CN205544230U - Ring -opening protection circuit and switching power supply circuit - Google Patents
Ring -opening protection circuit and switching power supply circuit Download PDFInfo
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- CN205544230U CN205544230U CN201620177011.1U CN201620177011U CN205544230U CN 205544230 U CN205544230 U CN 205544230U CN 201620177011 U CN201620177011 U CN 201620177011U CN 205544230 U CN205544230 U CN 205544230U
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Abstract
The utility model provides a ring -opening protection circuit, provide circuit, feedback opto -coupler receiver tube, first resistance and NPN triode including feedback pin link, overvoltage protection pin link, input filter voltage connection end, excessive pressure, the collecting electrode of feedback opto -coupler receiver tube, ground connection behind the first resistance of projecting pole connection of feedback opto -coupler receiver tube are connected to feedback pin link, the base of NPN triode is connected to the first end of first resistance, and overvoltage protection pin link, emitter ground are connected to the collecting electrode of NPN triode, the excessive pressure provides the feeding end connection input filter voltage connection end of circuit, and overvoltage protection pin link is connected to the output. Correspondingly, the utility model provides an otherness of component did not influence when switching power supply circuit, protect function did not receive the volume production, and because gather input filter voltage signal to make protect function trigger, input filter voltage signal can exist always, so protect function can lock always, goes up again up to the circuit.
Description
Technical field
This utility model relates to electronic technology field, particularly relates to a kind of open loop protection circuit and Switching Power Supply
Circuit.
Background technology
Switching Power Supply quickly popularized because of its efficiency is high, volume is little, lightweight, precision is high advantage and
It is widely applied.Power semiconductor electronic device high speed development in recent years, each power management chip manufacturer exists
The protection circuit done in chip is more and more complete, but prior art still has deficiency for open loop protection.
Switching power circuit ensures output voltage stability, common isolated form switch by arranging feedback control loop
Power circuit uses optocoupler to realize feedback exactly, and optocoupler transmitting tube is located at transformer secondary output winding, receives
Primary winding is located at by pipe, if the output voltage of secondary windings changes, can react at optocoupler transmitting tube
Electric current on, affect optocoupler receive pipe reception signal, armature winding gather optocoupler receive pipe feedback information
And according to this feedback information adjust switching tube conducting ratio just can burning voltage.In order to prevent working as feedback loop
Path loss bad time, the phenomenon that the output voltage that runaway electric circuit is caused persistently raises, power supply damages, prior art
The auxiliary winding increasing transformator is chip power supply, when circuit open loop, when output voltage raises, assists winding
Voltage also raise, and when chip power supply voltage reaches threshold value, chip can close driving, it is achieved protection.
Inventor is implementing during this utility model, finds that this scheme has its limitation: on the one hand by
In actual volume production time-varying depressor and the diversity of load, the threshold value of setting requires to mate with actual product,
On the other hand can't realize locking, simply supply voltage fluctuates repeatedly, i.e. has the hiccups, the half of circuit
Conductor element is still subject to high current stress opening moment, it may occur however that damage.
Utility model content
The technical problems to be solved in the utility model is, it is provided that a kind of not by the diversity shadow of element during volume production
Ring, and the open loop protection circuit that once trigger protection can lock always, improve circuit work stability, can
By property.
To achieve these goals, this utility model provides a kind of open loop protection circuit, including feedback pin even
Connect end, overvoltage protection pin connects end, input filter voltage connection, overvoltage offer circuit, feedback optocoupler
Receive pipe, the first resistance and NPN audion；
Described feedback pin connects the described feedback light of end connection and couples the colelctor electrode of closed tube, and described feedback light couples
The emitter stage of closed tube connects the first end of described first resistance, the second end ground connection of described first resistance；
First end of described first resistance connects the base stage of described NPN audion, described NPN audion
Colelctor electrode connects described overvoltage protection pin and connects end, the grounded emitter of described NPN audion；
Described overvoltage provides circuit to include feeder ear and outfan, and described feeder ear connects described input filter electricity
Pressure connects end, and described outfan connects described overvoltage protection pin and connects end.
