CN208046209U - A kind of output overvoltage protection circuit - Google Patents
A kind of output overvoltage protection circuit Download PDFInfo
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- CN208046209U CN208046209U CN201820427450.2U CN201820427450U CN208046209U CN 208046209 U CN208046209 U CN 208046209U CN 201820427450 U CN201820427450 U CN 201820427450U CN 208046209 U CN208046209 U CN 208046209U
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Abstract
The utility model discloses a kind of output overvoltage protection circuits; including input terminal, sample circuit, switching circuit, output end, locked circuit and supply voltage source VCC; the output voltage VO of sampling circuit samples Switching Power Supply; when output overvoltage occurs, sample circuit exports a high level to switching circuit；After switching circuit receives the high level of sample circuit, one low level of output drags down the voltage of Switching Power Supply control chip controls end CTRL, and Switching Power Supply is made to be stopped；One low level of Simultaneous Switching circuit output is to locked circuit; after locked circuit receives the low level of switching circuit; a high level is exported to switching circuit; switching circuit is set to continue to export the voltage that low level drags down Switching Power Supply control chip controls end CTRL; Switching Power Supply is set persistently to be stopped; to be effectively protected rear class electrical equipment, and circuit structure is simple, good reliability.
Description
Technical field
The utility model discloses a kind of output overvoltage protection circuit, more particularly to the output over-voltage protection electricity of Switching Power Supply
Road.
Background technology
In existing Switching Power Supply, generally require have output over-voltage protection function, the output over-voltage protection function
It is to cause electrical equipment because overtension is damaged more than normal output area in switch power source output voltage in order to prevent, simultaneously
Also for the damage for preventing Switching Power Supply itself.
Fig. 1 is existing output overvoltage protection circuit figure, overvoltage crowbar described in Fig. 1 include optocoupler U1, input circuit and
Output circuit；Input circuit includes resistance R1, resistance R2, resistance R3, resistance R4, capacitance C1, Zener diode V1 and controllable essence
One end of close source of stable pressure N1, resistance R1 are the input terminal of output overvoltage protection circuit, are used for the output voltage of input switch power supply
The other end of VO, resistance R1 are followed by input ground through resistance R2, cathode also successively through Zener diode V1 of one end of resistance R1, neat
Receive the anode of diode V1, resistance R3, the cathode of controllable accurate source of stable pressure N1 and controllable accurate source of stable pressure N1 anode be followed by it is defeated
Enter ground, capacitance C1 is in parallel with resistance R2, and the tie point of resistance R3 and resistance R4 are connect with the diode anode of optocoupler U1, controllable essence
The cathode of close source of stable pressure N1 is connect with the diode cathode of optocoupler U1, the control terminal of controllable accurate source of stable pressure N1 connection resistance R1 and
The tie point of resistance R2；Output circuit includes resistance R5, resistance R6, resistance R7, resistance R8, resistance R9, resistance R10, triode
The transistor emitter of V3, triode V4, capacitance C2 and diode V2, optocoupler U1 are followed by exporting through resistance R5 and resistance R6 successively
Ground, the transistor collector of the optocoupler U1 emitter through resistance R7, resistance R8, the collector of triode V3 and triode V3 successively
It is followed by output ground, the tie point of base stage connection the resistance R5 and resistance R6 of triode V3, capacitance C2 is in parallel with resistance R6, resistance R5
With the tie point of resistance R6 also successively through resistance R9, resistance R10, diode V2 anode and diode after form output overvoltage and protect
The output end of protection circuit, the emitter connection of the enable signal EN whether to work for exporting control power module, triode V4
The transistor collector of optocoupler U1, the tie point of collector connection the resistance R9 and resistance R10 of triode V4, the base of triode V4
Pole connects the tie point of resistance R7 and resistance R8.
Resistance R1 and resistance R2 form the first bleeder circuit in foregoing circuit；Controllable accurate source of stable pressure N1 composition voltage stabilizing electricity
Road；Resistance R5 and resistance R6 form the second bleeder circuit.
