Protection circuit for preventing OTG (On-The-Go) burning backflow

Abstract

The invention provides a protection circuit for preventing OTG burning backflow. The protection circuit for preventing OTG burning backflow comprises a control circuit, a power conversion circuit and a switching circuit, one end of the power conversion circuit is connected with the control circuit and a USB power supply and used for receiving a switching signal output by the control circuit, the other end of the power conversion circuit is connected with the connection interface and used for providing power supply voltage for the connection interface, and the connection interface is used for being connected with USB equipment or OTG equipment; one end of the switching circuit is connected with the control circuit and used for receiving a switching signal, and the other end of the switching circuit is connected with an OTG power supply; wherein when the connection interface is not connected with the OTG equipment, the power conversion circuit is conducted and provides power supply voltage for the connection interface, and when the connection interface is connected with the OTG equipment, the switching circuit is conducted, and the power conversion circuit is disconnected so as to prevent current of the OTG equipment from flowing backwards. According to the invention, current backflow can be prevented, and the connection interface can be used as a USB interface and an OTG interface at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, and particularly relates to a protection circuit for preventing OTG programming from backflowing. BACKGROUND

[0002] At present, most master control chips need to be programmed through OTG function to update the system, that is, connecting the OTG device with the master control chip to update the system of the master control chip through the OTG device. The OTG device is usually connected with the master control chip through the connection interface of the master control chip. However, the OTG device is usually powered by the OTG power supply. When the OTG device is connected with the connection interface, the current of the OTG device is easy to backflow into the mainboard of the master control chip, thereby damaging the mainboard. SUMMARY

[0003] The present application provides a protection circuit for preventing OTG programming from backflowing, which aims to solve the problem that the current of the OTG device is easy to backflow into the mainboard of the master control chip when the master control chip is programmed through OTG, thereby damaging the mainboard.

[0004] The present application provides a protection circuit for preventing OTG programming from backflowing, which includes a control circuit, a power conversion circuit and a switch circuit. One end of the power conversion circuit is connected with the control circuit and a USB power supply respectively, for receiving a switch signal output by the control circuit. The other end of the power conversion circuit is connected with a connection interface, for providing a power supply voltage for the connection interface. The connection interface is used for connecting with a USB device or an OTG device. One end of the switch circuit is connected with the control circuit, for receiving the switch signal. The other end of the switch circuit is used for connecting with the OTG power supply. When the connection interface is not connected with the OTG device, the power conversion circuit is turned on and provides the power supply voltage for the connection interface. When the connection interface is connected with the OTG device, the switch circuit is turned on, and the power conversion circuit is turned off to prevent the current of the OTG device from backflowing.

[0005] Further, the power conversion circuit includes a power conversion chip, which is connected with the control circuit, the USB power supply and the connection interface respectively.

[0006] Further, the power conversion chip includes an enable pin, an input pin and an output pin. The enable pin is connected with the control circuit, for receiving the switch signal. The input pin is connected with the USB power supply. The output pin is connected with the connection interface.

[0007] Further, the power conversion circuit further comprises a first resistor, a second resistor and a first capacitor; one end of the first resistor is connected with the USB power supply, the other end of the first resistor, one end of the second resistor and one end of the first capacitor are connected with the control circuit, the other end of the second resistor is grounded, and the other end of the first capacitor is grounded.

[0008] Further, the power conversion circuit further comprises a third resistor, a first diode and a second capacitor; one end of the third resistor and the positive electrode of the first diode are connected with the USB power supply, the other end of the third resistor and the negative electrode of the first diode are connected with one end of the second capacitor and the input pin respectively, and the other end of the second capacitor is grounded.

[0009] Further, the power conversion circuit further comprises a fourth resistor, a fifth resistor, a third capacitor and a fourth capacitor; one end of the fourth resistor, one end of the third capacitor and one end of the fourth capacitor are connected with the output pin, the other end of the fourth resistor, the other end of the third capacitor and the other end of the fourth capacitor are grounded, one end of the fifth resistor is connected with the fault flag pin of the power conversion chip, and the other end of the fifth resistor is grounded.

[0010] Further, the switch circuit comprises a switch chip, the first pin and the second pin of the switch chip are connected with the mainboard total power supply, the third pin and the fourth pin of the switch chip are connected with the OTG power supply, the fifth pin of the switch chip is connected with the control circuit, and the sixth pin of the switch chip is grounded.

