CN113690844B - A circuit, method and device for preventing current backflow for video interface - Google Patents

Abstract

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.

Description

A circuit, method and device for preventing current backflow for video interface

technical field

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

Background technique

Existing video interfaces include HDMI interface, DVI interface and VGA interface, while notebook computers generally only have 1~2 types of video interfaces. Display devices suitable for various video interfaces.

When the laptop is connected to the display device through the docking station, the docking station will read the EDID of the display device through the circuit shared by the HDMI, DVI and VGA interfaces, where the EDID is used by the display device to describe its own display capability and audio output capability. An electronic tag of EDID, the data reading of EDID is realized through the I2C bus, and the I2C bus needs to be pulled up to close to the rated voltage through an external resistor. Due to the settings of the I2C bus and external resistors, when the docking station is powered off 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 external resistors, resulting in a circuit in the docking station. exception and not working properly.

In the prior art, the problem of current reverse flow is solved by adding a diode in the internal circuit of the docking station. By using the unidirectional conduction characteristics of the diode, the current can only flow from the docking station to the video interface of the display device in one direction, and no current is allowed. Stream back from the video interface of the display device.

In view of the above-mentioned related technologies, the inventor believes that there are the following defects: the docking station is usually powered by 5V, and the voltage tolerance is ±5%, so the minimum power supply voltage of the docking station is 4.75V, and the current required for reading the EDID The voltage drop generated by the forward conduction of different types of diodes is about 0.2V ~ 0.7V, and because the minimum power supply voltage required by the video interface of the display device is usually 4.7V, therefore, when the power supply voltage of the docking station is less than At 4.9V, any diode cannot meet the minimum power supply voltage required by the video interface of the display device due to the voltage drop.

SUMMARY OF THE INVENTION

In order to improve the defect that the function of preventing current reverse flow may not meet the minimum power supply voltage of a video interface of a display device, the present application provides a circuit, method and device for preventing current reverse flow for a video interface.

In the first aspect, the present application provides a circuit for preventing current backflow for a video interface, using the following technical solutions:

A circuit for preventing current backflow for a video interface, comprising:

a control module for detecting and judging whether the first external device is connected;

a power supply module, connected to the control module to output power to the control module;

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

If the first external device is connected, the control module outputs a first control signal;

If the first external device is not connected, the control module outputs a second control signal;

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

When the circuit protection module receives the second control signal, the circuit protection module switches to the anti-backflow state to prevent the current of the second external device from flowing backwards.

By adopting the above technical solution, the initial state of the circuit protection module is the anti-backflow state. When the control module detects that the first external device is connected, it outputs the first control signal to the circuit protection module, so that the circuit protection module switches from the anti-backflow state to the positive state. In the conduction state, the power supply module can output the conduction voltage to the video interface of the second external device through the circuit protection module. Even if the conduction voltage passes through the voltage protection module, a voltage drop will occur, but the conduction module after the voltage drop is still greater than The minimum power supply voltage of the video interface on the second external device; when the control module detects that the first external device is not connected, the circuit protection module switches to the anti-backflow state to prevent the current in the second external device from flowing back through the video interface. cause circuit abnormalities.

Optionally, the circuit protection module includes:

The FET unit has two states of the forward conduction state and the anti-backflow state, and is connected to the power supply module and the second external device respectively. When in the forward conduction state, the power supply module passes the the FET unit outputs the on-voltage to the video interface of the second external device;

A driving unit, connected to the control module, receives the first control signal or the second control signal to switch the state of the FET unit.

By adopting the above technical solution, the state of the FET unit is switched by different control signals received by the driving unit. When the FET unit is in the forward conduction state, the power supply module can output conduction to the video interface of the second external device through the FET unit. Voltage; when the FET unit is in the anti-backflow state, the current in the second external device is prevented from flowing back through the video interface.

