CN215120123U - Protection circuit for video signal to power supply short circuit - Google Patents
Protection circuit for video signal to power supply short circuit Download PDFInfo
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- CN215120123U CN215120123U CN202121309237.XU CN202121309237U CN215120123U CN 215120123 U CN215120123 U CN 215120123U CN 202121309237 U CN202121309237 U CN 202121309237U CN 215120123 U CN215120123 U CN 215120123U
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Abstract
The utility model relates to a video signal is to protection circuit of power short circuit, is connected to camera connector, camera connector includes video input end and power supply end, the video input end is connected with matching resistance R7, its characterized in that, including overvoltage detection circuit and overvoltage control logic circuit, overvoltage detection circuit includes the transient voltage suppression diode RV1 who is connected with the video input end, overvoltage detection circuit is used for detecting the voltage variation condition of video input end; the overvoltage control logic circuit is connected to the overvoltage detection circuit and comprises a switching tube Q2, and the overvoltage control logic circuit controls the voltage value range of the video input end through the opening and closing of the switching tube Q2 so as to prevent the matching resistor R7 and an access circuit from being damaged when the video input end is short-circuited with a power line.
Description
Technical Field
The utility model relates to an automotive electronics technical field, concretely relates to video signal is to protection circuit of power short circuit.
Background
The camera of large-scale vehicles such as buses, tank trucks is generally far away from a video terminal, the camera line can exceed 5 meters generally, various adapters and power supply separating devices can be installed in the middle of the large-scale vehicles, the power line and the video signal line are easy to be short-circuited, and if no protection is provided, the matching resistor of 75R and the filter circuit of the camera end can be burnt out by a 12V power supply, so that electrical damage and equipment faults are caused.
The currently common solutions are: a power supply is added at the access end of the video signal camera to protect the video after short circuit, please refer to fig. 1, a high-power transient voltage suppressor is added at the signal input end, and the matching resistance of 75R is increased to 1210 for packaging (power 1W).
There are technical drawbacks in the above solutions: the minimum power value of the current transient voltage suppressor diode is 5V, for example, SMBJ5.0A of monarch glory, when the forward voltage exceeds 8.2V, the minimum power value to be borne is (12-8.2) × 3A =11.4W, the instantaneous power of the secondary power tube is 0.6kw, the continuous power is 5W, the transient voltage suppressor diode is very barely heated when resisting 12V, the heat is very serious, the transient voltage suppressor diode is inevitably burnt after the short-circuit time is long, the 75R matching resistor is also burnt, the 75R matching resistor needs to be propped against 8.2V × 8.2V/75R =0.89W, the resistance power needs to be 1W, and the chip package needs to be 2512 (namely, 6.4mm × 3.2mm, and the size is very large).
SUMMERY OF THE UTILITY MODEL
Accordingly, there is a need for an adaptive video signal short circuit protection circuit.
A video signal is connected to a camera connector, the camera connector comprises a video input end and a power supply end, the video input end is connected with a matching resistor R7, the protection circuit comprises an overvoltage detection circuit and an overvoltage control logic circuit, the overvoltage detection circuit comprises a transient voltage suppression diode RV1 connected with the video input end, and the overvoltage detection circuit is used for detecting the voltage change condition of the video input end; the overvoltage control logic circuit is connected to the overvoltage detection circuit and comprises a switching tube Q2, and the overvoltage control logic circuit controls the voltage value range of the video input end through the opening and closing of the switching tube Q2 so as to prevent the matching resistor R7 and an access circuit from being damaged when the video input end is short-circuited with a power line.
Further, the overvoltage detection circuit further comprises a diode D1 and a protection resistor R10, wherein one end of the protection resistor R10 is connected to the transient voltage suppression diode RV1, and the other end of the protection resistor R3526 is connected to a working ground.
Further, the anode of the diode D1 is connected to the connection point of the tvs RV1 and the protection resistor R10, and the cathode of the diode D1 is connected to the overvoltage control logic circuit.
Further, the overvoltage control logic circuit further includes a first transistor N2, a second transistor N3, and a first resistor R9, wherein one end of the first resistor R9 is connected to the collector of the first transistor N2, and the other end of the first resistor R9 is connected to the gate of the switching tube Q2.
Further, the overvoltage control logic circuit further includes a second resistor R12, one end of the second resistor R12 is connected to the base of the first transistor N2, and the other end of the second resistor R12 is connected to the collector of the second transistor N3.
Further, the overvoltage control logic circuit further includes a first capacitor C2, one end of the first capacitor C2 is connected to the base of the first transistor N2 through the second resistor R12, and the other end of the first capacitor C2 is connected to the emitter of the first transistor N2.
