WO2018076714A1 - 一种接口防护电路 - Google Patents

一种接口防护电路 Download PDF

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Publication number
WO2018076714A1
WO2018076714A1 PCT/CN2017/088455 CN2017088455W WO2018076714A1 WO 2018076714 A1 WO2018076714 A1 WO 2018076714A1 CN 2017088455 W CN2017088455 W CN 2017088455W WO 2018076714 A1 WO2018076714 A1 WO 2018076714A1
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Prior art keywords
video signal
analog video
mosfet
resistor
line
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PCT/CN2017/088455
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English (en)
French (fr)
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马海波
李先银
张勇进
程程
张�浩
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华为技术有限公司
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Publication of WO2018076714A1 publication Critical patent/WO2018076714A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/20—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage
    • H02H3/202—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage for dc systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/20—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage

Definitions

  • the present invention relates to the field of electronic circuit design, and in particular, to an interface protection circuit.
  • the signal line and the signal ground are in the open wiring condition, the signal line open wiring connection point C and the signal ground open wiring connection point D are easily connected to the 12V/24V open wiring connection point B of the vehicle power supply line.
  • the power supply voltage range is between 8V and 36V.
  • the existing analog signal output interface scheme is shown in Figure 2: adding transient voltage suppression (English full name: Transient Voltage Suppressor, English abbreviation: TVS) tube or varistor on the analog video signal line.
  • transient voltage suppression English full name: Transient Voltage Suppressor, English abbreviation: TVS
  • the first aspect of the present application provides an interface protection circuit for protecting a video output interface from resetting or interface damage.
  • the interface protection circuit includes:
  • Analog video signal line input terminal analog video signal ground line input terminal, analog video signal line output terminal, analog video signal ground line output terminal, first protection module, second protection module;
  • the first protection module is connected between the analog signal line and the analog signal ground line for protecting the analog video signal line;
  • the first protection module includes a Metal-Oxide-Semiconductor Field-Effect Transistor (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET) and voltage regulator, when the analog video signal line works normally, the MOSFET turns on the analog signal for normal transmission.
  • MOSFET Metal-Oxide-Semiconductor Field-Effect Transistor
  • the regulator controls the MOSFET so that the MOSFET is turned off and the video is cut off. Signal transmission;
  • the second protection module includes a capacitor connected to the analog video signal ground line and the positive pole of the capacitor is connected to the analog video signal ground output terminal for protecting the analog video signal ground line; when the analog signal ground line is working normally, The capacitor turns on the video signal for normal transmission; when the analog signal ground wire is connected to the DC power line, the capacitor is isolated from the DC signal due to the characteristics of the AC-DC blocking.
  • the first protection module controls the MOSFET to be turned off by the voltage regulator, and the analog video signal line can be isolated.
  • the second protection module protects the analog video by isolating the DC signal generated on the DC power line through a capacitor Ground wire.
  • the foregoing first protection module may further include:
  • the source of the MOSFET is connected to the input end of the analog video signal line, and the drain of the MOSFET is connected to the output end of the analog video signal line;
  • a diode having a cathode connected to a gate of the MOSFET, a cathode of the diode being coupled to a cathode pin of the regulator;
  • a second resistor connected between the anode of the diode and a DC supply voltage.
  • the first resistor and the second resistor divide the DC supply voltage, and the gate voltage of the MOSFET is clamped in the turn-on voltage range of the MOSFET through the diode, so that the MOSFET is turned on to simulate the normal transmission of the signal line.
  • the diode also acts as a protection regulator.
  • the foregoing first module further includes:
  • the anode pin of the voltage regulator is connected to the analog line of the analog video signal
  • a third resistor connected between a drain of the MOSFET and a reference voltage pin of the regulator
  • the voltage between the analog video signal line and the analog video signal ground is divided by the third resistor and the fourth resistor.
  • the analog video signal line is connected to the DC power line, even the actual reference voltage of the Zener diode is actually The voltage is higher than the preset reference voltage value, and the output voltage of the cathode pin of the regulator is not within the turn-on voltage range of the MOSFET gate, so that the MOSFET is turned off.
  • the interface protection circuit further includes:
  • a unidirectional TVS tube connected between the analog video signal line input end and the analog video signal ground line input end.
  • the one-way TVS tube can suppress the first instantaneous impact signal generated by the analog video signal line overlapping the vehicle power supply line.
  • the one-way TVS tube is turned on at the moment of lapping, and provides a bypass for the first instantaneous impact signal when conducting, so that the first instantaneous impact signal is rapidly attenuated.
  • the interface protection circuit further includes:
  • the fifth resistor can further attenuate the instantaneous impact signal generated by the analog video signal line lapped on the vehicle power supply line, thereby protecting the analog video signal line while also protecting the analog video output chip, and the analog video signal output chip is connected to the interface protection circuit Input.
  • the second protection module further includes:
  • a ground line connected to the analog line of the analog video signal.
