CN105186843A - Protective circuit, feedback unit and backlight drive circuit - Google Patents
Protective circuit, feedback unit and backlight drive circuit Download PDFInfo
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- CN105186843A CN105186843A CN201510552443.6A CN201510552443A CN105186843A CN 105186843 A CN105186843 A CN 105186843A CN 201510552443 A CN201510552443 A CN 201510552443A CN 105186843 A CN105186843 A CN 105186843A
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Abstract
The embodiment of the invention provides a protective circuit, a feedback unit and a backlight drive circuit, and relates to the technical field of electrons. The protective circuit is used for lowering an electric shock risk of a user. The protective circuit comprises a voltage input end, a voltage output end, a first level end and a voltage-dividing module, wherein the voltage-dividing module is connected with the voltage input end, the voltage output end and the first level end; when first voltage is input from the voltage input end, the voltage-dividing module is used for conducting the voltage input end and the voltage output end; when second voltage is input from the voltage input end, the voltage-dividing module is used for conducting the voltage input end and the first level end and discharging the voltage output end through the first level end; and the second voltage is greater than the first voltage. The protective circuit is used for protecting manufacturing of the circuit.
Description
Technical field
The present invention relates to electronic technology field, particularly relate to a kind of protective circuit, feedback unit and backlight drive circuit.
Background technology
Switching Power Supply utilizes power electronic technology, the duty ratio of the conducting of control switch pipe and cut-off, maintains a kind of power supply of regulated output voltage.In the backlight drive circuit of display; usually Switching Power Supply can be used as power supply in order to maintain regulated output voltage; and further in order to simplify the use of Switching Power Supply design, Convenient switch power supply; usually the control circuit of the high-pressure modulars such as integrated high voltage switching tube, high-voltage starting circuit and Switching Power Supply can be loaded and form switching power source chip in a package; this causes switching power source chip having occurred high pressure pin, and these high pressure pins can connect the high voltage sourcies such as large electrolysis, Transformer Winding.In addition, power supply chip also comprises a feedback (English full name: FeedBack, abbreviation: FB) pin; The feedback signal that FB pin exports for receiving photoelectrical coupler, thus the output of control switch power supply.But; when chip break down cause high pressure pin and the short circuit of FB pin time; to be broken down by high-voltage after shorted to earth before main fuse fuse protection during this period of time at be not broken down by high-voltage shorted to earth and FB pin of FB pin; high tension voltage can pour in photoelectrical coupler; cause the insulating properties of photoelectrical coupler to be damaged, and then cause the dielectric strength of the backlight drive circuit of display defective.
Exemplary, with reference to shown in Fig. 1, comprising integrated metal-oxide semiconductor tube (English full name: metal-oxidesemiconductor is called for short: metal-oxide-semiconductor) reverse exciting switching voltage regulator with the backlight drive circuit of display in Fig. 1 is that example is described.Concrete, this circuit comprises: flyback transformer 11, switching power source chip 12 and photoelectrical coupler 13, operating circuit 14; Wherein, the high pressure pin D of switching power source chip 12 connects the elementary of flyback transformer 11, the secondary of flyback transformer 11 is connected with operating circuit, and one end of photoelectrical coupler 13 is connected with operating circuit 14, and the other end is connected with the FB pin of switching power source chip 12.When backlight drive circuit normally works, photoelectrical coupler 13 1 aspect plays and feeds back to switching power source chip 12 to the operating state of operating circuit 14, play the effect blocking high pressure and operating circuit on the other hand, make operating circuit be in area of low pressure, avoid user to get an electric shock.And when the FB pin of switching power source chip 12 and the D short circuit of high pressure pin, the high tension voltage that flyback transformer 11 exports will pour in photoelectrical coupler 13, and high pressure pours in damage and even burns photoelectrical coupler, destroy the insulating properties of photoelectrical coupler, make photoelectrical coupler cannot continue to play the effect blocking high pressure and circuit downstream, now, user may get an electric shock.
To sum up, backlight drive circuit of the prior art in use user have electric shock risk.
Summary of the invention
Embodiments of the invention provide a kind of protective circuit, feedback unit and backlight drive circuit, for reducing the electric shock risk of user.
