MIC short-circuit protection circuit based on T-BOX
Technical Field
The invention relates to the technical field of electronic circuits, in particular to a T-BOX-based MIC short-circuit protection circuit.
Background
The T-BOX (Telematics BOX) is mainly used for interconnection and communication between a vehicle and a background system or a mobile phone APP, and vehicle information is acquired through the mobile phone or the background. The T-BOX acquires automobile bus data through the CAN bus, positions the vehicle through the GPS module, and transmits the data to the cloud server through the network by using the module. The vehicle owner can obtain the vehicle state, the airbag state and the vehicle anti-theft alarm on the mobile phone APP, and inquire the vehicle parking position; driving log: time, mileage, remaining oil amount, driving behavior analysis, and the like. And reporting the control result, the state and the like to a background, and pushing the execution result to a mobile phone APP or a website by a background server. Because the T-BOX has so many functions, it is an indispensable choice for both users and yards: for the car owner, the car owner does not worry about that the car cannot be found in a car yard, and an air bag, emergency rescue and the like are triggered when the car collides; for the parking lot, the full life cycle management of the vehicles can be really realized, so that the automobiles become a new generation of mobile terminals. However, the existing T-BOX MIC circuit cannot effectively cope with short-circuit protection of a 24V power supply of a vehicle, and thus damage of the MIC circuit occurs.
SUMMERY OF THE UTILITY MODEL
The MIC short-circuit protection circuit based on the T-BOX is characterized in that short-circuit automatic protection is realized through a circuit built by discrete devices, and the service life of T-BOX equipment is prolonged.
The technical scheme adopted for solving the technical problems is as follows:
according to one aspect herein, there is provided a T-BOX based MIC short-circuit protection circuit, comprising: a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1, a diode VD1, a triode VT1, a triode VT2 and a triode VT3, the negative electrode of the diode VD1 is connected with the MIC input end MIC-IN of the T-BOX, the positive electrode of the diode VD1 is connected with one end of a resistor R1, the other end of the resistor R1 is connected with the grid of a triode VT1, the drain of the triode VT1 is grounded, the source of the triode VT1 is connected with one end of a resistor R2, one end of a resistor R3 and the grid of a triode VT2, the other end of the resistor R2 is connected with an MCU-GPIO interface, the other end of the resistor R3 is grounded with the drain of the triode VT2, the source of the triode VT2 is connected with one end of a resistor R4 and the grid of a triode VT3, the other end of the resistor R4 is connected with the source of a triode VT3 and the MIC-IN end, the drain of the triode VT 42 is connected with one end of a capacitor C1, and the other end.
Optionally, the diode VD1 is a zener diode.
Optionally, the MCU-GPIO interface defaults to a high level, when the voltage of the cathode of the zener diode VD1 is less than the regulated voltage of VD1, the zener diode VD1 is turned off, the gate voltage of the transistor VT1 is 0V, the transistor VT1 is turned off, when the gate voltage of the transistor VT2 is greater than the turn-on voltage of the transistor VT2, the transistor VT2 is turned on, at this time, the gate voltage of the transistor VT3 is 0V, the transistor VT3 is turned on, the input terminal MIC-IN and the output terminal MIC-OUT of the T-BOX are turned on, and the T-BOX operates normally.
Optionally, the gate voltage of the transistor VT2 is the divided voltage of the resistors R2 and R3.
Optionally, the capacitor C1 is a dc blocking capacitor.
Optionally, when the cathode voltage of the zener diode VD1 is not less than the zener voltage of VD1, the zener diode VD1 is turned on, when the gate voltage of the transistor VT1 is greater than the turn-on voltage of the transistor VT1, the transistor VT1 is turned on, at this time, the gate voltage of the transistor VT2 is 0V, the transistor VT2 is turned off, the gate voltage and the source voltage of the transistor VT3 are approximately equal, the transistor VT3 is turned off, the input terminal MIC-IN of the T-BOX is disconnected from the output terminal MIC-OUT, and the MIC circuit is protected.
Optionally, the resistor R1 is a current limiting resistor.
Optionally, the transistor VT1 and the transistor VT2 are N-MOS FETs, and the transistor VT3 is a P-MOS FET.
The utility model discloses MIC short-circuit protection circuit based on T-BOX, this circuit includes: a T-BOX based MIC short circuit protection circuit comprises: a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1, a diode VD1, a triode VT1, a triode VT2 and a triode VT3, the negative electrode of the diode VD1 is connected with the MIC input end MIC-IN of the T-BOX, the positive electrode of the diode VD1 is connected with one end of a resistor R1, the other end of the resistor R1 is connected with the grid of a triode VT1, the drain of the triode VT1 is grounded, the source of the triode VT1 is connected with one end of a resistor R2, one end of a resistor R3 and the grid of a triode VT2, the other end of the resistor R2 is connected with an MCU-GPIO interface, the other end of the resistor R3 is grounded together with the drain of the triode VT2, the source of the triode VT2 is connected with one end of a resistor R4 and the grid of a triode VT3, the other end of the resistor R4 is connected with the source of a triode VT3 and the MIC-IN end, the drain of the triode VT 42 is connected with one end of a capacitor C1, and the other; the circuit built by discrete devices realizes the automatic short circuit protection, and the service life of the T-BOX equipment is prolonged.