  • the second instantaneous impact signal instantaneously generated by the analog video signal grounding wire and the DC power supply line can be quickly connected to the ground, so that the second instantaneous impact signal is suppressed from being rapidly attenuated, thereby protecting the second instantaneous impact signal.
  • the influence on the ground line of the analog video signal; similarly, the ground line can further accelerate the decay speed of the first instantaneous impact signal bypassed by the TVS tube.
  • the interface protection circuit further includes:
  • the LED has a positive pole connected to the other end of the sixth resistor, and a cathode of the LED is connected to the analog video signal ground output.
  • the LED emits light when the analog video signal line is connected to the DC power line, and does not emit light when the analog video signal line is not connected to the DC power line, thereby indicating the analog video signal.
  • the line is connected to the DC power line, which is the effect of the lap error.
  • the voltage regulator is a precision adjustable voltage regulator.
  • the precision adjustable regulator reduces the action time to microseconds, the response speed is faster, and the action is more sensitive, thus improving the protection effect of the analog video signal line.
  • Figure 1 is an open wiring scenario diagram of the vehicle environment
  • FIG. 2 is a schematic diagram of an analog signal interface scheme in the prior art
  • FIG. 3 is a schematic diagram of an embodiment of an interface protection circuit according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram of another embodiment of an interface protection circuit according to an embodiment of the present invention.
  • FIG. 5 is a schematic structural diagram of a circuit of an interface protection circuit according to an embodiment of the present invention.
  • the embodiment of the invention provides an interface protection circuit for protecting the interface device from resetting or interface damage.
  • the embodiment of the invention designs an interface protection circuit, and the circuit design of the basic electronic component makes the interface protection circuit have better protection effect on the analog video interface, and the design idea of the interface protection circuit is applicable to the simulation. In the scene where DC signal interference occurs during signal transmission.
  • the interface protection circuit of this embodiment is used for protecting the analog video signal line and the analog video signal ground line, and preventing the external DC interference signal from causing damage to the analog video signal line and the analog video signal ground line.
  • the interface protection circuit in the embodiment of the present invention is described in detail with reference to FIG. 3.
  • the interface protection circuit includes a first protection module 302 and a second protection module 303.
  • the first protection module 302 and the second protection module 303 are connected.
  • the first protection module 302 is located on the analog video signal line between the analog video chip output interface 301 and the analog video connector output 304; the second protection module 303 is located at the analog video chip output interface 301 and the analog video connector output 304.
  • the analog video signal is on the ground.
  • the first protection module 302 includes a MOSFET and a voltage regulator for protecting the analog video signal line. Specifically, when the voltage regulator detects that the voltage value on the analog video signal line is less than the preset voltage value, the voltage regulator does not operate. The MOSFET is in the on state, and the analog video signal line works normally; when the voltage regulator detects that the voltage value on the analog video signal line is not less than the preset voltage value, the regulator acts to turn off the MOSFET, and the analog video signal line Disconnected;
  • the second protection module 303 includes a capacitor, and the ground line for protecting the analog video signal is specifically: when the voltage value on the analog video signal line is not less than the preset voltage value, the capacitor isolates the DC interference signal at both ends of the capacitor, so that the DC interference The signal does not interfere with the analog video signal ground.
  • the first protection module 302 and the second protection module 303 respectively protect the analog video signal line and the analog video signal ground line, thereby preventing the external DC interference signal from damaging the analog video signal line and the analog video signal ground line. Therefore, the interface device is effectively protected from resetting or interface damage.
  • the interface protection circuit further includes:
  • the indication module 405 is connected to the analog video signal line and located between the first protection module 402 and the analog video connector output 404;
  • the indicating module 405 includes a resistor and a light emitting diode, wherein when the voltage value on the analog video signal line is less than the preset voltage value, the resistor does not light the LED through the voltage dividing; when the voltage value on the analog video signal line is not less than When the voltage value is preset, the resistor illuminates the LED through the voltage division function, thereby indicating that there is no DC signal interference and DC signal interference on the analog video signal line respectively by not lighting and lighting the two states.
  • the indication module 405 can indicate that the analog video signal line is connected to the DC power supply line by lighting, thereby reminding the wiring personnel to make an erroneous connection, so that the wiring personnel can find and eliminate the lap error in time.
  • the embodiment of the invention provides a reliable overall circuit protection scheme for an analog video output interface, which can be applied to the field of analog video signal transmission, especially in a vehicle environment such as a bus, a car, a bus, a subway, a high-speed train, and the like.
  • the in-vehicle device is designed with an analog video output interface for playing TV programs. Since there is no standard unified interface connector in the automotive field, the types of analog video output interface connectors are different, resulting in the video cable and power cable connected to the car display. It is a bare wire. When the stripping tool is used in the field for stripping, it is easy to make the video cable and the power cable overlap.
  • the transmission level of the analog video signal is generally 3.3V or less, and the vehicle power cable used is generally 12V or 24V DC voltage, the transient pulse in the range of 8V to 36V will be higher than the analog video during the ignition start process.
