CN101707347B - Undervoltage protection circuit and LED drive circuit - Google Patents
Undervoltage protection circuit and LED drive circuit Download PDFInfo
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- CN101707347B CN101707347B CN 200910110690 CN200910110690A CN101707347B CN 101707347 B CN101707347 B CN 101707347B CN 200910110690 CN200910110690 CN 200910110690 CN 200910110690 A CN200910110690 A CN 200910110690A CN 101707347 B CN101707347 B CN 101707347B
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Abstract
The invention is suitable for the field of switch power supply, and provides an undervoltage voltage circuit and an LED drive circuit. The undervoltage voltage circuit comprises an adjustable shunt regulator, a voltage-dividing sampling circuit, a switching tube, a first current limiting resistor, a second current limiting resistor and a biasing resistor; the input end of the adjustable shunt regulator is connected to a first output end of the voltage-dividing sampling circuit; one end of the first current limiting resistor is connected to a first power supply, while the other end is connected with the output end of the adjustable shunt regulator; the input end of the voltage-dividing sampling circuit is connected to a second power supply, and the second output end thereof is connected tothe first end of the switching tube; and the control end of the switching tube is connected to the output end of the adjustable shunt regulator through a second current limiting resistor. The undervoltage voltage circuit provided by the invention has the advantages of simple structure, low cost and small occupied area.
Description
Technical field
The invention belongs to field of switch power, relate in particular to a kind of under-voltage protecting circuit and led drive circuit.
Background technology
Fig. 1 shows the physical circuit of the under-voltage protecting circuit that prior art provides, and for convenience of explanation, only shows the part relevant with under-voltage protecting circuit; Under-voltage protecting circuit comprises: comparison circuit U7, the adjustable shunt regulator U8 of adjustable shunt regulator U8 and some resistance and electric capacity; Wherein, resistance R 11 and resistance R 12 are connected in series between power supply VIN and the ground, the end that is connected in series of resistance R 11 and resistance R 12 is by capacitor C 11 ground connection, and resistance R 11 and being connected in series of resistance R 12 are held also by the reverse input end of comparator A1 among resistance R 13 and the comparison circuit U7-be connected; Resistance R 16, resistance R 17 and resistance R 18 are connected in series between the output and CTRL end of adjustable shunt regulator U8 successively, the end that is connected in series of resistance R 17 and resistance R 18 is connected to the output (being the 1st pin of comparison circuit U7) of comparator A1 among the comparison circuit U7, the end that is connected in series of resistance R 16 and resistance R 17 be connected to the positive input of comparator A1 among the comparison circuit U7+; The ground end ground connection of adjustable shunt regulator U8, the input of adjustable shunt regulator U8 is connected to power supply VCC by resistance R 14, also by resistance R 15 ground connection, the input of adjustable shunt regulator U8 also is connected to the output of adjustable shunt regulator U8 to the input of adjustable shunt regulator U8 simultaneously; One end of capacitor C 12 is connected to the output of adjustable shunt regulator U8, the other end ground connection of capacitor C 12; The 8th pin of comparison circuit U7 connects power supply VCC.
Existing under-voltage protecting circuit adopts comparison circuit U7, adjustable shunt regulator U8 and some resistance and electric capacity to form a hysteresis comparator circuit, produces a significant level and controls other circuit; Since the comparison circuit U7 that has adopted integrated operational amplifier to form, so the cost of entire circuit is higher, and it is big to take up room; Because the output voltage low precision of integrated operational amplifier causes the bad control of precision of the protection voltage in the under-voltage protecting circuit, the hysteresis voltage scope also is not easy to debugging simultaneously.
Summary of the invention
The purpose of the embodiment of the invention is to provide a kind of under-voltage protecting circuit, is intended to solve existing under-voltage protecting circuit cost height, takes up room greatly, protects the bad control of precision of voltage and the problem that the hysteresis voltage scope is not easy to debug.
