CN103036414A - Low-voltage direct current output protection circuit - Google Patents
Low-voltage direct current output protection circuit Download PDFInfo
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- CN103036414A CN103036414A CN2012105171197A CN201210517119A CN103036414A CN 103036414 A CN103036414 A CN 103036414A CN 2012105171197 A CN2012105171197 A CN 2012105171197A CN 201210517119 A CN201210517119 A CN 201210517119A CN 103036414 A CN103036414 A CN 103036414A
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Abstract
The invention provides a low-voltage direct current output protection circuit and aims at enabling a low-voltage power supply circuit to provide power reliably for loading equipment. The low-voltage direct current output protection circuit comprises a reference voltage source, a comparator A and a constant current control circuit, wherein the constant current control circuit is composed of a comparator B, an audion N1 and a V groove metal oxide semiconductor (VMOS) pipe M5. An input end of a safe output control circuit is connected with direct-current output voltage of a low-voltage power supply and the output end of the safe output control circuit is connected with a load. The VMOS pipe M5 is arranged on a main circuit with the input end in a series connection mode and a current-limiting resistor R24 is arranged on a main circuit with the output end in a series connection mode. A base of the VMOS pipe M5 is connected with a negative terminal of the output end through the audion N1. A base of the audion N1 is connected with the reference voltage source. The output end is connected with a filter capacitor C15 and a feedback branch in parallel. A divider resistor R14 and a remote control (RC) circuit are connected on the feedback branch in series. According to the low-voltage direct current output protection circuit, automatic adjustment of low-voltage power supply output is guaranteed when the load is short-circuit, current output is limited, and low power consumption is guaranteed at the same time.
Description
Technical field
The present invention relates to a kind of safety control circuit, can be used as the intermediate circuit between low-voltage power circuit and the load.
Background technology
DC power supply can be simple independent current source, such as storage battery, also can be to obtain the DC power supply that needs by straight straight conversion or by rectifying and wave-filtering method conversion AC power.In the prior art; in order to prevent short circuit, protection DC source; in the circuit with DC power supply; and in the charging circuit of storage battery; be connected in series fuse in input circuit, in case be short-circuited, electric current is excessive in the circuit; fuse will fuse, thereby has avoided super-high-current to burn out DC source.
For example for low-voltage power circuit, when load equipment is carried out low-voltage power supply, more need to guarantee the fail safe of power supply, do not increase as far as possible in addition extra power consumption.
Short-circuit protection circuit is the Important Circuit of protection DC source, and its performance quality directly has influence on safety and the work of DC source and load.The existing short-circuit protection circuit that adopts serial connection fuse mode; certain parts damages in load circuit cause short circuit; perhaps because human operational error when the both positive and negative polarity of DC source is connect short circuit; be easy to make the serial connection blown fuse; the fuse that needs the machine of tearing open more to renew after the blown fuse so then greatly affects load and works continuously and stably.Therefore, more reliable short-circuit protection circuit need to be arranged, to keep the work of load equipment continuous high-efficient ground.
Summary of the invention
The invention provides a kind of low-voltage direct output protection circuit, thereby low-voltage power circuit is powered more reliably to load equipment, the work of continuous high-efficient ground.
The invention provides following basic scheme:
The low-voltage direct output protection circuit comprises reference voltage source, comparator A, comparator B and triode N1; The input termination low-tension supply VD of this output safety control circuit, the load of output termination, series connection is provided with VMOS pipe M5 and current-limiting resistance R24 on the major loop at described input and output place; Described comparator B, triode N1 and VMOS pipe M5 consists of constant-current control circuit, and wherein, the base stage of VMOS pipe M5 is connected to the negative terminal of described output through triode N1, and the base stage of triode N1 is connected to described reference voltage source; Described output is parallel with a filter capacitor C15 and a feedback branch, is in series with successively divider resistance R14 and RC circuit on this feedback branch;
The normal phase input end of comparator A accesses this feedback branch, be connected to the anode of described output through divider resistance R14, the negative-phase input of comparator A connects reference voltage, and the output of comparator A is connected to the negative terminal of described input successively through resistance R 13, resistance R 27, the resistance R 22 of series connection; Described reference voltage is provided by the voltage-stabiliser tube Z5 with the source-series 2.5V of described reference voltage;
The series arm at normal phase input end access resistance R 13, resistance R 27 and resistance R 22 places of comparator B, its access node is between resistance R 27 and resistance R 22; The negative-phase input of comparator B is connected to the negative terminal of described output through resistance R 6; The output of comparator B is connected to the base stage of triode N1;
The base stage of triode N1 also is connected to the negative-phase input of comparator B successively through resistance R 16, capacitor C 19.
Based on above-mentioned basic scheme, can also carry out following optimization and limit and improve:
Between the drain electrode of the base stage of VMOS pipe M5 and triode N1, draw a branch road to the source electrode that VMOS manages M5, be provided with voltage-stabiliser tube Z1 on this branch road.