Foregoing circuit operation principle is as follows：
When the output voltage VO of Switching Power Supply reached pressure point, resistance R1 and resistance R2 are divided and are made controllable accurate voltage stabilizing
Source N1 becomes being connected from ending, and Zener diode V1 is also switched at this time, the diode current flow of optocoupler U1 primary, to make optocoupler U1
Secondary triode ON, supply voltage source VCC make NPN triode V3 enter conducting shape by resistance R5 and resistance R6 partial pressures
State, the conducting of NPN triode V3 make PNP triode V4 be connected, supply voltage source VCC through PNP triode V4, resistance R10 and
The enable signal EN generated after diode V2 is high level so that power module is stopped, while supply voltage source VCC warps
PNP triode V4, resistance R9 and resistance R6 make NPN triode V3 constant conductions.
Realize that output over-voltage protection has the following disadvantages using the circuit：
1, the enable signal EN of output circuit output is high level, is only applicable to the field of high level control power cutoff module
It closes, existing most of control chip needs low level control, which cannot achieve low level control.
2, leakage current is the inherent characteristic of triode, and increases with the raising of operating temperature, tri- poles PNP in Fig. 1
The leakage current of pipe V4 can flow into output ground after resistance R9 and resistance R6, will be formed centainly in the base stage of NPN triode V3
Pressure drop, when the influence due to working environment, when the leakage current of PNP triode V4 causes NPN triodes V3 to be slightly connected, NPN tri-
The collector voltage of grade pipe V3 will decline, and the leakage current of PNP triode V4 can be caused to further increase, and form a positive feedback,
Protection circuit false triggering is eventually led to, therefore the circuit is influenced very greatly by the characteristic of environmental factor and device, work is very unstable
It is fixed.
Utility model content
In view of this, the technical problem to be solved by the present invention is to provide a kind of output overvoltage protection circuit, solve existing
There is output over-voltage protection to be high level effectively and be easy to be influenced the problem of false triggering occur by environmental factor and device property.
In order to solve the above technical problems, the technical scheme that the utility model is provided is as follows：
A kind of output overvoltage protection circuit, including input terminal and output end, input terminal are used for the output of input switch power supply
Voltage VO, output end are used for the control terminal CTRL of connecting valve power supply control chip；It is characterized in that：Further include sample circuit,
Switching circuit, locked circuit and supply voltage source VCC；
The input terminal of sample circuit is the input terminal of output overvoltage protection circuit, the output end connecting valve of sample circuit
The input terminal of circuit, the first output end of switching circuit are the output end of output overvoltage protection circuit, and the second of switching circuit
Output end connection locks the first input end of circuit, and the second input terminal for locking circuit is supply voltage source VCC, locks electricity
The input terminal of the output end connecting valve circuit on road；
Sample circuit is compared for being sampled to the output voltage VO of Switching Power Supply with setting value, works as output
When terminal voltage VO is more than setting value, output high level to switching circuit；
Switching circuit is used for when receiving sample circuit output high level, output low level to output end and locked electricity
Road；
Supply voltage source VCC is used to provide supply voltage source to locked circuit；
Locked circuit is used for when receiving switching circuit output low level, and output high level makes switch to switching circuit
The output end of circuit persistently exports low level；Locked circuit is additionally operable to after supply voltage source VCC stops power supply, stops output
High level makes the output end of switching circuit stop output low level to switching circuit.
As a kind of specific embodiment of sample circuit, sample circuit is composed in series by two resistance, after series connection
One end is the input terminal of sample circuit, and the tie point of another termination reference ground GND after series connection, two resistance are sample circuit
Output end.
As the first specific embodiment of switching circuit, switching circuit includes：First resistor, two pole of the first voltage stabilizing
Pipe and the first NPN triode；The cathode of first zener diode is the input terminal of switching circuit, one end of first resistor and first
Zener diode cathode is connected, and the other end of first resistor is connected with reference ground GND；The anode of first zener diode and first
The base stage of NPN triode is connected, and the emitter of the first NPN triode is connected with reference ground GND, the current collection of the first NPN triode
Extremely the first output end of switching circuit, the collector of the first NPN triode are also the second output terminal of switching circuit simultaneously.
