CN215009589U - Interface protection circuit and RS232 interface circuit - Google Patents
Interface protection circuit and RS232 interface circuit Download PDFInfo
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- CN215009589U CN215009589U CN202121467635.4U CN202121467635U CN215009589U CN 215009589 U CN215009589 U CN 215009589U CN 202121467635 U CN202121467635 U CN 202121467635U CN 215009589 U CN215009589 U CN 215009589U
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Abstract
The utility model discloses an interface protection circuit and a RS232 interface circuit, wherein the interface protection circuit comprises an input protection circuit and an output protection circuit; the input protection circuit comprises a front-stage current-limiting voltage-limiting circuit, a level conversion circuit and a rear-stage current-limiting voltage-limiting circuit; the output protection circuit comprises a signal amplification circuit, a push-pull circuit connected to the output end of the signal amplification circuit and a short-circuit protection circuit connected to the push-pull circuit. The input protection circuit of the scheme carries out primary current and voltage limiting on input current and voltage through the preceding stage current and voltage limiting circuit, and after the level conversion circuit converts the level, the subsequent stage current and voltage limiting circuit limits the current and voltage again, so that the input protection of the RS232 interface is ensured. The output protection circuit amplifies the output signal by the signal amplification circuit and outputs the amplified signal after being amplified by the push-pull circuit, and the short-circuit protection circuit performs short-circuit protection on the push-pull circuit. Meanwhile, the input protection circuit and the output protection circuit are adopted, so that the input and output protection functions of the RS232 interface can be greatly improved.
Description
Technical Field
The utility model belongs to the technical field of the interface protection circuit, specifically relate to an interface protection circuit and RS232 interface circuit.
Background
In serial communication, both communication parties are required to adopt a standard interface, so that different devices can be conveniently connected for communication. RS-232 is currently one of the most commonly used serial communication interfaces. The RS-232 standard interface is also called EIA RS-232, and is a standard for serial port communication commonly established by EIA of the american association with electronics and industry association bell systems, modem manufacturers, and computer terminal manufacturers in 1970, and the original serial number is fully called EIA-RS-232 (abbreviated as 232, RS232), and is fully called "technical standard for serial binary data exchange interface between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE)".
RS-232 is one of the mainstream serial communication interfaces at present and is widely used for peripheral connection of a serial interface of a computer. The RS232 port is used as an interface for debugging, an inter-board communication interface and a monitoring signal interface on the communication equipment, and the transmission distance is not more than 15 meters. The interface is used more frequently for debugging, and hot plugging often, therefore the interface can receive overvoltage, the impact of overcurrent, if not protect, damages interface chip very easily.
The RS232 interface protection is currently as shown in fig. 1, and a transient suppression diode is used for protection, but the protection effect is not good.
SUMMERY OF THE UTILITY MODEL
The not good problem of transient suppression diode guard action is adopted in order to solve current RS 232's interface protection, the utility model provides an interface protection circuit and RS232 interface circuit, its input/output guard action that can improve the RS232 interface.
The utility model discloses a following technical scheme realizes:
the utility model discloses a first aspect provides an interface protection circuit, which comprises an input protection circuit and an output protection circuit;
the input protection circuit comprises a front-stage current-limiting voltage-limiting circuit, a level conversion circuit and a rear-stage current-limiting voltage-limiting circuit which are sequentially connected;
the output protection circuit comprises a signal amplification circuit, a push-pull circuit connected to the output end of the signal amplification circuit and a short-circuit protection circuit connected to the push-pull circuit.
The input protection circuit is used for being connected with an RS232 input interface, the input current and voltage are limited in a current limiting and voltage limiting mode for the first time through the front stage current limiting and voltage limiting circuit, after the level conversion circuit converts the level, the current and voltage of the rear stage current limiting and voltage limiting circuit are limited again, and input protection of the RS232 interface is guaranteed. The output protection circuit is used for being connected with the RS232 output interface to realize output protection, and output signals are amplified by the signal amplification circuit and then output after being amplified by the push-pull circuit. The push-pull circuit is an output circuit connected between two transistors with different polarities, and when the circuit works, only one transistor is conducted at a time, so that the conduction loss is small, and the efficiency is high. The short-circuit protection circuit performs short-circuit protection on the push-pull circuit, and the protection effect of the output end is improved. Meanwhile, the input protection circuit and the output protection circuit are adopted, so that the input and output protection functions of the RS232 interface can be greatly improved.
In one possible design, the preceding stage current-limiting voltage-limiting circuit comprises a preceding stage current-limiting resistor and two diodes connected in series.
The preceding stage current-limiting voltage-limiting circuit adopts a resistor and diode structure, has a simple structure, can realize stable current-limiting voltage, and saves circuit construction cost.
In one possible design, a preceding stage filter capacitor is connected to the preceding stage current limiting voltage limiting circuit.