Drawings
Fig. 1 is a circuit diagram of an MIC short-circuit protection circuit based on a T-BOX according to an embodiment of the present invention.
The objects, features, and advantages described herein will be further explained with reference to the accompanying drawings.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer and more obvious, the present invention is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not restrictive.
Examples
As shown in fig. 1, in this embodiment, a T-BOX based MIC short-circuit protection circuit includes: a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1, a diode VD1, a triode VT1, a triode VT2 and a triode VT3, the negative electrode of the diode VD1 is connected with the MIC input end MIC-IN of the T-BOX, the positive electrode of the diode VD1 is connected with one end of a resistor R1, the other end of the resistor R1 is connected with the grid of a triode VT1, the drain of the triode VT1 is grounded, the source of the triode VT1 is connected with one end of a resistor R2, one end of a resistor R3 and the grid of a triode VT2, the other end of the resistor R2 is connected with an MCU-GPIO interface, the other end of the resistor R3 is grounded with the drain of the triode VT2, the source of the triode VT2 is connected with one end of a resistor R4 and the grid of a triode VT3, the other end of the resistor R4 is connected with the source of a triode VT3 and the MIC-IN end, the drain of the triode VT 42 is connected with one end of a capacitor C1, and the other end.
In the embodiment, the automatic short-circuit protection is realized through the discrete circuit, the requirement of automatic protection during MIC short circuit on T-BOX equipment can be met, and an automatic protection function is provided when the MIC circuit is short-circuited to a power supply and a ground, so that the T-BOX is protected, and the service life of the T-BOX equipment is prolonged.
In this embodiment, the diode VD1 is a zener diode, and plays a role of preventing reverse.
In this embodiment, the transistors VT1 and VT2 are N-MOS FETs, and the transistor VT3 is a P-MOS FET.
IN the embodiment, the normally on-off of the MIC-IN and MIC-OUT paths is realized through the switch of the MOS tube. When the MIC-IN is short-circuited to the power supply, the P-MOS tube is automatically closed, and protection is realized. The protection circuit in the embodiment is suitable for the application of overvoltage protection of an interface circuit of the T-BOX, in particular to the circuit application of MIC in BYPASS. Because a high-voltage switch is usually added for protection, the cost is high, the application of the circuit IN the embodiment can greatly reduce the cost, and the normal paths of MIC-IN and MIC-OUT and the over-high voltage protection can be effectively protected when the MIC is BYPASS. The parameters in the circuit can be configured in a hardware mode, different parameter requirements can be met, the requirements of vehicle-mounted reliability and stability of products can be met, and the circuit can be widely applied to industrial production.
IN this embodiment, the MCU-GPIO interface defaults to a high level, when the voltage of the cathode of the zener diode VD1 is less than the regulated voltage of VD1, the zener diode VD1 is turned off, the gate voltage of the transistor VT1 is 0V, the transistor VT1 is turned off, when the gate voltage of the transistor VT2 is greater than the turn-on voltage of the transistor VT2, the transistor VT2 is turned on, at this time, the gate voltage of the transistor VT3 is 0V, the transistor VT3 is turned on, the input MIC-IN and the output MIC-OUT of the T-BOX are turned on, and the T-BOX operates normally.
In the present embodiment, the gate voltage of the transistor VT2 is the divided voltage of the resistors R2 and R3. Assuming that the voltage at the MCU-GPIO interface is VF, the gate voltage of VT2 at this time
VG=R3/(R2+R3)VF。
In this embodiment, the capacitor C1 is a dc blocking capacitor, and can play a role of dc blocking protection when the MIC-OUT is short-circuited to a power supply.
IN this embodiment, when the cathode voltage of the zener diode VD1 is not less than the zener voltage of VD1, the zener diode VD1 is turned on, and when the gate voltage of the transistor VT1 is greater than the turn-on voltage of the transistor VT1, the transistor VT1 is turned on, and at this time, the gate voltage of the transistor VT2 is 0V, the transistor VT2 is turned off, the gate voltage and the source voltage of the transistor VT3 are approximately equal, the transistor VT3 is turned off, the input terminal MIC-IN of the T-BOX is disconnected from the output terminal MIC-OUT, and the MIC circuit is protected.
In this embodiment, the resistor R1 is a current limiting resistor, and plays a role of limiting current.
The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, without thereby limiting the scope of the invention. Any modification, equivalent replacement and improvement made by those skilled in the art without departing from the scope and spirit of the present invention should be within the scope of the claims of the present invention.