Further, the over-voltage control logic circuit further includes a third resistor R15, one end of the third resistor R15 is connected to a connection point of the first capacitor C2 and the second resistor R12, and the other end of the third resistor R15 is connected to a system power supply CAM _ POW.
Further, the overvoltage control logic circuit further includes a fourth resistor R14, one end of the fourth resistor R14 is connected to the base of the second transistor N3, and the other end of the fourth resistor R14 is connected to the overvoltage detection circuit.
Further, the bases of the first transistor N2 and the second transistor N3 are connected to an operating ground.
In the protection circuit for power supply short circuit caused by video signals, the overvoltage detection circuit and the matching resistor R7 are connected in parallel to the video input end, when the power supply end and the video input end are short-circuited, and the overvoltage detection circuit detects that the voltage value of the video input end exceeds 5V, the transient voltage suppression diode RV1 is turned on under the action of transient peak pulse current of the video input end, the overvoltage detection circuit releases electric energy of the video input end under the control of the overvoltage control logic circuit, so that the voltage value of the video input end is lower than 5V, the matching resistor R7 does not need to bear high-power current impact, and the matching resistor R7 and the access circuit are protected. The circuit of the utility model has the advantages of simple structure, easy production, low cost and convenient popularization.
Drawings
FIG. 1 is a schematic diagram of a protection circuit for power supply short circuit of video signals in the prior art
Fig. 2 is a schematic structural diagram of a protection circuit for power supply short circuit by video signals according to an embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to the following embodiments and drawings.
Referring to fig. 2, a protection circuit 100 for a video signal to power supply short circuit according to an embodiment of the present invention is shown, and is connected to a camera connector, where the camera connector includes a video input terminal and a power supply terminal, the video input terminal is connected to a matching resistor R7, the protection circuit includes an overvoltage detection circuit 10 and an overvoltage control logic circuit 20, the overvoltage detection circuit 10 includes a transient voltage suppression diode RV1 connected to the video input terminal, and the overvoltage detection circuit 10 is configured to detect a voltage variation condition of the video input terminal; the over-voltage control logic circuit 20 is connected to the over-voltage detection circuit 10, the over-voltage control logic circuit 20 includes a switch tube Q2, the over-voltage control logic circuit 20 controls the voltage value range of the video input end through the on/off of the switch tube Q2, so as to prevent the matching resistor R7 and the access circuit from being damaged when the video input end is short-circuited with a power line.
Further, the overvoltage detection circuit 10 further includes a diode D1 and a protection resistor R10, one end of the protection resistor R10 is connected to the transient voltage suppression diode RV1, and the other end is connected to a working ground; the anode of the diode D1 is connected to the connection point of the tvs RV1 and the protection resistor R10, and the cathode of the diode D1 is connected to the overvoltage control logic circuit 20.
Further, the overvoltage control logic circuit 20 further includes a first transistor N2, a second transistor N3, a first capacitor C2, a first resistor R9, a second resistor R12, a third resistor R15, and a fourth resistor R14, wherein a collector of the first transistor N2 is connected to the gate of the switching transistor Q2 through the first resistor R9; the base of the first triode N2 is connected to the collector of the second triode N3 through the second resistor R12; one end of the first capacitor C2 is connected to the base of the first triode N2 through the second resistor R12, and the other end is connected to the emitter of the first triode N2; the connection point of the first capacitor C2 and the second resistor R12 is connected to a system power supply CAM _ POW through the third resistor R15; the base of the second transistor N3 is connected to the overvoltage detection circuit 10 through the fourth resistor R14; the bases of the first transistor N2 and the second transistor N3 are connected to operational ground.
Specifically, the utility model discloses a video signal is as follows to the theory of operation of the protection circuit of power short circuit:
IN fig. 2, CON2 is a camera connector, the 12V network is a power supply for the camera, AUDIO _ IN is an AUDIO input, R7 is a matching resistor 75R, when the camera is normally operated, CVBS _ VIN1 is a 1Vpp voltage, TVS tube RV1 is not turned on, when CVBS _ VIN1 is shorted to the 12V network, the CVBS _ VIN1 voltage rises, when the voltage rises to 5V, RV1 is turned on, CVBS _ CTR1 is high, N3 transistor is turned on, the base voltage of N2 is pulled down, N2 is turned off, Q2 is turned off, when Q2 is turned off, the voltage of bs _ VIN1 starts to fall, RV1 is turned off, N3 transistor is turned off, CAM _ POW is 3.3V, when C2 voltage starts from 0, the charge is performed by R15, when the charge voltage reaches 2.2V, N2 is turned on, Q2 is pulled down, Q2 is turned on, Q2V gate 6865 is turned on, CVBS _ POW is turned on, maximum, CVBS _ POW is increased by 828653, and the cycle of the cycle is repeated above R2 (cycle). The packaging is carried out by 1206, the 0603 used in actual test can not be damaged, and the actual measurement waveform in short circuit is as shown in figure 2. When the 12V network is no longer short-circuited with the CVBS _ VIN1, the voltage of the CVBS _ VIN1 is lower than 5V, and the circuit recovers normal function
In the protection circuit for power supply short circuit caused by video signals, the overvoltage detection circuit 10 and the matching resistor R7 are connected in parallel to the video input terminal, when the power supply terminal and the video input terminal are short-circuited, and when the overvoltage detection circuit 10 detects that the voltage value of the video input terminal exceeds 5V, the transient voltage suppression diode RV1 is turned on under the action of transient peak pulse current of the video input terminal, and the overvoltage detection circuit 10 releases electric energy of the video input terminal under the control of the overvoltage control logic circuit 20, so that the voltage value of the video input terminal is lower than 5V, and the matching resistor R7 does not need to bear high-power current impact, and plays a role in protecting the matching resistor R7 and the access circuit. The circuit of the utility model has the advantages of simple structure, easy production, low cost and convenient popularization.
