CN105610314A - Input undervoltage protection circuit and method - Google Patents
Input undervoltage protection circuit and method Download PDFInfo
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- CN105610314A CN105610314A CN201610101819.6A CN201610101819A CN105610314A CN 105610314 A CN105610314 A CN 105610314A CN 201610101819 A CN201610101819 A CN 201610101819A CN 105610314 A CN105610314 A CN 105610314A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
Abstract
The invention discloses an input undervoltage protection circuit and method. A sampling circuit samples an input voltage and outputs a sampling signal; a control circuit receives the sampling signal and outputs a control signal to a switching circuit and a hysteresis circuit; when an undervoltage occurs, the switching circuit lowers a Vcc pin electrical level of a control IC of the switch power supply; a feedback circuit detects the Vcc pin electrical level and provides a feedback signal to the control circuit to enable the Vcc pin electrical level to be rapidly lowered, and a product is subjected to undervoltage protection; meanwhile, the hysteresis circuit lowers the sampling signal to generate a hysteresis voltage for performing undervoltage protection so as to enable the undervoltage protection for the product to be more reliable; when undervoltage recovers, the switching circuit stops the lowering of the Vcc pin electrical level; the feedback circuit detects the Vcc pin electrical level and provides a feedback signal to the control circuit to enable the switch circuit to rapidly release the Vcc pin electrical level; the Vcc pin electrical level is charged to an IC operating voltage range by an external start circuit, and the product smoothly recovers to operate; and a hiccup phenomenon in the recovery process of the product is eliminated.
Description
Technical field
The present invention discloses a kind of input undervoltage protection circuit and method, the particularly input undervoltage of Switching Power Supply protection.
Background technology
In existing module switch power supply, generally all require to possess input undervoltage defencive function, especially large at voltage ripple of power network orPerson is the occasions such as photovoltaic generation, described under-voltage protection function be for prevent power supply itself too low at input voltage and that cause orPower supply unit damages, and controls power remove and designed holding circuit, also prevents that product is in the time fluctuating compared with low input simultaneouslyConstantly restart, cause rear class equipment malfunction to be done.
Fig. 1 is existing under-voltage protecting circuit figure, described in Fig. 1 under-voltage protecting circuit comprise sample circuit 100, control circuit 200,Hysteresis circuit 300, on-off circuit 400. Sample circuit 100 is composed in series by resistance R 1, R2; Control circuit 200 is by resistanceR3, TL431 and capacitor C 1 form, the plus earth of the benchmark pin connecting resistance R1 of TL431 and the tie point of R2, TL431,Negative electrode connects the Vcc pin of Switching Power Supply control IC through resistance R 3, capacitor C 1 is parallel between the benchmark pin and anode of TL431;Hysteresis circuit 300 is made up of transistor Q2 and resistance R 4, and the base stage of transistor Q2 connects base stage, the emitter stage of transistor Q1Ground connection, colelctor electrode connect the benchmark pin of TL431 after resistance R 4; On-off circuit 400 is by transistor Q1 and Zener diode Z1Composition, COMP pin, grounded emitter, base stage that the colelctor electrode of transistor Q1 meets Switching Power Supply control IC connect voltage stabilizing two utmost pointsThe anode of pipe Z1, the negative electrode of Zener diode Z1 connects the negative electrode of TL431.
Sample circuit 100 is sampled after input voltage vin and is exported sampled signal, then sampled signal is input to control circuit 200The benchmark pin of TL431, TL431 according to sampled signal output control signal after Zener diode Z1 to hysteresis circuit 300Switching tube Q2 and the switching tube Q1 of on-off circuit; The transistor Q2 of hysteresis circuit 300 drags down the base of TL431 by conductingHysteresis voltage when accurate pin voltage provides under-voltage protection; The transistor Q1 of on-off circuit 400 drags down Switching Power Supply by conductingControl the COMP pin level of IC, reach the object of closing switch power supply.
Described hysteresis voltage is: the input electricity recovering again after the under-voltage protection point of input voltage and input voltage under-voltage protectionThe voltage difference of pressure point.