Optionally, the control module includes:

a voltage comparison unit, configured to connect to the first external device and receive a first voltage output by the first external device, and determine 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 outputs a first comparison signal;

If the first voltage is lower than the second voltage, the voltage comparison unit outputs a second comparison signal;

a control unit, connected to the voltage comparison unit to receive the first comparison signal or the second comparison signal, output the first control signal when receiving the first comparison signal, and receive the second comparison signal outputting the second control signal;

a signal amplifying unit, connected with the control unit to receive and amplify the first control signal or the second control signal, and connected with the driving unit to output the amplified first control signal or the second control signal to the driving unit Two control signals.

By adopting the above technical solution, when the first external device is connected to 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 voltage, it is judged that the first external device is successfully connected, and the first comparison signal is output to the control unit; if the first voltage is less than the second voltage, it is judged that the first external device is not connected or not successfully connected, and the control unit is sent to the Output the second comparison signal; the control unit outputs the first control signal to the signal amplifying unit after receiving the first comparison signal, the control unit outputs the second control signal to the signal amplifying unit after receiving the second comparison signal, and the signal amplifying unit receives the control signal After the signal is amplified, 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:

The undervoltage protection unit is connected to the power supply module and the drive unit respectively, and is used for undervoltage protection for the drive unit.

By adopting the above technical solutions, if the power supply module is short-circuited, the line voltage will be greatly reduced or even disappear in a short period of time, resulting in excessive current, which may cause damage to the drive unit. Therefore, through the setting of the undervoltage protection circuit, It plays the role of undervoltage protection for the drive unit.

Optionally, the circuit protection module further includes:

a current detection unit, connected to the FET unit to receive a first current output from the FET unit, and to determine whether the first current is greater than a preset second current;

If the first current is greater 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 overcurrent signal,

An overcurrent protection unit, connected to the current detection unit and the drive unit respectively, receives the overcurrent signal and outputs an adjustment signal to the drive unit in response to the overcurrent signal, the drive unit is connected to the drive unit A signal is adjusted and responsive to the adjustment signal to adjust the FET cell output current.

By adopting the above technical solution, the current detection unit is preset with a second current and monitors the first current output by the FET unit in real time. When the first current is greater than the second current, it may be caused by the instability of the current output from the FET unit. At this time, the current detection unit outputs an overcurrent signal to the overcurrent protection unit, and after receiving the overcurrent protection unit, the overcurrent protection unit outputs an adjustment signal to the driving unit, 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:

A filtering unit is connected to the FET unit to filter out stray current in the first current.

By adopting the above technical solution, since part of the stray current may be included in the first current output from the FET unit, the stray current will cause the current in the circuit to be unstable and also affect the service life of the circuit. setting, the stray current included in the first current can be filtered out.

Optionally, the circuit further includes:

a temperature detection module for detecting the real-time temperature of the circuit protection module and connected to the drive unit and the power supply module respectively;

If the real-time temperature is greater than a preset temperature threshold, an over-temperature signal is output to the drive unit, and the drive unit receives the over-temperature signal and responds to the over-temperature signal to change the state of the FET unit Switch to the anti-backflow state.

By adopting the above technical solution, if the first current output from the FET unit is continuously in an overcurrent state, the temperature of the entire circuit protection module may increase, and when the temperature of the circuit protection module is too high, the circuit protection module may be damaged. Therefore, through the setting of the temperature detection module, the real-time temperature of the circuit protection module can be monitored, and the real-time temperature can be compared with the preset temperature threshold. If the real-time temperature exceeds the temperature threshold, the temperature detection module will output an over-temperature signal to the drive unit. The driving unit is caused to switch the FET unit to the anti-backflow state, thereby interrupting the current output of the FET unit.

In the second aspect, the present application also provides a method for preventing current backflow for a video interface, using the following technical solutions:

A method for preventing current backflow for a video interface, comprising the following steps:

The control module determines whether the first external device is connected;

If the first external device is not connected, controlling the FET unit to be in the anti-backflow state through the driving unit;

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

If the power supply module supplies power to the FET unit, the driving unit controls the FET unit to switch to the forward conduction state, so that a power supply path is established between the power supply module and the second external device;

If the power supply module does not supply power to the FET unit, the driving unit controls the FET unit to maintain the anti-backflow state.