[0011] Further, the switch circuit further comprises a sixth resistor and a seventh resistor; one end of the sixth resistor is connected with the mainboard total power supply, the other end of the sixth resistor is connected with one end of the seventh resistor and the first pin respectively, and the other end of the seventh resistor is connected with the second pin.

[0012] Further, the switch circuit further comprises an eighth resistor; one end of the eighth resistor is connected with the power supply end, and the other end of the eighth resistor is connected with the fifth pin.

[0013] Further, the switch circuit further comprises a ninth resistor; one end of the ninth resistor is connected with the OTG power supply, and the other end of the ninth resistor is connected with the third pin and the fourth pin respectively.

[0014] The application discloses a protection circuit for preventing OTG burning and backflow, which comprises a control circuit, a power conversion circuit and a switch circuit. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 is a block diagram of the protection circuit for preventing OTG burning and backflow provided by an embodiment of the present application; Figure 2 is a circuit diagram of the power conversion circuit provided by an embodiment of the present application; Figure 3 is a circuit diagram of the switch circuit provided by an embodiment of the present application. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0018] It should be understood that when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of the described features, integers, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, operations, elements, components and / or groups thereof.

[0019] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used in this specification and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "and / or", as used herein, refers to and encompasses any and all possible combinations of one or more of the associated listed items. It is also to be understood that the term "or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0020] In addition, the terms of direction mentioned in the present application, such as "up", "down", "front", "back", "left", "right", "inner", "outer", "side" and the like, are only the directions of the attached drawings and the directions of the product in use. Therefore, the terms of direction used are for the purpose of illustration and understanding of the present application, but not for the purpose of limiting the present application. In addition, in the attached drawings, similar or identical structures are denoted by the same reference numerals.

[0021] Referring to Figures 1 to 3 , Figure 1 is a block schematic diagram of a protection circuit 100 for preventing OTG programming backflow provided by an embodiment of the present application; Figure 2 is a circuit diagram of a power conversion circuit 20 provided by an embodiment of the present application; Figure 3 is a circuit diagram of a switch circuit 30 provided by an embodiment of the present application. As shown in Figures 1 to 3 , the protection circuit 100 for preventing OTG programming backflow includes a control circuit 10, a power conversion circuit 20 and a switch circuit 30; one end of the power conversion circuit 20 is connected with the control circuit 10 and a USB power supply 200 respectively, for receiving a switch signal output by the control circuit 10, and the other end of the power conversion circuit 20 is connected with a connection interface 300, for providing a power supply voltage for the connection interface 300, wherein the connection interface 300 is used for connecting with a USB device or an OTG device; one end of the switch circuit 30 is connected with the control circuit 10, for receiving the switch signal, and the other end of the switch circuit 30 is used for connecting with an OTG power supply 400; wherein when the connection interface 300 is not connected with the OTG device, the power conversion circuit 20 is turned on and provides the power supply voltage for the connection interface 300, and when the connection interface 300 is connected with the OTG device, the switch circuit 30 is turned on, and the power conversion circuit 20 is turned off to prevent the current backflow of the OTG device.

[0022] Specifically, the OTG programming backflow prevention protection circuit 100 provided by the present application can be applied to electronic devices, such as industrial control devices, smart wearable devices, and vehicle control devices. The industrial control device can be an industrial PLC module, which needs to be connected to a computer through the connection interface 300 for program programming or parameter debugging. If the mainboard of the industrial PLC module is directly connected to two power supplies (USB power supply 200 and OTG power supply 400), backflow caused by voltage difference is easy to occur, which damages the main control chip in the module. The smart wearable device can be a smart bracelet. The main control chip of the smart bracelet needs to be connected to an OTG device through the connection interface 300, and the motion algorithm and system program are programmed through the OTG device. If the current of the OTG device enters the smart bracelet during programming, the mainboard of the smart bracelet is easy to be damaged, which further causes the smart bracelet to be damaged.

[0023] The OTG programming backflow prevention protection circuit 100 can include a control circuit 10, a power conversion circuit 20, and a switch circuit 30. The control circuit 10 is connected to the power conversion circuit 20 and the switch circuit 30, respectively, and is used to output a switch signal, which can control the conduction and the closing of the power conversion circuit 20.

