnected. At this time, by closing the first switch S1 to ground, the potential of VBUS_EN is low, or even if the first switch is not closed to ground, a low potential can be provided to VBUS_EN through the GPIO of the external control device, so that the NPN transistor Q4 is in a cut-off state, the potential of the USB ID of the USB interface is pulled up or left floating, and the device where the USB interface is located enters the Device mode; since the signal sources of the control of the master-slave mode and the control of the power supply switching are both input from the VBUS_EN port, when the mode of the device where the USB interface is located is the slave device mode, the NPN transistor Q3 is in a cut-off state, VBUS_IN is turned on through the parasitic diode of the PMOS tube Q1, and the current flows from the D end to the S end, but the PMOS tube Q2 is in a cut-off state and cannot reach the VBUS_OUT end. At this time, VBUS_OUT is turned on through the parasitic diode of the PMOS tube Q2, and the current flows from the D end to the S end, but because the PMOS tube Q1 is in a closed state, it cannot reach the VBUS_IN end, so that when the device where the USB interface is located is in the slave device state, it can avoid the conflict between the power supply of the device where the USB interface is located and the power supply of the external device, and avoid the port being burned due to the power supply conflict.

[0050] In the mass production stage, in order to reduce costs, in order to meet the USB OTG debugging power switching requirements in the research and development stage without increasing the cost of devices, an inductor is connected in series between the D pole of the PMOS tube Q1 and the D pole of the PMOS tube Q2. During mass production delivery, only the inductor is pasted, and the USB interface is set to HOST mode by default to directly power the external device. The power goes directly from VBUS_IN to VBUS_OUT through the inductor, and the remaining Q1~Q4, R1~R8 can be selectively left unpainted.

[0051] In summary, a USB OTG power switching circuit provided by an embodiment of the present invention controls the output voltage of the first end of the power switching control module 2 through the potential control signal received by the second end of the power switching control module 2, thereby controlling the conduction or cutoff of the two switch tubes in the power switching module 1, so that the power supply can switch the power supply mode following the master-slave switching of the USBOTG, thereby avoiding the port being burned out due to power supply conflicts.

[0052] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A USB OTG power supply switching circuit, characterized in that: include: A power supply switching module and a power supply switching control module, wherein the power supply switching module includes a first switch tube, a second switch tube and a first resistor; The input end of the first switch tube is used to connect to the VBUS port of the USB interface, the output end of the first switch tube is respectively connected to the input end of the second switch tube and the first end of the first resistor, the control end of the first switch tube is respectively connected to the control end of the second switch tube and the second end of the first resistor, the control end of the second switch tube is connected to the first end of the power supply switching control module, the output end of the second switch tube is used to connect to an external device, and the second end of the power supply switching control module is used to receive a potential control signal; The USB OTG power supply switching circuit also includes a potential control module and a mode switching control module; The potential control module specifically includes a first constant voltage power supply unit, a fifth resistor and a first switch; The first constant voltage power supply is connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the first end of the first switch for outputting the potential control signal, and the second end of the first switch is grounded; The mode switching control module includes a sixth resistor, a seventh resistor, an eighth resistor, a fourth switch tube and a second constant voltage power supply unit; the first end of the sixth resistor is used to receive the potential control signal, the second end of the sixth resistor is respectively connected to the first end of the seventh resistor and the control end of the fourth switch tube, the second end of the seventh resistor is grounded, the output end of the fourth switch tube is grounded, the input end of the fourth switch tube is connected to the first end of the eighth resistor, the input end of the fourth switch tube is also used to connect to the USB ID port of the USB interface, and the second end of the eighth resistor is connected to the second constant voltage power supply unit.

2. The USB OTG power supply switching circuit according to claim 1, characterized in that: The first switch tube is a MOS tube, and the second switch tube is a MOS tube.

3. The USB OTG power supply switching circuit according to claim 2, characterized in that: The first switch tube is a PMOS tube, the input end of the first switch tube is a drain, the output end of the first switch tube is a source, and the control end of the first switch tube is a gate; the second switch tube is a PMOS tube, the input end of the second switch tube is a source, the control end of the second switch tube is a gate, and the output end of the second switch tube is a drain.

4. The USB OTG power switching circuit according to claim 1, wherein: The power supply switching control module includes: a second resistor, a third resistor, a fourth resistor and a third switch tube; The first end of the second resistor is connected to the first end of the power supply switching control module, the second end of the second resistor is connected to the input end of the third switch tube, the output end of the third switch tube is grounded, the control end of the third switch tube is respectively connected to the first end of the third resistor and the first end of the fourth resistor, the second end of the third resistor is used to receive a potential control signal, and the second end of the fourth resistor is grounded.

5. The USB OTG power supply switching circuit according to claim 4, characterized in that: It also includes a micro control unit, the universal input and output port of the micro control unit is used to output the potential control signal.

6. The USB OTG power supply switching circuit according to claim 4, characterized in that: The third switch tube is a triode, the input end of the third switch tube is a collector, the output end of the third switch tube is an emitter, and the control end of the third switch tube is a base.

7. The USB OTG power supply switching circuit according to claim 4, characterized in that: The fourth switch tube is a triode, the control end of the fourth switch tube is a base, the output end of the fourth switch tube is a collector, and the input end of the fourth switch tube is an emitter.

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