The embodiment of the invention is achieved in that a kind of under-voltage protecting circuit, and described under-voltage protecting circuit comprises:
Adjustable shunt regulator, pressure sampling circuit, switching tube, first current-limiting resistance, second current-limiting resistance and biasing resistor;
The input of described adjustable shunt regulator is connected to first output of described pressure sampling circuit, the ground end ground connection of described adjustable shunt regulator;
One end of described first current-limiting resistance is connected to first power supply, and the other end of described first current-limiting resistance is connected to the output of described adjustable shunt regulator;
The input of described pressure sampling circuit connects second source, and second output of described pressure sampling circuit is connected to first end of described switching tube;
The second end ground connection of described switching tube, described control end of switching tube is connected to the output of described adjustable shunt regulator by described second current-limiting resistance, and described control end of switching tube is also by described biasing resistor ground connection.
Wherein, described pressure sampling circuit comprises: be connected in series in first divider resistance, second divider resistance and the 3rd divider resistance between second source and the ground successively;
The end that is connected in series of described first divider resistance and described second divider resistance is connected to the input of described adjustable shunt regulator as first output of described pressure sampling circuit;
The end that is connected in series of described second divider resistance and described the 3rd divider resistance is connected to first end of described switching tube as second output of described pressure sampling circuit.
Wherein, described switching tube is triode, the base stage of described triode is connected to the output of described adjustable shunt regulator by described second current-limiting resistance, the grounded emitter of described triode, and the collector electrode of described triode is connected to second output of described pressure sampling circuit.
Wherein, described triode is NPN type triode.
Wherein, described switching tube is metal-oxide-semiconductor, and the grid of described metal-oxide-semiconductor is connected to the output of adjustable shunt regulator by second current-limiting resistance, the source ground of described metal-oxide-semiconductor, and the drain electrode of described metal-oxide-semiconductor is connected to second output of pressure sampling circuit.
Wherein, described under-voltage protecting circuit also comprises: filter capacitor, an end of described filter capacitor are connected to the link that the input of described adjustable shunt regulator is connected with first output of pressure sampling circuit, the other end ground connection of described filter capacitor.
Wherein, described under-voltage protecting circuit also comprises: the 3rd current-limiting resistance; one end of described the 3rd current-limiting resistance is connected to the link that the output of described adjustable shunt regulator is connected with first current-limiting resistance, and the other end of described the 3rd current-limiting resistance is connected to described control end of switching tube by described second current-limiting resistance.
Wherein, described first power supply is low-tension supply, and described second source is direct voltage.
Wherein, described adjustable shunt regulator is the TL431 chip.
Another purpose of the embodiment of the invention is to provide a kind of led drive circuit, comprises above-mentioned under-voltage protecting circuit.
The under-voltage protecting circuit that the embodiment of the invention provides compares second source VIN and preset threshold voltage, control the break-make of adjustable shunt regulator and the break-make of switching tube according to comparative result, thereby output under-voltage protection control signal realizes under-voltage sluggish protection; This circuit structure is simple, cost is low, it is little to take up room; Improve the control precision of protection voltage simultaneously, be convenient to debug the hysteresis voltage scope.
Description of drawings
Fig. 1 is the circuit diagram of the under-voltage protecting circuit that provides of prior art;
Fig. 2 is the circuit diagram of the under-voltage protecting circuit that provides of the embodiment of the invention.
Embodiment
In order to make purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explaining the present invention, and be not used in restriction the present invention.
The under-voltage protecting circuit that the embodiment of the invention provides compares second source VIN and preset threshold voltage; control the break-make of adjustable shunt regulator and the break-make of switching tube according to comparative result, thereby output under-voltage protection control signal realizes under-voltage sluggish protection.
The under-voltage protecting circuit that the embodiment of the invention provides can be applied to Switching Power Supply etc. to be needed in the power consumption equipment of under-voltage protection, is applied to especially in the led drive circuit of DC/DC voltage conversion circuit and big electric current.Fig. 2 shows the circuit of the under-voltage protecting circuit that the embodiment of the invention provides, and for convenience of explanation, only shows the part relevant with the embodiment of the invention, and details are as follows.