The voltage limiting is realized by adopting a diode, under certain conditions, an instant burr phenomenon can occur, a front stage filter capacitor is connected on a front stage current limiting voltage limiting circuit, and burrs are filtered by adopting the capacitor, so that the stability of the circuit is improved.
In one possible design, the post current-limiting and voltage-limiting circuit comprises a post current-limiting resistor and two diodes connected in series.
The rear-stage current-limiting and voltage-limiting circuit adopts a resistor and diode structure, has a simple structure, can realize stable current-limiting voltage, and saves the circuit construction cost.
In one possible design, a post-stage filter capacitor is connected to the post-stage current-limiting and voltage-limiting circuit.
Similarly, the voltage limiting is realized by adopting a diode at the rear stage, under certain conditions, the phenomenon of instantaneous burr can occur, a front-stage filter capacitor is connected to the rear-stage current-limiting voltage-limiting circuit, and the burr is filtered by adopting the capacitor, so that the stability of the circuit is further improved.
In one possible design, the push-pull circuit includes a first triode and a second triode, a protection resistor is connected between the output end of the first triode and the output end of the second triode and the output end of the interface protection circuit, and a first resistor used for providing bias voltage for the first triode and the second triode is connected between the base level of the first triode and the second triode and the output end of the interface protection circuit.
The push-pull circuit of the scheme is composed of two triodes, and the output ends of the triodes are provided with the protection resistors, so that short-circuit protection is realized, and the output protection effect of the circuit is improved.
In one possible design, the signal amplification circuit includes a first operational amplifier and a reference voltage circuit connected to a positive input terminal of the first operational amplifier.
The scheme adopts the operational amplifier, which can realize the amplification of the output signal and can also utilize the isolation effect of the signal amplifier to avoid the interference of the output end signal, thereby further improving the safety performance of the interface.
The second aspect of the utility model provides a RS232 interface circuit, which comprises a RS232 communication interface and any one of the interface protection circuits of the first aspect,
the signal output end of the rear stage current-limiting voltage-limiting circuit of the interface protection circuit is connected with the signal input end of the RS232 communication interface,
and the signal output end of the RS232 communication interface is connected with the signal input end of the signal amplifying circuit.
Compared with the prior art, the utility model, following advantage and beneficial effect have at least:
the input protection circuit is used for being connected with an RS232 input interface, the input current and voltage are limited in a current limiting and voltage limiting mode for the first time through the front stage current limiting and voltage limiting circuit, after the level conversion circuit converts the level, the current and voltage of the rear stage current limiting and voltage limiting circuit are limited again, and input protection of the RS232 interface is guaranteed. The output protection circuit is used for being connected with the RS232 output interface to realize output protection, and output signals are amplified by the signal amplification circuit and then output after being amplified by the push-pull circuit. The push-pull circuit is an output circuit connected between two transistors with different polarities, and when the circuit works, only one transistor is conducted at a time, so that the conduction loss is small, and the efficiency is high. The short-circuit protection circuit performs short-circuit protection on the push-pull circuit, and the protection effect of the output end is improved. Meanwhile, the input protection circuit and the output protection circuit are adopted, so that the input and output protection functions of the RS232 interface can be greatly improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic diagram of a conventional RS232 interface circuit.
Fig. 2 is a schematic diagram of the RS232 interface circuit of the present embodiment.
Detailed Description
The invention will be further described with reference to the accompanying drawings and specific embodiments. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. Specific structural and functional details disclosed herein are merely illustrative of example embodiments of the invention.
It should also be noted that, in some alternative designs, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed substantially concurrently, or the figures may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
It should be understood that specific details are provided in the following description to facilitate a thorough understanding of example embodiments. However, it will be understood by those of ordinary skill in the art that the example embodiments may be practiced without these specific details. For example, systems may be shown in block diagrams in order not to obscure the examples in unnecessary detail. In other instances, well-known processes, structures and techniques may be shown without unnecessary detail in order to avoid obscuring example embodiments.
As shown in fig. 2, the present invention discloses an interface protection circuit, which comprises an input protection circuit and an output protection circuit; the output end of the input protection circuit is used for being connected to the signal input end of the communication interface, and the signal output end of the communication interface is connected to the signal input end of the output protection circuit. The input protection circuit comprises a front-stage current-limiting voltage-limiting circuit, a level conversion circuit and a rear-stage current-limiting voltage-limiting circuit which are sequentially connected; the output protection circuit comprises a signal amplification circuit, a push-pull circuit connected to the output end of the signal amplification circuit and a short-circuit protection circuit connected to the push-pull circuit.
Specifically, the preceding stage current-limiting voltage-limiting circuit comprises a preceding stage current-limiting resistor and two diodes connected in series.
And the preceding stage current-limiting voltage-limiting circuit is connected with a preceding stage filter capacitor.
The rear stage current-limiting voltage-limiting circuit comprises a rear stage current-limiting resistor and two diodes connected in series.