Fig. 2 is the under-voltage recovery waveform of existing under-voltage protecting circuit, and as we can see from the figure, input voltage is in under-voltage protection critical valueDescribed in when neighbouring there is the confusion region of conducting in the TL431 of control circuit 200, causes the transistor Q1 of described on-off circuit 200Also there is conducting confusion region with the transistor Q2 of hysteresis circuit 300, simultaneously because the conducting of transistor Q1 and transistor Q2 is pressedFalling can not be in full accord, in the time that transistor Q1 more first ends, just there will be the COMP pin level of the control IC of Switching Power SupplyNot dragged down, there is one-shot phenomenon in product, but because transistor Q2 does not end and produces hysteresis voltage, crystal in timePipe Q1 again likely conducting drag down and control the COMP pin level of IC product is started unsuccessfully.
Therefore, adopt this circuit to realize input undervoltage protection and mainly have following shortcoming:
1. the transistor Q1 parallel connection of the transistor Q2 of the hysteresis circuit of circuit and on-off circuit described in, due to two of batch property differencesTransistorized base stage conduction voltage drop can not be in full accord, this will cause two pipe ON times inconsistent even only have singleThe situation of transistor turns, makes output of products shakiness.
2. there is confusion region in error amplifier TL431 near critical value, can cause described under-voltage circuit can not thoroughly discharge power supplyControl end level, shows as product and can exist and restart or export unstable.
Summary of the invention
In view of this, the technical problem to be solved in the present invention is to provide a kind of input undervoltage protection circuit and method, solves existing defeatedEntering under-voltage technology makes product have output shakiness or occur the problem of restarting.
For solving the problems of the technologies described above, the invention provides a kind of input undervoltage protection circuit, be applied in Switching Power Supply, comprising:Sample circuit, control circuit, on-off circuit, hysteresis circuit and feedback circuit;
The input voltage of the Switching Power Supply described in described sample circuit sampling is also exported sampled signal to described control circuit;
Described control circuit receives described sampled signal and outputs a control signal to described on-off circuit and described hysteresis electricityRoad; Described on-off circuit and described hysteresis circuit receive described control signal, when described input voltage occurs when under-voltage,Described on-off circuit drags down the Vcc pin level of described Switching Power Supply control IC, and is detected and opened by described feedback circuitClose the Vcc pin level of power supply control IC and provide positive feedback signal to the input of described control circuit, making described switchThe Vcc pin level of power supply control IC is dragged down rapidly, when the Vcc pin level of described Switching Power Supply control IC is lower than instituteWhen the operating voltage range of the Switching Power Supply control IC stating, described Switching Power Supply control IC drives and stops, and product introduction is under-voltageProtection; Thereby described hysteresis circuit drags down described sampled signal and produces the hysteresis voltage Δ V of under-voltage protection simultaneously;
In the time of the under-voltage recovery of described input voltage, described on-off circuit stops dragging down the Vcc of described Switching Power Supply control ICPin level, and by the Vcc pin level of described feedback circuit sense switch power supply control IC and to described control circuitInput positive feedback signal is provided, make described on-off circuit discharge rapidly the Vcc pin electricity of described Switching Power Supply control ICFlat, the Vcc pin level of described Switching Power Supply control IC is charged to described Switching Power Supply by outside start-up circuit and controls ICOperating voltage range, described Switching Power Supply control IC recovers to drive, product recovers output.
The principle Analysis of technique scheme following (taking control signal as high level time trigger under-voltage protection as example):
In the time there is input undervoltage, described sample circuit output low level sampled signal is given to described control circuit, described controlCircuit receives described low level sampled signal and exports high-level control signal to described on-off circuit and described hysteresis electricityRoad, described on-off circuit receives described high-level control signal and drags down the Vcc pin electricity of described Switching Power Supply control ICPut down to forbid that described Switching Power Supply IC drives, product introduction under-voltage protection, described feedback circuit detects described Switching Power SupplyThe Vcc pin level of controlling IC reduces, and reduces control circuit by the electric current that reduces to be applied to described control circuit inputThe level of input, further makes the output level of control circuit raise, though the amplification of the control signal of described control circuit,Thereby eliminate near the duty that fuzzy conducting appears in control circuit critical voltage, described hysteresis circuit receives described heightThereby level controling signal also drags down described sampled signal and produces the hysteresis voltage Δ V of under-voltage protection;
In the time that input undervoltage recovers, described sample circuit output high level sampled signal, described control circuit receives described heightOutput low level control signal after level sampling signal, described on-off circuit no longer drags down described Switching Power Supply control IC'sVcc pin level, the Vcc pin level of described Switching Power Supply control IC raise by the charging of outside start-up circuit and arrive described inThe operating voltage of Switching Power Supply control IC, described Switching Power Supply control IC resumes work, product returns to from under-voltage conditionNormal operating conditions, the backward described control electricity of Vcc pin of the Switching Power Supply control IC described in the electric circuit inspection of described feedbackRoad input applies positive feedback signal further raises control circuit input level, and described control circuit further output is lowLevel, described hysteresis circuit no longer drags down described sampled signal and produces the hysteresis voltage Δ V of under-voltage protection, guarantees that product is steadyFixed work.