As second of specific embodiment of switching circuit, the first above-mentioned zener diode is replaced with into an electricity
Resistance.
Further include the first diode as the improvement of two kinds of specific implementation modes of said switching circuit, the first diode
First output end of anode connecting valve circuit, the cathode of the first diode connect the collector of the first NPN triode.
As a kind of specific embodiment of locked circuit, including：Second resistance, 3rd resistor, the 4th resistance, first
PNP triode；One end of second resistance is the first input end of locked circuit, tri- pole of the other end and the first PNP of second resistance
The base stage of pipe is connected, and the collector of the first PNP triode is connected with one end of 3rd resistor, the other end of 3rd resistor and power supply
Voltage source VCC is connected, and the emitter of the first PNP triode is connected with one end of the 4th resistance, and the other end of the 4th resistance is
The output end of locked circuit.
The beneficial effects of the utility model are as follows：
1, the first output end of the switching circuit of the utility model exports low level, needs low level suitable for control chip
The workplace of control.
2, for the first specific implementation mode of switching circuit, due in its input terminal and the first NPN transistor base
Between increase the first zener diode, avoid because the leakage current of the first PNP triodes cause protect circuit false triggering, carry
The high reliability of circuit.
3, for the improvement of two kinds of specific implementation modes of switching circuit, due to the collector in its first NPN triode
The first diode is increased between its first output end, effectively prevents starting in Switching Power Supply because of the voltage of control terminal CTRL
When voltage rise lag behind supply voltage source VCC voltage and control terminal CTRL normal working voltage be less than power supply electricity
Potential source end VCC causes PNP triode Q2 to be connected.
Description of the drawings
Fig. 1 is the locked type output overvoltage protection circuit schematic diagram of the prior art；
Fig. 2 is the functional block diagram of the utility model output overvoltage protection circuit；
Fig. 3 is the circuit diagram of the utility model output overvoltage protection circuit embodiment one；
Fig. 4 is the circuit diagram of the utility model output overvoltage protection circuit embodiment two.
Specific implementation mode
It is illustrated in figure 2 the functional block diagram of the utility model output overvoltage protection circuit, including input, output end, adopts
Sample circuit 1, switching circuit 2, locked circuit 3 and supply voltage source VCC；Input terminal is used for the output voltage of input switch power supply
VO, output end are used for the control terminal CTRL of connecting valve power supply control chip；The input terminal of sample circuit 1 is that output overvoltage is protected
The input terminal of protection circuit, the input terminal of the output end connecting valve circuit 2 of sample circuit 1, the first output end of switching circuit 2 are
For the output end of output overvoltage protection circuit, the second output terminal connection of switching circuit 2 locks the first input end of circuit 3, lock
Second input terminal of dead circuit 3 is supply voltage source VCC, locks the input terminal of the output end connecting valve circuit of circuit 3.
It is further to the utility model below in conjunction with specific embodiment in order to make the utility model be more clearly understood
It is described in detail.It should be appreciated that specific embodiment described herein is only used to explain the utility model, it is not used to limit this
Utility model.