[0024] The power conversion circuit 20 is connected with the connection interface 300, which can be a USB interface, for connecting with a USB device and an OTG device. When the connection interface 300 is connected with the USB device, the USB power supply 200 in the device supplies power to the connection interface 300, and in turn, can supply power to the USB device, and when the connection interface 300 is connected with the OTG device, the OTG power supply 400 supplies power to the OTG device, at this time, there is a risk of current in the OTG device flowing back into the device. The power conversion circuit 20 is used to connect the USB power supply 200 and the connection interface 300, when the power conversion circuit 20 is turned on, the USB power supply 200 can supply power to the connection interface 300 through the power conversion circuit 20, and when the power conversion circuit 20 is turned off, the USB power supply 200 is disconnected from the connection interface 300, at this time, even if the OTG device is connected with the connection interface 300, the current in the OTG device cannot flow back into the device. For example, the switch signal can be a level signal, the level signal includes a first level signal and a second level signal, and it is set that the power conversion circuit 20 is turned on when receiving the first level signal and is turned off when receiving the second level signal, then when the connection interface 300 is not connected with the OTG device, the control circuit 10 outputs the first level signal, at this time, the power conversion circuit 20 is turned on, and the USB power supply 200 supplies power to the connection interface 300 through the power conversion circuit 20, when the connection interface 300 is connected with the OTG device, the control circuit 10 outputs the second level signal, at this time, the power conversion circuit 20 is turned off, and the USB power supply 200 is disconnected from the connection interface 300, preventing current from flowing back. It can be understood that the control circuit 10 can actively detect whether the connection interface 300 is connected with the OTG device, and in turn, output the first level signal or the second level signal according to the detection result, or adjust the switch signal through a hardware circuit.

[0025] The switch circuit 30 is connected with the OTG power supply 400, and the switch circuit 30 is also connected with the control circuit 10 and can receive the switch signal, that is, the switch signal output by the control circuit 10 is output to the switch circuit 30 and the power conversion circuit 20 respectively, when the connection interface 300 is not connected with the OTG device, the control circuit 10 outputs the first level signal, at this time, the power conversion circuit 20 is turned on, and the switch circuit 30 is turned off, when the connection interface 300 is connected with the OTG device, the OTG power supply 400 is connected, at this time, the switch circuit 30 is turned on, and the first level signal can be adjusted to the second level signal, the power conversion circuit 20 is turned off, and current flowing back is prevented.

[0026] Referring to Figure 2As a further embodiment, the power conversion circuit 20 comprises a power conversion chip U1 connected with the control circuit 10, the USB power supply 200 and the connection interface 300 respectively. Further, the power conversion chip U1 comprises an enable pin, an input pin and an output pin; the enable pin is connected with the control circuit 10 for receiving the switch signal, the input pin is connected with the USB power supply 200, and the output pin is connected with the connection interface 300. Further, the power conversion circuit 20 further comprises a first resistor R1, a second resistor R2 and a first capacitor C1; one end of the first resistor R1 is connected with the USB power supply 200, the other end of the first resistor R1, one end of the second resistor R2 and one end of the first capacitor C1 are all connected with the control circuit 10, the other end of the second resistor R2 is grounded, and the other end of the first capacitor C1 is grounded. Further, the power conversion circuit 20 further comprises a third resistor R3, a first diode D1 and a second capacitor C2; one end of the third resistor R3 and the positive electrode of the first diode D1 are both connected with the USB power supply 200, the other end of the third resistor R3 and the negative electrode of the first diode D1 are respectively connected with one end of the second capacitor C2 and the input pin, and the other end of the second capacitor C2 is grounded. Further, the power conversion circuit 20 further comprises a fourth resistor R4, a fifth resistor R5, a third capacitor C3 and a fourth capacitor C4; one end of the fourth resistor R4, one end of the third capacitor C3 and one end of the fourth capacitor C4 are all connected with the output pin, the other end of the fourth resistor R4, the other end of the third capacitor C3 and the other end of the fourth capacitor C4 are all grounded, and one end of the fifth resistor R5 is connected with the fault flag pin of the power conversion chip U1, and the other end of the fifth resistor R5 is grounded.