The open loop protection circuit that this utility model provides, the break-make being coupled closed tube by feedback light directly reflects electricity
Road is normal or the information of open loop, and during normal work, NPN triode ON makes overvoltage protection pin connect end to keep
Low voltage value, NPN audion cut-off when feedback control loop disconnects, provide circuit Gather and input filtered electrical by overvoltage
Pressure signal, exports higher voltage, makes overvoltage protection pin voltage raise, and triggers the control in application circuit
The defencive function of chip, closes output voltage.The defencive function of the open loop protection circuit that this utility model provides
Do not affected by the diversity of element during volume production, and because be that Gather and input filtering voltage signal makes defencive function touch
Sending out, input filter voltage signal can exist always, so defencive function can lock always, until circuit is again
Power on.
Wherein in an embodiment, described overvoltage provides circuit also to include the first sectional pressure element and the second dividing potential drop
Element, the first end of described first sectional pressure element connects described feeder ear, the second of described first sectional pressure element
End connects the first end of the second sectional pressure element, the second end ground connection of described second sectional pressure element；Described second point
First end of pressure element connects described outfan.
Overvoltage provides circuit directly the input filter voltage signal dividing potential drop of feeder ear to be exported, and exports from outfan
End is connected, it is achieved the sensitiveest signal provides process to overvoltage protection pin.
In another embodiment, described overvoltage provides circuit also to include the first sectional pressure element, the second dividing potential drop unit
Part, the first switching tube and the second resistance；
First end of described first sectional pressure element connects described feeder ear, the second end of described first sectional pressure element
Connect the first end of the second sectional pressure element, the second end ground connection of described second sectional pressure element；
Described feeder ear connects the first end of described second resistance；First end of described second sectional pressure element connects
The control end of described first switching tube, the first end of described first switching tube connects the second of described second resistance
End, the second end of described first switching tube connects described outfan.
Overvoltage offer circuit is by the input filter voltage signal dividing potential drop of feeder ear, by the first switching tube of conducting
By input filter voltage signal by the second resistance from outfan export to overvoltage protection pin connect end, due to
Signal power needed for overvoltage protection pin connects end is the least, when overvoltage protection pin connects the voltage foot of end
Enough within a period of time, be maintained at needs overpressure value time, control end and the second end due to the first switching tube
Voltage difference is less, is not enough to turn on the first switching tube, therefore turns off, and treats the voltage of overvoltage pin protection end
Time not enough, the first switching tube turns on again, therefore, arranges the first switching tube and overvoltage can be made to provide circuit need not
Will when close output, reduce power consumption, play energy-conservation effect.
Further, described first sectional pressure element is the connection in series-parallel combination of single resistor or multiple resistor
Body；Described second sectional pressure element is stabilivolt, and the negative pole of described stabilivolt is the of described second sectional pressure element
One end, the second end of the most described second sectional pressure element of described stabilivolt.
Use stabilivolt outfan output can be made stable, to adapt to feeder ear voltage model as the second sectional pressure element
The fluctuation enclosed.
Preferably, described open loop protection circuit also includes the first electric capacity and the second electric capacity；
First end of described first electric capacity connects the colelctor electrode of described NPN audion, the of described first electric capacity
Two end ground connection；
First end of described second electric capacity connects the first end of described first resistance, the second of described second electric capacity
End ground connection.
Preferably, described open loop protection circuit also includes the 3rd resistance；
The colelctor electrode of described NPN audion connects described overvoltage protection pin and connects end, particularly as follows: described
The colelctor electrode of NPN audion is by described 3rd resistance connection described overvoltage protection pin connection end, wherein,
First end of described 3rd resistance connects the colelctor electrode of described NPN audion, the second end of described 3rd resistance
Connect described overvoltage protection pin and connect end.
Preferably, described overvoltage provides circuit also to include the 3rd electric capacity and the 4th electric capacity；
First end of described 3rd electric capacity connects the first end of described second sectional pressure element, described 3rd electric capacity
Second end ground connection；
First end of described 4th electric capacity connects the second end of described first switching tube, the of described 4th electric capacity
Two end ground connection.
Preferably, it is characterised in that described overvoltage provides circuit also to include the 4th resistance, described first switch
Second end of pipe connects described outfan, particularly as follows: the second end of described first switching tube is by the described 4th
Resistance connects described outfan, and wherein, the first end of described 4th resistance connects the second end of described switching tube,
Second end of described 4th resistance connects described outfan.