As a kind of concrete embodiment of sample circuit, comprising: resistance R 1 and resistance R 2; Described input voltage successivelyGround connection after described resistance R 1, described resistance R 2, the tie point output of described resistance R 1 and described resistance R 2Be described sampled signal.
As a kind of concrete embodiment of control circuit, comprising: capacitor C 1, error amplifier TL431 and resistance R 5;The Vcc pin of described Switching Power Supply control IC successively through the negative electrode of described resistance R 5, described error amplifier TL431,Ground connection after the anode of described error amplifier TL431; Described capacitor C 1 is parallel to described error amplifier TL431'sBetween anode and benchmark pin; The benchmark pin of described error amplifier TL431 is described control circuit input, receives instituteThe sampled signal of stating; The described control signal of negative electrode output of described error amplifier TL431.
As a kind of concrete embodiment of hysteresis circuit, comprising: FET TR1 and resistance R 4; Described resistance R 4One end receives the drain electrode of the FET TR1 described in described sampled signal, other end connection; Described FET TR1Source ground, the grid of described FET TR1 receive described control signal.
As a kind of concrete embodiment of on-off circuit, comprising: resistance R 6, transistor Q1 and Zener diode D4;The Vcc pin of described Switching Power Supply control IC is successively through colelctor electrode, the institute of described resistance R 6, described transistor Q1Ground connection after the emitter stage of the transistor Q1 stating; The base stage of described transistor Q1 through the anode of described Zener diode D4,After the negative electrode of described Zener diode D4, receive described control signal.
As the improvement for the first time of said switching circuit detailed description of the invention, also comprise diode D1, diode D2; DescribedResistance R 6 described in the anodic bonding of diode D1, the negative electrode of described diode D1 connects the current collection of described transistor Q1The utmost point; The control end of the Vcc pin mu balanced circuit of the Switching Power Supply control IC described in the anodic bonding of described diode D2, instituteThe negative electrode of the diode D2 stating connects the negative electrode of described diode D1.
Described mu balanced circuit is the mu balanced circuit being between Vcc pin and the auxiliary winding of Switching Power Supply control IC, generally byThe formation such as triode and Zener diode, as the electricity of the transistor Q2 in Fig. 8, resistance R 7, Zener diode D7/D8 formationRoad, is used to the Vcc pin of Switching Power Supply control IC that a stable voltage is provided, the base stage of transistor Q2 and voltage stabilizing two utmost pointsThe control end that the tie point of pipe D7 anode is mu balanced circuit, drags down this point voltage and can turn-off mu balanced circuit.
As the improvement for the second time of said switching circuit, on improved basis, also comprising Zener diode D3 for the first time, described inThe anodic bonding of Zener diode D3 described in the colelctor electrode, the negative electrode that negative electrode connects described diode D1 of transistor Q1.
As a kind of concrete embodiment of feedback circuit, comprising: resistance R 3; Described resistance R 3 one end connect describedThe Vcc pin of Switching Power Supply control IC, the other end connects the input of described control circuit.