  • the signal transmission level is 3.3V. Therefore, if the video cable is connected to the power cable, the voltage on the power cable is likely to cause damage and reset of the vehicle equipment when the vehicle is fired or the lap is not removed in time. Phenomenon, it can be seen that the overall protection design of the analog video output interface circuit of the vehicle equipment is particularly important. In order to facilitate the understanding of the practical application scenarios of the embodiments of the present invention in the vehicle-mounted field, a preferred embodiment of the interface protection circuit in the embodiment of the present invention will be described in detail below.
  • the interface protection circuit includes:
  • the first protection module includes a MOSFET Q1, a precision adjustable voltage regulator U1, a first resistor R1, a second resistor R2, a diode D1, a third resistor R3, and a fourth resistor R4;
  • the second protection module includes a capacitor C1 and a ground line GND;
  • the unidirectional TVS tube D2, the fifth resistor R5, the sixth resistor R6, and the light emitting diode D3 have the above four devices in the order of 507, 508, 509 and 510.
  • the above interface protection circuit is connected as follows:
  • the fifth resistor 508 is connected between the analog video signal line input terminal 501 and the source of the MOSFET Q1;
  • the unidirectional TVS tube 507 is connected between the source of the MOSFET Q1 and the analog video signal ground input 503, and the conduction direction is turned from the source of the MOSFET Q1 to the analog video signal ground input 503;
  • the first resistor R1 is connected between the analog video signal ground input terminal 503 and the gate of the MOSFET Q1;
  • the diode D1 is connected between the gate of the MOSFET Q1 and the cathode pin 1 of the precision adjustable regulator U1;
  • the second resistor R2 is connected between the cathode pin 1 of the precision adjustable regulator U1 and the supply voltage Vcc, and the supply voltage Vcc is the operating voltage of the precision adjustable regulator U1;
  • the third resistor R3 and the fourth resistor R4 are connected in series between the analog video signal line output terminal 502 and the analog video signal ground line input terminal 503;
  • the reference voltage pin 2 of the precision adjustable voltage regulator U1 is connected between the third resistor R3 and the fourth resistor R4, and the anode pin 3 of the precision adjustable voltage regulator U1 is connected to the analog video signal ground line input terminal 503;
  • the sixth resistor 509 is connected between the analog video signal line output terminal 502 and the anode of the light emitting diode 510;
  • the cathode of the LED 510 is connected to the analog video signal ground input 503;
  • the anode of the capacitor C1 is connected to the analog video signal ground output 504, the cathode of the capacitor C1 is connected to the analog video signal ground input 503;
  • the ground line GND is connected to the analog video signal ground input terminal 503.
  • the supply voltage Vcc is DC 5V
  • the reference voltage of the reference voltage pin 2 of the precision adjustable regulator U1 is 2.5V
  • the third resistor R3 and the fourth resistor R4 are two resistances and MOSFETs having the same resistance value.
  • the turn-on voltage is in the range of 1V to 2.5 and the capacitance of the capacitor C1 is 220 micrometers.
  • the rated voltage is greater than 48V.
  • the device parameters of the other devices are described within a reasonable design range.
  • the actual voltage value of the reference voltage pin 2 of the precision adjustable voltage regulator U1 after the third resistor R3 and the fourth resistor R4 are divided is smaller than the reference voltage, and the precision is adjustable.
  • Regulator U1 into a high configuration Equivalent to the precision adjustable regulator U1 is in an open state, the gate voltage of the MOSFET is divided by the first resistor R1, the second resistor R2 and the diode D1 to control the supply voltage Vcc to be controlled within the turn-on voltage range of the MOSFET.
  • the MOSFET is turned on normally, and the analog video signal line input terminal 501 and the analog video signal line output terminal 502 are in an on state.
  • the lap transient MOSFET When the analog video signal line is connected to the direct vehicle power line, the lap transient MOSFET is still in an on state, and an analog pulse signal line will generate an electrical pulse signal to the unidirectional TVS tube 507 and the fifth resistor 508, since The electric pulse signal is greater than the normal working voltage of the unidirectional TVS tube 507, and the unidirectional TVS tube 507 is turned on instantaneously to form a bypass.
  • the electric pulse signal is drained to the analog video signal ground line, and the ground is quickly introduced into the ground through the ground line GND.
  • the signal is attenuated, and the unidirectional TVS tube 507 is quickly turned back to the normal off state after being turned on, and the fifth resistor 508 simultaneously consumes the portion of the electric pulse signal that is not introduced into the earth to the chip connected to the analog video signal line input terminal 501.
  • the third resistor R3 and the fourth resistor R4 are divided, and the actual voltage value of the reference voltage pin 2 of the precision adjustable regulator U1 is greater than the reference voltage, and the precision adjustable voltage regulator U1 is turned on, and the cathode pin 1 of the precision adjustable regulator U1 has a voltage output, so that the diode clamps the gate voltage of the MOSFET Q1 outside the turn-on voltage range of the MOSFET Q1, and the MOSFET Q1 is turned off. Therefore, the analog video signal line input terminal 501 and the analog video signal line output terminal 502 are in an off state; after the lap, the sixth resistor 509 divides the generated high voltage on the analog video signal line to trigger the light emitting diode 310. It changes from no light to light.