Meanwhile, this utility model also provides for a kind of switching power circuit, including power input, input rectifying
Circuit, input filter capacitor, power output end, transformator, second switch pipe, switching power source chip, anti-
Feedback optocoupler transmitting tube, adjustable reference source, the 5th resistance, the 6th resistance, the 7th resistance and above-mentioned open loop
Protection circuit；
Described power input connects the input of described input rectification circuit, described input rectification circuit defeated
Go out end and connect the first end of described input filter capacitor, the second end ground connection of described input filter capacitor；Described
First end of input filter capacitor connects at the beginning of the first end of the primary coil of described transformator, described transformator
Second end of level coil connects the first end of second switch pipe, the second end ground connection of described second switch pipe；Institute
First end of the secondary coil stating transformator connects described power output end, the secondary coil of described transformator
Second end ground connection；
First end of described input filter capacitor connects the input filter voltage of described open loop protection circuit and connects
End；
Described switching power source chip includes drive output, feedback pin, overvoltage protection pin；Described driving
Outfan connects the control end of described second switch pipe；Described feedback pin connects described open loop protection circuit
Feedback pin connects end, and described overvoltage protection pin connects the low-voltage variation pin of described open loop protection circuit even
Connect end；
Described power output end connects the first end of described 5th resistance, and the second end of described 5th resistance connects
First end of described 6th resistance, the second end ground connection of described 6th resistance；
First end of described 5th resistance connects the first end of described 7th resistance, the second of described 7th resistance
End connects the positive pole of described feedback optocoupler transmitting tube；
Described adjustable reference source includes negative electrode, anode and reference pole；Described negative electrode connects described feedback optocoupler
The negative pole of transmitting tube, described plus earth, described the second end connecting the 5th resistance with reference to pole.
The switching power circuit that this utility model provides, the voltage of power output end can affect adjustable reference source
Conducting electric current, i.e. feeds back the electric current of optocoupler transmitting tube；Feedback light in open loop protection circuit couples closed tube, collection
The feedback pin of electrode connection chip realizes the feedback function of circuit, regulated output voltage, emitter stage and first
Resistance connects, and whether controls NPN triode ON, it is achieved the function of above-mentioned open loop protection circuit.And,
The scheme of this electric current by adjustable reference source regulation feedback optocoupler transmitting tube, when output short-circuit, adjustable
A reference source is not turned on, and therefore can close output by the protection act of open loop protection circuit flip chip equally,
The switching power circuit that i.e. this utility model provides not only has not by volume production element differentia influence and can protect always
Hold the open loop defencive function of locking, also there is short-circuit protection function.
Further, described switching power circuit also includes the 8th resistance, the 9th resistance, the 5th electric capacity and
Six electric capacity；
First end of described 8th resistance connects the positive pole of described feedback optocoupler transmitting tube, described 8th resistance
Second end connects the negative pole of described feedback optocoupler transmitting tube；
First end of described 9th resistance connects described negative electrode, and the second end of described 9th resistance connects described the
First end of five electric capacity, the second end of described 5th electric capacity connects the first end of described 6th resistance；
First end of described 6th electric capacity connects described negative electrode, and the second end of described 6th electric capacity connects described the
First end of six resistance.
Accompanying drawing explanation
Fig. 1 is the block diagram of the open loop protection circuit that this utility model provides；
Fig. 2 is the schematic diagram of the first embodiment of the open loop protection circuit that this utility model provides；
Fig. 3 is the schematic diagram of the second embodiment of the open loop protection circuit that this utility model provides；
Fig. 4 is the schematic diagram of an embodiment of the switching power circuit that this utility model provides.
Detailed description of the invention
Below in conjunction with the accompanying drawing in this utility model embodiment, to the technical side in this utility model embodiment
Case is clearly and completely described, it is clear that described embodiment is only that this utility model part is real
Execute example rather than whole embodiments.Based on the embodiment in this utility model, ordinary skill people
The every other embodiment that member is obtained under not making creative work premise, broadly falls into this utility model
The scope of protection.