By adopting the above technical solution, first determine whether the first external device is connected, and then determine whether the power supply module supplies power to the FET unit after confirming that the first external device is connected. If the power supply module supplies power to the FET unit, the drive unit controls the FET unit from The initial anti-backflow state is switched to the forward conduction state, so that a power supply path is established between the power supply module and the second external device. At this time, the power supply module can output the conduction voltage to the video interface of the second external device through the FET unit; if the power supply module When the power supply to the FET unit is stopped or the control module detects that the first external device is not connected, the driving unit controls the FET unit to switch from the forward conduction state to the anti-backflow state.

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

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

If the first current is smaller than the second current, the FET unit is not controlled to adjust the output current;

If the first current is greater than the second current, the current detection unit, the overcurrent protection unit and the driving unit are used to control the FET unit to adjust the output current, and the temperature detection module determines the output current. Whether the real-time temperature of the circuit protection module is greater than the temperature threshold;

If the temperature is greater than the temperature threshold, controlling the FET unit to switch to the anti-backflow state through the driving unit;

If the temperature is less than the temperature threshold, the FET cell maintains the forward conducting state.

By adopting the above technical solution, when the power supply module supplies power to the second external device through the FET unit, the FET unit will output the first current. Due to the internal reasons of the FET unit, the outputted first current may be unstable and cause overcurrent. Current detection The unit will detect and judge whether the first current is greater than the preset second current, and if it is greater, the signal transmission between the current detection unit, the overcurrent protection unit and the drive unit will enable the drive unit to control the FET unit and adjust the output current; After adjustment, the first current output by the FET unit may still be greater than the second current, and the continuous overcurrent may cause the temperature of the circuit protection module to continue to rise. At this time, the temperature detection module detects the real-time temperature of the circuit protection module, and judges the real-time temperature Whether the temperature is greater than a preset temperature threshold, if it exceeds the threshold, the drive unit controls the FET unit to switch to the anti-backflow state to interrupt the current output of the FET unit, thereby protecting the entire circuit.

In a third aspect, the present application further provides a device, which includes the circuit for preventing current backflow for a video interface according to any one of the above first aspects.

To sum up, the present application includes at least one of the following beneficial technical effects:

1. Through the setting of the FET unit in the circuit protection module, when the FET unit is in the anti-backflow state, the current in the second external device can be prevented from flowing back; when the FET unit is in the forward conduction state, the power supply module can pass the FET unit to the The video interface of the second external device outputs a turn-on voltage, and the turn-on voltage meets the minimum power supply voltage of the video interface of the second external device;

2. Through the setting of the current detection unit and the overcurrent protection unit, it is possible to monitor whether the first current output from the FET unit is overcurrent in real time. In the overcurrent state, the real-time temperature of the circuit protection module can be monitored through the settings of the temperature protection module. If the temperature of the circuit protection module exceeds the temperature threshold, the FET unit can be switched to the anti-backflow state through the drive circuit in time to protect the overall circuit.

Description of drawings

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

FIG. 2 is a specific module structure diagram of a control module and a circuit protection module according to an embodiment of the present application.

FIG. 3 is a schematic flowchart of a method for preventing current backflow for a video interface according to an embodiment of the present application.

FIG. 4 is a schematic flowchart of monitoring processing of circuit overcurrent and overtemperature according to an embodiment of the present application.

Description of reference numbers:

1. Control module; 2. Power supply module; 3. Circuit protection module; 4. First external device; 5. Second external device; 6. Temperature detection module; 7. Power adapter; 8. Audio and video module; 11. Voltage comparison unit; 12, control unit; 13, signal amplification unit; 31, FET unit; 32, drive unit; 33, undervoltage protection unit; 34, current detection unit; 35, overcurrent protection unit; 36, filtering unit.

Detailed ways

The present application will be further described in detail below in conjunction with accompanying drawings 1-4.