[0027] The power conversion circuit 20 can include a power conversion chip U1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, and a first diode D1. The first resistor R1 and the second resistor R2 constitute a voltage dividing circuit, divide the voltages of VCCS5V0_SYS and OTG_VBUS_DRV_R, and input the adjusted voltages to the enable pin of the power conversion chip U1, so as to realize accurate enable control of the power conversion chip U1. The third resistor R3 is a current limiting resistor connected between the USB power supply 200 and the input pin, used to limit the current of VCCS5V0_SYS to the input pin of the power conversion chip U1, and prevent overcurrent damage to the chip. The fourth resistor R4 is a bleeder resistor connected to the output pin, used to release the charges stored in the third capacitor C3 and the fourth capacitor C4 when the power conversion chip U1 is turned off, and prevent voltage residue from causing the OTG device to be mistakenly powered. The fifth resistor R5 is connected to the FLG# pin of the power conversion chip U1, used to stabilize the flag level. The first capacitor C1, the second capacitor C2, the third capacitor C3, and the fourth capacitor C4 are all filter capacitors. The first capacitor C1 is connected to the USB power supply 200 and the control circuit 10, used to filter high-frequency noise of the enable pin, make the enable signal more stable, and avoid false triggering of the power conversion chip U1. The second capacitor C2 is connected to the USB power supply 200, used to filter voltage ripple of the input pin, make the voltage input to the power conversion chip U1 more stable, and improve the purity of the output power. The third capacitor C3 and the fourth capacitor C4 are connected in parallel and connected to the output pin, used to reduce the ripple of VCC_OTG_5V, improve the stability of the output voltage, and provide clean 5V power for the connection interface 300. The first diode D1 is used to prevent damage to the power conversion chip U1 caused by reverse current of the input pin, and to clamp the input voltage when the power fluctuates.

[0028] As shown in Figure 2 , EN is the enable pin, VIN is the input pin, VOUT is the output pin, OTG_VBUS_DRV_R is the switching signal, VCC5V0_SYS is the power supply voltage provided by the USB power supply 200, and VCC_OTG_5V is the power supply voltage output by the power conversion chip U1, used to power the connection interface 300. When OTG_VBUS_DRV_R is a high-level signal, the power conversion chip U1 is turned on, at this time, VCC5V0_SYS is output to the connection interface 300 through the input pin and the output pin, and provides power supply voltage for the connection interface 300. When the connection interface 300 is connected with the USB device, the USB device can be powered. When OTG_VBUS_DRV_R is a low-level signal, the power conversion chip U1 is turned off, at this time, VCC5V0_SYS cannot power the connection interface 300, and the current of the OTG device cannot flow back.

[0029] Referring to Figure 3 , as a further embodiment, the switch circuit 30 comprises a switch chip U2, the first pin and the second pin of the switch chip U2 are connected with the mainboard total power supply, the third pin and the fourth pin of the switch chip U2 are connected with the OTG power supply 400, the fifth pin of the switch chip U2 is connected with the control circuit 10, and the sixth pin of the switch chip U2 is grounded. Further, the switch circuit 30 further comprises a sixth resistor R6 and a seventh resistor R7; one end of the sixth resistor R6 is connected with the mainboard total power supply, the other end of the sixth resistor R6 is connected with the first pin and the other end of the seventh resistor R7 respectively, and the other end of the seventh resistor R7 is connected with the second pin. Further, the switch circuit 30 further comprises an eighth resistor R8; one end of the eighth resistor R8 is connected with the power supply end, and the other end of the eighth resistor R8 is connected with the fifth pin. Further, the switch circuit 30 further comprises a ninth resistor R9; one end of the ninth resistor R9 is connected with the OTG power supply 400, and the other end of the ninth resistor R9 is connected with the third pin and the fourth pin respectively.

[0030] Wherein, the switch circuit 30 can comprise a switch chip U2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8 and a ninth resistor R9, the sixth resistor R6 is a current limiting resistor, connected between the mainboard total power supply and the switch chip U2, the seventh resistor R7 is a pull-down resistor, connected between the sixth resistor R6 and the switch chip U2, the seventh resistor R7 is a current limiting resistor, connected between the power supply end and the switch chip U2, and the ninth resistor R9 is connected between the OTG power supply 400 and the switch chip U2.

[0031] As Figure 3 shown, the switch chip U2 can be composed of two MOS tubes, which are a first MOS tube and a second MOS tube, the gate G1 of the first MOS tube is connected with the mainboard total power supply through the sixth resistor R6, the source S1 of the first MOS tube is connected with the mainboard total power supply through the seventh resistor R7 and the sixth resistor R6, the drain of the first MOS tube is connected with the OTG power supply 400 through the ninth resistor R9, the gate G2 of the second MOS tube is connected with the OTG power supply 400 through the ninth resistor R9, the drain D2 of the second MOS tube is connected with the control circuit 10, and the source S2 of the second MOS tube is grounded. When the OTG power supply 400 is connected, Figure 2 VCC_OTG_5V is connected with the gate G2 of the second MOS tube, the second MOS tube is turned on, at this time, OTG_VBUS_DRV_R is output to low through the second MOS tube, and then the level of OTG_VBUS_DRV_R can be pulled down, OTG_VBUS_DRV_R is converted from high level to low level, and then the power conversion circuit 20 is turned off.