See Fig. 1, be the block diagram of the open loop protection circuit that this utility model provides；Open loop protection circuit
10 include that feedback pin connects end COMP1, overvoltage protection pin connects end FB1, input filter voltage connects
End V_Bridge, overvoltage provide circuit 101, feedback light to couple closed tube U1B, the first resistance R1 and NPN
Audion Q2；
Feedback pin connects end COMP1 connection feedback light and couples the colelctor electrode of closed tube U1B, and feedback light couples
The emitter stage of closed tube U1B connects first end of the first resistance R1, the second end ground connection of the first resistance R1；The
First end of one resistance R1 connects the base stage of NPN audion Q2, and the colelctor electrode of NPN audion Q2 connects
Overvoltage protection pin connects the grounded emitter of end COMP1, NPN audion Q2；
Overvoltage provides circuit to include feeder ear and outfan, and feeder ear connects input filter voltage connection
V_Bridge, outfan connects overvoltage protection pin and connects end FB1.
The open loop protection circuit 10 that this utility model provides is mainly used in the switch power supply using chip controls
Lu Zhong, wherein, feedback pin connects end COMP1 for connecting the feedback pin of chip, overvoltage protection pin
Connecting end FB1 and be used for connecting the overvoltage protection pin of chip, input filter voltage connection V_Bridge is used for
Gather the voltage on the filter capacitor in the input rectification circuit of switching power circuit；Feedback light couples closed tube
U1B and the first resistance R1 series connection dividing potential drop, when normally working, feedback light couples closed tube U1B and turns on, and first
The dividing potential drop of first end of resistance R1 makes NPN audion Q2 turn on, therefore the overvoltage protection pin FB1 of chip
Keep electronegative potential, do not affect normal work；When circuit feedback loop disconnects, feedback light couples closed tube U1B
Not having electric current, therefore first terminal voltage of the first resistance R1 does not obtain feedback pin connection end COMP1's
Dividing potential drop, NPN audion Q2 ends, and the voltage of now overvoltage protection pin connection end FB1 is provided by overvoltage
The outfan of circuit 101 determines, and overvoltage provides circuit 101 to take input filter voltage connection V_Bridge
Voltage, and the voltage on the filter capacitor in the input rectification circuit of switching power circuit once to power on be one
Straight existence, therefore overvoltage provides circuit 101 to provide the voltage of a lasting threshold value exceeding trigger protection
Connect end FB1 to overvoltage protection pin, make the defencive function of chip be triggered, close and export, and always
It is maintained at guard mode, until user's power cutoff re-powers.
Participate in Fig. 2, be the schematic diagram of the first embodiment of the open loop protection circuit 10 that this utility model provides；
In the present embodiment, overvoltage provides circuit 101 to include the first sectional pressure element and the second sectional pressure element, the first dividing potential drop
First end of element connects feeder ear, and the second end of the first sectional pressure element connects the first end of the second sectional pressure element,
Second end ground connection of the second sectional pressure element；First end of the second sectional pressure element connects described outfan.By right
The voltage of input filter voltage connection V_Bridge carries out dividing potential drop, takes partial pressure value and exports to outfan；Wherein,
First sectional pressure element is resistance R10 and the series combination of resistance R11, and described first sectional pressure element can also
For the parallel combination body of single resistor or multiple resistor, the second sectional pressure element is stabilivolt Z1, stabilivolt
The negative pole of Z1 is the first end of described second sectional pressure element, the most described second dividing potential drop unit of stabilivolt Z1
Second end of part；With stabilivolt Z1 as the second sectional pressure element, outfan output can be made stable, to adapt to supply
The fluctuation of electricity voltage reference terminal.
Additionally, open loop protection circuit 10 also includes the first electric capacity C1, the second electric capacity C2 and in the present embodiment
Three resistance R3；First end of the first electric capacity C1 connects the colelctor electrode of NPN audion Q2, the first electric capacity C1
The second end ground connection；First end of the second electric capacity C2 connects first end of the first resistance R1, the second electric capacity C2
The second end ground connection；The colelctor electrode of described NPN audion Q2 connects overvoltage protection pin and connects end FB1,
Particularly as follows: the colelctor electrode of NPN audion Q2 connects overvoltage protection pin by the 3rd resistance R3 connects end
FB1, wherein, first end of the 3rd resistance R3 connects the colelctor electrode of NPN audion Q2, the 3rd resistance
Second end of R3 connects overvoltage protection pin and connects end FB1.First electric capacity C1 and the second electric capacity C2 acts primarily as
Filter action, and the 3rd resistance R3 plays metering function.
