阅读说明：本技术 一种用于视频接口的防止电流倒流的电路、方法及设备 (Circuit, method and equipment for preventing current backflow for video interface ) 是由 何杰 严武 于 2021-08-07 设计创作，主要内容包括：本申请公开了一种用于视频接口的防止电流倒流的电路、方法及设备,其涉及防电流倒流技术领域,该电路包括：控制模块,用于检测判断第一外部设备是否接入；若是,则控制模块输出第一控制信号；若否,则控制模块输出第二控制信号；供电模块,向控制模块输出电能；电路保护模块,接收到第一控制信号时切换至正向导通状态,以使供电模块向第二外部设备输出导通电压,导通电压不小于第二外部设备上视频接口的最低供电电压,接收到第二控制信号时切换至防倒流状态以防止第二外部设备的电流倒流。本申请具有能防止电流倒流又具有很低的电压落差的优点。(The application discloses a circuit, a method and equipment for preventing current backflow for a video interface, which relates to the technical field of current backflow prevention, wherein the circuit comprises: the control module is used for detecting and judging whether the first external equipment is accessed; if so, the control module outputs a first control signal; if not, the control module outputs a second control signal; the power supply module outputs electric energy to the control module; and the circuit protection module is switched to a forward conduction state when receiving the first control signal so as to enable the power supply module to output conduction voltage to the second external equipment, the conduction voltage is not less than the lowest power supply voltage of a video interface on the second external equipment, and the circuit protection module is switched to a backflow prevention state when receiving the second control signal so as to prevent the current backflow of the second external equipment. The current backflow preventing device has the advantages of being capable of preventing current backflow and having low voltage drop.)

1. A circuit for preventing reverse current flow for a video interface, comprising:

the control module (1) is used for detecting and judging whether the first external equipment (4) is accessed or not;

the power supply module (2) is connected with the control module (1) to output electric energy to the control module (1);

the circuit protection module (3) is respectively connected with the control module (1), the power supply module (2) and a second external device (5);

if the first external equipment (4) is accessed, the control module (1) outputs a first control signal;

if the first external equipment (4) is not accessed, the control module (1) outputs a second control signal;

when receiving the first control signal, the circuit protection module (3) switches to a forward conduction state, so that the power supply module (2) outputs a conduction voltage to the second external device (5) through the circuit protection module (3), and the conduction voltage is not less than the lowest power supply voltage of a video interface on the second external device (5);

and when receiving the second control signal, the circuit protection module (3) is switched to a backflow prevention state to prevent the current backflow of the second external device (5).

2. A circuit for preventing current backflow for a video interface according to claim 1, wherein the circuit protection module (3) comprises:

the FET unit (31) has two states of the forward conduction state and the backflow prevention state, is respectively connected with the power supply module (2) and the second external equipment (5), and when the power supply module (2) is in the forward conduction state, the conduction voltage is output to a video interface of the second external equipment (5) by the FET unit (31);

and the driving unit (32) is connected with the control module (1) and receives the first control signal or the second control signal to switch the state of the FET unit (31).

3. A circuit for preventing current backflow for a video interface according to claim 2, wherein the control module (1) comprises:

the voltage comparison unit (11) is connected with the first external device (4), receives a first voltage output by the first external device (4), and judges whether the first voltage is greater than a preset second voltage;

if the first voltage is greater than the second voltage, the voltage comparison unit (11) outputs a first comparison signal;

if the first voltage is smaller than the second voltage, the voltage comparison unit (11) outputs a second comparison signal;

the control unit (12) is connected with the voltage comparison unit (11) to receive the first comparison signal or the second comparison signal, outputs the first control signal when receiving the first comparison signal, and outputs the second control signal when receiving the second comparison signal;

the signal amplification unit (13) is connected with the control unit (12) to receive and amplify the first control signal or the second control signal, and is connected with the driving unit (32) to output the amplified first control signal or the amplified second control signal to the driving unit (32).

4. A circuit for preventing current backflow for a video interface according to claim 2, wherein the circuit protection module (3) further comprises:

and the under-voltage protection unit (33) is respectively connected with the power supply module (2) and the drive unit (32) and is used for playing an under-voltage protection role on the drive unit (32).

