The content of the invention
Based on this, it is necessary to easily fuse in surge for fuse in the prior art, and tieed up after blown fuseThe problem of shield inconvenience, there is provided a kind of power filter protects circuit.
A kind of power filter protects circuit, including：Power input connectors, to connect input power；Safety element, stringIt is connected on the firewire of the power input connectors, when short circuit, the safety element self-heating enters high-impedance state, so thatSuppress electric current；After short trouble excludes, the safety element is restored to low resistive state automatically；Filter circuit, with the insuranceElement is connected, to filtering common mode noise and differential mode noise；Circuit is protected, is connected with the filter circuit, to absorb surge；Rectifier bridge, is connected, the alternating current the filter circuit to be exported is converted to the filter circuit and the protection circuitDirect current.
In one of the embodiments, the safety element is resettable fuse.
In one of the embodiments, institute's filter circuit includes two-stage differential mode filter circuit and two-stage common mode filtering electricityRoad, i.e. first order differential mode filter circuit, second level differential mode filter circuit, first order common mode filtering circuit, second level common mode filteringCircuit.
In one of the embodiments, the first order differential mode filter circuit includes：First filter capacitor, first filterThe first end of ripple capacitance connects firewire and the safety element, the second end connection zero curve of first filter capacitor at the same time；AltogetherMould inductance, the common mode inductance have two coils, four ports, and first end is located at the both ends of same coil with second end, and the 3rdEnd is located at the both ends of same coil with the 4th end, and the first end of the common mode inductance connects the first end of first capacitance, instituteThe 3rd end for stating common mode inductance connects the second end of first filter capacitor.
In one of the embodiments, the second level differential mode filter circuit includes：Second filter capacitor, second filterThe first end of ripple capacitance connects the second end of firewire and the common mode inductance, the second end of second filter capacitor at the same timeThe 4th end of zero curve and the common mode inductance is connected at the same time；First differential mode inductance, the first end connection of first differential mode inductanceThe first end of second capacitance；Second differential mode inductance, the first end of second differential mode inductance connect second capacitanceSecond end.
In one of the embodiments, the differential mode filter circuit includes：Two groups of protection components, to control wave filterQuality factor；The first end of first group of protection component connects the first end of firewire and the common mode inductance at the same time, and describedThe second end of one group of protection component connects the second end of the common mode inductance, and the first end of second group of protection component connects at the same timeThe 3rd end of zero curve and the common mode inductance is connect, the second end of second group of protection component connects the 4th of the common mode inductance theEnd.
In one of the embodiments, the first order common mode filtering circuit includes：Common mode inductance；3rd filter capacitor,The first end of 3rd filter capacitor connects the second end of the common mode inductance, the second termination of the 3rd filter capacitorGround；4th filter capacitor, the first end of the 4th filter capacitor connect the 4th end of the common mode inductance, the 4th filteringThe second end ground connection of capacitance.
In one of the embodiments, the second level common mode filtering circuit includes：First differential mode inductance, the second differential mode electricitySense；5th filter capacitor, the first end of the 5th filter capacitor connect the second end of first differential mode inductance；First protectionResistance, the first end of first protective resistance connect the second end of the 5th filter capacitor, first protective resistanceSecond end is grounded；6th filter capacitor, the first end of the 6th filter capacitor connect the second end of second differential mode inductance；Second protective resistance, the first end of second protective resistance connect the second end of the 6th filter capacitor, and described second protectsProtect the second end ground connection of resistance.
In one of the embodiments, the protection circuit includes：First protects branch and protects branch with described firstSecond protection branch in parallel；Described first protects branch to include the first discharge tube and connect with first discharge tube firstVaristor, the first discharge tube first end are connected to the second end of the common mode inductance, and the second of first discharge tubeEnd is connected to the first end of first varistor, and the second end of first varistor is connected to the common mode inductance4th end；The second varistor that the second protection branch includes the second discharge tube and connects with second discharge tube, instituteThe second end that the second discharge tube first end is connected to first differential mode inductance is stated, the second end of second discharge tube is connected toThe first end of second varistor, the second end of second varistor are connected to the second of second differential mode inductanceEnd.
In one of the embodiments, the circuit element for forming the filter circuit, protection circuit and rectifier bridge is patchPiece element.
The application has the advantages that：
The safety element that above-mentioned power filter protection circuit uses can reset into low-resistance shape automatically after fault exclusionState, avoids and replaces the inconvenience that fuse is brought.
Circuit element of the above-mentioned power filter protection circuit in addition to resettable fuse uses surface mount elements, has volumeSmall, the advantages of cost is low.