For achieving the above object, embodiments of the invention adopt following technical scheme:
First aspect, provides a kind of protective circuit, comprising: voltage input end, voltage output end, the first level end and division module, and described division module connects described voltage input end, voltage output end and the first level end;
When described voltage input end inputs the first voltage, described division module is used for described voltage input end and described voltage output end conducting;
When described voltage input end inputs the second voltage, described division module is used for described voltage input end and described first level end conducting, is discharged to described voltage output end by described first level end;
Wherein, described second voltage is greater than described first voltage.
Second aspect, provides a kind of feedback unit, and described feedback unit comprises: protective circuit, switch chip and photoelectrical coupler;
Wherein, described protective circuit is the protective circuit described in first aspect; Described switch chip comprises high pressure pin and feedback pin, and the feedback pin of described switch chip is connected with the voltage input end of described protective circuit; When described switch chip normally works, described feedback pin exports the first voltage, and when described high pressure pin and described feedback pin short circuit, described feedback pin exports the second voltage; Described photoelectrical coupler is connected with the voltage output end of described protective circuit.
The third aspect, provides a kind of backlight drive circuit, comprises the feedback unit described in second aspect.
The protective circuit that the embodiment of the present invention provides, feedback unit and backlight drive circuit comprise: voltage input end, voltage output end, first level end and division module, division module connects voltage input end, voltage output end, first level end, and division module can by voltage input end and voltage output end conducting when voltage input end inputs the first voltage, when voltage input end inputs the second voltage, by voltage input end and the first level end conducting, so division module can ensure the normal work of circuit when voltage output end exports the first voltage, and when voltage input end input is greater than the second voltage of the first voltage, by the second potential conduction to the first level end, by described first level end, described voltage output end is discharged, the voltage reducing voltage output end exports, so embodiments of the invention can reduce the electric shock risk of user.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is the schematic diagram of prior art breaker in middle power supply;
The schematic diagram of the protective circuit that Fig. 2 provides for the embodiment of the present invention;
The schematic diagram of the another kind of protective circuit that Fig. 3 provides for the embodiment of the present invention;
The schematic diagram of the another kind of protective circuit that Fig. 4 provides for the embodiment of the present invention;
The circuit diagram of the protective circuit that Fig. 5 provides for the embodiment of the present invention;
The circuit diagram of the another kind of protective circuit that Fig. 6 provides for the embodiment of the present invention;
The circuit diagram of the another kind of protective circuit that Fig. 7 provides for the embodiment of the present invention;
The circuit diagram of the another kind of protective circuit that Fig. 8 provides for the embodiment of the present invention;
The another kind of protective circuit circuit diagram that Fig. 9 provides for the embodiment of the present invention;
The schematic diagram of the feedback unit that Figure 10 provides for the embodiment of the present invention;
The schematic diagram of the backlight drive circuit that Figure 11 provides for the embodiment of the present invention;
The circuit diagram of the another kind of backlight drive circuit that Figure 12 provides for the embodiment of the present invention.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.
It should be noted that, for the ease of the technical scheme of the clear description embodiment of the present invention, in an embodiment of the present invention, have employed the printed words such as " first ", " second " to distinguish the substantially identical identical entry of function and efficacy or similar item, it will be appreciated by those skilled in the art that the printed words such as " first ", " second " are not limiting quantity and execution order.
The triode adopted in all embodiments of the present invention can be thin-film transistor or field effect transistor or the identical device of other characteristics.In embodiments of the present invention, for distinguishing triode the two poles of the earth except base stage, wherein will be called first end by collector electrode, emitter is called the second end.Specify that the intermediate ends of transistor is base stage, signal input part is collector electrode, signal output part is emitter by the form in accompanying drawing.In addition the switching transistor that the embodiment of the present invention adopts is N-type switch triode, and N-type switching transistor is the conducting when base stage is high level, ends when base stage is low level.Unidirectional triode, then except the characteristic except having above-mentioned triode, also has electric current can only flow to emitter characteristic from collector electrode.
In addition, the voltage stabilizing didoe adopted in all embodiments of the present invention is one-way conduction within the scope of certain voltage, namely electric current is only allowed to flow to the negative electrode of voltage stabilizing didoe from the anode of voltage stabilizing didoe, but when the reverse voltage of voltage stabilizing didoe negative electrode and positive electrode is greater than the puncture voltage of voltage stabilizing didoe, voltage stabilizing didoe can be reversed and puncture, and now electric current can flow to the anode of voltage stabilizing didoe from the negative electrode of voltage stabilizing didoe.