  • the capacitor C1 When the analog video signal ground line is not connected to the direct vehicle power supply line, there is no DC voltage signal on the analog video signal ground line, the capacitor C1 is in an on state, the analog video signal ground line input end 503 and the analog video signal ground line output end 504 It is working normally in the on state.
  • the analog video signal ground wire When the analog video signal ground wire is connected to the straight vehicle power line, there is a DC voltage signal on the analog video signal ground. Since the capacitor has the characteristics of AC-DC blocking, the DC voltage signal is isolated at both ends of the capacitor, and the analog video signal The ground line input terminal 503 and the analog video signal ground line output end 504 still work normally; since an electrical pulse signal is generated at the moment of the lap, the capacitor C1 cannot isolate the electric pulse signal. At this time, the ground line GND electrically pulses the electric pulse. The signal is diverted into the earth such that the electrical pulse signal is attenuated without affecting the normal operation of the analog video signal ground.
  • the interface protection circuit has the following advantages: First, the following three abnormal overlapping scenarios are solved: 1. The analog video signal line is connected to the power line. 2. The analog video signal ground wire is connected to the power line. 3. The analog video signal line and the analog video signal ground line are simultaneously connected to the power line. In addition, it not only protects the long-term lap joint, but also suppresses the instantaneous electric pulse generated immediately after the splicing instant, that is, the ignition start; after the lap is eliminated, the automatic recovery of the analog video signal can be realized. Second, the protection circuit can be made into a separate circuit module, and the protection specifications of the vehicle equipment can be improved without modifying the original equipment hardware.
  • the LED can be used as an indicator light to indicate the presence of the user's analog video signal line and the vehicle power supply, so that the user can quickly implement positioning and repair. 4. Adjust the reference voltage of the third resistor R3, the fourth resistor R4 and the precision adjustable regulator U1, and the interface protection circuit can realize the lap protection of the 50DC or higher DC power supply.