And the rear stage current-limiting and voltage-limiting circuit is connected with a rear stage filter capacitor.
The push-pull circuit comprises a first triode and a second triode, a protection resistor is connected between the output end of the first triode and the output end of the second triode and the output end of the interface protection circuit, and a first resistor used for providing bias voltage for the first triode and the second triode is connected between the base level of the first triode and the second triode and the output end of the interface protection circuit.
The signal amplification circuit comprises a first operational amplifier and a reference voltage circuit connected to the positive input end of the first operational amplifier.
Based on the above principle, a specific circuit structure is disclosed, and referring to fig. 2, taking an RS232 interface circuit as an example, an RS232 communication interface of the RS232 interface circuit includes a signal input port P1.0 and a signal output port P1.1.
The resistor R16 and the resistor R52 form a front stage current limiting resistor, the diode D5 and the diode D6 are connected in series to form a part of a front stage current limiting and voltage limiting circuit, and the capacitor C38 is a front stage filter capacitor. The second operational amplifier B and its peripheral circuits constitute a level conversion circuit. The resistor R47 and the resistor R44 form a rear-stage current-limiting resistor, the diode D7 and the diode D8 are connected in series to form a part of a rear-stage current-limiting voltage-limiting circuit, and the capacitor C36 is a rear-stage filter capacitor. The output end of the input protection circuit is connected to the signal input port P1.0 to realize input protection.
The voltage divider circuit including the resistor R55 and the resistor R58 forms a reference voltage circuit, and supplies a reference voltage to the first operational amplifier a. The triode Q4 and the triode Q5 form a push-pull circuit, the resistor R57 and the resistor R53 respectively form protective resistors of the triode Q4 and the triode Q5, and short-circuit protection is achieved; the resistor R54 is connected to the base stage of the transistor Q4 and the transistor Q5 to provide bias voltage for the transistor Q4 and the transistor Q5. The signal output port P1.1 is connected to the inverting input terminal of the first operational amplifier to realize output protection.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: modifications may be made to the embodiments described above, or equivalents may be substituted for some of the features described. Such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present invention.
Finally, it should be noted that the present invention is not limited to the above-mentioned alternative embodiments, and that various other forms of products can be obtained by anyone in light of the present invention. The above detailed description should not be taken as limiting the scope of the invention, which is defined in the following claims, and which can be used to interpret the claims.
Claims (8)
1. An interface protection circuit, comprising an input protection circuit and an output protection circuit;
the input protection circuit comprises a front-stage current-limiting voltage-limiting circuit, a level conversion circuit and a rear-stage current-limiting voltage-limiting circuit which are sequentially connected;
the output protection circuit comprises a signal amplification circuit, a push-pull circuit connected to the output end of the signal amplification circuit and a short-circuit protection circuit connected to the push-pull circuit.
2. The interface protection circuit of claim 1, wherein the pre-stage current-limiting voltage-limiting circuit comprises a pre-stage current-limiting resistor and two diodes connected in series.
3. The interface protection circuit of claim 1, wherein a pre-filter capacitor is connected to the pre-stage current-limiting voltage-limiting circuit.
4. The interface protection circuit of claim 1, wherein said post current limiting and voltage limiting circuit comprises a post current limiting resistor and two diodes connected in series.
5. The interface protection circuit of claim 1, wherein a post-stage filter capacitor is connected to the post-stage current-limiting voltage-limiting circuit.
6. The interface protection circuit of claim 1, wherein the push-pull circuit comprises a first transistor and a second transistor, a protection resistor is connected between the output terminal of the first transistor and the output terminal of the second transistor and the output terminal of the interface protection circuit, and a first resistor for providing a bias voltage for the first transistor and the second transistor is connected between the base stage of the first transistor and the second transistor and the output terminal of the interface protection circuit.
7. The interface protection circuit of claim 1 or 6, wherein the signal amplification circuit comprises a first operational amplifier and a reference voltage circuit connected to a positive input terminal of the first operational amplifier.
8. An RS232 interface circuit, comprising an RS232 communication interface and an interface protection circuit according to any one of claims 1 to 7,
the signal output end of the rear stage current-limiting voltage-limiting circuit of the interface protection circuit is connected with the signal input end of the RS232 communication interface,
and the signal output end of the RS232 communication interface is connected with the signal input end of the signal amplifying circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121467635.4U CN215009589U (en) | 2021-06-29 | 2021-06-29 | Interface protection circuit and RS232 interface circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121467635.4U CN215009589U (en) | 2021-06-29 | 2021-06-29 | Interface protection circuit and RS232 interface circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN215009589U true CN215009589U (en) | 2021-12-03 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202121467635.4U Active CN215009589U (en) | 2021-06-29 | 2021-06-29 | Interface protection circuit and RS232 interface circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN215009589U (en) |
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2021
- 2021-06-29 CN CN202121467635.4U patent/CN215009589U/en active Active
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