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

Referring to FIG. 1 , the circuit for preventing the reverse current flow of the video interface includes a power supply module 2, and the power supply module 2 is respectively electrically connected with the temperature detection module 6, the circuit protection module 3 and the control module 1, and the power supply module 2 can send the temperature detection module 6, The circuit protection module 3 and the control module 1 are powered. The control module 1 is used to electrically connect with the first external device 4 and detect the access state of the first external device 4. If the first external device 4 is successfully connected and the power supply module 2 is supplying power to the circuit protection module 3, the circuit protection The module 3 is switched to the forward conduction state, so that the power supply module 2 can output the conduction voltage to the video interface of the 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 is not connected to the circuit When the protection module 3 supplies power, the circuit protection module 3 switches to the anti-backflow state to prevent the current in the second external device 5 from flowing backward 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 and video module 8. The audio and video module 8 can be a PS171 chip, a PS176 chip or a PS186 chip. The audio and video module 8 is electrically connected to the second external device 5 through the I2C bus, and the Setting, the audio and video of the first external device 4 can be transmitted to the second external device 5 . The first external device 4 may be a notebook computer or a computer host, and the second external device 5 may be a display screen.

Referring to FIG. 2 , the control module 1 includes a voltage comparison unit 11 including a voltage comparator. The voltage comparison unit 11 is electrically connected with the control unit 12 , and the voltage comparison unit 11 is also used for electrical connection with the first external device 4 . When the first external device 4 is in the running state and is electrically connected to the voltage comparison unit 11, the first external device 4 will output the first voltage to the voltage comparison unit 11, and the voltage comparison unit 11 is preset with a second voltage, and the voltage comparison unit 11 compares the first voltage with the preset second voltage after receiving the first voltage, if the first voltage is greater than the second voltage, the voltage comparison unit 11 outputs the first comparison signal to the control unit 12; if the first voltage is less than the second voltage, the voltage comparison unit 11 outputs a second comparison signal to the control unit 12 .

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 used to supply power to the control unit 12 . After receiving the first comparison signal, the control unit 12 will output the first control signal to the signal amplifying unit 13 ; the control unit 12 will output the second control signal to the signal amplifying unit 13 after receiving the second comparison signal. The signal amplifying unit 13 includes a signal amplifier. The signal amplifying unit 13 can amplify the first control signal or the second control signal, and then output the amplified first control signal or the second control signal to the circuit protection module 3 .

2, the circuit protection module 3 includes an FET unit 31, the FET unit 31 includes a field effect transistor, the drain of the field effect transistor in the FET unit 31 is electrically connected to the power supply module 2, and the source of the field effect transistor in the FET unit 31 is connected to the first The two external devices 5 are electrically connected, and the 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. When the driving unit 32 receives the amplified first control signal output by the signal amplifying unit 13, the driving unit 32 switches the control FET unit 31 to a forward conduction state. At this time, the power supply unit can pass the FET The unit 31 outputs the turn-on voltage to the video interface of the second external device 5 ; when the driving unit 32 receives the amplified second control signal output by the signal amplifying unit 13 , it switches the control FET unit 31 to the anti-backflow state.

Specifically, the video interface of the second external device 5 can be an HDMI interface, a VGA interface or a DVI interface, and the minimum power supply voltage of the video interface of the second external device 5 is 4.7V, and the voltage output by the power supply module 2 is 5V, And the power supply module 2 has a voltage tolerance of ±5%, so the voltage range output by the power supply module 2 is 4.75V~5.25V. The internal resistance of the field effect transistor in the FET unit 31 is less than 0.07Ω, and the maximum load current of the video interface of the second external device 5 is 500mA, so even if the field effect transistor in the FET unit 31 is under the current of 500mA, the resulting The voltage drop will also be less than 0.035V. If the power supply module 2 outputs a minimum voltage of 4.75V, a voltage drop occurs after passing through the FET unit 31 , so the final turn-on voltage output to the video interface of the second external device 5 is 4.715V, and the turn-on voltage at this time is still greater than that of the second external device 5 . The minimum power supply voltage of the video interface of the device 5 is 4.7V, so 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.