Can adopt a capacitor C 20 in parallel with described voltage-stabiliser tube Z5.
The access node of the normal phase input end of comparator B also is connected to the negative terminal of described output by filter capacitor C16.
Comparator A and comparator B consist of a two encapsulation comparator.
The preferred LH2903 of this pair encapsulation comparator, LM2903 or other similar device.
The present invention has the following advantages:
Low-voltage direct output protection circuit provided by the invention can guarantee that low-tension supply output adjusts automatically when load short circuits, current limliting output still guarantees low-power consumption simultaneously.
Description of drawings
Fig. 1 is the structural representation of output protection circuit of the present invention.
Embodiment
The input termination direct current output of output safety control circuit of the present invention, the load of output termination.The output that is DC power supply provides burning voltage through this output safety control circuit to load.
As shown in Figure 1, this output safety control circuit comprises reference voltage source, comparator A, comparator B (comparator A and comparator B are encapsulated as a dual comparator among the figure), triode N1 and voltage-stabiliser tube Z5; Series connection is provided with VMOS pipe M5 and current-limiting resistance R24 on the major loop at described input and output place, and wherein, the base stage of VMOS pipe M5 is connected to the negative terminal of described output through triode N1, and the base stage of triode N1 is connected to described reference voltage source; Described output is parallel with a filter capacitor and a feedback branch, is in series with successively divider resistance R14 and RC circuit on this feedback branch;
The normal phase input end of comparator A accesses this feedback branch, be connected to the anode of described output through divider resistance R14, the negative-phase input of comparator A connects reference voltage, and the output of comparator A is connected to the negative terminal of described input successively through resistance R 13, resistance R 27, the resistance R 22 of series connection;
The series arm at normal phase input end access resistance R 13, resistance R 27 and resistance R 22 places of comparator B, its access node is between resistance R 27 and resistance R 22; The negative-phase input of comparator B is connected to the negative terminal of described output through resistance R 6; The output of comparator B is connected to the base stage of triode N1.
Between the drain electrode of the base stage of VMOS pipe M5 and triode N1, draw a branch road to the source electrode that VMOS manages M5, be provided with voltage-stabiliser tube Z1 on this branch road.
Described reference voltage is by providing with the source-series 2.5V voltage-stabiliser tube of described reference voltage.
The access node of the normal phase input end of comparator B also is connected to the negative terminal of described output by filter capacitor.
The preferred LH2903 of two encapsulation comparators, LM2903 or other similar devices of comparator A and comparator B formation; Can certainly adopt discrete component to realize.
IC5 is standard high-speed comparator circuit (dual comparator), and comparator B, N1, M5 form constant-current control circuit.B-terminal voltage V3=0V, the B+ terminal voltage is:
V2=R22×V1/(R22+R27)-Us
In the following formula, Us=Is * Rs=Is * R24
V1 voltage is controlled by comparator A, A-terminal voltage VR=2.5V, and the A+ terminal voltage is:
VL=UL×R7/(R7+R14)=RL×Is。
1, current-limited startup
During circuit start (powering on), VL＜2.5V, comparator A output is low, then R13 access dividing potential drop.
Wherein: R13＜＜R25, R13＜＜R27, VR=2.5V;
V1≈VR×R13/(R13+R25)=2.5×R13/(R13+R25)
V2=R22×V1/(R22+R27)-Us=R22×(2.5×R13/(R13+R25))/(R22+R27)-Us?=2.5×R22×R13/((R13+R25)(R22+R27))-Is×Rs
If: c1=2.5 * R22 * R13/ ((R13+R25) (R22+R27))
That is: V2=c1-Rs * Is
When V2=c1-Rs * Is＜=0, comparator B, N1, the output of M5 current limliting, cut-off current is: Is=c1/Rs.
Can guarantee that namely low-tension supply output starts with current limliting (Is=c1/Rs).
VL=UL×R7/(R7+R14)=RL×Is=c1×RL/Rs
Therefore, only need the corresponding resistance of configuration, so that during low-tension supply load impedance less (short circuit), VL＜2.5V is operated under the safe limited current state.Such as, according to Is=c1/Rs, Is is set between routine value 1/4-1/10.
2, operating conventional current limliting
Comparator A output high (open circuit) when low-tension supply load impedance fault-free VL＞=2.5V, R13 disengaging dividing potential drop then, V2=2.5 * R22/ (R22+R27+R25)-Us;
If: c2=2.5 * R22/ (R22+R27+R25)
That is: V2=c2-Rs * IL
When V2=c2-Rs * IL＜=0, comparator B, N1, the output of M5 current limliting, cut-off current is: IL=c2/Rs,
Can guarantee that namely low-tension supply output works with current limliting (IL=c2/Rs).
Therefore, only need the corresponding resistance of configuration, make IL greater than running current, and VMOS is limited in the safe range of electric current, power.Usually, IL is set between 1.1 times to 1.5 times of conventional value.