Under-voltage protecting circuit comprises: adjustable shunt regulator U1, pressure sampling circuit 11, switching tube 12, the first current-limiting resistance R4, the second current-limiting resistance R6 and biasing resistor R7; Wherein, the input of adjustable shunt regulator U1 is connected to the first output S1 of pressure sampling circuit 11, the ground end ground connection of adjustable shunt regulator U1; The end of the first current-limiting resistance R4 is connected to the first power supply VCC, and the other end of the first current-limiting resistance R4 is connected to the output of adjustable shunt regulator U1; The input of pressure sampling circuit 11 connects second source VIN, and the second output S2 of pressure sampling circuit 11 is connected to first end of switching tube 12; The second end ground connection of switching tube 12, the control end of switching tube 12 is connected to the output of adjustable shunt regulator U1 by the second current-limiting resistance R6, and the control end of switching tube 12 is also by biasing resistor R7 ground connection.
In embodiments of the present invention, pressure sampling circuit 11 comprises: be connected in series in the first divider resistance R1, the second divider resistance R2 and the 3rd divider resistance R3 between second source VIN and the ground successively; Wherein, the end S1 that is connected in series of the first divider resistance R1 and the second divider resistance R2 is connected to the input of adjustable shunt regulator U1 as the first output S1 of pressure sampling circuit 11; The end S2 that is connected in series of the second divider resistance R2 and the 3rd divider resistance R3 is connected to first end of switching tube 12 as the second output S2 of pressure sampling circuit 11.
As one embodiment of the present of invention, pressure sampling circuit 11 can also comprise a plurality of resistance that are connected in series; Be not limited to three divider resistances, also should belong to the scope of protection of the invention greater than three divider resistances.
In embodiments of the present invention, switching tube can be triode Q1, and wherein, the base stage of triode Q1 is connected to the output of adjustable shunt regulator U1 by the second current-limiting resistance R6, the grounded emitter of triode Q1, the collector electrode of triode Q1 are connected to the second output S2 of pressure sampling circuit 11.
As one embodiment of the present of invention, triode Q1 is NPN type triode.
In embodiments of the present invention, switching tube can also be metal-oxide-semiconductor, wherein the grid of metal-oxide-semiconductor is connected to the output of adjustable shunt regulator U1 by the second current-limiting resistance R6, the source ground of metal-oxide-semiconductor, and the drain electrode of metal-oxide-semiconductor is connected to the second output S2 of pressure sampling circuit 11.
In embodiments of the present invention; under-voltage protecting circuit also comprises: filter capacitor C1; the end of filter capacitor C1 is connected to the link that the input of adjustable shunt regulator U1 is connected with the first output S1 of pressure sampling circuit 11, the other end ground connection of filter capacitor C1.
In embodiments of the present invention; under-voltage protecting circuit also comprises: the 3rd current-limiting resistance R5; the end of the 3rd current-limiting resistance R5 is connected to the link that the output of adjustable shunt regulator U1 is connected with the first current-limiting resistance R4, and the other end of the 3rd current-limiting resistance R5 is connected to the control end of switching tube 12 by the second current-limiting resistance R6.
In embodiments of the present invention, the first power supply VCC can be low-tension supply, and second source VIN can or exchange voltage behind rectifying and wave-filtering for direct voltage.
In embodiments of the present invention, adjustable shunt regulator U1 can be the TL431 chip.The reference voltage of adjustable shunt regulator U1 can be 1.25V or 2.5V; Owing to adopted the high TL431 of precision and the high resistance of precision, solved the low problem of integrated operational amplifier output accuracy; Reduced cost simultaneously.
For the under-voltage protecting circuit that illustrates that further the embodiment of the invention provides, it is as follows now in conjunction with Fig. 2 in detail its operation principle to be described in detail, and for convenience of explanation, the electronic equipment that needs under-voltage protection is example with the led drive circuit, and switching tube 12 is example with triode Q1:
After the energising, as second source VIN during greater than the first threshold voltage Von that sets, cancelled the under-voltage protection to led drive circuit, led drive circuit begins operate as normal; As second source VIN during less than the second threshold voltage Voff that sets, led drive circuit is protected, and led drive circuit quits work; Wherein, first threshold voltage Von is less than the second threshold voltage Voff.