Concrete, with reference to shown in Fig. 2, the bright embodiment of this law provides a kind of protective circuit, and comprising: voltage input end Vin, voltage output end Vout, the first level end V1 and division module 21, division module 21 connects described voltage input end Vin, voltage output end Vout and the first level end V1;
When voltage input end Vin inputs the first voltage, division module 22 is for by voltage input end Vin and voltage output end Vout conducting;
When voltage input end Vin inputs the second voltage, division module 22, for by voltage input end Vin and the first level end V1 conducting, is discharged to voltage output end Vout by described first level end V1;
Wherein, the second voltage is greater than the first voltage.
It should be noted that, the first voltage and the second voltage can be all a fixing magnitude of voltage, can also for the voltage range fluctuated within the specific limits.Exemplary, voltage input end Vin can the feedback pin of connecting valve chip, voltage output end can connect photoelectrical coupler, first voltage is through division module conduction and the photoelectrical coupler that can make after dividing potential drop carries out the voltage range of Normal Feedback, and the second voltage is when being feedback pin short circuit high pressure pin, the voltage range of high pressure pin; When the second voltage pours in photoelectrical coupler, then may damage photoelectrical coupler, destroy the insulating properties of photoelectrical coupler, make photoelectrical coupler cannot continue to play blocking-up high pressure, now, user has electric shock risk.
The protective circuit that the embodiment of the present invention provides, feedback unit and backlight, drive circuit comprises: voltage input end, voltage output end, first level end and division module, division module connects voltage input end, voltage output end, first level end, and division module can by voltage input end and voltage output end conducting when voltage input end inputs the first voltage, when voltage input end inputs the second voltage, by voltage input end and the first level end conducting, so division module can ensure the normal work of circuit when voltage output end exports the first voltage, and when voltage input end input is greater than the second voltage of the first voltage, by the second potential conduction to the first level end, by described first level end, described voltage output end is discharged, the electric current reducing voltage output end exports, so embodiments of the invention can reduce the electric shock risk of user.
Further, with reference to shown in Fig. 3, the protective circuit that above-described embodiment provides also comprises: clamper module 22;
The first end of clamper module 22 connects voltage output end Vout, and the second end of clamper module 22 connects the first level end V1,
When voltage input end Vin inputs the first voltage, clamper module 22 is for by voltage output end Vout and the first level end V1 open circuit;
When voltage input end Vin input the second voltage and division module 22 and the first level end V1 open circuit time, clamper module 22 is for making the voltage difference of the described voltage output end Vout of maintenance and first end flush end V1.
The protective circuit that above-described embodiment provides inputs the second voltage and the second voltage makes division module and the first level end open circuit at voltage input end Vin; division module cannot by high second potential conduction to the first level end time; clamper module can the voltage of clamper division module voltage output end; what make the second end of division module keeps stable with the voltage difference of the first level end V1; the voltage that voltage output end namely can be made to input circuit downstream keeps stable; thus the second voltage can be avoided further to pour in circuit downstream, so the electric shock risk of user can be reduced further.
Concrete, with reference to shown in Fig. 4, the division module 21 that above-described embodiment provides comprises: the first resistance R1, resistance unit R, the first voltage stabilizing didoe VZ1 and triode M1;
The first end of the first resistance R1 connects voltage input end Vin, and second end of the first resistance R1 connects the negative electrode of the first voltage stabilizing didoe VZ1;
The base stage of the anode connecting triode M1 of the first voltage stabilizing didoe VZ1;
The first end of resistance unit R connects second end of the first resistance R1; The first end of the second end connecting triode M1 of resistance unit R;
Second end of triode M1 connects the first level end V1;
Voltage output end Vout is connected with second end of the first resistance R1;
Wherein, the reverse breakdown voltage of described first voltage stabilizing didoe VZ1 is greater than described first voltage and is less than described second voltage.