Embodiment one
As shown in figure 3, the output overvoltage protection circuit of the present embodiment, includes for input switch electric power output voltage VO
Input terminal, sample circuit 1, switching circuit 2, the output end for connecting valve power supply control chip control terminal CTRL, locked electricity
Road 3 and supply voltage source VCC；
Sample circuit 1 includes：Resistance R11 and resistance R12；
Switching circuit 2 includes：Resistance R1, zener diode D1, NPN triode Q1 and diode D2；
Locking circuit 3 includes：Resistance R2, resistance R3, resistance R4 and PNP triode Q2；
The connection relation of circuit is：One end of resistance R11 is the input terminal of sample circuit 1, and the other end of resistance R11 is through electricity
It is connected with reference ground GND after resistance R12, the tie point of resistance R11 and resistance R12 are the output end of sample circuit 1；Zener diode
The cathode of D1 is the input terminal of switching circuit 2, which is connected with the output end of sample circuit 1, one end of resistance R1 and surely
The cathode of diode D1 is pressed to be connected, the other end of resistance R1 is connected with reference ground GND, anode and the NPN tri- of zener diode D1
The base stage of pole pipe Q1 is connected, and the emitter of NPN triode Q1 is connected with reference ground GND, and the current collection of NPN triode Q1 extremely switchs
The second output terminal of circuit 2, the second output terminal are connected with the cathode of diode D2, and the anode of diode D2 is switching circuit 2
The first output end, which is the output end of the utility model output overvoltage protection circuit；One end of resistance R2
It is connected with the cathode of diode D2, which is the first input end of locked circuit 3, the other end and tri- poles PNP of resistance R2
The base stage of pipe Q2 is connected, and the collector of PNP triode Q2 is connected with one end of resistance R3, and the other end of resistance R3 is locked circuit
3 the second input terminal, second input terminal are connected with supply voltage source VCC, and the emitter of PNP triode Q2 is with resistance R4's
One end is connected, and the other end of resistance R4 is the output end of locked circuit 4, which is connected with the cathode of zener diode D1.
The operation principle of foregoing circuit is as follows：
The output voltage VO of 1 sampling switch power supply of sample circuit, when the voltage value of output voltage VO is more than sample circuit 1
When setting value, sample circuit 1 exports a high level signal to switching circuit 2, makes zener diode D1 reverse breakdowns, makes simultaneously
NPN triode Q1 saturation conduction；After NPN triode Q1 saturation conduction, collector voltage becomes low level, and diode D2 is made to lead
It is logical, Switching Power Supply control chip controls end CTRL is dragged down, shutdown control chip makes Switching Power Supply be stopped；Tri- poles NPN simultaneously
The collector of pipe Q1, which becomes low level, leads to PNP triode Q2 saturation conductions, and supply voltage source VCC is through tri- pole resistance R3, PNP
Pipe Q2, resistance R4, resistance R1 are connected with reference ground GND, and one is generated in the tie point of resistance R1 and zener diode D1 cathodes
High level maintains zener diode D1 reverse breakdowns, while maintaining NPN triode Q1 saturation conduction.At this point, although Switching Power Supply
Output voltage VO is zero, and for sample circuit 1 without output, switching circuit, which still exports a low level, makes Switching Power Supply control chip control
End CTRL processed remains low level state, and product is made persistently to be stopped.
Embodiment two
As shown in figure 4, the difference between this embodiment and the first embodiment lies in zener diode D1 is substituted for resistance R5, remaining
Connection type, the operation principle of device are identical, and which is not described herein again.
The embodiment of the utility model is without being limited thereto, according to the above of the utility model, utilizes the general of this field
Logical technological know-how and customary means, under the premise of not departing from the utility model above-mentioned basic fundamental thought, the utility model may be used also
To make the modification, replacement or change of other diversified forms, such as remove the diode D2 in Fig. 3 and Fig. 4, these modifications are replaced
Or change is all fallen within the utility model rights protection scope.
Claims (6)
1. a kind of output overvoltage protection circuit, including input terminal and output end, output electricity of the input terminal for input switch power supply
VO, output end is pressed to be used for the control terminal CTRL of connecting valve power supply control chip；It is characterized in that：Further include sample circuit, open
Powered-down road, locked circuit and supply voltage source VCC；
The input terminal of sample circuit is the input terminal of output overvoltage protection circuit, the output end connecting valve circuit of sample circuit
Input terminal, the first output end of switching circuit is the output end of output overvoltage protection circuit, the second output of switching circuit
End connection locks the first input end of circuit, and the second input terminal for locking circuit is supply voltage source VCC, locks circuit
The input terminal of output end connecting valve circuit；
Sample circuit is compared for being sampled to the output voltage VO of Switching Power Supply with setting value, when output end electricity
When VO being pressed to be more than setting value, output high level to switching circuit；
Switching circuit is used for when receiving sample circuit output high level, output low level to output end and locked circuit；
Supply voltage source VCC is used to provide supply voltage source to locked circuit；
Locked circuit is used for when receiving switching circuit output low level, and output high level makes switching circuit to switching circuit
Output end persistently export low level；Locked circuit is additionally operable to after supply voltage source VCC stops power supply, stops the high electricity of output
It puts down to switching circuit, the output end of switching circuit is made to stop output low level.