2, the circuit protection module 3 further includes an undervoltage protection unit 33, the undervoltage protection unit 33 includes an undervoltage protector, and the undervoltage protection unit 33 is electrically connected to the power supply module 2 and the drive unit 32, respectively. If the power supply module 2 is short-circuited At this time, the voltage in the circuit will drop or even disappear, and the current in the circuit will increase. If the excessive current is output to the drive unit 32, the drive unit 32 may be overloaded and damaged. Therefore, the undervoltage protection unit 33 can When the power supply module 2 is short-circuited, the drive unit 32 is protected against under-voltage, so as to prevent the drive unit 32 from being damaged due to overcurrent and overload.

2 , the circuit protection module 3 further includes a filtering unit 36, which is electrically connected to the source of the field effect transistor in the FET unit 31. Due to the existence of the field effect transistor in the FET unit 31, the output from the FET unit 31 The current may contain stray current, and the stray current will cause the current in the circuit to be unstable and affect the service life of the circuit. Therefore, setting the filtering unit 36 can filter the stray current in the current to improve the circuit current. stability.

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 the source of the field effect transistor in the FET unit 31, and the current detection unit 34 is also electrically connected with a 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 current detection unit 34 is preset with a second current and can detect the first current output by the FET unit 31, and compare the first current with the second current. If the first current is greater than the second current, it may be the FET unit at this time. The current output of the field effect transistor in 31 is unstable, the current detection unit 34 outputs an overcurrent signal to the overcurrent protection unit 35, the overcurrent protection unit 35 receives the overcurrent signal and then outputs an adjustment signal to the drive unit 32, and the drive unit 32 receives the adjustment signal Afterwards, the FET unit 31 will be controlled to adjust the stability of the current output, so as to prevent the current output by the FET unit 31 from being in an overcurrent state for a long time and causing the temperature in the circuit to rise.

Referring to FIG. 2 , the power supply module 2 is also electrically connected with a temperature detection module 6 , the temperature detection module 6 includes a temperature sensor, and the temperature detection module 6 is electrically connected with the drive 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 adjusting the current output, or the circuit protection is caused by other reasons The temperature of the module 3 rises until the real-time temperature detected by the temperature detection module 6 is greater than the temperature threshold, and the temperature monitoring module will output an over-temperature signal to the drive unit 32. After the drive unit 32 receives the over-temperature signal, it will switch the control FET unit 31 to the anti-temperature signal. In the reverse current state, the current output of the FET unit 31 is interrupted, so that the circuit protection module 3 naturally dissipates heat. The temperature detection module 6 is also preset with a restart temperature threshold. When the real-time temperature detected by the temperature detection module 6 exceeds the temperature threshold, and the real-time temperature after heat dissipation is less than the restart temperature threshold, the temperature detection module 6 will output to the drive unit 32 to restart After receiving the restart signal, the driving unit 32 switches the control FET unit 31 to the forward conduction state again.

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

Referring to FIG. 3, the method for preventing current flow back for a video interface specifically includes the following steps:

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

Wherein, different judgment methods can be adopted according to different access modes of the first external device 4. If the access channel of the first external device 4 includes the Aux channel, the judgment can be made by detecting the voltage value of the Aux channel; If the access channel of the external device 4 is the power channel, the judgment is made directly by the power supply voltage value; if the access channel of the first external device 4 adopts the Type-C interface, the voltage value of the CC pin in the Type-C interface can be detected. make a judgment.

101 , controlling the FET unit 31 to be in the anti-backflow state through the driving unit 32 .

The driving unit 32 maintains the initial state of the FET unit 31 as the anti-backflow state through logic control. When the FET unit 31 is in the anti-backflow state, even if the second external device 5 is still in the running state, the current in the second external device 5 cannot be The FET unit 31 is turned on.

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

103 , controlling the FET unit 31 to switch 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 .

The 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 of the second external device 5 after the voltage drop generated by the field effect transistor. at the interface.