Below, with reference to circuit diagram shown in Fig. 4, the operation principle of the protective circuit that above-described embodiment provides is described.Wherein, the first level end V1 provides low level, exemplary, and the first level end can be ground connection.The feedback pin FB of voltage input end Vin connecting valve chip, voltage output end connects photoelectrical coupler, first voltage is the voltage that the feedback pin of switch chip switch chip when normally working exports, second voltage is the feedback pin of switch chip and high pressure pin when there is short circuit, and the voltage that the feedback pin of switch chip exports is that example is described.
When the feedback pin FB of switch chip exports the first voltage, because the first voltage is less than the reverse breakdown voltage of the first voltage stabilizing didoe VZ1, so the first voltage stabilizing didoe VZ1 ends, the base stage low level of triode M1, triode M1 ends; Electric current flows to photoelectrical coupler by the feedback pin of switch chip, thus ensure that the normal work of circuit.
When the feedback pin of switch chip exports the second voltage, first, because the second voltage is greater than the reverse breakdown voltage of the first voltage stabilizing didoe VZ1, first voltage stabilizing didoe VZ1 is inverted and punctures, the base stage high level of triode M1, triode saturation conduction, electric current flows to the first level end after the first resistance R1 and resistance unit R.If the first resistance R1 is burnt open circuit, the then feedback pin FB of switch chip and photoelectrical coupler open circuit, second voltage can not enter photoelectrical coupler, if resistance R1 and R is burnt open circuit, division module connects feedback pin and the first level end V1 by the loop of the first resistance R1, resistance unit R and triode M1 composition, by the first level end V1, feedback pin FB is discharged, the voltage being entered photoelectrical coupler by voltage output end Vout can be reduced equally.
It should be noted that, the concrete structure of the division module provided in above-described embodiment to be only in the invention process one preferred embodiment, those skilled in the art are in the technical scope that the present invention discloses, and the change that can expect easily or replacement can as the division module in the embodiment of the present invention.Such as: in the connection line of division module series resistance or at the two ends of resistance again a resistance in parallel all belong to the change or replacement that those skilled in the art can expect easily.
Further, with reference to shown in Fig. 5, clamper module 22 comprises: the second voltage stabilizing didoe VZ2;
The negative electrode of the second voltage stabilizing didoe VZ2 connects second end of the first resistance R1, and the anode of the second voltage stabilizing didoe VZ2 connects the first level end V1;
Wherein, the reverse breakdown voltage of the second voltage stabilizing didoe VZ2 is greater than described first voltage and is less than described second voltage.
Below, with reference to circuit diagram shown in Fig. 5, be described the operation principle of the protective circuit that above-described embodiment provides, wherein, provide low level with the first level end, exemplary, the first level end can be ground connection.The feedback pin FB of voltage input end Vin connecting valve chip, voltage output end connects photoelectrical coupler, first voltage is the voltage that the feedback pin of switch chip switch chip when normally working exports, second voltage is the feedback pin of switch chip and high pressure pin when there is short circuit, and the voltage that the feedback pin of switch chip exports is that example is described.
When the feedback pin FB of switch chip exports the first voltage, because the first voltage is less than the reverse breakdown voltage of the first voltage stabilizing didoe VZ1 and the second voltage stabilizing didoe VZ2, so the first voltage stabilizing didoe VZ1, the second voltage stabilizing didoe VZ2 all end, the base stage low level of triode M1, triode M1 ends; Electric current flows to photoelectrical coupler by the feedback pin FB of switch chip, thus ensure that the normal work of circuit.
When the feedback pin FB of switch chip exports the second voltage, first, because the second voltage is greater than the reverse breakdown voltage of the first voltage stabilizing didoe VZ1, first voltage stabilizing didoe VZ1 is inverted and punctures, the base stage high level of triode M1, triode saturation conduction, electric current flows to the first level end after the first resistance R1 and resistance unit R.If the first resistance R1 is first burnt open circuit, then the feedback pin FB of switch chip and photoelectrical coupler open circuit, the second voltage can not enter photoelectrical coupler; If resistance unit R is burnt open circuit prior to the first resistance R1, first resistance R1 and VZ2 forms clamp circuit, the voltage of the first resistance R1 second end can by clamper, the voltage difference of the first resistance R1 second end and the first level end is kept to stablize, and then making R1 burn open circuit, feedback pin and photoelectrical coupler open circuit second voltage of switch chip can not pour in photoelectrical coupler.