5. A circuit for preventing current backflow for a video interface according to claim 2, wherein the circuit protection module (3) further comprises:

a current detection unit (34) connected with the FET unit (31) to receive a first current output from the FET unit (31) and judge whether the first current is larger than a preset second current;

if the first current is larger than the second current, the current detection unit (34) outputs an overcurrent signal;

if the first current is less than the second current, the current detection unit (34) does not output the over-current signal,

and the overcurrent protection unit (35) is respectively connected with the current detection unit (34) and the drive unit (32), receives the overcurrent signal and responds to the overcurrent signal to output an adjusting signal to the drive unit (32), and the drive unit (32) receives the adjusting signal and responds to the adjusting signal to adjust the output current of the FET unit (31).

6. A circuit for preventing current backflow for a video interface according to claim 5, wherein the circuit protection module (3) further comprises:

a filtering unit (36) connected to the FET unit (31) to filter stray currents in the first current.

7. A circuit for preventing reverse current flow for a video interface according to any of claims 1-6, further comprising:

the temperature detection module (6) is used for detecting the real-time temperature of the circuit protection module (3) and is respectively connected with the driving unit (32) and the power supply module (2);

if the real-time temperature is larger than a preset temperature threshold value, outputting an over-temperature signal to the driving unit (32), and the driving unit (32) receiving the over-temperature signal and responding to the over-temperature signal so as to switch the state of the FET unit (31) to the backflow prevention state.

8. A method for preventing current backflow for a video interface, applied to a circuit for preventing current backflow for a video interface according to any one of claims 1-7, comprising the steps of:

the control module (1) judges whether the first external equipment (4) is accessed;

if the first external device (4) is not connected, controlling the FET unit (31) to be in the backflow prevention state through the driving unit (32);

if the first external device (4) is connected, judging whether the power supply module (2) supplies power to the FET unit (31);

if the power supply module (2) supplies power to the FET unit (31), the FET unit (31) is controlled to be switched to the forward conduction state through the driving unit (32), so that a power supply path is established between the power supply module (2) and the second external device (5);

if the power supply module (2) does not supply power to the FET unit (31), the drive unit (32) controls the FET unit (31) to maintain the anti-backflow state.

9. A method for preventing current backflow for a video interface according to claim 8, wherein said method further comprises the steps of:

the current detection unit (34) determines whether the first current is greater than the second current;

-not controlling the FET unit (31) to regulate the output current if the first current is less than the second current;

if the first current is larger than the second current, controlling the FET unit (31) to regulate output current through the current detection unit (34), the overcurrent protection unit (35) and the driving unit (32), and judging whether the real-time temperature of the circuit protection module (3) is larger than the temperature threshold value through the temperature detection module (6);

if the temperature is larger than the temperature threshold value, controlling the FET unit (31) to be switched to the backflow prevention state through the driving unit (32);

the FET unit (31) maintains the forward conduction state if the temperature is less than the temperature threshold.

10. An apparatus, characterized in that the apparatus comprises a current backflow prevention circuit for a video interface according to any one of the preceding claims 1-7.

Technical Field

The present application relates to the field of current backflow prevention technologies, and in particular, to a circuit, a method, and a device for preventing current backflow for a video interface.

Background

The existing video interfaces comprise HDMI interfaces, DVI interfaces and VGA interfaces, and the notebook computer generally only has video interfaces of 1-2 types, so that the types of the video interfaces of the notebook computer can be expanded through the docking station, and the notebook computer can be suitable for display equipment with various different video interfaces.

When the notebook computer is connected with the display device through the docking station, the docking station reads the EDID of the display device through a circuit shared by HDMI, DVI and VGA interfaces, wherein the EDID is an electronic tag used by the display device to describe the display capability and audio output capability of the display device, the data reading of the EDID is realized through an I2C bus, and the I2C bus needs to be pulled up to a voltage close to the rated voltage through an external resistor. Due to the I2C bus and the external resistor, when the docking station is in the power-off state and the display device is not powered off, the current in the display device may flow back into the docking station through the I2C bus and the external resistor, causing the circuits in the docking station to be abnormal and unable to work normally.

In the prior art, the problem of current backflow is solved by additionally arranging a diode in an internal circuit of the docking station, and the current can only flow from the docking station to a video interface of the display device in a one-way mode but not flow back from the video interface of the display device by utilizing the one-way conductive characteristic of the diode.