Embodiment
In order to make the purpose , technical scheme and advantage of the present invention be clearer, by the following examples, and combine attachedFigure, is further elaborated the inductive ballast circuit of the present invention.It should be appreciated that specific embodiment described hereinOnly to explain the present invention, it is not intended to limit the present invention.
It should be noted that when an element is considered as " connection " another element, it can be directly to separatelyOne element may be simultaneously present centering elements.On the contrary, when element is connected referred to as " direct " with another element, do not depositIn intermediary element.
One embodiment of the application provides a kind of power filter protection circuit, available for air standard DO-160G and 75WQuasi-resonance flyback power supply.Circuit uses resettable fuse, and when the overcurrent overheat failure of circuit is excluded, self- recoverage insuresSilk can reset into low resistance state automatically, and nothing needs to change, easy to use, is capable of the safety of protection power source system.
A kind of power filter protects circuit, including：Power input connectors, to connect input power.It is serially connected with power supplyInsurance device on the firewire of input connector, to provide overcurrent protection for power supply.The filtered electrical being connected with insurance deviceRoad, to filtering common mode noise and differential mode noise.The protection circuit being connected with filter circuit, to absorb surge protection power supply.The rectifier bridge being connected with protection circuit, filtered alternating current is converted to direct current.
Power input connectors are a kind of devices for allowing electric power to realize flowing in circuit.Power input connectors lead toCross and be connected on main power source to obtain electric current.In one embodiment of the application, main power source is 115V alternating currents.In the applicationOne embodiment in, power input connectors J1 has four ports.Wherein, first port and second port connect fire respectivelyLine and zero curve, the 3rd port and the 4th port ground connection.
In the another embodiment of the application, the input terminal of power input connectors can access High frequency filter element to filterExcept hyperfrequency noise.The application selects high frequency magnetic bead as filter element.Magnetic bead is the coil of single turn, i.e. single turn inductors.ThereforeInductance value is small, high thus relatively good to the inhibitory action of high frequency with the resonant frequency of its parasitic capacitance.In the application, by twoMagnetic bead FB1, FB2 are connected on two input ports of power input connectors respectively.The wherein first end of FB1 is connected to power inputOn the port of connector firewire, the first end of FB2 is connected on the port of power input connectors zero curve.
It is protection element most basic in electronic circuit to insure device, and in power supply, insurance device is connected on input circuitFront end.Its effect is exactly when input current has exceeded the rated current of insurance device, cuts off AC power in time, prevents eventBarrier further expands.
In one embodiment of the application, the insurance device used is resettable fuse F1.Resettable fuse F1It is polymer resin by specially treated and is distributed in the conducting particles composition of the inside.Polymer resin is closely under normal operationConducting particles is strapped in outside crystalloid structure, forms chain conduction electric pathway, resettable fuse F1 at this time is low-resistanceState, it is small to flow through thermal energy caused by the electric current of resettable fuse on circuit, will not change crystal structure.When circuit generation is shortWhen road or overload, flowing through the heat of the high current generation of resettable fuse F1 melts polymer resin, and volume increases rapidly, shapeInto high-impedance state, operating current reduces rapidly, so as to be limited circuit and be protected.When the overcurrent and overheating fault of circuit are arrangedAfter removing, resettable fuse F1 resets into low resistance state automatically.Both avoid maintenance to replace, it also avoid circuit may being caused to damagePersistent loop open and-shut mode.Specifically, in the embodiment that the application provides, it is defeated that resettable fuse F1 is serially connected in power supplyEnter on the firewire at end.The second end of its first end connection magnetic bead FB1, second end are connected with filter circuit.
Since noise can impact device, cause circuit operation irregularity, reduce the service life of device.Therefore needPower grid filters out noise between equipment plus filter circuit.One embodiment of the application provides a kind of filter circuit, canFiltering common mode noise and differential mode noise.
Specifically, the filter circuit includes two-stage differential mode filter circuit and two-stage common mode filtering circuit, i.e. first order differential modeFilter circuit, second level differential mode filter circuit, first order common mode filtering circuit and second level common mode filtering circuit.
