CN212435354U - Low current output current limiting protection circuit - Google Patents
Low current output current limiting protection circuit Download PDFInfo
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- CN212435354U CN212435354U CN202020561622.2U CN202020561622U CN212435354U CN 212435354 U CN212435354 U CN 212435354U CN 202020561622 U CN202020561622 U CN 202020561622U CN 212435354 U CN212435354 U CN 212435354U
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Abstract
The application relates to a low current output current-limiting protection circuit which is characterized by comprising a first resistor, a first transistor and a second transistor; the first resistor is electrically connected between the base electrode of the first transistor and the emitter electrode of the first transistor; the connection end of the first resistor and the emitter of the first transistor is used as a power supply input end and is used for being electrically connected to a power supply; the collector of the first transistor is electrically connected with the base of the second transistor; the connecting end of the first resistor and the base electrode of the first transistor is electrically connected with the emitter electrode of the second transistor; the collector of the second transistor is used as an output end and is used for outputting supply current; the first transistor and the second transistor are both PNP transistors. The purpose of current limiting protection can be achieved through two PNP transistors and a resistor. Compared with the mode that an operational amplifier or a comparator is adopted to design a protection circuit in the related technology, the circuit cost is greatly reduced, and the problem that the integrated circuit development cost is overhigh is effectively solved.
Description
Technical Field
The disclosure relates to the technical field of integrated circuits, in particular to a low-current output current-limiting protection circuit.
Background
A current-limiting protection circuit is usually disposed in an integrated circuit to ensure electronic devices in the integrated circuit and avoid the situation that the electronic devices are burned down due to sudden increase of current or excessive current. In the related art, an operational amplifier or a comparator is generally adopted in a current-limiting protection circuit, and a current-limiting protection function is realized by combining some precision resistors and other electronic components. Although the current-limiting protection function can be well realized by adopting electronic devices such as an operational amplifier or a comparator, the cost of the current-limiting protection circuit is higher, and the development of integrated circuit products is not facilitated.
SUMMERY OF THE UTILITY MODEL
In view of this, the present disclosure provides a low current output current limiting protection circuit, which can effectively reduce the cost of the current limiting protection circuit.
According to an aspect of the present disclosure, there is provided a small current output current limiting protection circuit, including a first resistor, a first transistor, and a second transistor;
the first resistor is electrically connected between the base of the first transistor and the emitter of the first transistor; and is
The connection end of the first resistor and the emitter of the first transistor is used as a power supply input end and is used for being electrically connected to a power supply;
a collector of the first transistor is electrically connected with a base of the second transistor;
the connection end of the first resistor and the base of the first transistor is electrically connected with the emitter of the second transistor;
a collector of the second transistor is used as an output end and used for outputting a supply current;
wherein the first transistor and the second transistor are both PNP transistors.
In one possible implementation, the device further comprises a diode;
the cathode of the diode is electrically connected to the connection end of the first resistor and the emitter of the first transistor;
the anode of the diode is used for being electrically connected to the power supply.
In one possible implementation, the circuit further comprises a second resistor and a third transistor;
the second resistor is electrically connected between the emitter of the first transistor and the base of the third transistor;
a collector of the third transistor is electrically connected to a base of the second transistor;
an emitter of the third transistor is grounded;
wherein the third transistor is an NPN transistor.
In a possible implementation manner, the device further comprises a third resistor;
the third resistor is electrically connected between the emitter of the first transistor and the base of the second transistor.
In a possible implementation manner, the device further comprises a fourth resistor;
the fourth resistor is electrically connected between the base of the second transistor and the collector of the third transistor.
In a possible implementation manner, a fifth resistor is further included;
the fifth resistor is electrically connected to the base of the third transistor and is configured to limit a current flowing through the third transistor.
In one possible implementation, the rated current of the diode is greater than 3 x (0.7 Vcc/R1);
and Vcc is the output voltage of the power supply, and R1 is the resistance value of the first resistor.