With respect to the related art among the above, the inventors consider that the following drawbacks exist: the docking station is usually powered by 5V with a voltage tolerance of ± 5%, so the minimum power supply voltage of the docking station is 4.75V, and under the current required for reading the EDID, the voltage drop generated by the forward conduction of the diodes of different models is about 0.2V to 0.7V, and the minimum power supply voltage required by the video interface of the display device is usually 4.7V, so when the power supply voltage of the docking station is less than 4.9V, any one of the diodes cannot meet the minimum power supply voltage required by the video interface of the display device due to the voltage drop.

Disclosure of Invention

In order to overcome the defect that the minimum supply voltage of a video interface of a display device may not be met with the function of preventing current backflow, the application provides a circuit, a method and a device for preventing current backflow for the video interface.

In a first aspect, the present application provides a circuit for preventing current backflow for a video interface, which adopts the following technical solution:

a circuit for preventing a reverse current flow for a video interface, comprising:

the control module is used for detecting and judging whether the first external equipment is accessed;

the power supply module is connected with the control module to output electric energy to the control module;

the circuit protection module is respectively connected with the control module, the power supply module and second external equipment;

if the first external equipment is accessed, the control module outputs a first control signal;

if the first external equipment is not accessed, the control module outputs a second control signal;

the circuit protection module is switched to a forward conduction state when receiving the first control signal, so that the power supply module outputs conduction voltage to the second external equipment through the circuit protection module, and the conduction voltage is not less than the lowest power supply voltage of a video interface on the second external equipment;

and the circuit protection module is switched to a backflow prevention state to prevent the current backflow of the second external equipment when receiving the second control signal.

By adopting the technical scheme, the initial state of the circuit protection module is a backflow prevention state, when the control module detects that the first external equipment is connected, the control module outputs a first control signal to the circuit protection module, so that the circuit protection module is switched from the backflow prevention state to a forward conduction state, the power supply module can output conduction voltage to the video interface of the second external equipment through the circuit protection module, and even if the conduction voltage passes through the voltage protection module, voltage drop can be generated, the conduction module after the voltage drop is still larger than the lowest power supply voltage of the video interface on the second external equipment; when the control module detects that the first external equipment is not connected, the circuit protection module is switched to a backflow prevention state to prevent current in the second external equipment from flowing back through the video interface to cause circuit abnormity.

Optionally, the circuit protection module includes:

the FET unit has two states of the forward conduction state and the backflow prevention state, is respectively connected with the power supply module and the second external equipment, and when the FET unit is in the forward conduction state, the power supply module outputs the conduction voltage to a video interface of the second external equipment through the FET unit;

and the driving unit is connected with the control module and receives the first control signal or the second control signal so as to switch the state of the FET unit.

By adopting the technical scheme, the state of the FET unit is switched by different control signals received by the driving unit, and when the FET unit is in a forward conduction state, the power supply module can output conduction voltage to a video interface of the second external device through the FET unit; when the FET unit is in a backflow prevention state, current in the second external device is prevented from flowing back through the video interface.

Optionally, the control module includes:

the voltage comparison unit is used for being connected with the first external equipment, receiving a first voltage output by the first external equipment and judging whether the first voltage is greater than a preset second voltage or not;

if the first voltage is greater than the second voltage, the voltage comparison unit outputs a first comparison signal;

if the first voltage is smaller than the second voltage, the voltage comparison unit outputs a second comparison signal;

the control unit is connected with the voltage comparison unit to receive the first comparison signal or the second comparison signal, outputs the first control signal when receiving the first comparison signal, and outputs the second control signal when receiving the second comparison signal;

the signal amplification unit is connected with the control unit to receive and amplify the first control signal or the second control signal, and is connected with the driving unit to output the amplified first control signal or the amplified second control signal to the driving unit.

By adopting the technical scheme, when the first external equipment is connected with the voltage comparison unit and outputs the first voltage to the voltage comparison unit, the voltage comparison unit compares the first voltage with the preset second voltage, if the first voltage is greater than the second voltage, the first external equipment is judged to be successfully accessed, and a first comparison signal is output to the control unit; if the first voltage is less than the second voltage, judging that the first external equipment is not accessed or is not successfully accessed, and outputting a second comparison signal to the control unit at the moment; the control unit receives the first comparison signal and outputs a first control signal to the signal amplification unit, the control unit receives the second comparison signal and outputs a second control signal to the signal amplification unit, the signal amplification unit receives the control signal and amplifies the control signal, and the amplified control signal is output to the driving unit, so that the driving unit receives the control signal and controls the state of the FET unit.