See Fig. 3, be the schematic diagram of the second embodiment of the open loop protection circuit that this utility model provides；This reality
Execute the example difference from first embodiment to be, overvoltage provide circuit 101 include the first sectional pressure element, second
Sectional pressure element, the first switching tube Q1, the second resistance R2, the 3rd electric capacity C3, the 4th electric capacity EB2 and the 4th
Resistance R4；
First end of described first sectional pressure element connects described feeder ear, the second end of described first sectional pressure element
Connect the first end of the second sectional pressure element, the second end ground connection of described second sectional pressure element；Wherein, first point
Pressure element is resistance R12, and described first sectional pressure element can also be the connection in series-parallel assembly of multiple resistor, the
Two sectional pressure elements are stabilivolt Z1, and the negative pole of stabilivolt Z1 is the first end of described second sectional pressure element, surely
Second end of the most described second sectional pressure element of pressure pipe Z1；Described feeder ear connects the second resistance R1's
First end；The negative pole of stabilivolt Z1 connects the control end of the first switching tube Q1, the of the first switching tube Q1
One end connects second end of the second resistance R2, and second end of the first switching tube Q1 is by the 4th resistance R4 even
Connect described outfan.First end of the 3rd electric capacity C3 connects the negative pole of stabilivolt Z1, the 3rd electric capacity C3's
Second end ground connection, first end of the 4th electric capacity C4 connects second end of the first switching tube Q1, the 4th electric capacity C4
The second end ground connection, the 3rd electric capacity C3, the 4th electric capacity C4 all strobe.
Below by the operation principle of overvoltage offer circuit 101 in illustration the present embodiment that element is selected:
First switching tube can be NPN silicon audion, and conducting voltage is 0.7V, and the voltage stabilizing value of stabilivolt Z1 is
3.3V, open loop protection circuit 10 is applied in switching power circuit and in the control chip of this switching power circuit
The overvoltage threshold of overvoltage protection pin is 2V, and overvoltage provides circuit 101 to be believed by the input filter voltage of feeder ear
Number dividing potential drop, the 3.3V that control terminal voltage is stabilivolt Z1 of the first switching tube Q1, the second end passes through resistance
R4 is connected to the overvoltage protection pin ground connection of chip, therefore turns on；Input filter voltage signal is by the second electricity
Resistance R2, the first switching tube Q1 of conducting export to the overvoltage protection pin of chip, now overvoltage protection pin
Voltage more than 2V, even greater than 2.6V, owing to the signal power needed for overvoltage protection pin is the least, when
When the voltage of overvoltage protection pin is enough maintained at overpressure value 2V of needs within a period of time, owing to first opens
The voltage difference controlling end and the second end closing pipe is less than or equal to 0.7V, is not enough to turn on the first switching tube
Q1, therefore the first switching tube Q1 cut-off, when the undertension 2.6V of overvoltage pin protection end, first opens
Close pipe to turn on again, therefore, the first switching tube is set overvoltage can be made to provide circuit to close defeated unnecessary when
Go out, reduce power consumption, play energy-conservation effect.
See Fig. 4, be the schematic diagram of an embodiment of the switching power circuit that this utility model provides；Including
Power input VIN, input rectification circuit 20, input filter capacitor EB1, power output end VOUT,
Transformator T1, second switch pipe Q2, switching power source chip U2, feedback optocoupler transmitting tube U1A, adjustable substrate
Quasi-source U3, the 5th resistance R5, the 6th resistance R6, the 7th resistance R7 and above-mentioned open loop protection circuit
10；
Power input VIN connects the input of input rectification circuit 20, the output of input rectification circuit 20
End connects first end of input filter capacitor EB1, the second end ground connection of input filter capacitor EB1；Input filter
First end of the primary coil T1A of the first end connection transformer T1 of ripple electric capacity EB1, at the beginning of transformator T1
Second end of level coil T1A connects first end of second switch pipe Q2, second termination of second switch pipe Q2
Ground；First end of the secondary coil T1B of transformator T1 connects the secondary of power output end OUT, transformator T1
The second end ground connection of level coil T1B；First end of input filter capacitor EB1 connects open loop protection circuit 10
Input filter voltage connection V_Bridge；