3, the low-power consumption of normal operation
During low-tension supply output normal operation, output current is less than IL, and comparator (A, B) is exported high (open circuit), and P raceway groove VMOS (M5) is operated in ultralow conducting resistance (R
DS=0.005 Ω) under the state.
For example: power output 200W output voltage 50V, then output current is: Io=200/50=4A,
The upper pressure drop of VMOS (M5) is: 4 * 0.005=0.02,
VMOS (M5) control power consumption is: Pe=0.02 * 4=0.08W, can find out that the control power consumption when normally moving is very low.
4, short-circuit protection
If if the fault such as output short-circuit occurs in the low-voltage power circuit course of work, cause VL＜2.5V, then comparator A output is low, make comparator B, N1, M5 current limliting output (referring to aforementioned the 1st kind of situation), circuit reenters clean boot (Is) state, behind Failure elimination, low-tension supply is recovered normal output automatically.
Claims (6)
1. the low-voltage direct output protection circuit is characterized in that: comprise reference voltage source, comparator A, comparator B and triode N1; The input termination low-tension supply VD of this output safety control circuit, the load of output termination, series connection is provided with VMOS pipe M5 and current-limiting resistance R24 on the major loop at described input and output place; Described comparator B, triode N1 and VMOS pipe M5 consists of constant-current control circuit, and wherein, the base stage of VMOS pipe M5 is connected to the negative terminal of described output through triode N1, and the base stage of triode N1 is connected to described reference voltage source; Described output is parallel with a filter capacitor C15 and a feedback branch, is in series with successively divider resistance R14 and RC circuit on this feedback branch;
The normal phase input end of comparator A accesses this feedback branch, be connected to the anode of described output through divider resistance R14, the negative-phase input of comparator A connects reference voltage, and the output of comparator A is connected to the negative terminal of described input successively through resistance R 13, resistance R 27, the resistance R 22 of series connection; Described reference voltage is provided by the voltage-stabiliser tube Z5 with the source-series 2.5V of described reference voltage;
The series arm at normal phase input end access resistance R 13, resistance R 27 and resistance R 22 places of comparator B, its access node is between resistance R 27 and resistance R 22; The negative-phase input of comparator B is connected to the negative terminal of described output through resistance R 6; The output of comparator B is connected to the base stage of triode N1;
The base stage of triode N1 also is connected to the negative-phase input of comparator B successively through resistance R 16, capacitor C 19.
2. low-voltage direct output protection circuit according to claim 1 is characterized in that: draw a branch road to the source electrode that VMOS manages M5 between the drain electrode of the base stage of VMOS pipe M5 and triode N1, be provided with voltage-stabiliser tube Z1 on this branch road.
3. low-voltage direct output protection circuit according to claim 1 is characterized in that: adopt a capacitor C 20 in parallel with described voltage-stabiliser tube Z5.
4. low-voltage direct output protection circuit according to claim 1, it is characterized in that: the access node of the normal phase input end of comparator B also is connected to the negative terminal of described output by filter capacitor C16.
5. low-voltage direct output protection circuit according to claim 1 is characterized in that: two encapsulation comparator of comparator A and comparator B formation.
6. low-voltage direct output protection circuit according to claim 5 is characterized in that: described two encapsulation comparators employing LH2903 or LM2903.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201210517119.7A CN103036414B (en) | 2012-11-30 | 2012-11-30 | Low-voltage direct current output protection circuit |
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| CN201210517119.7A CN103036414B (en) | 2012-11-30 | 2012-11-30 | Low-voltage direct current output protection circuit |
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| CN103036414A true CN103036414A (en) | 2013-04-10 |
| CN103036414B CN103036414B (en) | 2016-04-13 |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2728096Y (en) * | 2004-09-20 | 2005-09-21 | 赵树林 | FET automotive alternator voltage regulator with multiple protective functions |
| CN201699585U (en) * | 2010-05-21 | 2011-01-05 | 深圳市易能电气技术有限公司 | Novel intelligent voltage stabilizing circuit |
| CN102035388A (en) * | 2009-09-29 | 2011-04-27 | 北京为华新光电子有限公司 | Switching power supply |
| CN203193493U (en) * | 2012-11-30 | 2013-09-11 | 胡家培 | A low-voltage DC output protection circuit |
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2012
- 2012-11-30 CN CN201210517119.7A patent/CN103036414B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2728096Y (en) * | 2004-09-20 | 2005-09-21 | 赵树林 | FET automotive alternator voltage regulator with multiple protective functions |
| CN102035388A (en) * | 2009-09-29 | 2011-04-27 | 北京为华新光电子有限公司 | Switching power supply |
| CN201699585U (en) * | 2010-05-21 | 2011-01-05 | 深圳市易能电气技术有限公司 | Novel intelligent voltage stabilizing circuit |
| CN203193493U (en) * | 2012-11-30 | 2013-09-11 | 胡家培 | A low-voltage DC output protection circuit |
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| CN103036414B (en) | 2016-04-13 |
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