104. Control the FET unit 31 through the driving unit 32 to maintain the anti-backflow state.

The implementation principle of this embodiment is:

First, according to the different access methods of the first external device 4, it is judged whether the different voltage values exceed the threshold, so as to determine whether the first external device 4 is connected. The unit 31 supplies power. If the power supply module 2 supplies power to the FET unit 31, the drive unit 32 controls the FET unit 31 to switch from the initial anti-backflow state to the forward conduction state, so that a power supply path is established between the power supply module 2 and the second external device 5 , at this time, the power supply module 2 can output the on-voltage to the 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, Then, the driving unit 32 controls the FET unit 31 to switch from the forward conduction state to the anti-backflow state.

In the embodiment shown in FIG. 3, since the circuit may be over-current or over-temperature due to various conditions, and long-term over-current and over-temperature will cause damage to the circuit, it is necessary to control the over-current or over-temperature of the circuit. Monitoring and timely processing are performed, and the specific steps are described in detail through the embodiment shown in FIG. 4 .

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

200. The current detection unit 34 determines whether the first current is greater than the second current, and if not, executes step 201; if yes, executes step 202.

201, the FET unit 31 is not controlled to adjust the output current.

202 , control the FET unit 31 to adjust the output current through 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 drive unit 32, and the drive unit 32 adjusts and controls the field effect transistor in the FET unit 31 so that the output of the FET unit 31 is constant smooth current.

203 , determine whether the real-time temperature of the circuit protection module 3 is greater than the temperature threshold by the temperature detection module 6 , if yes, go to step 204 ; if not, go to step 205 .

204 , controlling the FET unit 31 to switch to the anti-backflow state through the driving unit 32 .

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

The implementation principle of this embodiment is:

When the power supply module 2 supplies power to the second external device 5 through the FET unit 31, the FET unit 31 will output the first current. Due to the existence of the field effect transistor in the FET unit 31, the outputted first current may be unstable, and the current detection unit 34 It will detect and judge whether the first current is greater than the preset second current. If it is greater than the preset second current, the circuit is in an overcurrent state, the current detection unit 34 outputs an overcurrent signal to the overcurrent protection unit 35, and the overcurrent protection unit 35 sends an overcurrent signal to the drive unit 32. Outputting the adjustment signal, the driving unit 32 adjusts the field effect transistor in the control FET unit 31 to make the FET unit 31 output a constant and stable current; after the adjustment, the first current output by the FET unit 31 may still be larger than the second current, and the continuous overcurrent The current may cause the temperature of the circuit protection module 3 to continue to rise. At this time, the temperature detection module 6 detects the real-time temperature of the circuit protection module 3, and judges whether the real-time temperature is greater than the preset temperature threshold. If it exceeds the threshold, the drive unit 32 controls The FET unit 31 is switched to the anti-backflow state to interrupt the current output of the FET unit 31, thereby protecting the entire circuit.

The embodiment of the present application also discloses a device. The device includes the circuits in the embodiments 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 to the power supply module 2. The power switch can Control the power supply of the power supply module 2 . Additional circuitry is included within the device to extend other video interfaces.

The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore: all equivalent changes made according to the structure, shape and principle of the present application should be covered within the scope of the present application. Inside.

Claims (6)