Optionally, the circuit protection module further includes:

and the undervoltage protection unit is respectively connected with the power supply module and the driving unit and is used for performing undervoltage protection on the driving unit.

Through adopting above-mentioned technical scheme, if the short circuit appears in power module, line voltage can appear reducing by a wide margin in the short time or even disappearance's phenomenon to produce excessive electric current, probably lead to the drive unit to damage, consequently through undervoltage protection circuit's setting, play undervoltage protection effect to the drive unit.

Optionally, the circuit protection module further includes:

the current detection unit is connected with the FET unit to receive a first current output from the FET unit and judge whether the first current is larger than a preset second current or not;

if the first current is larger than the second current, the current detection unit outputs an overcurrent signal;

if the first current is smaller than the second current, the current detection unit does not output the over-current signal,

and the overcurrent protection unit is respectively connected with the current detection unit and the drive unit, receives the overcurrent signal and responds to the overcurrent signal to output an adjusting signal to the drive unit, and the drive unit is connected with the adjusting signal and responds to the adjusting signal to adjust the output current of the FET unit.

By adopting the technical scheme, the second current is preset in the current detection unit, the first current output by the FET unit is monitored in real time, when the first current is larger than the second current, the first current is possibly caused by instability of the current output from the FET unit, the current detection unit outputs an overcurrent signal to the overcurrent protection unit at the moment, and the overcurrent protection unit outputs an adjustment signal to the driving unit after receiving the overcurrent signal, so that the driving unit controls the FET unit and keeps the output current of the FET unit in a constant state.

Optionally, the circuit protection module further includes:

and the filtering unit is connected with the FET unit to filter the stray current in the first current.

Through adopting above-mentioned technical scheme, because probably mingled with some stray current in the first current from the output of FET unit, stray current can lead to the current instability in the circuit, still can influence the life of circuit, consequently through the setting of filtering unit, can filter the stray current of mingling in the first current.

Optionally, the circuit further includes:

the temperature detection module is used for detecting the real-time temperature of the circuit protection module and is respectively connected with the driving unit and the power supply module;

if the real-time temperature is larger than a preset temperature threshold value, outputting an over-temperature signal to the driving unit, and the driving unit receives the over-temperature signal and responds to the over-temperature signal to switch the state of the FET unit to the backflow prevention state.

Through adopting above-mentioned technical scheme, if the first electric current of following the output of FET unit is in the overcurrent state continuously, can lead to the temperature of whole circuit protection module to rise, when circuit protection module high temperature, then can lead to circuit protection module to damage, consequently, through the setting of temperature detection module, can monitor circuit protection module's real-time temperature, and compare real-time temperature and predetermined temperature threshold value, if real-time temperature surpasses temperature threshold value, then temperature detection module exports the overtemperature signal to drive unit, make drive unit switch the FET unit to prevent the backflow state, thereby interrupt FET unit's current output.

In a second aspect, the present application further provides a method for preventing current backflow for a video interface, which adopts the following technical solution:

a method for preventing a reverse current flow for a video interface, comprising the steps of:

the control module judges whether the first external equipment is accessed;

if the first external equipment is not connected, the FET unit is controlled to be in the backflow prevention state through the driving unit;

if the first external device is connected, judging whether the power supply module supplies power to the FET unit;

if the power supply module supplies power to the FET unit, the FET unit is controlled to be switched to the forward conduction state through the driving unit, so that a power supply path is established between the power supply module and the second external equipment;

and if the power supply module does not supply power to the FET unit, the drive unit controls the FET unit to maintain the anti-backflow state.

By adopting the technical scheme, whether the first external equipment is accessed is judged firstly, whether the power supply module supplies power to the FET unit is judged after the first external equipment is confirmed to be accessed, if the power supply module supplies power to the FET unit, the drive unit controls the FET unit to be switched from an initial anti-backflow state to a forward conduction state, so that a power supply path is established between the power supply module and the second external equipment, and at the moment, the power supply module can output conduction voltage to a video interface of the second external equipment through the FET unit; and if the power supply module stops supplying power to the FET unit or the control module detects that the first external equipment is not connected, the driving unit controls the FET unit to be switched from a forward conduction state to a reverse flow prevention state.