Correspondingly, the invention provides a kind of input undervoltage guard method, be applied in Switching Power Supply, comprise the steps:
Sampled signal produces and transmitting step: sample circuit sampling input voltage is also exported sampled signal to control circuit;
Control signal produces and transmitting step: described control circuit receives described sampled signal and outputs a control signal to switchCircuit and hysteresis circuit;
When described input voltage occurs when under-voltage, trigger under-voltage protection and hysteresis voltage and produce step:
Described under-voltage protection step is: described on-off circuit drags down the Vcc pin level of described Switching Power Supply control IC,And provide to the input of described control circuit by the Vcc pin level that feedback circuit detects described Switching Power Supply control ICPositive feedback signal, is dragged down rapidly the Vcc pin level of described Switching Power Supply control IC, when described Switching Power Supply controlThe Vcc pin level of IC is during lower than the operating voltage range of described Switching Power Supply control IC, described Switching Power Supply control ICDriving stops, product introduction under-voltage protection;
Described hysteresis voltage produces step: described hysteresis circuit drags down described sampled signal and produces the hysteresis of under-voltage protectionVoltage;
In the time of the under-voltage recovery of described input voltage, trigger input undervoltage recovering step: described in described on-off circuit stops dragging downThe Vcc pin level of Switching Power Supply control IC, and draw by the Vcc of described feedback circuit sense switch power supply control ICPin level provides positive feedback signal to the input of described control circuit, makes described on-off circuit discharge rapidly described switchThe Vcc pin level of power supply control IC, the Vcc pin level of described Switching Power Supply control IC is charged by outside start-up circuitTo the operating voltage range of described Switching Power Supply control IC, described Switching Power Supply control IC recovers to drive, and it is defeated that product recoversGo out.
Beneficial effect of the present invention is as follows:
1, the present invention is by advanceing to the input of hysteresis circuit the output of control circuit, avoided two transistor parallel connectionsSituation, is used by input undervoltage protection circuit of the present invention, has eliminated on-off circuit and has used two or more transistorsThe unstable phenomenon of asynchronous the caused output of parallel connection and conducting.
2,, in the time of transistor Q1 conducting, due to the pressure stabilization function of Zener diode D3, can ensure that hysteresis circuit is in workState, solves product and in the time of low pressure input voltage fluctuation, constantly restarts problem.
3, in the time of under-voltage recovery, provide positive feedback by the Vcc of Switching Power Supply control IC to control circuit, make error amplifierThe rapid conducting of TL431, has solved existing under-voltage protecting circuit under under-voltage recovery critical voltage, and product exists the phenomenon of having the hiccups,Prevent application terminal misoperation.
Brief description of the drawings
Fig. 1 is existing under-voltage protecting circuit figure;
Fig. 2 is the under-voltage recovery waveform of existing under-voltage protecting circuit;
Fig. 3 is functional block diagram of the present invention;
Fig. 4 is first embodiment of the invention circuit theory diagrams;
Fig. 5 is the circuit theory diagrams that first embodiment of the invention is applied in DC-C Switching Power Supply;
Fig. 6 is the under-voltage recovery waveform of DC-DC Switching Power Supply that uses the first embodiment under-voltage protecting circuit;
Fig. 7 is second embodiment of the invention circuit theory diagrams;
Fig. 8 is the circuit theory diagrams that second embodiment of the invention is applied in DC-C Switching Power Supply;
Fig. 9 is third embodiment of the invention circuit theory diagrams;
Figure 10 is the circuit theory diagrams that third embodiment of the invention is applied in DC-C Switching Power Supply.
Detailed description of the invention
The design of the technology of the present invention is: sample circuit sampling input voltage is also exported sampled signal, and control circuit receives sampled signalAnd export control signal to on-off circuit and hysteresis circuit, on-off circuit drags down the Vcc of Switching Power Supply control IC in the time of under-voltage generationPin level, the Vcc pin level of feedback circuit sense switch power supply control IC also feeds back to the defeated of control circuit by feedback signalEnter end, finally make the Vcc pin level of Switching Power Supply control IC be dragged down rapidly, when the Vcc pin of Switching Power Supply control ICLevel is during lower than the operating voltage range of Switching Power Supply control IC, and Switching Power Supply control IC drives and stops, product introduction is under-voltage guarantorProtect, meanwhile, hysteresis circuit drags down sampled signal and produces the hysteresis voltage of under-voltage protection in the time of under-voltage generation, makes the under-voltage of productProtect more reliable. In the time of under-voltage recovery, on-off circuit stops dragging down the Vcc pin level of Switching Power Supply control IC, by feedbackThe Vcc pin level of electric circuit inspection Switching Power Supply control IC also provides feedback signal to control circuit, and on-off circuit is discharged rapidlyThe Vcc pin level of Switching Power Supply control IC, the Vcc pin level of Switching Power Supply control IC is charged to by outside start-up circuitThe operating voltage range of Switching Power Supply control IC, product is resumed work smoothly, has eliminated the have the hiccups phenomenon of product in recovery process.