In one possible implementation, the power rating of the second transistor is greater than 1.5 x (0.7 Vcc/R1);
and Vcc is the output voltage of the power supply, and R1 is the resistance value of the first resistor.
In one possible implementation, the rated current of the first resistor is greater than 2 x (0.7/R1);
wherein R1 is the resistance of the first resistor.
Therefore, the low-current output current-limiting protection circuit provided by the embodiment of the disclosure realizes that current is drawn out through the first transistor when the circuit current is abnormal (i.e., increased) by arranging the two transistors (i.e., the first transistor and the second transistor) as the current-limiting protection switch and the second transistor as the normal output current switch and using one resistor as the pull-up resistor, so that the condition that a larger current still flows through the output of the first transistor is avoided, and the current-limiting protection effect on the current is realized. That is, the low-current output current-limiting protection circuit according to the embodiment of the present disclosure can achieve the purpose of current-limiting protection by two PNP transistors (i.e., a first transistor and a second transistor) and one resistor. Compared with the mode that an operational amplifier or a comparator is adopted to design a protection circuit in the related technology, the circuit cost is greatly reduced, and the problem that the integrated circuit development cost is overhigh is effectively solved.
Other features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments, which proceeds with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments, features, and aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure.
Fig. 1 shows a circuit diagram of a low current output current limiting protection circuit of an embodiment of the present disclosure.
Detailed Description
Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers can indicate functionally identical or similar elements. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present disclosure. It will be understood by those skilled in the art that the present disclosure may be practiced without some of these specific details. In some instances, methods, means, elements and circuits that are well known to those skilled in the art have not been described in detail so as not to obscure the present disclosure.
Fig. 1 shows a circuit diagram of a low current output current limiting protection circuit according to an embodiment of the present disclosure. As shown in fig. 1, the circuit includes: a first resistor R1, a first transistor Q1, and a second transistor Q2. It should be noted that, in the embodiment of the present disclosure, the first transistor Q1 and the second transistor Q2 are both PNP transistors. The first resistor R1 is electrically connected between the base of the first transistor Q1 and the emitter of the first transistor Q1. The connection of the first resistor R1 and the emitter of the first transistor Q1 serves as a power input terminal for electrical connection to a power supply Vcc. The collector of the first transistor Q1 is electrically connected to the base of the second transistor Q2. Meanwhile, the connection end of the first resistor R1 and the base of the first transistor Q1 is electrically connected to the emitter of the second transistor Q2. The collector of the second transistor Q2 serves as an Output terminal Output for outputting the supply current.
Based on the above circuit, in normal operation, the current generates a voltage drop through the first resistor R1. When the voltage drop is not enough to reach the turn-on voltage of the first transistor Q1, current is normally output through the second transistor Q2. When the current gradually increases, so that the voltage drop generated by the first resistor R1 reaches the turn-on voltage (Vbe) of the first transistor Q1, at this time, the first transistor Q1 is turned on, the voltage difference between the connection end of the first resistor R1 and the emitter of the first transistor Q1 (i.e., TP2) and the base of the second transistor Q2 (TP3) is about the turn-on voltage of the two first transistors Q1, at this time, the circuit enters a constant current output state, the output current value is substantially 0.7/5.1A, the output current is small, and the protection purpose can be achieved even if the connected load is abnormal. After the current drops to the normal range, the voltage drop across the first resistor R1 is not enough to reach the turn-on voltage of the first transistor Q1, the first transistor Q1 is automatically turned off, and the second transistor Q2 is turned on to operate normally, so as to continue outputting the required current.
Therefore, the low-current output current-limiting protection circuit of the embodiment of the disclosure can achieve the purpose of current-limiting protection through two PNP transistors (i.e., the first transistor Q1 and the second transistor Q2) and one resistor. Compared with the mode that an operational amplifier or a comparator is adopted to design a protection circuit in the related technology, the circuit cost is greatly reduced, and the problem that the integrated circuit development cost is overhigh is effectively solved.
