CN213425783U - Load open-circuit protection circuit of constant-current output DC-DC constant-voltage chip - Google Patents
Load open-circuit protection circuit of constant-current output DC-DC constant-voltage chip Download PDFInfo
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- CN213425783U CN213425783U CN202022009325.XU CN202022009325U CN213425783U CN 213425783 U CN213425783 U CN 213425783U CN 202022009325 U CN202022009325 U CN 202022009325U CN 213425783 U CN213425783 U CN 213425783U
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Abstract
The utility model relates to a load open circuit protection circuit of a DC-DC constant voltage chip with constant current output, which comprises a DC-DC constant voltage chip, wherein the input end of the DC-DC constant voltage chip is connected with a power supply, the enabling end is connected with a switch triode and a divider resistor which are connected in parallel, the feedback end is connected with a load and a feedback resistor which are connected in parallel, and the output end is connected with the other end of the load; the emitter of the switching triode is grounded, the collector is connected with the enabling end, the base is connected with two sampling resistors which are connected in parallel, and the sampling resistors are grounded through one sampling resistor and connected with the output end through the other sampling resistor; if the load is not open-circuited, the switching triode is not conducted, the enable pin is biased at a high level, and the chip is in a working state; when the load is in an open circuit, the voltage of the output power supply is increased, the switching triode is conducted, the enable pin is biased at a low level, and the chip is in a closed state, so that an open circuit protection effect is achieved; therefore, the device has the characteristics of simple structure, reasonable design, small volume, high reliability, stable work, high cost performance and the like.
Description
Technical Field
The utility model relates to a DC-DC constant voltage chip technical field, more specifically say, relate to a constant current output's DC-DC constant voltage chip's load protection circuit of opening a way.
Background
Constant voltage chip need adopt the constant current mode output under some scenes, if LED illumination load ageing leads to the resistance to reduce, the electric current increase, concatenate the load between feedback circuit and output power supply this moment, can realize the constant current through adjusting feedback resistance, but if the chip during operation, open circuit (not meeting) appears in the load, can make feedback circuit and output power supply's disconnection, lead to the output voltage of chip constantly to rise, can burn out the chip at last.
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model lies in, to the above-mentioned defect of prior art, a load open circuit protection circuit of DC-DC constant voltage chip of constant current output is provided.
The utility model provides a technical scheme that its technical problem adopted is:
the load open-circuit protection circuit of the DC-DC constant voltage chip with constant current output is constructed, wherein the load open-circuit protection circuit comprises the DC-DC constant voltage chip, the input end of the DC-DC constant voltage chip is connected with a power supply, the enabling end of the DC-DC constant voltage chip is connected with a switching triode and a divider resistor which are connected in parallel, the feedback end of the DC-DC constant voltage chip is connected with a load and a feedback resistor which are connected in parallel, and the output end of the DC-; the emitter of the switching triode is grounded, the collector of the switching triode is connected with the enabling end of the DC-DC constant voltage chip, the base of the switching triode is connected with a first sampling resistor and a second sampling resistor which are connected in parallel, the other end of the first sampling resistor is grounded, and the other end of the second sampling resistor is connected with the output end of the DC-DC constant voltage chip; the other end of the divider resistor is connected with a power supply; the other end of the feedback resistor is grounded.
Preferably, a diode is connected between the output end of the DC-DC constant voltage chip and the load in series, the anode of the diode is connected with the load, and the cathode of the diode is connected with the output end of the DC-DC constant voltage chip.
Preferably, a first filter capacitor, a second filter capacitor, a third filter capacitor and a fourth filter capacitor which are connected in parallel are arranged between the power supply and the input end of the constant voltage chip, and the other ends of the first filter capacitor, the second filter capacitor, the third filter capacitor and the fourth filter capacitor are all grounded; and a fifth filter capacitor, a sixth filter capacitor and a seventh filter capacitor which are connected in parallel are arranged between the diode and the load, and the other ends of the fifth filter capacitor, the sixth filter capacitor and the seventh filter capacitor are all grounded.
Preferably, an inductor is connected in series between the input end and the output end of the DC-DC constant voltage chip.
Preferably, the switching transistor is an NPN transistor.
The beneficial effects of the utility model reside in that: the load open-circuit protection circuit provided by the invention can detect the output voltage in real time, if the open-circuit condition does not occur in the load, the feedback end of the chip is not disconnected with the output end, the chip regulates the voltage through the feedback end, the switching triode is not conducted, the high level of the enabling pin is biased, and the chip is in a working state; when the load is in an open circuit condition, the feedback end of the chip is not disconnected with the output end, the chip cannot adjust output voltage through the feedback end, the voltage output by the chip is increased, the switching triode is conducted, the low level of the enable pin is biased, and the chip is in a closed state, so that an open circuit protection effect is achieved;
the circuit can automatically start the chip after the load is reconnected, and has the characteristics of convenience and quickness; the circuit has the advantages of less peripheral elements, low power consumption, low cost and simple structure, can respond to open circuit of a load, reduces the fault rate of the chip, increases the reliability of safe operation of the chip, and effectively avoids harm to workers; therefore, the device has the characteristics of simple structure, reasonable design, small volume, high reliability, stable work, high cost performance and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the present invention will be further described with reference to the accompanying drawings and embodiments, wherein 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 without inventive efforts according to the drawings:
fig. 1 is a schematic diagram of a load open circuit protection circuit of a DC-DC constant voltage chip with constant current output according to a preferred embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, a clear and complete description will be given below with reference to the technical solutions of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, belong to the scope of protection of the present invention.