Switching power source chip includes drive output GATE, feedback pin COMP, overvoltage protection pin FB；
Drive output GATE connects the control end of second switch pipe Q2, drive output GATE output square wave
Control the dutycycle of second switch pipe Q2, to adjust the electric current in transformator；Feedback pin COMP connects
The feedback pin of open loop protection circuit 10 connects end COMP1, and feedback pin COMP is externally a constant current
Source, couples closed tube U1B for the feedback light in open loop protection circuit 10 and the first resistance R1 provides voltage, instead
Feedback pin COMP acts the effect of the feedback information providing output voltage for chip internal, according to output electricity
The feedback information of pressure adjusts the square wave dutycycle of drive output GATE；Overvoltage protection pin FB connects institute
The low-voltage variation pin stating open loop protection circuit connects end FB1, and when overvoltage protection pin FB is unsettled, voltage is relatively low,
When overvoltage protection pin FB is connected to the voltage higher than 2V or other threshold values, the protection merit of meeting flip chip
Can, close output；
Power output end VOUT connects first end of the 5th resistance R5, and second end of the 5th resistance R5 connects
First end of the 6th resistance R6, the second end ground connection of the 6th resistance R6；5th resistance R5 and the 6th resistance
R6 carries out dividing potential drop to output voltage；
First end of the 5th resistance R5 connects first end of the 7th resistance R7, second end of the 7th resistance R7
Connect the positive pole of feedback optocoupler transmitting tube U1A；
Described adjustable reference source U3 includes negative electrode K, anode A and reference pole R；Negative electrode K connects feedback
The negative pole of optocoupler transmitting tube U1A, anode A ground connection, second end of the 5th resistance R5 is connected with reference to pole R.
The dividing potential drop of output voltage is exported and makes adjustable reference source U3 turn on by the 5th resistance R5 and the 6th resistance R6, and
And output voltage floating can cause the current floating of adjustable reference source U3, so that feedback optocoupler transmitting tube U1A
Curent change, this change information i.e. feedback information of output voltage, anti-by open loop protection circuit 10
Feedback optocoupler receives pipe U1B and receives, it is provided that to feedback pin COMP, and then chip is made adjustment.
By the setting of foregoing circuit structure, feedback optocoupler transmitting tube U1A is to have electric current when normally working always
Passing through, feedback light couples closed tube U1B has electric current to pass through the most always, and therefore NPN audion Q2 keeps leading
Logical state, the voltage of overvoltage protection pin FB is less than 2V threshold value；But when feedback control loop disconnects, i.e. feed back
Optocoupler receives pipe U1B and does not receives feedback information, and when not having electric current to pass through, NPN audion Q2 cut-off makes
The voltage of overvoltage protection pin FB provides the magnitude of voltage higher than 2V threshold value of circuit 101 offer for overvoltage, i.e.
The defencive function of flip chip, closes output voltage.Additionally, this circuit structure is at output short-circuit, i.e. electricity
During source output terminal VOUT ground connection, can be because first end of the 6th resistance R6 powers on to force down causes adjustable reference
Source U3 is not turned on, thus feeds back optocoupler transmitting tube U1A and do not have electric current, will also result in the cut-off of NPN audion,
Therefore, the switching power circuit that this utility model provides not only has open loop defencive function, also has short circuit guarantor
Protective function.
Further, described switching power circuit also includes the 8th resistance R8, the 9th resistance R9, the 5th electric capacity
C5 and the 6th electric capacity C6；
First end of the 8th resistance R8 connects the positive pole of feedback optocoupler transmitting tube U1A, the of the 8th resistance R8
Two ends connect the negative pole of feedback optocoupler transmitting tube U1A；The effect of the 8th resistance R8 is to be easy to arrange feedback
Optocoupler transmitting tube U1A and the operating current of adjustable reference source U3.
First end of the 9th resistance R9 connects second end of negative electrode K, the 9th resistance R9 and connects the 5th electric capacity C5
The first end, the 5th electric capacity C5 second end connect the 6th resistance R6 the first end；Described 6th electric capacity
First end connects described negative electrode, and the second end of described 6th electric capacity connects the first end of described 6th resistance.The
Nine resistance R9, the 5th electric capacity C5 and the 6th electric capacity C6 constitute loop compensation circuit, it is ensured that the accuracy of feedback.