In a possible implementation manner, referring to fig. 1, in order to further improve the safety and reliability of the low-current output current-limiting protection circuit of the embodiment of the present disclosure, a diode D1 may be connected in series between the first resistor R1 and the power supply Vcc, so as to achieve the protection effect on the first resistor R1.
When the diode D1 is connected in series between the first resistor R1 and the power supply Vcc, the anode of the diode D1 may serve as an input terminal of the low-current output current-limiting protection circuit of the embodiment of the disclosure and be electrically connected to the power supply Vcc. The cathode of the diode D1 is electrically connected to the connection terminal of the first resistor R1 and the emitter of the first transistor Q1. Thus, the current output from the power supply Vcc may pass through the diode D1 first, and then through the first resistor R1 when the diode is turned on.
In addition, it should be further noted that, in the small-current output current-limiting protection circuit according to the embodiment of the present disclosure, a second resistor R2 and a third transistor Q3 are further included. The second resistor R2 is electrically connected between the emitter of the first transistor Q1 and the base of the third transistor Q3. The collector of the third transistor Q3 is electrically connected to the base of the second transistor Q2. The emitter of the third transistor Q3 is grounded. Here, it should be noted that the third transistor Q3 is an NPN transistor.
Further, referring to fig. 1, the low-current output current-limiting protection circuit according to the embodiment of the present disclosure further includes a third resistor R3. Wherein the third resistor R3 is electrically connected between the emitter of the first transistor Q1 and the base of the second transistor Q2. In addition, the low-current output current-limiting protection circuit of the embodiment of the disclosure further comprises a fourth resistor R4. The fourth resistor R4 is electrically connected between the base of the second transistor Q2 and the collector of the third transistor Q3.
In the above embodiment, the second resistor R2 is also used as a pull-up resistor, which prevents the third transistor Q3 from being turned on under the interference condition, so that the low-current output current-limiting protection circuit of the embodiment is turned on only after receiving the control signal, which effectively improves the anti-interference performance of the low-current output current-limiting protection circuit of the embodiment of the disclosure.
Meanwhile, the third resistor R3 is used as a pull-up resistor in the above embodiment, which ensures that the second transistor Q2 is turned on without overcurrent. The fourth resistor R4 is used as a current limiting resistor to limit the on-state current of the third transistor Q3, thereby preventing the device from being burnt out due to an excessive current passing through the third transistor Q3.
Referring to fig. 1, in an embodiment, the low current output current limiting protection circuit of the embodiment of the disclosure further includes a fifth resistor R5. The fifth resistor R5 is electrically connected to the base of the third transistor Q3 for limiting the current flowing through the third transistor Q3.
In this embodiment, a fifth resistor R5 is further provided as a current-limiting resistor to further limit the current of the third transistor Q3, so that the reliability and stability of the low-current output current-limiting protection circuit according to the embodiment of the disclosure are further improved.
It should be noted that in the embodiment of the low-current output current-limiting protection circuit of the present disclosure shown in fig. 1, the rating parameters of each electronic device used need to be paid extra attention, so as to ensure the functional stability and reliability of the low-current output current-limiting protection circuit of the embodiment of the present disclosure.
Specifically, the diode D1 used has a rated current greater than 3 x (0.7 Vcc/R1). The Vcc is the output voltage of the power supply Vcc, and R1 is the resistance of the first resistor R1. The power rating of the second transistor Q2 is greater than 1.5 x (0.7 Vcc/R1). The rated current of the first resistor R1 is more than 2 x (0.7/R1).
It should be noted that, although fig. 1 is taken as an example to describe the low current output current limiting protection circuit of the embodiment of the present disclosure, those skilled in the art can understand that the present disclosure should not be limited thereto. In fact, the user can flexibly set the model, size and the like of the electronic device in the circuit according to personal preference and/or practical application scenes as long as the function of current limiting protection can be achieved.