Further, with reference to shown in Fig. 6, resistance unit R comprises: the second resistance R2 and the 3rd resistance R3;
The first end of the second resistance R2 and the first end of the 3rd resistance R3 are all connected to second end of described first resistance R1, and second end of described second resistance R2 and second end of described 3rd resistance R3 are all connected to the first end of described first triode M1.
It should be noted that, above mentioned embodiment provide resistance unit and comprise the second resistance in parallel and the scheme of the 3rd resistance, but resistance unit comprises a kind of implementation that the second in parallel resistance and the 3rd resistance are only the embodiment of the present invention, and can not as the restriction to the embodiment of the present invention, resistance unit can also only include a resistance, or comprises plural parallel connection or series resistance.Because in the manufacturing process of protective circuit; the resistance of resistance unit R is determined jointly by multiple factor such as resistance, the occurrence of the first voltage, the occurrence of the second voltage of the first resistance R1; so the resistance of resistance unit may be a specific resistance in the manufacturing process of side circuit; and the resistance of a resistance possibly cannot reach the demand of protective circuit to resistance unit resistance; and more resistance can be combined into by the resistant series of more than two or parallel connection, and then to be more suitable in protective resistance circuit resistance unit to the demand of different resistance.
Further, with reference to shown in Fig. 7, division module also comprises: the 4th resistance R4;
Between the anode that 4th resistance R4 is series at the first voltage stabilizing didoe ZV1 and the base stage of triode M1.
When the first voltage stabilizing didoe ZV1 is inverted the base stage of puncture voltage arrival triode M1, triode M1 may be damaged because electric current is excessive, and the 4th resistance R4 is set between triode at the first voltage stabilizing didoe ZV1, then can limit the electric current flowing through triode M1 base stage, thus avoid triode damaged.
Further, with reference to shown in Fig. 8, division module 21 also comprises: electric capacity C1 and the 5th resistance R5;
The base stage of the first pole connecting triode M1 of electric capacity C1, second pole of electric capacity C1 connects the first level end V1;
The base stage of the first end connecting triode M1 of the 5th resistance R5, second end of the 5th resistance R5 connects the first level end V1.
Interference source can be there is in the use procedure of protective circuit; voltage input end Vin may input the high pressure of moment; and the high pressure of moment may make to puncture the first voltage stabilizing didoe VZ1; make the base stage high level of triode M1; triode M1 malfunction conducting; drag down the voltage of low pressure input Vin, and then it is abnormal that circuit is occurred.The electric capacity C1 increased then can absorb the high pressure of moment, and is discharged gradually by energy by the 5th resistance R5, and then avoids and does not occur exception with circuit during high tension voltage terminal shortcircuit with voltage input end.
Preferably, with reference to shown in Fig. 9, clamper module also comprises: the 6th resistance R6; 6th resistance R6 is series between second end of the first resistance R1 and the negative electrode of the second voltage stabilizing didoe VZ2.
In above-mentioned enforcement, when resistance unit R is burnt open circuit, the second voltage stabilizing didoe VZ2 may be damaged because of the overtension of the first resistance R1 second end, the second voltage stabilizing didoe VZ2 is made not have the effect of the some position of clamper R1 second end, therefore connect the 6th resistance R6 between the first resistance R1 and the negative electrode of the second voltage stabilizing didoe VZ2, the voltage of the first resistance R1 second end entered again by the second voltage stabilizing didoe VZ2 clamper after the 6th resistance R6 dividing potential drop, thus avoided the second voltage stabilizing didoe VZ2 to be damaged by high pressure.
Preferably, the first resistance R1 in above-described embodiment and the maximum overload voltage of the 6th resistance R6 are all greater than 250V.
Usual alternating voltage is 220V, and voltage can be higher after entering over commutation, if the maximum overload voltage of resistance is too little, then resistance may be directly breakdown, and puncture rear high voltage and directly can get over resistance, so the maximum overload voltage arranging the first resistance and the 6th resistance is all greater than 250V.
Yet another embodiment of the invention provides a kind of feedback unit, concrete, and with reference to shown in Figure 10, this feedback unit comprises:
Protective circuit 101, switch chip 102 and photoelectrical coupler 103;
Wherein, the protective circuit that provides for above-mentioned any embodiment of described protective circuit 101.