Optionally, a method for preventing current backflow for a video interface further includes the following steps:

the current detection unit judges whether the first current is larger than the second current;

if the first current is smaller than the second current, the FET unit is not controlled to regulate output current;

if the first current is larger than the second current, controlling the FET unit to regulate output current through the current detection unit, the overcurrent protection unit and the driving unit, and judging whether the real-time temperature of the circuit protection module is larger than the temperature threshold value through the temperature detection module;

if the temperature is larger than the temperature threshold value, the FET unit is controlled to be switched to the backflow prevention state through the driving unit;

if the temperature is less than the temperature threshold, the FET unit maintains the forward conduction state.

By adopting the technical scheme, when the power supply module supplies power to the second external device through the FET unit, the FET unit outputs a first current, the output first current is possibly unstable and causes overcurrent due to internal reasons of the FET unit, the current detection unit detects and judges whether the first current is larger than a preset second current or not, and if the first current is larger than the preset second current, the driving unit controls the FET unit and adjusts the output current through signal transmission among the current detection unit, the overcurrent protection unit and the driving unit; after adjustment, the first current output by the FET unit is probably still larger than the second current, the continuous overcurrent can cause the temperature of the circuit protection module to be continuously increased, at the moment, the temperature detection module detects the real-time temperature of the circuit protection module and judges whether the real-time temperature is larger than a preset temperature threshold value, if the real-time temperature exceeds the threshold value, the drive unit controls the FET unit to be switched to a backflow prevention state so as to interrupt the current output of the FET unit, and therefore the whole circuit is protected.

In a third aspect, the present application further provides an apparatus comprising the circuit for preventing current backflow for a video interface of any one of the first aspect above.

In summary, the present application includes at least one of the following beneficial technical effects:

1. through the arrangement of the FET unit in the circuit protection module, when the FET unit is in a backflow prevention state, the current in the second external device can be prevented from flowing back; when the FET unit is in a forward conduction state, the power supply module can output conduction voltage to a video interface of the second external device through the FET unit, and the conduction voltage meets the lowest power supply voltage of the video interface of the second external device;

2. through the setting of current detection unit and overcurrent protection unit, can real-time supervision from the first electric current of FET unit output whether overflow, if overflow can make drive signal adjust the FET unit through signal transmission, if still be in the state of overflowing after the adjustment, then can monitor the real-time temperature of circuit protection module through the setting of temperature protection module, if the temperature of circuit protection module surpasss the temperature threshold value, then can in time switch over the FET unit to the anti-backflow state through drive circuit to protect whole circuit.

Drawings

Fig. 1 is a block diagram of a circuit for preventing a reverse current flow of a video interface according to an embodiment of the present application.

Fig. 2 is a specific block diagram of a control module and a circuit protection module according to an embodiment of the present disclosure.

Fig. 3 is a flowchart illustrating a method for preventing a reverse current flow for a video interface according to an embodiment of the present application.

Fig. 4 is a schematic flow chart of a process for monitoring overcurrent and overtemperature of a circuit according to an embodiment of the present application.

Description of reference numerals:

1. a control module; 2. a power supply module; 3. a circuit protection module; 4. a first external device; 5. a second external device; 6. a temperature detection module; 7. a power adapter; 8. an audio/video module; 11. a voltage comparison unit; 12. a control unit; 13. a signal amplification unit; 31. an FET cell; 32. a drive unit; 33. an undervoltage protection unit; 34. a current detection unit; 35. an overcurrent protection unit; 36. and a filtering unit.

Detailed Description

The present application is described in further detail below with reference to figures 1-4.

The embodiment of the application discloses a circuit for preventing current backflow for a video interface.

Referring to fig. 1, the circuit for preventing current backflow for a video interface includes a power supply module 2, the power supply module 2 is electrically connected to a temperature detection module 6, a circuit protection module 3 and a control module 1, respectively, and the power supply module 2 can supply power to the temperature detection module 6, the circuit protection module 3 and the control module 1. The control module 1 is used for being electrically connected with a first external device 4 and detecting the access state of the first external device 4, if the first external device 4 is successfully accessed and the power supply module 2 is supplying power to the circuit protection module 3, the circuit protection module 3 is switched to a forward conduction state, so that the power supply module 2 can output conduction voltage to a video interface of a second external device 5 through the circuit protection module 3; if the first external device 4 is not connected or the power supply module 2 does not supply power to the circuit protection module 3, the circuit protection module 3 switches to a backflow prevention state to prevent the current in the second external device 5 from flowing backwards through the video interface.