  • FIG. 5 is only the most preferred component connection mode in the embodiment of the present invention.
  • the interface protection circuit is connected in many ways, and only one specific connection embodiment is described above.

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Abstract

一种接口防护电路，用于保护接口设备不易出现复位或接口损坏现象。包括：模拟视频信号线输入端，模拟视频信号地线输入端，模拟视频信号线输出端，模拟视频信号地线输出端，第一保护模块（302），第二保护模块（303）；第一保护模块分别与模拟视频信号线输入端、模拟视频信号线输出端和模拟视频信号地线输入端相连接；第二保护模块连接于模拟视频信号地线输入端与模拟视频信号地线输出端之间；第一保护模块包括MOSFET和稳压器，当稳压器检测到模拟视频信号线上的电压值高于预置电压值时，则关断MOSFET，使得模拟视频信号线输入端与模拟视频信号线输出端断开；第二保护模块包括电容，电容用于隔开直流电压。

Description

一种接口防护电路 技术领域
本发明涉及电子电路设计领域，尤其涉及一种接口防护电路。
背景技术
现有车载领域，不少车载设备设计有模拟视频输出接口用于播放电视节目。此类接口一般由信号线和信号地线两根线组成。在车载环境中，由于无标准统一的接口连接器，各种类车辆所使用的视频接口连接器类型也不同；而车载显示屏所接出的视频线和电源线是裸线，无连接器，导致此类接口现场连接时需要进行开放接线即现场使用工具进行剥线接线。如图1所示，信号线和信号地两根线在开放接线情况下，信号线开放接线连接点C与信号地开放接线连接点D容易接到车载电源线的12V/24V开放接线连接点B上，在车辆打火启动过程中，电源电压的电源范围是8V到36V之间。
现有模拟信号输出接口方案如图2所示：在模拟视频信号线上增加瞬间电压抑制(英文全称：Transient Voltage Suppressor，英文简称：TVS)管或压敏电阻。
在现有模拟信号输出接口方案中，在车辆打火启动过程中，在车载电源线上会产生一个高于24V的高脉冲，当模拟视频信号线和/或模拟视频信号地线搭接到车载电源线上时，此时TVS管或压敏电阻瞬间导通形成旁路使得该高脉冲被抑制，但若不及时消除搭接，则TVS管或压敏电阻将起不到保护作用。因此在车辆打火启动过程中，模拟视频信号线和/或模拟视频信号地线长期搭接在车载电源线上时，TVS管或压敏电阻将失去保护作用，容易导致车载设备出现复位或接口损坏现象。
发明内容
本申请第一方面提供了一种接口防护电路，用于保护视频输出接口不易出现复位或接口损坏现象。
所述接口防护电路，包括：
模拟视频信号线输入端，模拟视频信号地线输入端，模拟视频信号线输出端，模拟视频信号地线输出端，第一保护模块，第二保护模块；
第一保护模块连接于模拟信号线与模拟信号地线之间，用于对模拟视频信号线进行防护；第一保护模块包括金属氧化物半导体场效应管(Metal-Oxide-Semiconductor Field-Effect Transistor，MOSFET)和稳压器，当模拟视频信号线正常工作时，MOSFET导通模拟信号正常传输，当模拟视频信号搭接直流电源线时，稳压器对MOSFET进行控制使得MOSFET被关断，切断视频信号传输；
第二保护模块包括电容，该电容连接于模拟视频信号地线上且电容正极与模拟视频信号地线输出端连接，用于对模拟视频信号地线的防护；当模拟信号地线正常工作时，电容导通视频信号正常传输；当模拟信号地线搭接直流电源线时，电容由于通交流隔直流的特性，因此电容便将直流信号隔离开。
采用上述接口防护电路，即便是在模拟视频信号线和/或模拟视频信号地线搭接到直流电源线上时，第一保护模块通过稳压器控制MOSFET关断，可以将模拟视频信号线隔离保护，第二保护模块通过电容将直流电源线上产生的直流信号隔离开来，从而保护模拟视频 地线。通过同时对模拟视频信号线和模拟视频信号地线进行保护，可以将车载模拟视频输出设备出现复位或接口损坏现象的可能性将降至最低，减少了模拟视频输出出现复位或接口损坏现象。
在第一方面的第一种可能的实现方式中，上述第一保护模块还可以包括：
该MOSFET的源极与该模拟视频信号线输入端连接，该MOSFET的漏极与该模拟视频信号线输出端连接；
第一电阻，该第一电阻连接于该模拟视频信号地线输入端与该MOSFET的栅极之间；
二极管，该二极管的负极与该MOSFET的栅极连接，该二极管的正极与该稳压器的阴极管脚连接；
第二电阻，该第二电阻连接于该二极管的正极与直流供电电压之间。
该实现方式中，第一电阻和第二电阻通过对直流供电电压进行分压，并且通过二极管将MOSFET的栅极电压钳位在MOSFET的开启电压范围内使得该MOSFET导通从而模拟信号线正常传输数据，此外该二极管还起到保护稳压器的作用。