Described switch chip 102 comprises high pressure pin FB and feedback pin D, and the feedback pin FB of described switch chip 102 is connected with the voltage input end Vin of described protective circuit 101; When described switch chip 102 normally works, described feedback pin FB exports the first voltage, and when described high pressure pin D and described feedback pin FB short circuit, described feedback pin FB exports the second voltage; Described photoelectrical coupler 103 is connected with the voltage output end Vout of described protective circuit 101.
The feedback unit that the embodiment of the present invention provides comprises: protective circuit, switch chip and photoelectrical coupler, wherein, the protective circuit that described protective circuit provides for above-mentioned any embodiment, described switch chip comprises high pressure pin FB and feedback pin, and the feedback pin of described switch chip is connected with the voltage input end of described protective circuit; When described switch chip normally works, described feedback pin exports the first voltage, and when described high pressure pin and described feedback pin short circuit, described feedback pin exports the second voltage; Described photoelectrical coupler is connected with the voltage output end of described protective circuit, so protective circuit by feedback pin and photoelectrical coupler conducting, can ensure the Normal Feedback of circuit when feedback pin exports the first voltage; And when feedback pin exports the second voltage, by feedback pin and the first level end conducting, by the first level end, feedback pin is discharged, avoid the second voltage and pour in photoelectrical coupler and the insulating properties destroying photoelectrical coupler, and then avoid making photoelectrical coupler cannot continue to play the effect blocking high pressure, so inventive embodiment can avoid the user caused when high pressure pin and feedback pin short circuit to get an electric shock, reduce the electric shock risk of user.
Yet another embodiment of the invention provides a kind of backlight drive circuit, and this backlight drive circuit comprises the feedback unit that above-described embodiment provides.
The feedback unit of the backlight drive circuit that the embodiment of the present invention provides comprises: protective circuit, switch chip and photoelectrical coupler, wherein, the protective circuit that described protective circuit provides for above-mentioned any embodiment, described switch chip comprises high pressure pin FB and feedback pin, and the feedback pin of described switch chip is connected with the voltage input end of described protective circuit; When described switch chip normally works, described feedback pin exports the first voltage, and when described high pressure pin and described feedback pin short circuit, described feedback pin exports the second voltage; Described photoelectrical coupler is connected with the voltage output end of described protective circuit, so protective circuit by feedback pin and photoelectrical coupler conducting, can ensure the Normal Feedback of circuit when feedback pin exports the first voltage; And when feedback pin exports the second voltage, by feedback pin and the first level end conducting, by the first level end, feedback pin is discharged, avoid the second voltage and pour in photoelectrical coupler and the insulating properties destroying photoelectrical coupler, and then avoid making photoelectrical coupler cannot continue to play the effect blocking high pressure, so inventive embodiment can avoid the user caused when high pressure pin and feedback pin short circuit to get an electric shock, reduce the electric shock risk of user.
Concrete, with reference to shown in Figure 11, this backlight drive circuit comprises:
PFC) 104, flyback transformer 105, power supply circuits 106 rectifying output circuit 107, testing circuit 108 and feedback module 110 (English full name: PowerFactorCorrector, is called for short: power factor corrector; Wherein, feedback module 110 specifically comprises: protective circuit 101, integrated MOS pipe switch chip 102 and photoelectrical coupler 103 are protected.
Wherein, power factor correction device 104 connects flyback transformer 105, for correcting the ratio of effective power and total power consumption.
Integrated MOS pipe switch chip 101 comprises: multiple source lead (being described to comprise 4 pins S1, S2, S3, S4 in figure), energization pins VCC, idle pin NA, feedback pin and high pressure pin D.Energization pins connects power supply circuits 106; Source lead ground connection; Feedback pin FB connects protective circuit 101, and high pressure pin D connects flyback transformer 105, and integrated MOS pipe switch chip 102 is for controlling the output voltage of flyback transformer device 105.
Flyback transformer 105 connects rectifying output circuit 107, for voltage being outputted to rectifying output circuit 107 under the control of integrated MOS pipe switch chip 102.
Power supply circuits 106 also connect flyback transformer 105, for powering to integrated MOS pipe switch chip 102.