Referring to fig. 1, the power source of the power supply module 2 may be the first external device 4 or the power adapter 7. The first external device 4 is electrically connected with an audio/video module 8, the audio/video module 8 can be a PS171 chip, a PS176 chip or a PS186 chip, the audio/video module 8 is electrically connected with the second external device 5 through an I2C bus, and the audio/video of the first external device 4 can be transmitted to the second external device 5 through the arrangement of the audio/video module 8. The first external device 4 may be a notebook computer or a mainframe computer, and the second external device 5 may be a display screen.

Referring to fig. 2, the control module 1 includes a voltage comparing unit 11, the voltage comparing unit 11 includes a voltage comparator, the voltage comparing unit 11 is electrically connected to the control unit 12, and the voltage comparing unit 11 is further configured to be electrically connected to the first external device 4. When the first external device 4 is in an operating state and is electrically connected with the voltage comparison unit 11, the first external device 4 outputs a first voltage to the voltage comparison unit 11, a second voltage is preset in the voltage comparison unit 11, the voltage comparison unit 11 receives the first voltage and then compares the first voltage with the preset second voltage, and if the first voltage is greater than the second voltage, the voltage comparison unit 11 outputs a first comparison signal to the control unit 12; if the first voltage is less than the second voltage, the voltage comparing unit 11 outputs a second comparison signal to the control unit 12.

Referring to fig. 2, the control unit 12 may be an MCU chip, the control unit 12 is electrically connected to the power supply module 2 and the signal amplification unit 13, respectively, and the power supply module 2 is configured to supply power to the control unit 12. The control unit 12 receives the first comparison signal and outputs a first control signal to the signal amplifying unit 13; the control unit 12 receives the second comparison signal and outputs a second control signal to the signal amplifying unit 13. The signal amplifying unit 13 includes a signal amplifier, and the signal amplifying unit 13 may amplify the first control signal or the second control signal, and then output the amplified first control signal or the amplified second control signal to the circuit protection module 3.

Referring to fig. 2, the circuit protection module 3 includes an FET unit 31, the FET unit 31 includes a field effect transistor, a drain of the field effect transistor in the FET unit 31 is electrically connected to the power supply module 2, a source of the field effect transistor in the FET unit 31 is electrically connected to the second external device 5, and a gate of the field effect transistor in the FET unit 31 is electrically connected to the driving unit 32. The driving unit 32 is electrically connected to the signal amplifying unit 13, and when the driving unit 32 receives the amplified first control signal output by the signal amplifying unit 13, the FET unit 31 is controlled to switch to a forward conduction state, and at this time, the power supply unit may output a conduction voltage to the video interface of the second external device 5 through the FET unit 31; when receiving the amplified second control signal output from the signal amplifying unit 13, the driving unit 32 switches the control FET unit 31 to the backflow prevention state.

Specifically, the video interface of the second external device 5 may be an HDMI interface, a VGA interface or a DVI interface, the lowest power supply voltage of the video interface of the second external device 5 is 4.7V, the voltage output by the power supply module 2 is 5V, and the power supply module 2 has a voltage tolerance of ± 5%, so that the voltage range output by the power supply module 2 is 4.75V to 5.25V. The internal resistance of the field effect transistor in the FET unit 31 is less than 0.07 Ω, and the maximum load current of the video interface of the second external device 5 is 500mA, so that the voltage drop generated by the field effect transistor in the FET unit 31 will be less than 0.035V even if it is at a current of 500 mA. If the power supply module 2 outputs the lowest voltage of 4.75V, a voltage drop is generated after passing through the FET unit 31, so that the on-voltage finally output to the video interface of the second external device 5 is 4.715V, and the on-voltage at this time is still greater than the lowest power supply voltage of 4.7V of the video interface of the second external device 5, so that the FET unit 31 can ensure that the on-voltage output to the video interface of the second external device 5 is not less than 4.7V when the overall circuit is normal.