Technical scheme for a better understanding of the present invention, comes the present invention further detailed below in conjunction with the drawings and specific embodimentsThin explanation.
Referring to Fig. 3, be functional block diagram of the present invention, comprise input voltage vin, sample circuit 100, control circuit 200, stagnantTelegram in reply road 300, on-off circuit 400 and feedback circuit 500.
Further illustrate below in conjunction with specific implementation circuit.
Embodiment mono-
Fig. 4 is first embodiment of the invention circuit theory diagrams, and sample circuit 100 comprises: resistance R 1 and resistance R 2; DescribedInput voltage is ground connection after described resistance R 1, described resistance R 2 successively, described resistance R 1 and described resistance R 2What tie point was exported is described sampled signal. Control circuit 200 comprises: capacitor C 1, error amplifier TL431 (Fig. 4In U1) and resistance R 5; The Vcc pin of Switching Power Supply control IC (U2 in Fig. 5) successively through described resistance R 5,Ground connection after the anode of the negative electrode of described error amplifier TL431, described error amplifier TL431; Described capacitor C 1Be parallel between the anode and benchmark pin of described error amplifier TL431; The benchmark pin of described error amplifier TL431 connectsReceive described sampled signal; The described control signal of negative electrode output of described error amplifier TL431; Described error is amplifiedThe benchmark pin of device TL431 is the input of described control circuit. Hysteresis circuit 300 comprises: FET TR1 and resistanceR4; The input of described control circuit is successively through described resistance R 4, the drain electrode of described FET TR1, describedGround connection after the source electrode of FET TR1; The tie point of described resistance R 4 receives described sampled signal; Described field-effectThe grid of pipe TR1 receives described control signal. On-off circuit 400 comprises: resistance R 6, transistor Q1 and Zener diodeD4; The Vcc pin of described Switching Power Supply control IC successively through the colelctor electrode of described resistance R 6, described transistor Q1,Ground connection after the emitter stage of described transistor Q1; The base stage of described transistor Q1 through the anode of described Zener diode D4,After the negative electrode of described Zener diode D4, connect described control signal. Feedback circuit 500 comprises resistance R 3, connecting valveThe Vcc pin of power supply control IC and the benchmark pin of TL431.
The present embodiment operation principle is as follows:
Sample circuit 100 input voltage vin of sampling, output sampled signal is to control circuit 200.
Interference in capacitor C 1 filtering sampled signal in control circuit 200, prevents that circuit from producing misoperation, avoids low simultaneouslyWhen the lower startup of temperature, because input voltage was dragged down by moment the under-voltage protection that starts early, affect startup ability, control circuit 200Sampled signal after error amplifier TL431 receives after filtering, and according to sampled signal output control signal, resistance R 5 connectsConnecing Vcc pin and the error amplifier TL431 negative electrode of Switching Power Supply control IC, is control circuit power supply.
The grid of hysteresis circuit 300 FET TR1 connects the output (A point) of control circuit, controls electricity in the time of under-voltage generationRoad output high level, resistance R 4 is connected in parallel on resistance R 2 two ends by FET TR1 conducting, by error amplifier TL431 baseAccurate pin level drags down, and to produce the hysteresis voltage Δ V of under-voltage protection, the computational process of Δ V is as follows:
On-off circuit 400 zener diode D4 remain off in the time of control circuit 200 output low level prevents that transistor Q1 from misleadingLogical, on-off circuit 400 drags down the work in IC by transistor Q1 conducting by the Vcc pin level of Switching Power Supply control ICThreshold voltage and make IC stop drive, product introduction protected mode.