When the voltage of second source VIN rises gradually from 0, when VIN＜Von, the voltage of the reference level end Vref of adjustable shunt regulator U1 is less than 2.5V, not conducting of adjustable shunt regulator U1, under-voltage protection control signal output CTRL is high level, triode Q1 conducting, at this moment, 2.5V＞Vref=VIN * R2/ (R1+R2), led drive circuit is protected; When the voltage of second source VIN rises to the first threshold voltage Von of setting, 2.5V=Von * R2/ (R1+R2), adjustable shunt regulator U1 conducting, under-voltage protection control signal output CTRL is low level, triode Q1 turn-offs, at this moment, 2.5V＜Vref=VIN * (R2+R3)/(R1+R2+R3), led drive circuit is cancelled protection; When VIN voltage drops to the second threshold voltage Voff from normal voltage; 2.5V=Vref=VIN * (R2+R3) (/R1+R2+R3); adjustable shunt regulator U1 turn-offs; under-voltage protection control signal output CTRL is high level; triode Q1 conducting; at this moment, 2.5V＞Vref=VIN * R2/ (R1+R2), led drive circuit is protected.
Than prior art, the under-voltage protecting circuit that the embodiment of the invention provides compares second source VIN and preset threshold voltage, control the break-make of adjustable shunt regulator and the break-make of switching tube according to comparative result, thereby output under-voltage protection control signal realizes under-voltage sluggish protection; This circuit structure is simple, cost is low, it is little to take up room; Improve the control precision of protection voltage simultaneously, be convenient to debug the hysteresis voltage scope.
The above only is preferred embodiment of the present invention, not in order to limiting the present invention, all any modifications of doing within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.
Claims (9)
1. a under-voltage protecting circuit is characterized in that, described under-voltage protecting circuit comprises:
Adjustable shunt regulator, pressure sampling circuit, switching tube, first current-limiting resistance, second current-limiting resistance and biasing resistor;
The input of described adjustable shunt regulator is connected to first output of described pressure sampling circuit, the ground end ground connection of described adjustable shunt regulator;
One end of described first current-limiting resistance is connected to first power supply, and the other end of described first current-limiting resistance is connected to the output of described adjustable shunt regulator;
The input of described pressure sampling circuit connects second source, and second output of described pressure sampling circuit is connected to first end of described switching tube;
The second end ground connection of described switching tube, described control end of switching tube is connected to the output of described adjustable shunt regulator by described second current-limiting resistance, and described control end of switching tube is also by described biasing resistor ground connection;
Described pressure sampling circuit comprises:
Be connected in series in first divider resistance, second divider resistance and the 3rd divider resistance between second source and the ground successively;
The end that is connected in series of described first divider resistance and described second divider resistance is connected to the input of described adjustable shunt regulator as first output of described pressure sampling circuit;
The end that is connected in series of described second divider resistance and described the 3rd divider resistance is connected to first end of described switching tube as second output of described pressure sampling circuit.
2. under-voltage protecting circuit as claimed in claim 1; it is characterized in that; described switching tube is triode; the base stage of described triode is connected to the output of described adjustable shunt regulator by described second current-limiting resistance; the grounded emitter of described triode, the collector electrode of described triode are connected to second output of described pressure sampling circuit.
3. under-voltage protecting circuit as claimed in claim 2 is characterized in that, described triode is NPN type triode.
4. under-voltage protecting circuit as claimed in claim 1; it is characterized in that; described switching tube is metal-oxide-semiconductor; the grid of described metal-oxide-semiconductor is connected to the output of adjustable shunt regulator by second current-limiting resistance; the source ground of described metal-oxide-semiconductor, the drain electrode of described metal-oxide-semiconductor are connected to second output of pressure sampling circuit.