Referring to fig. 2, circuit protection module 3 further includes an undervoltage protection unit 33, undervoltage protection unit 33 includes an undervoltage protector, undervoltage protection unit 33 is electrically connected with power supply module 2 and drive unit 32 respectively, if power supply module 2 appears the short circuit, voltage in the circuit will suddenly drop or even disappear, the current in the circuit will increase this moment, if excessive current output to drive unit 32 probably can make drive unit 32 transship and damage, consequently undervoltage protection unit 33 can play the undervoltage protection effect to drive unit 32 when power supply module 2 short circuit, thereby avoid drive unit 32 to damage because of overcurrent overload.

Referring to fig. 2, the circuit protection module 3 further includes a filtering unit 36, the filtering unit 36 is electrically connected to the source of the FET unit 31, and due to the presence of the FET unit 31, the current output from the FET unit 31 may include stray current, which may cause current instability in the circuit and may affect the service life of the circuit, so that the filtering unit 36 is configured to filter the stray current in the current to improve the stability of the circuit current.

Referring to fig. 2, the circuit protection module 3 further includes a current detection unit 34, the current detection unit 34 includes a current sensor, the current detection unit 34 is electrically connected to a source of the field effect transistor in the FET unit 31, the current detection unit 34 is further electrically connected to an overcurrent protection unit 35, the overcurrent protection unit 35 includes an overcurrent protection circuit, and the overcurrent protection unit 35 is electrically connected to the driving unit 32. The second current is preset in the current detection unit 34 and can detect the first current output by the FET unit 31, the first current is compared with the second current, if the first current is greater than the second current, it may be that the current output of the field effect transistor in the FET unit 31 is unstable at this time, the current detection unit 34 outputs an overcurrent signal to the overcurrent protection unit 35, the overcurrent protection unit 35 outputs an adjustment signal to the driving unit 32 after receiving the overcurrent signal, the driving unit 32 controls the FET unit 31 to adjust the stability of the current output after receiving the adjustment signal, and the temperature rise in the circuit caused by the long-time overcurrent state of the current output by the FET unit 31 is avoided.

Referring to fig. 2, the power supply module 2 is further electrically connected to a temperature detection module 6, the temperature detection module 6 includes a temperature sensor, and the temperature detection module 6 is electrically connected to the driving unit 32. The temperature detection module 6 can detect the real-time temperature of the circuit protection module 3, and a temperature threshold is preset in the temperature detection module 6, when the FET unit 31 still outputs an overcurrent current after current output is adjusted, or the temperature of the circuit protection module 3 rises due to other reasons, until the real-time temperature detected by the temperature detection module 6 is greater than the temperature threshold, the temperature monitoring module outputs an over-temperature signal to the driving unit 32, the driving unit 32 switches the FET unit 31 to a backflow prevention state after receiving the over-temperature signal, so as to interrupt the current output of the FET unit 31, and the circuit protection module 3 naturally dissipates heat. A restart temperature threshold is also preset in the temperature detection module 6, when the real-time temperature detected by the temperature detection module 6 exceeds the temperature threshold and is lower than the restart temperature threshold after heat dissipation, the temperature detection module 6 outputs a restart signal to the driving unit 32, and the driving unit 32 switches the FET unit 31 to the forward conduction state again after receiving the restart signal.

The embodiment of the application also discloses a method for preventing current backflow for the video interface.

Referring to fig. 3, the method for preventing current backflow for a video interface specifically includes the following steps:

100, the control module 1 determines whether the first external device 4 is accessed, and if not, executes step 101; if yes, go to step 102.

If the access channel of the first external device 4 includes an Aux channel, the judgment can be performed by detecting a voltage value of the Aux channel; if the access channel of the first external device 4 is a power channel, directly judging through a power voltage value; if the Type-C interface that the access channel of first external equipment 4 adopted, then can detect the voltage value of CC foot in the Type-C interface and judge.

101, the FET unit 31 is controlled to be in the backflow prevention state by the driving unit 32.

Wherein, the driving unit 32 maintains the initial state of the FET unit 31 in the anti-backflow state through logic control, and when the FET unit 31 is in the anti-backflow state, the current in the second external device 5 cannot turn on the FET unit 31 even if the second external device 5 is still in the operating state.