The open loop protection circuit that this utility model provides, the break-make being coupled closed tube by feedback light directly reflects electricity
Road is normal or the information of open loop, and during normal work, NPN triode ON makes overvoltage protection pin connect end to keep
Low voltage value, NPN audion cut-off when feedback control loop disconnects, provide circuit Gather and input filtered electrical by overvoltage
Pressure signal, exports higher voltage, makes overvoltage protection pin voltage raise, and triggers the control in application circuit
The defencive function of chip, closes output voltage.The defencive function of the open loop protection circuit that this utility model provides
Do not affected by the diversity of element during volume production, and because be that Gather and input filtering voltage signal makes defencive function touch
Sending out, input filter voltage signal can exist always, so defencive function can lock always, until circuit is again
Power on.
The switching power circuit that this utility model provides, the voltage of power output end can affect adjustable reference source
Conducting electric current, i.e. feeds back the electric current of optocoupler transmitting tube；Feedback light in open loop protection circuit couples closed tube, collection
The feedback pin of electrode connection chip realizes the feedback function of circuit, regulated output voltage, emitter stage and first
Resistance connects, and whether controls NPN triode ON, it is achieved the function of above-mentioned open loop protection circuit.And,
The scheme of this electric current by adjustable reference source regulation feedback optocoupler transmitting tube, when output short-circuit, adjustable
A reference source is not turned on, and therefore can close output by the protection act of open loop protection circuit flip chip equally,
The switching power circuit that i.e. this utility model provides not only has not by volume production element differentia influence and can protect always
Hold the open loop defencive function of locking, also there is short-circuit protection function.
The above is preferred implementation of the present utility model, it is noted that general for the art
For logical technical staff, on the premise of without departing from this utility model principle, it is also possible to make some improvement and
Deformation, these improve and deformation is also considered as protection domain of the present utility model.
Claims (10)
1. an open loop protection circuit, it is characterised in that include that feedback pin connects end, overvoltage protection pin
Connect end, input filter voltage connection, overvoltage provide circuit, feedback light couple closed tube, the first resistance and
NPN audion；
Described feedback pin connects the described feedback light of end connection and couples the colelctor electrode of closed tube, and described feedback light couples
The emitter stage of closed tube connects the first end of described first resistance, the second end ground connection of described first resistance；
First end of described first resistance connects the base stage of described NPN audion, described NPN audion
Colelctor electrode connects described overvoltage protection pin and connects end, the grounded emitter of described NPN audion；
Described overvoltage provides circuit to include feeder ear and outfan, and described feeder ear connects described input filter electricity
Pressure connects end, and described outfan connects described overvoltage protection pin and connects end.
2. open loop protection circuit as claimed in claim 1, it is characterised in that described overvoltage provides circuit also
Including the first sectional pressure element and the second sectional pressure element, the first end of described first sectional pressure element connects described power supply
End, the second end of described first sectional pressure element connects the first end of the second sectional pressure element, described second dividing potential drop unit
Second end ground connection of part；First end of described second sectional pressure element connects described outfan.
3. open loop protection circuit as claimed in claim 1, it is characterised in that described overvoltage provides circuit also
Including the first sectional pressure element, the second sectional pressure element, the first switching tube and the second resistance；
First end of described first sectional pressure element connects described feeder ear, the second end of described first sectional pressure element
Connect the first end of the second sectional pressure element, the second end ground connection of described second sectional pressure element；
Described feeder ear connects the first end of described second resistance；First end of described second sectional pressure element connects
The control end of described first switching tube, the first end of described first switching tube connects the second of described second resistance
End, the second end of described first switching tube connects described outfan.
4. open loop protection circuit as claimed in claim 2 or claim 3, it is characterised in that described first dividing potential drop unit
Part is the connection in series-parallel assembly of single resistor or multiple resistor；Described second sectional pressure element is stabilivolt,
The negative pole of described stabilivolt is the first end of described second sectional pressure element, the most described the of described stabilivolt
Second end of two sectional pressure elements.
5. the open loop protection circuit as described in any one of claims 1 to 3, it is characterised in that described open loop
Protection circuit also includes the first electric capacity and the second electric capacity；
First end of described first electric capacity connects the colelctor electrode of described NPN audion, the of described first electric capacity
Two end ground connection；
First end of described second electric capacity connects the first end of described first resistance, the second of described second electric capacity
End ground connection.