5. under-voltage protecting circuit as claimed in claim 1; it is characterized in that; described under-voltage protecting circuit also comprises: filter capacitor; one end of described filter capacitor is connected to the link that the input of described adjustable shunt regulator is connected with first output of pressure sampling circuit, the other end ground connection of described filter capacitor.
6. under-voltage protecting circuit as claimed in claim 1; it is characterized in that; described under-voltage protecting circuit also comprises: the 3rd current-limiting resistance; one end of described the 3rd current-limiting resistance is connected to the link that the output of described adjustable shunt regulator is connected with first current-limiting resistance, and the other end of described the 3rd current-limiting resistance is connected to described control end of switching tube by described second current-limiting resistance.
7. under-voltage protecting circuit as claimed in claim 1 is characterized in that, described first power supply is low-tension supply, and described second source is direct voltage.
8. under-voltage protecting circuit as claimed in claim 1 is characterized in that, described adjustable shunt regulator is the TL431 chip.
9. a led drive circuit is characterized in that, described led drive circuit comprises each described under-voltage protecting circuit of claim 1-8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200910110690 CN101707347B (en) | 2009-10-21 | 2009-10-21 | Undervoltage protection circuit and LED drive circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200910110690 CN101707347B (en) | 2009-10-21 | 2009-10-21 | Undervoltage protection circuit and LED drive circuit |
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| Publication Number | Publication Date |
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| CN101707347A CN101707347A (en) | 2010-05-12 |
| CN101707347B true CN101707347B (en) | 2013-10-09 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN 200910110690 Active CN101707347B (en) | 2009-10-21 | 2009-10-21 | Undervoltage protection circuit and LED drive circuit |
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Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101958527A (en) * | 2010-10-16 | 2011-01-26 | 深圳茂硕电源科技股份有限公司 | Boost type LED constant flow source under-voltage protection circuit |
| CN102593789A (en) * | 2011-01-14 | 2012-07-18 | 鸿富锦精密工业（深圳）有限公司 | Resistance setting system and resistance setting method |
| CN103281834B (en) * | 2013-06-06 | 2015-04-01 | 东莞博用电子科技有限公司 | Overvoltage protection circuit applied to alternative current LED drive system |
| CN103354685B (en) * | 2013-07-22 | 2015-03-11 | 广州晶锐信息技术有限公司 | LED driving chip |
| CN106972461A (en) * | 2017-05-22 | 2017-07-21 | 中国电子科技集团公司第四十三研究所 | A kind of line under-voltage protection circuit inputted with retarding window wide scope |
| CN108964436B (en) * | 2017-05-27 | 2020-10-23 | 许继集团有限公司 | Switching power supply starting circuit |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5073837A (en) * | 1989-08-10 | 1991-12-17 | Samsung Electronics Co., Ltd. | Low voltage protection circuit |
| CN101436771A (en) * | 2007-11-16 | 2009-05-20 | 艾默生网络能源***有限公司 | Power supply under-voltage protection circuit and power supply comprising same |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54108250A (en) * | 1978-02-15 | 1979-08-24 | Fujitsu Ltd | Low voltage detecting circuit |
| JP2000184577A (en) * | 1998-12-18 | 2000-06-30 | Fujitsu General Ltd | Ac low voltage protecting circuit |
| TWI354423B (en) * | 2005-06-30 | 2011-12-11 | Delta Electronics Inc | Under voltage protection device |
-
2009
- 2009-10-21 CN CN 200910110690 patent/CN101707347B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5073837A (en) * | 1989-08-10 | 1991-12-17 | Samsung Electronics Co., Ltd. | Low voltage protection circuit |
| CN101436771A (en) * | 2007-11-16 | 2009-05-20 | 艾默生网络能源***有限公司 | Power supply under-voltage protection circuit and power supply comprising same |
Non-Patent Citations (2)
| Title |
|---|
| JP昭54-108250A 1979.08.24 |
| JP特开2000-184577A 2000.06.30 |
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| CN101707347A (en) | 2010-05-12 |
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