In summary, the low-current output current-limiting protection circuit according to the embodiment of the present disclosure can implement a current-limiting protection function by providing the first transistor, the second transistor, and the first resistor. Meanwhile, a configuration diode, a third transistor and other resistors are additionally arranged in the circuit, so that the purpose of reverse connection prevention of the low-current output current-limiting protection circuit in the embodiment of the disclosure can be realized. Moreover, even if the output end is connected with the ground by mistake, the electronic devices in the circuit cannot be damaged, and only the circuit connection mode needs to be corrected. Meanwhile, the connection end of the fifth resistor and the third transistor is set as a control end (namely, a control end), so that the control end is grounded when the output is required to be turned off, and the circuit connection mode is effectively simplified. In addition, the low-current output current-limiting protection circuit disclosed by the embodiment of the disclosure is integrated on the PCB, and only a small part of area of the PCB is occupied, so that the space of the PCB is effectively saved, and the integration of other electronic devices is possible.
Having described embodiments of the present disclosure, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein were chosen in order to best explain the principles of the embodiments, the practical application, or technical improvements to the techniques in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (9)
1. A low current output current-limiting protection circuit is characterized by comprising a first resistor, a first transistor and a second transistor;
the first resistor is electrically connected between the base of the first transistor and the emitter of the first transistor; and is
The connection end of the first resistor and the emitter of the first transistor is used as a power supply input end and is used for being electrically connected to a power supply;
a collector of the first transistor is electrically connected with a base of the second transistor;
the connection end of the first resistor and the base of the first transistor is electrically connected with the emitter of the second transistor;
a collector of the second transistor is used as an output end and used for outputting a supply current;
wherein the first transistor and the second transistor are both PNP transistors.
2. The small current output current limiting protection circuit according to claim 1, further comprising a diode;
the cathode of the diode is electrically connected to the connection end of the first resistor and the emitter of the first transistor;
the anode of the diode is used for being electrically connected to the power supply.
3. The small current output current limiting protection circuit according to claim 1, further comprising a second resistor and a third transistor;
the second resistor is electrically connected between the emitter of the first transistor and the base of the third transistor;
a collector of the third transistor is electrically connected to a base of the second transistor;
an emitter of the third transistor is grounded;
wherein the third transistor is an NPN transistor.
4. The small current output current limiting protection circuit according to claim 1, further comprising a third resistor;
the third resistor is electrically connected between the emitter of the first transistor and the base of the second transistor.
5. The small current output current-limiting protection circuit according to claim 3, further comprising a fourth resistor;
the fourth resistor is electrically connected between the base of the second transistor and the collector of the third transistor.
6. The small current output current-limiting protection circuit according to claim 3, further comprising a fifth resistor;
the fifth resistor is electrically connected to the base of the third transistor and is configured to limit a current flowing through the third transistor.
7. The low current output current-limiting protection circuit of claim 2, wherein the rated current of said diode is greater than 3 x (0.7 Vcc/R1);
and Vcc is the output voltage of the power supply, and R1 is the resistance value of the first resistor.
8. The low current output current-limiting protection circuit of claim 1, wherein the rated power of said second transistor is greater than 1.5 x (0.7 Vcc/R1);
and Vcc is the output voltage of the power supply, and R1 is the resistance value of the first resistor.
9. The low current output current-limiting protection circuit of claim 1, wherein a rated current of said first resistor is greater than 2 x (0.7/R1);
wherein R1 is the resistance of the first resistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020561622.2U CN212435354U (en) | 2020-04-15 | 2020-04-15 | Low current output current limiting protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020561622.2U CN212435354U (en) | 2020-04-15 | 2020-04-15 | Low current output current limiting protection circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN212435354U true CN212435354U (en) | 2021-01-29 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202020561622.2U Active CN212435354U (en) | 2020-04-15 | 2020-04-15 | Low current output current limiting protection circuit |
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| Country | Link |
|---|---|
| CN (1) | CN212435354U (en) |
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2020
- 2020-04-15 CN CN202020561622.2U patent/CN212435354U/en active Active
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