Rectifying output circuit 107 is for the voltage commutation that inputs flyback transformer 105 and export.
Testing circuit 108 connects rectifying output circuit 107, and the voltage exported for exporting rectifying output circuit 107 to voltage detects, and the voltage detected and reference voltage is compared, the difference voltage of the voltage that output detections arrives and reference voltage.
Photoelectrical coupler 103 connection detection circuit 108, carry out opto-electronic conversion for the difference voltage exported by testing circuit 108.
Between the feedback pin FB that protective circuit 101 is connected to integrated MOS pipe switch chip 102 and photoelectrical coupler 103, the protective circuit that this protective circuit 101 can provide for above-mentioned any embodiment.
Further, with reference to shown in Figure 12, power factor corrector 104 comprises: diode VZ3, diode VZ4, electric capacity C2, electric capacity C3, resistance R7, resistance R8 and resistance R9, wherein, first pole of C2 connects ground connection, and second pole of C2 connects anode and the flyback transformer of VZ3, and the negative electrode of VZ3 connects the negative electrode of VZ4, R7, C3 are in parallel, one end connects the anode of VZ3, and the other end connects the negative electrode of VZ3, and R8 and R9 is in parallel, one end connects the anode of VZ4, and the second end connects flyback transformer.
Power supply circuits 106 comprise: resistance R10, resistance R11, resistance R12, resistance R13, electric capacity C4, electric capacity C5, electric capacity C6, diode VZ5, VZ6.Wherein, the first end of C4 connects energization pins, second end of C4 connects first pole of C5, and second pole of C5 connects second end of R11, and the first end of R10 connects the first end of C4, second end of R10 connects the first end of R11, the anode of VZ5 connects R10 first end, and the negative electrode of VZ5 connects R10 second end, and second end of R11 connects second electrical level end V2, be series between the anode of VZ6 and flyback transformer after negative electrode connection V2, R13 and the R13 parallel connection of VZ6.Exemplary.The voltage of second electrical level end V2 is 20V.
Rectifying output circuit 107 comprises: diode VZ7, electric capacity C7, electric capacity C8, electric capacity C9 and inductance L; Wherein, the anode of VZ7 connects flyback transformer, the negative electrode of VZ7 connects C7 first pole, C7 second pole ground connection, and C8 first pole connects C7 first pole, C8 second pole ground connection, C7, C8 are all connected with secondary voltage output end vo ut-1, and L first end connects C8 first pole, and L second end connects voltage output end Vout, C9 first pole connects voltage output end Vout, C9 second pole ground connection.
Testing circuit 108 comprises: resistance R14, resistance R15, resistance R16, resistance R17, resistance R18, resistance R19, electric capacity C10, electric capacity C11 and unidirectional triode T.Wherein, R14 first end connects photoelectrical coupler 108, R14 second end connects secondary voltage output end vo ut-1, R15 first end connects secondary voltage output end vo ut-1, R15 second end connects C10 first pole, R16 first end connects C11 second pole, second end of R16 connects R17 first end, R17 second end connects secondary voltage output end vo ut-1, R18 first end connects T base stage, R18 second end ground connection, R19 first end connects R16 second end, R19 second end ground connection, C10 first pole connects R15 second end, C10 second pole connects R18 first end, C11 first pole connects photoelectrical coupler 108, the collector electrode of T connects C10 first pole, the grounded emitter of T.
Photoelectrical coupler 103 comprises: light-emitting diode VZ8 and phototriode M2, and wherein VZ7 first end connects R14 first end, and VZ7 second end connects R15 second end; M3 base stage arranges the position relative with VZ7, and M2 first end connects protective circuit, the second end ground connection of M2.
Further, switching circuit can also comprise R20 and C12, first pole of C12 connects the feedback pin of integrated MOS switch chip 102, C12 second pole ground connection, and R20 first end connects the feedback pin of integrated MOS switch chip 102, R20 second pole ground connection.
Can there is interference in the course of the work at backlight drive circuit, C12 then can adjust the feedback speed of feedback unit, and R20 can open-circuit-protection time of extended back light drive circuit, so increase the stability that C12 and R20 can strengthen backlight drive circuit.
The above; be only the specific embodiment of the present invention, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.