6. the open loop protection circuit as described in any one of claims 1 to 3, it is characterised in that described open loop
Protection circuit also includes the 3rd resistance；
The colelctor electrode of described NPN audion connects described overvoltage protection pin and connects end, particularly as follows: described
The colelctor electrode of NPN audion is by described 3rd resistance connection described overvoltage protection pin connection end, wherein,
First end of described 3rd resistance connects the colelctor electrode of described NPN audion, the second end of described 3rd resistance
Connect described overvoltage protection pin and connect end.
7. open loop protection circuit as claimed in claim 3, it is characterised in that described overvoltage provides circuit also
Including the 3rd electric capacity and the 4th electric capacity；
First end of described 3rd electric capacity connects the first end of described second sectional pressure element, described 3rd electric capacity
Second end ground connection；
First end of described 4th electric capacity connects the second end of described first switching tube, the of described 4th electric capacity
Two end ground connection.
8. open loop protection circuit as claimed in claim 3, it is characterised in that described overvoltage provides circuit also
Including the 4th resistance, the second end of described first switching tube connects described outfan, particularly as follows: described first
Second end of switching tube connects described outfan, wherein, the of described 4th resistance by described 4th resistance
One end connects the second end of described switching tube, and the second end of described 4th resistance connects described outfan.
9. a switching power circuit, it is characterised in that include power input, input rectification circuit, defeated
Enter filter capacitor, power output end, transformator, second switch pipe, switching power source chip, feedback optocoupler are sent out
Penetrate pipe, adjustable reference source, the 5th resistance, the 6th resistance, the 7th resistance and such as claim 1 to 8 times
One described open loop protection circuit；
Described power input connects the input of described input rectification circuit, described input rectification circuit defeated
Go out end and connect the first end of described input filter capacitor, the second end ground connection of described input filter capacitor；Described
First end of input filter capacitor connects at the beginning of the first end of the primary coil of described transformator, described transformator
Second end of level coil connects the first end of described second switch pipe, the second end ground connection of described second switch pipe；
First end of the secondary coil of described transformator connects described power output end, the secondary coil of described transformator
The second end ground connection；
First end of described input filter capacitor connects the input filter voltage of described open loop protection circuit and connects
End；
Described switching power source chip includes drive output, feedback pin, overvoltage protection pin；Described driving
Outfan connects the control end of described second switch pipe；Described feedback pin connects described open loop protection circuit
Feedback pin connects end, and described overvoltage protection pin connects the low-voltage variation pin of described open loop protection circuit even
Connect end；
Described power output end connects the first end of described 5th resistance, and the second end of described 5th resistance connects
First end of described 6th resistance, the second end ground connection of described 6th resistance；
First end of described 5th resistance connects the first end of described 7th resistance, the second of described 7th resistance
End connects the positive pole of described feedback optocoupler transmitting tube；
Described adjustable reference source includes negative electrode, anode and reference pole；Described negative electrode connects described feedback optocoupler
The negative pole of transmitting tube, described plus earth, described the second end connecting the 5th resistance with reference to pole.
10. switching power circuit as claimed in claim 9, it is characterised in that described switching power circuit
Also include the 8th resistance, the 9th resistance, the 5th electric capacity and the 6th electric capacity；
First end of described 8th resistance connects the positive pole of described feedback optocoupler transmitting tube, described 8th resistance
Second end connects the negative pole of described feedback optocoupler transmitting tube；
First end of described 9th resistance connects described negative electrode, and the second end of described 9th resistance connects described the
First end of five electric capacity, the second end of described 5th electric capacity connects the first end of described 6th resistance；
First end of described 6th electric capacity connects described negative electrode, and the second end of described 6th electric capacity connects described the
First end of six resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620177011.1U CN205544230U (en) | 2016-03-08 | 2016-03-08 | Ring -opening protection circuit and switching power supply circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620177011.1U CN205544230U (en) | 2016-03-08 | 2016-03-08 | Ring -opening protection circuit and switching power supply circuit |
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| Publication Number | Publication Date |
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| CN205544230U true CN205544230U (en) | 2016-08-31 |
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| CN201620177011.1U Active CN205544230U (en) | 2016-03-08 | 2016-03-08 | Ring -opening protection circuit and switching power supply circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112467967A (en) * | 2020-11-23 | 2021-03-09 | 无锡科索电子有限公司 | Overvoltage protection structure of switching power supply |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112467967A (en) * | 2020-11-23 | 2021-03-09 | 无锡科索电子有限公司 | Overvoltage protection structure of switching power supply |
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