First order differential mode filter circuit is made of the first filter capacitor C1 and common mode inductance L1.First filter capacitor C1 connectionsBetween zero curve and firewire.The first end of first filter capacitor C1 connects the second end of resettable fuse F1, common mode electricity at the same timeFeel the first end and firewire of L1, the second end of the first filter capacitor C1 connects the second end of magnetic bead FB2, common mode inductance L1 at the same time3rd end and zero curve.First order differential mode filter circuit further includes common mode inductance L1.Common mode inductance L1 is wound on same by two windingsFormed on iron core, share four ports.Wherein, first port 1 and second port 2 are on same coil, the 3rd port 3 and the 4thPort 4 is on same coil.Since common mode inductance L1 there are two windings, there is gap between the two windings, therefore leakage can be causedSense, this leakage inductance is differential mode inductance.When differential-mode current is flowed through, differential mode noise can be filtered out.
Second level differential mode filter circuit is by the second filter capacitor C2 and the first differential mode inductance L2, the second differential mode inductance L3 groupsInto.Second filter capacitor C2 is connected between zero curve and firewire.It is poor that the first end of second filter capacitor C2 connects first at the same timeThe first end and firewire of mould inductance L2, the second end of the second filter capacitor C2 connect at the same time the second differential mode inductance L3 first end andZero curve.Differential mode inductors L2, L3 and filter capacitor C2 circuits in series.Since the characteristic of inductance is that logical low frequency hinders high frequency, electricityThe characteristic of appearance is logical high frequency, resistance low frequency.Differential mode inductance L2, L3 are big to the induction reactance of differential mode High-frequency Interference, and filter capacitor C2 is X electricityHold, the capacitive reactance to differential mode High-frequency Interference is small, therefore can be with the high frequency differential mode noise in filtering circuit.
More specifically, the first filter capacitor C1 and the second filter capacitor C2 is safety capacitance, and is all X2 capacitances.X2 electricityAppearance can suppress powered electromagnetic interference, high pressure resistant for eliminating differential mode noise.The first filter capacitor C1 in the present embodiment andThe capacity of two filter capacitor C2 is 0.1uF, model C2220.
Two-stage differential mode filter circuit further includes protection component, for controlling the quality factor of wave filter, i.e. Q values, while canThere is spike to avoid frequency response.Specifically, the protection component employed in the present embodiment is two groups of resistance.First group of resistanceComprising tri- resistance of R1, R2, R3, a winding both ends of common mode inductance F1 are then parallelly connected with after three resistance series connection.Second group of electricityResistance includes tri- resistance of R4, R5, R6, and another winding both ends of common mode inductance F1 are then parallelly connected with after three resistance series connection.SixThe resistance value of resistance is identical, is 10k Ω, model R0805.
Due to the influence of external magnetic field, induced voltage can be produced on conducting wire, and then produce electric current.On the other hand, due to leadingThere is potential difference between line and ground wire, common mode current can be produced on conducting wire.If equipment produces common mode current, cable on device cableStrong electromagnetic radiation can be produced, causes equipment to meet the limitation requirement in electromagnetic compatibility standard to radiation-emitting, also canInterference is produced to other equipment.Therefore need to eliminate the interference that common mode current produces in circuit.
One embodiment of the application provides two-stage common mode filtering circuit, including first order common mode filtering circuit and the second levelCommon mode filtering circuit.
First order common mode filtering circuit includes common mode inductance L1, the 3rd capacitance C3, the 4th capacitance C4.The of 3rd capacitance C3The second end of one end connection common mode inductance L1, the second end ground connection of the 3rd capacitance C3.The first end connection common mode of 4th capacitance C4The 4th end of inductance L1, the second end ground connection of the 4th capacitance C4.
When common mode current flows through common mode inductance L1, common mode current flowing in two windings of common mode inductance L1 is identical,The magnetic direction that electric current in two windings produces is identical, increases the inductance value of two windings, namely increases winding to altogetherThe induction reactance of mould electric current.Big induction reactance is suppressed common mode current, has reached attenuation common-mode electric current, the mesh of suppression common mode noise's.
More specifically, the 3rd capacitance C3, the 4th capacitance C4 are safety capacitance, and are all Y2 capacitances, and capacity is2.2nF, model C1812.Plus filter actions of two Y capacitance C3 and C4 to common mode interference noise, obtain common mode interferenceObvious suppression.
Second level common mode filtering circuit includes the first differential mode inductance L2, the second differential mode inductance L3, the 5th capacitance C5, the 6th electricityHold C6, the first protective resistance R7, the second protective resistance R8.The second end of first differential mode inductance L2 connects the first of the 5th capacitance C5End.The second end of 5th capacitance C5 connects the first end of the first protective resistance R7.The second end ground connection of first protective resistance R7.TheThe second end of two differential mode inductance L3 connects the first end of the 6th capacitance C6.The second end of 6th capacitance C6 connects the second protective resistanceThe first end of R8.The second end ground connection of second protective resistance R8.