The load open-circuit protection circuit of the DC-DC constant voltage chip of the preferred embodiment of the present invention is shown in fig. 1, and includes a DC-DC constant voltage chip U1, wherein the input terminal of the DC-DC constant voltage chip U1 is connected to the power supply, the enabling terminal is connected to a switch triode Q1 and a divider resistor R1 which are connected in parallel, the feedback terminal is connected to a load 1 and a feedback resistor R4 which are connected in parallel, and the output terminal is connected to the other end of the load 1; an emitting electrode of the switching triode Q1 is grounded, a collector electrode of the switching triode Q1 is connected with an enabling end of the DC-DC constant voltage chip U1, a base electrode of the switching triode Q1 is connected with a first sampling resistor R2 and a second sampling resistor R3 which are connected in parallel, the other end of the first sampling resistor R2 is grounded, and the other end of the second sampling resistor R3 is connected with an output end of the DC-DC constant voltage chip U1; the other end of the divider resistor R1 is connected with a power supply; the other end of the feedback resistor R4 is grounded;
by setting the resistance values of the first sampling resistor R2 and the second sampling resistor R3, when the DC-DC constant voltage chip U1 works normally, the output voltage Vout is input to the base electrode of the switching triode Q1 through the first sampling resistor R2 and the second sampling resistor R3, the voltage of the base electrode is smaller than the base electrode conducting voltage, the switching triode Q1 is in a cut-off state, because the enabling end of the DC-DC constant voltage chip U1 is connected to a power supply through the voltage dividing resistor R1, the enabling end receives a high level signal, and the DC-DC constant voltage chip U1 works normally;
after the load 1 is opened, the feedback end of the DC-DC constant voltage chip U1 is disconnected with the output end, the DC-DC constant voltage chip U1 cannot adjust the output voltage Vout of the output end through the feedback end, so that the output voltage Vout is increased, when the actual output value of the output voltage Vout is greater than the protection limit value, the voltage of the output voltage Vout input to the base of the switching triode Q1 is greater than the base conducting voltage, the switching triode Q1 is in a conducting state, the enabling end of the DC-DC constant voltage chip U1 is grounded, and therefore the DC-DC constant voltage chip U1 stops working after receiving a low-level signal;
the circuit can automatically start the chip after the load is reconnected, and has the characteristics of convenience and quickness; the circuit has the advantages of less peripheral elements, low power consumption, low cost and simple structure, can respond to open circuit of a load, reduces the fault rate of the chip, increases the reliability of safe operation of the chip, and effectively avoids harm to workers; therefore, the device has the characteristics of simple structure, reasonable design, small volume, high reliability, stable work, high cost performance and the like;
specifically, the DC-DC constant voltage chip U1 is an MT3608 chip, and the MT3608 chip has 6 pins, which are: the resistance value of the first sampling resistor is 1K omega, the resistance value of the second sampling resistor is 22K omega, the base electrode breakover voltage of the switching triode Q1 is 0.7v, the conventional value of the output voltage Vout is 14v, and the protection limit value of the output voltage Vout is 16 v;
when the load 1 is not opened, the output voltage Vout is 14v, and the base voltage VB of the switching transistor Q1 is [ R2/(R3+ R2) ] + 14 [1/(22+1) ] + 14 ≈ 0.6v, which is lower than 0.7v, so that the switching transistor Q1 is in a cut-off state, the EN pin is connected with a power supply through a voltage dividing resistor R1 to receive a high-level signal, and the DC-DC constant voltage chip U1 normally operates;
when the load 1 is open and the output voltage Vout is greater than 16v, the base voltage VB of the switching transistor Q1 is greater than [ R2/(R3+ R2) ] -16 [1/(22+1) ] -16 ≈ 0.7v, so that the switching transistor Q1 is in a conducting state, the EN pin is grounded through the transistor Q1, a low level signal is received, and the DC-DC constant voltage chip U1 stops operating.