Feedback circuit 500 in the time that input undervoltage returns to critical voltage, error amplifier TL431 conducting, control circuit 200 is defeatedGo out low level, the transistor Q1 cut-off of on-off circuit 400, the Vcc pin level of Switching Power Supply control IC is started electricity by outsideCharge and raise in road, level raises and feeds back to the benchmark pin of error amplifier TL431 by resistance R 3, makes error amplifierThe further conducting of TL431, forms positive feedback with this, and the Vcc pin level of final Switching Power Supply control IC is increased to rapidly ICUnlatching threshold values, control IC and enter start-up course, product recovers normal work.
Fig. 5 is the circuit theory diagrams that first embodiment of the invention is applied in DC-DC Switching Power Supply, and Fig. 6 is for using first in factExecute the under-voltage recovery waveform of DC-DC Switching Power Supply of routine under-voltage protecting circuit; Can see by test waveform, adopt this enforcement caseWhen example, the shake of control circuit output level is eliminated, and output does not also exist " having the hiccups " phenomenon, once just successfully starts.
Embodiment bis-
Fig. 7 is second embodiment of the invention circuit theory diagrams, and Fig. 8 is that second embodiment of the invention should in DC-C Switching Power SupplyWith circuit theory diagrams, embodiment bis-is also to comprise diode D1 and diode D2 with the difference of embodiment mono-, described inThe anodic bonding of diode D1 described in resistance R 6, the negative electrode of described diode D1 connects the collection of described transistor Q1Electrode. The control end of the Vcc pin mu balanced circuit of the anodic bonding Switching Power Supply control IC of described diode D2, describedThe negative electrode of diode D2 connects the negative electrode of described diode D1.
Above-mentioned mu balanced circuit is the mu balanced circuit being between Vcc pin and the auxiliary winding of Switching Power Supply control IC, generally by three utmost pointsPipe and Zener diode form, and as the circuit that the transistor Q2 in Fig. 8, resistance R 7, Zener diode D7/D8 form, useIn providing a stable voltage, the company of the base stage of transistor Q2 and Zener diode D7 anode for the Vcc pin of controlling ICContact is the control end of mu balanced circuit, drags down this point voltage and can turn-off mu balanced circuit.
The present embodiment is accelerated the decline of the Vcc pin level of Switching Power Supply control IC by turn-offing mu balanced circuit, can accelerate electricityRoad drags down the speed of Vcc, makes under-voltage protection faster.
Embodiment tri-
Fig. 9 is third embodiment of the invention circuit theory diagrams, and Figure 10 is that third embodiment of the invention should in DC-C Switching Power SupplyWith circuit theory diagrams, embodiment tri-is also to comprise zener diode D3, described voltage stabilizing two with the difference of embodiment bis-The colelctor electrode of the anodic bonding transistor Q1 of utmost point pipe D3, the negative electrode that negative electrode connects diode D1. Voltage-stabiliser tube D3 is at transistorWhen Q1 conducting, the Vcc pin level of controlling IC is maintained to suitable sizes values, ensure that described hysteresis circuit 300 is in workState, while avoiding the under-voltage rear input voltage of product input generation to fluctuate among a small circle, product restarts.
Certainly when, above-described embodiment also can be high level by control signal by circuit design, trigger under-voltage protection and be revised as controlSignal triggers under-voltage protection while being low level, this is the skill that is equal to of the application's claim for a person skilled in the artArt scheme in order to save length, does not repeat in embodiment and claims.
Embodiments of the present invention are not limited to this, according to foregoing of the present invention, utilize ordinary skill knowledge and the strong hand of this areaSection, do not departing under the above-mentioned basic fundamental thought of the present invention prerequisite, the present invention can also make other various ways amendment, replaceChange or change, within metal-oxide-semiconductor etc. all drops on rights protection scope of the present invention as triode Q1 is replaced with.