结合第一方面的第一种可能的实现方式，在第一方面的第二种可能的实现方式中，上述第一模块还包括：
该稳压器的阳极管脚连接于该模拟视频信号地线输入端；
第三电阻，该第三电阻连接于该MOSFET的漏极与该稳压器的参考电压管脚之间；
第四电阻，该第四电阻连接于该模拟视频信号地线输入端与该稳压器的参考电压管脚之间。
通过第三电阻和第四电阻对模拟视频信号线与模拟视频信号地线之间的电压进行分压，当模拟视频信号线搭接直流电源线时，即便稳压管的参考电压管脚的实际电压高于预置的参考电压值，也可以使稳压器阴极管脚的输出电压不在MOSFET栅极的开启电压范围内，从而使得MOSFET被关断。
结合第一方面的第二种可能的实现方式，在第一方面的第三种可能的实现方式中，接口防护电路还包括：
单向TVS管，该单向TVS管连接于该模拟视频信号线输入端与该模拟视频信号地线输入端之间。
单向TVS管可以抑制模拟视频信号线搭接车载电源线瞬间产生的第一瞬间冲击信号。该单向TVS管在搭接瞬间导通，导通时为该第一瞬间冲击信号提供旁路，从而使该第一瞬间冲击信号迅速衰减。
结合第一方面的第三种可能的实现方式，在第一方面的第四种可能的实现方式中，接口防护电路还包括：
第五电阻，该第五电阻连接于该模拟视频信号线输入端与该MOSFET的源极之间。
第五电阻可以进一步将模拟视频信号线搭接车载电源线瞬间产生的瞬间冲击信号衰减，从而保护模拟视频信号线的同时也保护模拟视频输出芯片，该模拟视频信号输出芯片连接于该接口防护电路的输入端。
结合第一方面，以及第一方面的第一种至第四种可能的实现方式中任一种，在第一方面的第五种可能的实现方式，第二保护模块还包括：
接地线，该接地线连接与该模拟视频信号地线输入端。
通过接地线，可以将模拟视频信号地线搭接直流电源线瞬间产生的第二瞬间冲击信号迅速接入大地，从而使得该第二瞬间冲击信号被抑制快速衰减，从而保护该第二瞬间冲击信号对模拟视频信号地线的影响；同理，该接地线还可以进一步加快该TVS管旁路过来的该第一瞬间冲击信号的衰减速度。
结合第一方面的第五种可能的实现方式，在第一方面的第六种可能的实现方式种，接口防护电路还包括：
第六电阻，该第六电阻一端连接于该MOSFET的漏极；
发光二极管，该发光二极管的正极与该第六电阻另一端连接，该发光二极管的负极与该模拟视频信号地线输出端连接。
通过合理设计第六电阻的阻值，使得发光二极管在模拟视频信号线搭接直流电源线时发光，在该模拟视频信号线未搭接直流电源线时不发光，从而起到指示该模拟视频信号线搭接直流电源线，即搭接出错的作用。
结合第一方面第五种可能的实现方式，在第一方面的第七种可能的实现方式中，稳压器为精密可调稳压器。
精密可调稳压器将动作时间缩短至微秒级，反应速度更快，动作更加灵敏，从而提高了模拟视频信号线的防护效果。
附图说明
图1为车载环境开放式接线场景图；
图2为现有技术中一种模拟信号接口方案图；
图3为本发明实施例中接口防护电路的一种实施例示意图；
图4为本发明实施例中接口防护电路的另一种实施例示意图；
图5为本发明实施例中接口防护电路的一种电路原理结构图。
具体实施方式
本发明实施例提供了一种接口防护电路，用于保护接口设备不易出现复位或接口损坏现象。
为了使本技术领域的人员更好地理解本发明方案，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分的实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都应当属于本发明保护的范围。
本发明的说明书和权利要求书及上述附图中的术语“第一”、“第二”、“第三”、“第四”等(如果存在)是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。应该理解这样使用的数据在适当情况下可以互换，以便这里描述的实施例能够以除了在这里图示或描述的内容以外的顺序实施。此外，术语“包括”和“具有”以及他们的任何变形，意图在于覆盖不排他的包含。
本发明实施例设计了一种接口防护电路，通过基本电子元器件进行电路设计使得此接口防护电路对模拟视频接口具有更好的防护效果，此接口防护电路设计思路适用于在模拟 信号传输过程中出现直流电信号干扰的场景中。
为了便于理解本发明实施例，下面通过功能化模块设计来对本发明实施例进行说明。
本实施例的接口防护电路用于对模拟视频信号线和模拟视频信号地线的保护，防止外界直流干扰信号对模拟视频信号线和模拟视频信号地线造成损坏。
请参阅图3对本发明实施例中接口防护电路进行详细说明，如图所示上述接口防护电路包括第一保护模块302和第二保护模块303，第一保护模块302和第二保护模块303均连接于模拟视频芯片输出接口301和模拟视频连接器输出304之间。
其中，第一保护模块302位于模拟视频芯片输出接口301和模拟视频连接器输出304之间的模拟视频信号线上；第二保护模块303位于模拟视频芯片输出接口301和模拟视频连接器输出304之间的模拟视频信号地线上。
另外，第一保护模块302包括MOSFET、稳压器，用于保护模拟视频信号线具体为：当稳压器检测到模拟视频信号线上的电压值小于预置电压值时，稳压器不动作，MOSFET处于导通状态，模拟视频信号线正常工作；当稳压器检测到模拟视频信号线上的电压值不小于预置电压值时，稳压器动作使得MOSFET处于截止状态，模拟视频信号线被断开；
第二保护模块303包括电容，用于保护模拟视频信号地线具体为：当模拟视频信号线上的电压值不小于预置电压值时，电容将直流干扰信号隔离在电容两端，使得直流干扰信号不对模拟视频信号地线造成干扰。