The load 1 is specifically an led lighting load, the load 1 comprises one or more light emitting diodes which are arranged in series, the anode of the light emitting diode in the load 1 is connected with the output end of a DC-DC constant voltage chip U1, and the cathode of the light emitting diode in the load 1 is connected with the feedback end of a DC-DC constant voltage chip U1; the DC-DC constant voltage chip U1 is an MT3608 chip, the constant voltage output by the FB pin is 0.6V, and the current of the load 1 can be set by setting the resistance of the feedback resistor R4, specifically, the current of the load 1 is I1 is 0.6/R3, so that the load 1 can obtain the constant current.
As shown in fig. 1, a diode D1 is connected in series between the output terminal of the DC-DC constant voltage chip U1 and the load 1, the anode of the diode D1 is connected to the load 1, and the cathode is connected to the output terminal of the DC-DC constant voltage chip U1; the diode D1 is specifically a rectifier diode.
As shown in fig. 1, an inductor L1 is connected in series between the input terminal and the output terminal of the DC-DC constant voltage chip U1; the inductor L1 is used to boost the input dc power.
As shown in fig. 1, a first filter capacitor C1, a second filter capacitor C2, a third filter capacitor C3 and a fourth filter capacitor C4 which are connected in parallel are arranged between a power supply and an input end of a DC-DC constant voltage chip U1, and the other ends of the first filter capacitor C1, the second filter capacitor C2, the third filter capacitor C3 and the fourth filter capacitor C4 are all grounded; a fifth filter capacitor C5, a sixth filter capacitor C6 and a seventh filter capacitor C7 which are connected in parallel are arranged between the diode D1 and the load 1, and the other ends of the fifth filter capacitor C5, the sixth filter capacitor C6 and the seventh filter capacitor C7 are all grounded; the filtering capacitor can filter noise waves by grounding, so that the power supply is more stable, the load is not influenced by a fluctuating power supply, and the service lives of the load 1 and the DC-DC constant voltage chip U1 are prolonged.
As shown in fig. 1, the switching transistor Q1 is NPN type.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are considered to be within the scope of the invention as defined by the following claims.
Claims (5)
1. A load open-circuit protection circuit of a DC-DC constant voltage chip with constant current output is characterized by comprising a DC-DC constant voltage chip, wherein the input end of the DC-DC constant voltage chip is connected with a power supply, the enabling end of the DC-DC constant voltage chip is connected with a switching triode and a divider resistor which are connected in parallel, the feedback end of the DC-DC constant voltage chip is connected with a load and a feedback resistor which are connected in parallel, and the output end of the DC-DC constant voltage chip is connected with the other end; the emitter of the switching triode is grounded, the collector of the switching triode is connected with the enabling end of the DC-DC constant voltage chip, the base of the switching triode is connected with a first sampling resistor and a second sampling resistor which are connected in parallel, the other end of the first sampling resistor is grounded, and the other end of the second sampling resistor is connected with the output end of the DC-DC constant voltage chip; the other end of the divider resistor is connected with a power supply; the other end of the feedback resistor is grounded.
2. The load open-circuit protection circuit of a constant current output DC-DC constant voltage chip as claimed in claim 1, wherein a diode is connected in series between the output terminal of the DC-DC constant voltage chip and the load, the anode of the diode is connected with the load, and the cathode of the diode is connected with the output terminal of the DC-DC constant voltage chip.
3. The load open-circuit protection circuit of a constant current output DC-DC constant voltage chip as claimed in claim 2, wherein a first filter capacitor, a second filter capacitor, a third filter capacitor and a fourth filter capacitor are arranged in parallel between the power supply and the input terminal of the constant voltage chip, and the other ends of the first filter capacitor, the second filter capacitor, the third filter capacitor and the fourth filter capacitor are all grounded; and a fifth filter capacitor, a sixth filter capacitor and a seventh filter capacitor which are connected in parallel are arranged between the diode and the load, and the other ends of the fifth filter capacitor, the sixth filter capacitor and the seventh filter capacitor are all grounded.
4. The load open-circuit protection circuit of a constant current output DC-DC constant voltage chip as claimed in claim 1, wherein an inductor is connected in series between the input terminal and the output terminal of the DC-DC constant voltage chip.
5. The load open-circuit protection circuit of a DC-DC constant voltage chip with constant current output as claimed in claim 1, wherein the switching transistor is an NPN transistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022009325.XU CN213425783U (en) | 2020-09-15 | 2020-09-15 | Load open-circuit protection circuit of constant-current output DC-DC constant-voltage chip |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022009325.XU CN213425783U (en) | 2020-09-15 | 2020-09-15 | Load open-circuit protection circuit of constant-current output DC-DC constant-voltage chip |
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| Publication Number | Publication Date |
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| CN213425783U true CN213425783U (en) | 2021-06-11 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202022009325.XU Active CN213425783U (en) | 2020-09-15 | 2020-09-15 | Load open-circuit protection circuit of constant-current output DC-DC constant-voltage chip |
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| CN (1) | CN213425783U (en) |
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- 2020-09-15 CN CN202022009325.XU patent/CN213425783U/en active Active
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