Claims (9)
1. an input undervoltage protection circuit, is applied in Switching Power Supply, comprising: sample circuit, control circuit, on-off circuit, stagnantTelegram in reply road and feedback circuit;
The input voltage of the Switching Power Supply described in described sample circuit sampling is also exported sampled signal to described control circuit;
Described control circuit receives described sampled signal and outputs a control signal to described on-off circuit and described hysteresis electricityRoad; Described on-off circuit and described hysteresis circuit receive described control signal, when described input voltage occurs when under-voltage,Described on-off circuit drags down the Vcc pin level of described Switching Power Supply control IC, and is detected and opened by described feedback circuitClose the Vcc pin level of power supply control IC and provide positive feedback signal to the input of described control circuit, making described switchThe Vcc pin level of power supply control IC is dragged down rapidly, when the Vcc pin level of described Switching Power Supply control IC is lower than instituteWhen the operating voltage range of the Switching Power Supply control IC stating, described Switching Power Supply control IC drives and stops, and product introduction is under-voltageProtection; Thereby described hysteresis circuit drags down described sampled signal and produces the hysteresis voltage Δ V of under-voltage protection simultaneously;
In the time of the under-voltage recovery of described input voltage, described on-off circuit stops dragging down the Vcc of described Switching Power Supply control ICPin level, and by the Vcc pin level of described feedback circuit sense switch power supply control IC and to described control circuitInput positive feedback signal is provided, make described on-off circuit discharge rapidly the Vcc pin electricity of described Switching Power Supply control ICFlat, the Vcc pin level of described Switching Power Supply control IC is charged to described Switching Power Supply by outside start-up circuit and controls ICOperating voltage range, described Switching Power Supply control IC recovers to drive, product recovers output.
2. input undervoltage protection circuit according to claim 1, is characterized in that: described sample circuit comprises: resistance R 1With resistance R 2; Described input voltage is ground connection after described resistance R 1, described resistance R 2 successively, described resistance R 1The described sampled signal that is with the tie point output of described resistance R 2.
3. input undervoltage protection circuit according to claim 1, is characterized in that: described control circuit comprises: capacitor C 1,Error amplifier TL431 and resistance R 5; The Vcc pin of described Switching Power Supply control IC successively through described resistance R 5,Ground connection after the anode of the negative electrode of described error amplifier TL431, described error amplifier TL431; Described capacitor C 1Be parallel between the anode and benchmark pin of described error amplifier TL431; The benchmark pin of described error amplifier TL431For described control circuit input, receive described sampled signal; Described in the negative electrode output of described error amplifier TL431Control signal.
4. input undervoltage protection circuit according to claim 1, is characterized in that: described hysteresis circuit comprises: FETTR1 and resistance R 4; Described resistance R 4 one end receive described sampled signal, the other end connects described FET TR1Drain electrode; The grid of the source ground of described FET TR1, described FET TR1 receives described control signal.
5. input undervoltage protection circuit according to claim 1, is characterized in that: described on-off circuit comprises: resistance R 6,Transistor Q1 and Zener diode D4; The Vcc pin of described Switching Power Supply control IC is successively through described resistance R 6, instituteGround connection after the emitter stage of the colelctor electrode of the transistor Q1 stating, described transistor Q1; The base stage of described transistor Q1 is through instituteAfter the negative electrode of the anode of the Zener diode D4 stating, described Zener diode D4, receive described control signal.
6. input undervoltage protection circuit according to claim 5, is characterized in that: described on-off circuit also comprises diodeD1, diode D2; Resistance R 6 described in the anodic bonding of described diode D1, the negative electrode of described diode D1 connectsThe colelctor electrode of described transistor Q1; The Vcc of Switching Power Supply control IC described in the anodic bonding of described diode D2 drawsThe control end of pin mu balanced circuit, the negative electrode of described diode D2 connects the negative electrode of described diode D1.
7. input undervoltage protection circuit according to claim 6, is characterized in that: described on-off circuit also comprises voltage stabilizing two utmost pointsPipe D3, colelctor electrode, the negative electrode of the transistor Q1 described in the anodic bonding of described Zener diode D3 connect the two described utmost pointsThe negative electrode of pipe D1.
8. input undervoltage protection circuit according to claim 1, is characterized in that: described feedback circuit comprises: resistance R 3;Described resistance R 3 one end connect the Vcc pin of described Switching Power Supply control IC, the control circuit described in the other end connectsInput.