2. output overvoltage protection circuit according to claim 1, it is characterised in that：Sample circuit is by two resistance series connection groups
At one end after series connection is the input terminal of sample circuit, another termination reference ground GND after series connection, the tie point of two resistance
For the output end of sample circuit.
3. output overvoltage protection circuit according to claim 1, it is characterised in that：Switching circuit includes first resistor,
One zener diode and the first NPN triode；The cathode of first zener diode is the input terminal of switching circuit, first resistor
One end is connected with the first zener diode cathode, and the other end of first resistor is connected with reference ground GND；First zener diode
Anode is connected with the base stage of the first NPN triode, and the emitter of the first NPN triode is connected with reference ground GND, the first NPN tri-
First output end of the current collection of pole pipe extremely switching circuit, the collector of the first NPN triode are also the of switching circuit simultaneously
Two output ends.
4. output overvoltage protection circuit according to claim 1, it is characterised in that：Switching circuit includes first resistor,
Two resistance and the first NPN triode；One end of second resistance is the input terminal of switching circuit, one end of first resistor and the second electricity
One end of resistance is connected, and the other end of first resistor is connected with reference ground GND；The other end of second resistance and the first NPN triode
Base stage be connected, the emitter of the first NPN triode is connected with reference ground GND, and the current collection of the first NPN triode extremely switchs electricity
First output end on road, the collector of the first NPN triode are also the second output terminal of switching circuit simultaneously.
5. output overvoltage protection circuit according to claim 3 or 4, it is characterised in that：Switching circuit further includes the one or two
The cathode of pole pipe, the first output end of the anode connecting valve circuit of the first diode, the first diode connects tri- poles the first NPN
The collector of pipe.
6. output overvoltage protection circuit according to claim 1, it is characterised in that：Locked circuit includes second resistance,
Three resistance, the 4th resistance, the first PNP triode；One end of second resistance is the first input end of locked circuit, second resistance
The other end is connected with the base stage of the first PNP triode, and the collector of the first PNP triode is connected with one end of 3rd resistor, the
The other end of three resistance is connected with supply voltage source VCC, one end phase of the emitter of the first PNP triode and the 4th resistance
Even, the other end of the 4th resistance is the output end of locked circuit.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820427450.2U CN208046209U (en) | 2018-03-28 | 2018-03-28 | A kind of output overvoltage protection circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820427450.2U CN208046209U (en) | 2018-03-28 | 2018-03-28 | A kind of output overvoltage protection circuit |
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| Publication Number | Publication Date |
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| CN208046209U true CN208046209U (en) | 2018-11-02 |
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ID=63946211
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| Application Number | Title | Priority Date | Filing Date |
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| CN201820427450.2U Active CN208046209U (en) | 2018-03-28 | 2018-03-28 | A kind of output overvoltage protection circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108270199A (en) * | 2018-03-28 | 2018-07-10 | 广州金升阳科技有限公司 | A kind of output overvoltage protection circuit |
-
2018
- 2018-03-28 CN CN201820427450.2U patent/CN208046209U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108270199A (en) * | 2018-03-28 | 2018-07-10 | 广州金升阳科技有限公司 | A kind of output overvoltage protection circuit |
| CN108270199B (en) * | 2018-03-28 | 2023-12-12 | 广州金升阳科技有限公司 | Output overvoltage protection circuit |
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