本实施例中，通过第一保护模块302和第二保护模块303分别对模拟视频信号线和模拟视频信号地线进行保护防止了外界直流干扰信号对模拟视频信号线和模拟视频信号地线造成损坏，从而有效地保护接口设备不易出现复位或接口损坏现象。
另外，如图4所示，上述接口防护电路还包括：
指示模块405；
指示模块405连接于上述模拟视频信号线上且位于第一保护模块402和模拟视频连接器输出404之间；
指示模块405包括电阻和发光二极管，用于当模拟视频信号线上的电压值小于预置电压值时，电阻通过分压作用使得发光二极管不点亮；当模拟视频信号线上的电压值不小于预置电压值时，电阻通过分压作用使得发光二极管点亮，从而通过不点亮和点亮两种状态起到分别指示模拟视频信号线上无直流信号干扰和有直流信号干扰。
本实施例中，指示模块405可以通过点亮来指示模拟视频信号线搭接到直流电源线上，从而提醒接线人员搭接出错，以便接线人员及时发现和消除搭接错误。
上述实施例对本发明实施例的总体设计进行了说明，为了理解更加直观和清晰，下面将对本发明实施例中接口防护电路的电路原理结构进行说明。
本发明实施例提供了一种可靠的模拟视频输出接口整体电路防护方案，可以应用于模拟视频信号传输领域，尤其是应用于公交车、小汽车、大巴车、地铁、高铁列车等车载环境中，车载设备设计有模拟视频输出接口用于播放电视节目，由于目前车载领域无标准统一的接口连接器，各类模拟视频输出接口连接器类型也不相同导致车载显示屏接出的视频线和电源线是裸线，在现场使用剥线工具进行剥线连接时容易使得视频线和电源线搭接在一起，目前模拟视频信号的传输电平一般为3.3V以下，而使用的车载电源线上一般是12V或24V的直流电压，在打火启动过程中会出现8V至36V范围内的瞬间脉冲高于模拟视频 信号的传输电平3.3V，因此，若视频线与电源线搭接，当在车辆打火启动过程中或是搭接没有被及时消除时，电源线上的电压容易造成车载设备出现损坏和复位现象，由此可见对于车载设备的模拟视频输出接口电路进行整体防护设计显得尤为重要。为了便于理解本发明实施例在车载领域的实际应用场景，下面将对本发明实施例中的接口防护电路的一种优选实施例进行详细描述。
请参阅图5对本发明实施例中接口防护电路的优选实施例进行详细说明，接口防护电路包括：
模拟视频信号线输入端501，模拟视频信号线输出端502，模拟视频信号地线输入端503，模拟视频信号地线输出端504，第一保护模块505，第二保护模块506；
第一保护模块包括MOSFET Q1、精密可调稳压器U1、第一电阻R1、第二电阻R2、二极管D1、第三电阻R3和第四电阻R4；
第二保护模块包括电容C1和接地线GND；
单向TVS管D2，第五电阻R5，第六电阻R6，发光二极管D3，其上述四器件的标号依次为507、508、509和510。
上述接口防护电路的连接方式如下：
第五电阻508连接于模拟视频信号线输入端501和MOSFET Q1的源极之间；
单向TVS管507连接与MOSFET Q1的源极与模拟视频信号地线输入端503之间，并且导通时导通方向由MOSFET Q1的源极指向模拟视频信号地线输入端503；
第一电阻R1连接于模拟视频信号地线输入端503和MOSFET Q1的栅极之间；
二极管D1连接于MOSFET Q1的栅极和精密可调稳压器U1的阴极管脚1之间；
第二电阻R2连接于精密可调稳压器U1的阴极管脚1和供电电压Vcc之间，供电电压Vcc为精密可调稳压器U1工作电压；
第三电阻R3和第四电阻R4串联于模拟视频信号线输出端502和模拟视频信号地线输入端503之间；
精密可调稳压器U1的参考电压管脚2连接与第三电阻R3和第四电阻R4之间，精密可调稳压器U1的阳极管脚3连接与模拟视频信号地线输入端503；
第六电阻509连接于模拟视频信号线输出端502和发光二极管510的正极之间；
发光二极管510的负极连接于模拟视频信号地线输入端503；
电容C1的正极连接于模拟视频信号地线输出端504，电容C1的负极连接于模拟视频信号地线输入端503；
接地线GND连接于模拟视频信号地线输入端503。
上面对图5所示的接口防护电路的组成及连接方式进行了描述，下面将对此接口防护电路的工作流程进行说明：
以下说明内容中供电电压Vcc以直流5V、精密可调稳压器U1的参考电压管脚2的参考电压以2.5V、第三电阻R3和第四电阻R4为两个电阻值相等的电阻、MOSFET的开启电压在1V至2.5范围内以及电容C1的电容值为220微法额定电压大于48V为例，其余器件的器件参数均在合理设计范围内进行说明。
当模拟视频信号线未搭接直车载电源线时，第三电阻R3和第四电阻R4分压后精密可调稳压器U1的参考电压管脚2的实际电压值小于参考电压，精密可调稳压器U1成高组态 等效于精密可调稳压器U1处于断路状态，MOSFET的栅极电压由第一电阻R1、第二电阻R2和二极管D1对供电电压Vcc进行分压将其控制在MOSFET的开启电压范围内使得MOSFET导通正常工作，模拟视频信号线输入端501与模拟视频信号线输出端502之间处于导通状态。