102, determining whether the power supply module 2 supplies power to the FET unit 31, if yes, executing step 103; if not, go to step 104.

103, the FET unit 31 is controlled by the driving unit 32 to switch to the forward conducting state, so that a power supply path is established between the power supply module 2 and the second external device 5.

A power supply path is established between the power supply module 2 and the second external device 5 through the field effect transistor of the FET unit 31, and the voltage output by the power supply module 2 is output to the video interface of the second external device 5 after voltage drop is generated by the field effect transistor.

104, controlling the FET unit 31 to maintain the backflow prevention state by the driving unit 32.

The implementation principle of the embodiment is as follows:

firstly, judging whether different voltage values exceed a threshold value according to different access modes of the first external device 4 so as to judge whether the first external device 4 is accessed, judging whether the power supply module 2 supplies power to the FET unit 31 after the first external device 4 is confirmed to be accessed, if the power supply module 2 supplies power to the FET unit 31, controlling the FET unit 31 to be switched from an initial anti-backflow state to a forward conduction state by the driving unit 32, so that a power supply path is established between the power supply module 2 and the second external device 5, and at the moment, the power supply module 2 can output conduction voltage to a video interface of the second external device 5 through the FET unit 31; if the power supply module 2 stops supplying power to the FET unit 31 or the control module 1 detects that the first external device 4 is not connected, the driving unit 32 controls the FET unit 31 to switch from the forward conduction state to the backflow prevention state.

In the embodiment shown in fig. 3, since the circuit may have an over-current or over-temperature condition due to various conditions, and the over-current or over-temperature condition will cause damage to the line due to a long time, the over-current or over-temperature condition of the circuit needs to be monitored and processed in time, and the specific steps are described in detail by the embodiment shown in fig. 4.

Referring to fig. 4, the monitoring process of the overcurrent and overtemperature of the circuit specifically includes the following steps:

200, the current detecting unit 34 determines whether the first current is greater than the second current, if not, step 201 is executed; if yes, go to step 202.

The FET unit 31 is not controlled to regulate the output current 201.

202, the FET unit 31 is controlled to regulate the output current by the current detection unit 34, the overcurrent protection unit 35, and the driving unit 32.

The current detection unit 34 outputs an overcurrent signal to the overcurrent protection unit 35, the overcurrent protection unit 35 outputs an adjustment signal to the driving unit 32, and the driving unit 32 adjusts and controls the field effect transistor in the FET unit 31 so that the FET unit 31 outputs a constant and stable current.

203, judging whether the real-time temperature of the circuit protection module 3 is greater than the temperature threshold value through the temperature detection module 6, if so, executing a step 204; if not, go to step 205.

204, controlling the FET unit 31 to switch to the backflow prevention state by the driving unit 32.

205, the FET unit 31 maintains the forward conduction state.

The implementation principle of the embodiment is as follows:

when the power supply module 2 supplies power to the second external device 5 through the FET unit 31, the FET unit 31 outputs a first current, the output first current may be unstable due to the presence of a field effect transistor in the FET unit 31, the current detection unit 34 detects and determines whether the first current is greater than a preset second current, if so, the circuit is in an overcurrent state, the current detection unit 34 outputs an overcurrent signal to the overcurrent protection unit 35, the overcurrent protection unit 35 outputs an adjustment signal to the driving unit 32, and the driving unit 32 adjusts and controls the field effect transistor in the FET unit 31 so that the FET unit 31 outputs a constant and stable current; after adjustment, the first current output by the FET unit 31 may still be greater than the second current, and continuous overcurrent may cause the temperature of the circuit protection module 3 to continuously rise, at this time, the temperature detection module 6 detects the real-time temperature of the circuit protection module 3, and determines whether the real-time temperature is greater than a preset temperature threshold, and if the real-time temperature exceeds the threshold, the driving unit 32 controls the FET unit 31 to switch to the backflow prevention state, so as to interrupt the current output of the FET unit 31, thereby protecting the entire circuit.

The embodiment of the application further discloses a device, the device includes the circuit in the embodiment shown in fig. 1 and fig. 2, the device can be a docking station, the device is provided with a power switch, the power switch is electrically connected with the power supply module 2, and the power switch can control the power supply of the power supply module 2. Other circuitry for extending other video interfaces is also included within the device.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.