9. an input undervoltage guard method, is applied in Switching Power Supply, comprises the steps:
Sampled signal produces and transmitting step: sample circuit sampling input voltage is also exported sampled signal to control circuit;
Control signal produces and transmitting step: described control circuit receives described sampled signal and outputs a control signal to switchCircuit and hysteresis circuit;
When described input voltage occurs when under-voltage, trigger under-voltage protection and hysteresis voltage and produce step:
Described under-voltage protection step is: described on-off circuit drags down the Vcc pin level of described Switching Power Supply control IC,And provide to the input of described control circuit by the Vcc pin level that feedback circuit detects described Switching Power Supply control ICPositive feedback signal, is dragged down rapidly the Vcc pin level of described Switching Power Supply control IC, when described Switching Power Supply controlThe Vcc pin level of IC is during lower than the operating voltage range of described Switching Power Supply control IC, described Switching Power Supply control ICDriving stops, product introduction under-voltage protection;
Described hysteresis voltage produces step: described hysteresis circuit drags down described sampled signal and produces the hysteresis of under-voltage protectionVoltage;
In the time of the under-voltage recovery of described input voltage, trigger input undervoltage recovering step: described in described on-off circuit stops dragging downThe Vcc pin level of Switching Power Supply control IC, and draw by the Vcc of described feedback circuit sense switch power supply control ICPin level provides positive feedback signal to the input of described control circuit, makes described on-off circuit discharge rapidly described switchThe Vcc pin level of power supply control IC, the Vcc pin level of described Switching Power Supply control IC is charged by outside start-up circuitTo the operating voltage range of described Switching Power Supply control IC, described Switching Power Supply control IC recovers to drive, and it is defeated that product recoversGo out.
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| CN201610101819.6A CN105610314B (en) | 2016-02-24 | 2016-02-24 | A kind of input undervoltage protection circuit and method |
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| CN201610101819.6A CN105610314B (en) | 2016-02-24 | 2016-02-24 | A kind of input undervoltage protection circuit and method |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108336716A (en) * | 2018-03-13 | 2018-07-27 | 广州金升阳科技有限公司 | A kind of power supply module |
| CN108418186A (en) * | 2018-05-08 | 2018-08-17 | 广州金升阳科技有限公司 | A kind of under-voltage and short-circuit protection circuit of output |
| CN108964436A (en) * | 2017-05-27 | 2018-12-07 | 许继集团有限公司 | A kind of Switching Power Supply start-up circuit |
| CN110943429A (en) * | 2019-12-31 | 2020-03-31 | 广州金升阳科技有限公司 | Undervoltage protection circuit and control method thereof |
| CN113991611A (en) * | 2021-12-03 | 2022-01-28 | 阳光电源股份有限公司 | Switching power supply and protection circuit thereof |
| CN114123833A (en) * | 2021-10-29 | 2022-03-01 | 广东汇芯半导体有限公司 | Semiconductor circuit having a plurality of transistors |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108964436A (en) * | 2017-05-27 | 2018-12-07 | 许继集团有限公司 | A kind of Switching Power Supply start-up circuit |
| CN108336716A (en) * | 2018-03-13 | 2018-07-27 | 广州金升阳科技有限公司 | A kind of power supply module |
| CN108418186A (en) * | 2018-05-08 | 2018-08-17 | 广州金升阳科技有限公司 | A kind of under-voltage and short-circuit protection circuit of output |
| CN110943429A (en) * | 2019-12-31 | 2020-03-31 | 广州金升阳科技有限公司 | Undervoltage protection circuit and control method thereof |
| CN110943429B (en) * | 2019-12-31 | 2022-02-18 | 广州金升阳科技有限公司 | Undervoltage protection circuit and control method thereof |
| CN114123833A (en) * | 2021-10-29 | 2022-03-01 | 广东汇芯半导体有限公司 | Semiconductor circuit having a plurality of transistors |
| CN114123833B (en) * | 2021-10-29 | 2023-07-25 | 广东汇芯半导体有限公司 | Semiconductor circuit with a high-voltage power supply |
| CN113991611A (en) * | 2021-12-03 | 2022-01-28 | 阳光电源股份有限公司 | Switching power supply and protection circuit thereof |
| CN113991611B (en) * | 2021-12-03 | 2024-04-12 | 阳光电源股份有限公司 | Switch power supply and protection circuit thereof |
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