It should be noted that the present invention is not limited to the above embodiments, and other changes can be made by those skilled in the art according to the spirit of the present invention, and all the changes made according to the spirit of the present invention should be included in the scope of the present invention.
Claims (9)
1. A video signal is to the protective circuit of the short circuit of the power, connect to the connector of the camera, the said camera connector includes video input end and power supply end, the said video input end connects with matching resistance R7, characterized by, including overvoltage detection circuit and overvoltage control logic circuit, the said overvoltage detection circuit includes the transient voltage that is connected with said video input end and suppresses the diode RV1, the said overvoltage detection circuit is used for detecting the voltage change situation of the said video input end; the overvoltage control logic circuit is connected to the overvoltage detection circuit and comprises a switching tube Q2, and the overvoltage control logic circuit controls the voltage value range of the video input end through the opening and closing of the switching tube Q2 so as to prevent the matching resistor R7 and an access circuit from being damaged when the video input end is short-circuited with a power line.
2. The video signal power supply short-circuit protection circuit according to claim 1, wherein said overvoltage detection circuit further comprises a diode D1 and a protection resistor R10, and said protection resistor R10 is connected to said tvs RV1 at one end and to a working ground at the other end.
3. The video signal power supply short-circuit protection circuit according to claim 2, wherein an anode of the diode D1 is connected to a connection point of the tvs RV1 and the protection resistor R10, and a cathode of the diode D1 is connected to the overvoltage control logic circuit.
4. The video signal short-circuit protection circuit as claimed in claim 2, wherein said over-voltage control logic circuit further comprises a first transistor N2, a second transistor N3 and a first resistor R9, one end of said first resistor R9 is connected to the collector of said first transistor N2, and the other end of said first resistor R9 is connected to the gate of said switching transistor Q2.
5. The video signal short-circuit protection circuit as claimed in claim 4, wherein the over-voltage control logic circuit further comprises a second resistor R12, one end of the second resistor R12 is connected to the base of the first transistor N2, and the other end of the second resistor R12 is connected to the collector of the second transistor N3.
6. The video signal protection circuit for power supply short circuit according to claim 5, wherein said over-voltage control logic circuit further comprises a first capacitor C2, one end of said first capacitor C2 is connected to the base of said first transistor N2 through said second resistor R12, and the other end of said first capacitor C2 is connected to the emitter of said first transistor N2.
7. The video signal power supply short-circuit protection circuit of claim 6, wherein said over-voltage control logic circuit further comprises a third resistor R15, one end of said third resistor R15 is connected to the connection point of said first capacitor C2 and said second resistor R12, and the other end of said third resistor R15 is connected to a system power supply CAM _ POW.
8. The video signal short-circuit protection circuit as claimed in claim 7, wherein said over-voltage control logic circuit further comprises a fourth resistor R14, one end of said fourth resistor R14 is connected to the base of said second transistor N3, and the other end of said fourth resistor R14 is connected to said over-voltage detection circuit.
9. The video signal short-circuit protection circuit as claimed in claim 4, wherein the bases of the first transistor N2 and the second transistor N3 are connected to the working ground.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121309237.XU CN215120123U (en) | 2021-06-11 | 2021-06-11 | Protection circuit for video signal to power supply short circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121309237.XU CN215120123U (en) | 2021-06-11 | 2021-06-11 | Protection circuit for video signal to power supply short circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN215120123U true CN215120123U (en) | 2021-12-10 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202121309237.XU Active CN215120123U (en) | 2021-06-11 | 2021-06-11 | Protection circuit for video signal to power supply short circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN215120123U (en) |
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2021
- 2021-06-11 CN CN202121309237.XU patent/CN215120123U/en active Active
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