[0032] The disclosed prevention OTG burning back-in protection circuit controls the power conversion circuit to be turned on by outputting a switch signal from the control circuit when no OTG device is connected, and the USB power supply supplies power to the connection interface through the power conversion circuit, at this time, the connection interface is a USB interface, which is used for connecting a USB device, when an OTG device is connected, the control circuit detects the OTG power supply, the switch circuit is turned on, and the power conversion circuit is turned off, so that the current of the OTG device cannot back in the mainboard, which not only prevents the current from back in, but also allows the connection interface to be used as a USB interface and an OTG interface at the same time.

[0033] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A circuit for preventing backflow during OTG programming, characterized in that, The OTG programming backflow protection circuit includes: Control circuit; A power conversion circuit, one end of which is connected to the control circuit and the USB power supply respectively, for receiving the switching signal output by the control circuit, and the other end of which is connected to the connection interface for providing power supply voltage to the connection interface, wherein the connection interface is used to connect to a USB device or an OTG device. A switching circuit, one end of which is connected to the control circuit for receiving the switching signal, and the other end of which is connected to the OTG power supply; When the connection interface is not connected to the OTG device, the power conversion circuit is turned on and provides power supply voltage to the connection interface. When the connection interface is connected to the OTG device, the switch circuit is turned on and the power conversion circuit is turned off to prevent current backflow from the OTG device.

2. The OTG programming backflow protection circuit as described in claim 1, characterized in that, The power conversion circuit includes a power conversion chip, which is connected to the control circuit, the USB power supply, and the connection interface.

3. The OTG programming backflow protection circuit as described in claim 2, characterized in that, The power conversion chip includes an enable pin, an input pin, and an output pin; The enable pin is connected to the control circuit and is used to receive the switch signal; the input pin is connected to the USB power supply; and the output pin is connected to the connection interface.

4. The OTG programming backflow protection circuit as described in claim 3, characterized in that, The power conversion circuit also includes a first resistor, a second resistor, and a first capacitor; One end of the first resistor is connected to the USB power supply, and the other end of the first resistor, one end of the second resistor, and one end of the first capacitor are all connected to the control circuit. The other end of the second resistor is grounded, and the other end of the first capacitor is grounded.

5. The OTG programming backflow protection circuit as described in claim 3, characterized in that, The power conversion circuit also includes a third resistor, a first diode, and a second capacitor; One end of the third resistor and the positive terminal of the first diode are both connected to the USB power supply. The other end of the third resistor and the negative terminal of the first diode are respectively connected to one end of the second capacitor and the input pin. The other end of the second capacitor is grounded.

6. The OTG programming backflow protection circuit as described in claim 3, characterized in that, The power conversion circuit also includes a fourth resistor, a fifth resistor, a third capacitor, and a fourth capacitor; One end of the fourth resistor, one end of the third capacitor, and one end of the fourth capacitor are all connected to the output pin. The other ends of the fourth resistor, the third capacitor, and the fourth capacitor are all grounded. One end of the fifth resistor is connected to the fault flag pin of the power conversion chip, and the other end of the fifth resistor is grounded.

7. The OTG programming backflow protection circuit as described in claim 3, characterized in that, The switching circuit includes a switching chip. The first and second pins of the switching chip are both connected to the main power supply of the motherboard. The third and fourth pins of the switching chip are both connected to the OTG power supply. The fifth pin of the switching chip is connected to the control circuit. The sixth pin of the switching chip is grounded.

8. The OTG programming backflow protection circuit as described in claim 7, characterized in that, The switching circuit also includes a sixth resistor and a seventh resistor; One end of the sixth resistor is connected to the main power supply of the motherboard, the other end of the sixth resistor is connected to one end of the seventh resistor and the first pin, and the other end of the seventh resistor is connected to the second pin.

9. The OTG programming backflow protection circuit as described in claim 7, characterized in that, The switching circuit also includes an eighth resistor; One end of the eighth resistor is connected to the power supply terminal, and the other end of the eighth resistor is connected to the fifth pin.

10. The OTG programming backflow protection circuit as described in claim 7, characterized in that, The switching circuit also includes a ninth resistor; One end of the ninth resistor is connected to the OTG power supply, and the other end of the ninth resistor is connected to the third pin and the fourth pin respectively.

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