当模拟视频信号线搭接直车载电源线时，搭接瞬间MOSFET仍处于导通状态，模拟视频信号线上将产生一个电脉冲信号至单向TVS管507和第五电阻508，由于此时该电脉冲信号大于单向TVS管507的正常工作电压，单向TVS管507便瞬间导通形成旁路将该电脉冲信号引流至模拟视频信号地线上通过接地线GND快速引入大地将该电脉冲信号衰减，单向TVS管507瞬间导通后又迅速恢复正常关断状态，第五电阻508同时将未被引流入大地的部分该电脉冲信号消耗至与模拟视频信号线输入端501连接的芯片的可抵抗范围内；当短暂的瞬间过后，第三电阻R3和第四电阻R4分压后精密可调稳压器U1的参考电压管脚2的实际电压值大于参考电压，精密可调稳压器U1导通，精密可调稳压器U1的阴极管脚1有电压输出，使得二极管将MOSFET Q1的栅极电压钳位于MOSFET Q1的开启电压范围之外，MOSFET Q1被关断，从而模拟视频信号线输入端501与模拟视频信号线输出端502之间处于断开状态；搭接之后，第六电阻509对模拟视频信号线上的产生的高电压进行分压触发发光二极管310由不发光变为点亮状态。
当模拟视频信号地线未搭接直车载电源线时，模拟视频信号地线上无直流电压信号，电容C1处于导通状态，模拟视频信号地线输入端503和模拟视频信号地线输出端504处于导通状态正常工作。
当模拟视频信号地线搭接直车载电源线时，模拟视频信号地线上存在直流电压信号，由于电容具有通交流隔直流的特性，因此该直流电压信号被隔离在电容两端，模拟视频信号地线输入端503和模拟视频信号地线输出端504仍然正常工作；由于搭接瞬间会产生一个电脉冲信号，电容C1不能对该电脉冲信号进行隔离，此时，接地线GND将该电脉冲信号引流入大地使得该电脉冲信号被衰减不会影响模拟视频信号地线正常工作。
本实施例中，接口防护电路具有以下优点：一、解决了以下三种异常搭接场景：1、模拟视频信号线搭接到电源线上。2、模拟视频信号地线搭接到电源线上。3、模拟视频信号线和模拟视频信号地线同时搭接到电源线上。另外，不仅对长期搭接起到保护作用，还能抑制搭接瞬间即打火启动瞬间产生的瞬间电脉冲；搭接消除后可以实现自动恢复模拟视频信号传输。二、防护电路可单独做成一个独立电路模块，无需修改原设备硬件即可提升车载设备的防护规格。三、可以通过发光二极管作为指示灯指示用户模拟视频信号线存在与车载电源搭接情况，方便用户快速实施定位和修复。四、调节第三电阻R3、第四电阻R4和精密可调稳压器U1的参考电压，接口防护电路可以实现50DC甚至更高DC电源的搭接防护。
对于本领域技术人员而言，图5仅仅是本发明实施例中最优选的一种组成连接方式，具体实现中接口防护电路连接方式很多，上述描述的仅一个具体的连接实施例。
以上对本发明所提供的一种接口防护电路进行了详细介绍，对于本领域的一般技术人员，依据本发明实施例的思想，在具体实施方式及应用范围上均会有改变之处，综上所述，本说明书内容不应理解为对本发明的限制。

Claims (8)

  1. 一种接口防护电路，其特征在于，包括：
    模拟视频信号线输入端，模拟视频信号地线输入端，模拟视频信号线输出端，模拟视频信号地线输出端，第一保护模块，第二保护模块；
    所述第一保护模块分别与所述模拟视频信号线输入端、所述模拟视频信号线输出端和所述模拟视频信号地线输入端相连接；
    所述第二保护模块连接于所述模拟视频信号地线输入端与所述模拟视频信号地线输出端之间；
    所述第一保护模块包括金属氧化物半导体场效应管MOSFET和稳压器，当所述稳压器检测到模拟视频信号线上的电压值不小于预置电压值时，则关断所述MOSFET，使得所述模拟视频信号线输入端与所述模拟视频信号线输出端断开；
    所述第二保护模块包括电容，所述电容正极与所述模拟信号地线输出端连接，所述电容负极与所述模拟信号地线输入端连接，所述电容用于隔开直流电压。
  2. 根据权利要求1所述的接口防护电路，其特征在于，所述第一保护模块还包括：
    所述MOSFET的源极与所述模拟视频信号线输入端连接，所述MOSFET的漏极与所述模拟视频信号线输出端连接；
    第一电阻，所述第一电阻连接于所述模拟视频信号地线输入端与所述MOSFET的栅极之间；
    二极管，所述二极管的负极与所述MOSFET的栅极连接，所述二极管的正极与所述稳压器的阴极管脚连接；
    第二电阻，所述第二电阻连接于所述二极管的正极与直流供电电压之间。
  3. 根据权利要求2所述的接口防护电路，其特征在于，所述第一保护模块还包括：
    所述稳压器的阳极管脚连接于所述模拟视频信号地线输入端；
    第三电阻，所述第三电阻连接于所述MOSFET的漏极与所述稳压器的参考电压管脚之间；
    第四电阻，所述第四电阻连接于所述模拟视频信号地线输入端与所述稳压器的参考电压管脚之间。
  4. 根据权利要求3所述的接口防护电路，其特征在于，所述电路还包括：
    单向TVS管，所述单向TVS管连接于所述模拟视频信号线输入端与所述模拟视频信号地线输入端之间。
  5. 根据权利要求4所述的接口防护电路，其特征在于，所述电路还包括：
    第五电阻，所述第五电阻连接于所述模拟视频信号线输入端与所述MOSFET的源极之间。
  6. 根据权利要求1至5中任一项所述的接口防护电路，所述第二报护模块还包括：
    接地线，所述接地线连接与所述模拟视频信号地线输入端。
  7. 根据权利要求6所述的接口防护电路，其特征在于，所述电路还包括：
    第六电阻，所述第六电阻一端连接于所述MOSFET的漏极；
    发光二极管，所述发光二极管的正极与所述第六电阻另一端连接，所述发光二极管的 负极与所述模拟视频信号地线输出端连接。
  8. 根据权利要求6所述的接口防护电路，其特征在于，所述稳压器为精密可调稳压器。
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