Claims (11)
1. a protective circuit, is characterized in that, comprising: voltage input end, voltage output end, the first level end and division module, and described division module connects described voltage input end, voltage output end and the first level end;
When described voltage input end inputs the first voltage, described division module is used for described voltage input end and described voltage output end conducting;
When described voltage input end inputs the second voltage, described division module is used for described voltage input end and described first level end conducting, is discharged to described voltage output end by described first level end;
Wherein, described second voltage is greater than described first voltage.
2. protective circuit according to claim 1, is characterized in that, described circuit also comprises: clamper module;
The first end of described clamper module connects described voltage output end, and the second end of described clamper module connects described first level end;
When described voltage input end inputs the first voltage, described clamper module is used for described voltage output end and described first level end open circuit;
When described voltage input end input the second voltage and described division module and described first level end open circuit time, described clamper module is for keeping the voltage difference of described voltage output end and described first end flush end.
3. the protective circuit according to claim 1 or 2 any one, it is characterized in that, described division module comprises: the first resistance, resistance unit, the first voltage stabilizing didoe and triode;
The first end of described first resistance connects described voltage input end, and the second end of described first resistance connects the negative electrode of described first voltage stabilizing didoe;
The anode of described first voltage stabilizing didoe connects the base stage of described triode;
The first end of described resistance unit connects the second end of described first resistance; Second end of described resistance unit connects the first end of described triode;
Second end of described triode connects described first level end;
Described voltage output end is connected with the second end of described first resistance;
Wherein, the reverse breakdown voltage of described first voltage stabilizing didoe is greater than described first voltage and is less than described second voltage.
4. protective circuit according to claim 3, is characterized in that, described clamper module comprises: the second voltage stabilizing didoe;
The negative electrode of described second voltage stabilizing didoe connects the second end of described first resistance, and the anode of described second voltage stabilizing didoe connects described first level end;
Wherein, the reverse breakdown voltage of described second voltage stabilizing didoe is greater than described first voltage and is less than described second voltage.
5. protective circuit according to claim 4, is characterized in that, described resistance unit comprises: the second resistance and the 3rd resistance;
The first end of described second resistance and the first end of described 3rd resistance are all connected to the second end of described first resistance, and the second end of described second resistance and the second end of described 3rd resistance are all connected to the first end of described first triode.
6. protective circuit according to claim 4, is characterized in that, described division module also comprises: the 4th resistance;
Described 4th resistant series is between the anode and the base stage of described triode of described first voltage stabilizing didoe.
7. protective circuit according to claim 4, is characterized in that, described division module also comprises: electric capacity and the 5th resistance;
First pole of described electric capacity connects the base stage of described triode, and the second pole of described electric capacity connects described first level end;
The first end of described 5th resistance connects the base stage of described triode, and the second end of described 5th resistance connects described first level end.
8. protective circuit according to claim 4, is characterized in that, described clamper module also comprises: the 6th resistance;
Described 6th resistant series is between the second segment and the negative electrode of described second voltage stabilizing didoe of described first resistance.
9. protective circuit according to claim 8, is characterized in that, the maximum overload voltage of described first resistance and described 6th resistance is all greater than 250V.
10. a feedback unit, is characterized in that, described feedback unit comprises: protective circuit, switch chip and photoelectrical coupler;
Wherein, described protective circuit is the protective circuit described in any one of claim 1-9; Described switch chip comprises high pressure pin and feedback pin, and the feedback pin of described switch chip is connected with the voltage input end of described protective circuit; When described switch chip normally works, described feedback pin exports the first voltage, and when described high pressure pin and described feedback pin short circuit, described feedback pin exports the second voltage; Described photoelectrical coupler is connected with the voltage output end of described protective circuit.
11. 1 kinds of backlight drive circuits, is characterized in that, comprising: feedback unit according to claim 10.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510552443.6A CN105186843A (en) | 2015-09-01 | 2015-09-01 | Protective circuit, feedback unit and backlight drive circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510552443.6A CN105186843A (en) | 2015-09-01 | 2015-09-01 | Protective circuit, feedback unit and backlight drive circuit |
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| CN105186843A true CN105186843A (en) | 2015-12-23 |
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| CN201510552443.6A Pending CN105186843A (en) | 2015-09-01 | 2015-09-01 | Protective circuit, feedback unit and backlight drive circuit |
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