1. a circuit for preventing the reverse current flow of video interface, is characterized in that, comprises: a control module (1) for detecting and judging whether the first external device (4) is connected; If the first external device (4) is connected, the control module (1) outputs a first control signal; If the first external device (4) is not connected, the control module (1) outputs a second control signal; a power supply module (2), connected to the control module (1) to output electrical energy to the control module (1); A circuit protection module (3), comprising: The FET unit (31) has two states of a forward conduction state and an anti-backflow state, and is respectively connected to the power supply module (2) and the second external device (5). When in the forward conduction state, the The power supply module (2) outputs a turn-on voltage to the video interface of the second external device (5) through the FET unit (31); a driving unit (32), connected to the control module (1), and receiving the first control signal or the second control signal to switch the state of the FET unit (31); When the driving unit (32) receives the first control signal, the FET unit (31) is switched to the forward conduction state, so that the power supply module (2) is directed to the forward conduction state through the FET unit (31). The second external device (5) outputs a turn-on voltage, and the turn-on voltage is not less than the minimum power supply voltage of the video interface on the second external device (5); When the driving unit (32) receives the second control signal, the FET unit (31) is switched to the anti-backflow state to prevent the current of the second external device (5) from flowing backward; An undervoltage protection unit (33), which is connected to the power supply module (2) and the drive unit (32) respectively, and is used to protect the drive unit (32) from undervoltage; a current detection unit (34), connected to the FET unit (31) to receive a first current output from the FET unit (31), and to determine whether the first current is greater than a preset second current; If the first current is greater than the second current, the current detection unit (34) outputs an overcurrent signal; If the first current is smaller than the second current, the current detection unit (34) does not output the overcurrent signal; An overcurrent protection unit (35), connected to the current detection unit (34) and the drive unit (32), respectively, receives the overcurrent signal and responds to the overcurrent signal to report to the drive unit (32) ) to output an adjustment signal, and the drive unit (32) receives the adjustment signal and responds to the adjustment signal to adjust the output current of the FET unit (31); a temperature detection module (6), configured to detect the real-time temperature of the circuit protection module (3) and connected to the drive unit (32) and the power supply module (2) respectively; If the real-time temperature is greater than a preset temperature threshold, an over-temperature signal is output to the drive unit (32), and the drive unit (32) receives the over-temperature signal and responds to the over-temperature signal to The state of the FET unit (31) is switched to the anti-backflow state. 2. The circuit for preventing current backflow for a video interface according to claim 1, wherein the control module (1) comprises: A voltage comparison unit (11), configured to be connected to the first external device (4) and receive a first voltage output by the first external device (4), and determine whether the first voltage is greater than a preset second voltage 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 lower than the second voltage, the voltage comparison unit (11) outputs a second comparison signal; A control unit (12), connected to the voltage comparison unit (11) to receive the first comparison signal or the second comparison signal, output the first control signal when receiving the first comparison signal, and receive the first comparison signal outputting the second control signal when the second comparison signal is reached; a signal amplifying unit (13), connected with the control unit (12) to receive and amplify the first control signal or the second control signal, and connected to the drive unit (32) to provide the drive unit (32) 32) Output the amplified first control signal or the second control signal. 3. The circuit for preventing current backflow for a video interface according to claim 1, wherein the circuit protection module (3) further comprises: A filtering unit (36) is connected to the FET unit (31) to filter out the stray current in the first current. 4. a method for preventing the reverse current flow of a video interface, applied to a circuit for preventing the reverse current flow of a video interface according to any one of claims 1-3, it is characterized in that, comprises the steps: The control module (1) judges whether the first external device (4) is connected; If the first external device (4) is not connected, the FET unit (31) is controlled by the driving unit (32) to be in the anti-backflow state; If the first external device (4) is connected, determine 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 driving unit (32) controls the FET unit (31) to switch to the forward conduction state, so that the power supply module (31) 2) establishing a power supply path with 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. 5. a kind of method for preventing current backflow for video interface according to claim 4, is characterized in that, described method also comprises the steps: The current detection unit (34) determines whether the first current is greater than the second current; If the first current is smaller than the second current, the FET unit (31) is not controlled to adjust the output current; If the first current is greater than the second current, the current detection unit (34), the overcurrent protection unit (35) and the driving unit (32) are used to control the adjustment of the FET unit (31) output current, and judge whether the real-time temperature of the circuit protection module (3) is greater than the temperature threshold through the temperature detection module (6); If the temperature is greater than the temperature threshold, the FET unit (31) is controlled by the driving unit (32) to switch to the anti-backflow state; If the temperature is less than the temperature threshold, the FET unit (31) maintains the forward conduction state. 6 . A device for preventing current backflow for a video interface, wherein the device comprises the circuit for preventing current backflow for a video interface according to any one of claims 1 to 3 above. 7 .

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