After first order common mode filtering circuit filters out most of common mode interference, second level common mode filtering circuit filters out remainderDisturb part.When common mode current flows through second level common mode filtering circuit, the magnetic flux increase in differential mode inductance, and then can press downCommon mode current processed, filtering common mode interference.Protective resistance R7, R8 is used for the Q values for controlling wave filter, avoids frequency response from point occurPeak.
More specifically, the 5th capacitance C5, the 6th capacitance C6 are safety A Rong, and are all Y capacitance, capacity 4.7nF,Model C1812.First differential mode inductance L2, the inductance value of the second differential mode inductance L3 are 820uH.The resistance of protective resistance R7, R8Value is 100 Ω.
Under conditions of electrical technology index meets the requirements, in order to make power supply pacify in the case of adverse circumstances and catastrophic failureReliably work entirely, multi-level protection circuit need to be designed.In one embodiment of the application, wave is absorbed using dual-electrode protecting circuitGush and thunder and lightning.Wherein, first order protection circuit includes the first discharge tube GD2 and the first varistor RV1.
Specifically, the first discharge tube GD2 first ends are connected to the second end of common mode inductance L1.The of first discharge tube GD2Two ends are connected to the first end of the first varistor RV1.The second end of first varistor RV1 is connected to the of common mode inductance L1Four ends.
Since varistor has larger parasitic capacitance, when alternating current flows through, current leakage can be produced.And useAfter a period of time, parasitic capacitance becomes larger, and causes Leakage Current to become larger, and then causes varistor fever self-destruction.Therefore use electric dischargePipe is connected with varistor.Discharge tube has less parasitic capacitance, and the total capacitance of series arm can be made to be reduced to several pico farads,And then reduce leakage current.In embodiments herein, the first discharge tube GD2 is gas-discharge tube.First discharge tube GD2 canAs switch, when no transient voltage, first gas discharge tube is short-circuit condition, and the first varistor is separated from circuit,Make varistor almost without leakage current.Make conducting wire there are during surge pulse when running into lightning stroke, if pulse voltage is less than pressure-sensitiveThe threshold voltage of resistance, varistor flow through the electric current very little of varistor equivalent to the resistance of resistance value infinity.Therefore there is waveWhen gushing pulse, varistor can absorb surge protection circuit.
Second level protection circuit includes the second discharge tube GD2 and the first varistor RV1.The second discharge tube first endThe second end of first differential mode inductance is connected to, the second end of second discharge tube is connected to second varistorFirst end, the second end of second varistor are connected to the second end of second differential mode inductance.
The operation principle of second level protection branch protects branch with the first order, and details are not described herein.
Patch rectifier bridge D13 is connected to filter circuit and protects the output terminal of circuit, filtered alternating current to be turnedDirect current is changed to, and direct current is conveyed to electrical appliance.
Fig. 2 is referred to, the application has the advantages that small, technique is simple using pcb board connection circuit element.CircuitIn inductance use chip inductor, its operating temperature is up to 150 DEG C.Capacitance selects X, Y ceramic paster capacitance, operating temperatureUp to 125 DEG C.In addition to resettable fuse F1, the equal selection work temperature of remaining original paper is low up to 125 DEG C of surface mount elements, cost.Above surface mount elements and cabling are placed in the top layer of pcb board.The second layer of pcb board is large area copper sheet, for being grounded, is risen at the same timeTo shielding outside electromagnetic interference effect.Third layer is large area copper sheet in addition to a small amount of cabling, for being grounded.Bottom places plug-in unit memberPart resettable fuse F1.The PCB circuit board that the application provides uses vacuum glue pouring technique, and glue is organosilicon heat conduction embeddingGlue.The operating temperature range of glue is at -60 DEG C to 220 DEG C, thermal conductivity factor 0.9W/MK.Therefore, it is possible to reinforced insulation with dissipatingHeat.The distance between cabling is reduced at the same time, and then reduces the volume of circuit.And casting glue plays very to shaking and impactingGood protective action.
Embodiment described above only expresses the several embodiments of the present invention, its description is more specific and detailed, but simultaneouslyTherefore the limitation to the scope of the claims of the present invention cannot be interpreted as.It should be pointed out that for those of ordinary skill in the artFor, without departing from the inventive concept of the premise, various modifications and improvements can be made, these belong to the guarantor of the present inventionProtect scope.Therefore, the protection domain of patent of the present invention should be determined by the appended claims.