Be based on pilot of peak value electric current the application of complete bridge transformer in welder of high frequency inversion

Time:2023-06-14 11:50:10
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source:KAIHER CNC Machining

Summary: The complete bridge that designed a kind to be based on peak value electric current to control mode moves syntonic transformer. Use special move photograph chip UC3879 serves as advocate charge unit, realize complete bridge transformer move photograph control and advocate the ZVS of switch parts of an apparatus. The circuit of control of welder external characteristic that matchs syncretic to decide and peak value electric current detect technology, successful trial-produce the prototype of power source of solder of arc of high frequency inversion of a 6kW/l00kHz, gave out finally relevant circuit graph and experimental weaveform. Keyword: Peak value electric current is controlled; Move to be controlled; Brae compensation; 0 voltage switch; Electric welder of inversion welder foreword is industrial ox produce and machine the equipment with indispensable domain, among them because inversion welder has volume small, weight good, trends answers function of light, control fast, come true easily solder the superior performance such as the real time control of the process, the main trend that makes welder product develops way. Job of product of major inversion welder is in on purpose market hard switch condition, switch loss is severe, switch frequency limitation puts a few KHz to a few KHz, cannot develop the characteristic of inversion welder miniaturization and portable sex completely. Additional, welder kind the power consumption of equipment takes our country year generate electricity the 5 ‰ of gross, be labelled one of products of 10 big tall specific power consumption. Accordingly, technology of will soft switch introduces inversion welder domain, to reducing switch loss, increase switch frequency, reduce bulk weight and managing the sources of energy to wait have crucial effect. Complete bridge transformer because the characteristic of oneself structure, can work to fall at a variety of soft switch mode conveniently, have rating of voltage of power parts of an apparatus utilization rate of small, transformer inductance of wave of tall, filter is small wait for an advantage, and can work in voltage, electric current two kinds of mode fall. Among them on the control that voltaic mode suits to apply in welder of high frequency inversion particularly. Accordingly, the complete bridge that the article designed a kind to be based on peak value electric current to control mode moves power source of solder of arc of syntonic inversion. The complete bridge that 1 structure composition and function are based on mode of peak value electric current moves if the structural block diagram of system of power source of solder of arc of syntonic inversion pursues 1 is shown. The as complete bridge inverter dc after wave of filter of commutate of classics of report of 220V communication town is inputted, its output is arteries and veins wide square wave of adjustable high frequency alternating voltage, after keeping apart step-down through high frequency transformer, repass outputs the direct current source that rectification filter wave gets satisfaction soldering asking. Be based on pilot of peak value electric current to move to dominate circuit is the core part that whole system designs. Electric current of so-called peak value is controlled, namely limitation of electric current of pulse of one by one, the electric current that has shed transformer former edge through detecting in real time namely is undee, by its peak value arrives given the width that always decides to output PWM pulse. Make winner switch is in charge of guide electrify sheds transient state value to have opposite independent character. Can the curve of character of ideal electric current that apace obtains welder T to make place need. Raise its trends to answer speed and dependability. Conduce to overcome complete bridge transformer place solid some slants magnetism problem. Peak value of electric current of former edge of basis of circuit of external characteristic control and the feedback quantity that deputy edge exports voltage and the error that give an amount judge systematic operating mode, output arteries and veins through moving to control circuit adjustment wide, realize the closed-loop control to exporting electricity, the working character curve that makes inversion welder has ideal. The graph shows the external characteristic curve that the constant current of a kind of effective that uses generally for place of welder of high frequency inversion namely pulls outside the belt 2 times. Among them Uk is carry voltage for nothing, namely the output voltage when welder does not work. A taller sky carries voltage to conduce to phase removing arc building stable working position quickly. Ordinary air carries voltage to be 90V left and right sides; AB paragraph to have arc level, namely welder builds working position transfer process, approximate Yu Heng presses output. The transformer in this process with wide output of the biggest arteries and veins, when achieving set job electric current with the rapiddest rate, this phases ends; BC paragraph to stabilize working level, it is constant current process approximately, make welder has a smooth, constant job electricity; CD paragraph level procrastinates outside be, because welder is in,the frequent welding torch in having arc and working process is mixed very easily adhesion of workpiece short circuit, cause solder the process is not smooth, if right now the system detects,an inferior short circuit can increase cost of output electric current accordingly after voltage, OK adhesion part fusing, obtain thereby successive, smooth solder process. In addition, this system still includes a series of inputs to pass, owe pressure protection, shed protection, short circuit too protection and give electric current and switch of real work electric current to show wait for a function. The complete bridge transformer that 2 main circuit design this systematic place to use develop attacks the structure is shown 3 times like the graph. MOSFET was chosen to make in main circuit give priority to power switch parts of an apparatus, because the design frequency of this system is 100 KHz,this is, and as general as IGBT top job is compared in photograph of a few KHz, the working frequency of MOSFET wants many tall. Because MOSFET oneself is contained,turn over shunt-wound diode and larger output electric capacity additionally, if pursue 3 in place of D1 ～ D4, C1~C4 is shown, the implementation that is soft switch offerred convenience condition. Structure of commutate of output of transformer deputy edge has complete wave commutate (transformer deputy edge 3 take a percentage of a deal + two diode) with complete bridge commutate (transformer deputy edge two take a percentage of a deal + 4 diode) two kinds of structures can offer an alternative, former agree with the circumstance that exports low-pressure big electricity, latter agrees with circumstance of small electric current of output high pressure. Because inversion welder can be regarded,be a low-pressure big current source. Because this chooses complete wave commutate. This plan is chosen move the control means of the photograph, agree with quite choose MOSFET to make the develop that gives priority to switch attack structure. Its job process can be divided roughly transmit phase of resonance of arm of phase of level, lead arm resonance, circumfluent phase, lag and electricity for power a few processes such as retrorse phase. Those who need ambitious shift is, in phase of lag arm resonance, because D5 and D6 are changed at the same time,shed short circuit of will deputy edge, lf of inductance of output filter wave cannot assist Llk of feeling of leakage of transformer former edge to participate in syntonic process, because this lag arm is soft,switch requirement is satisfied not easily. With convention complete bridge transformer is compared, this plan did following improvement on circuit structure. (1) is on the foundation of Llk, former edge strings together Ls of an auxiliary and syntonic inductance. This conduces to in overcoming process of lag arm resonance, only Llk participates in resonance alone, bring about limits of syntonic energy inadequacy, soft switch to suffer bounds defect. But another and, it is good that former edge electric current hopes former edge inductance is worth Yue Xiaoyue again in retrorse process, in order to increase electric current metabolic slope, reduce take sky comparing loss. Because this assists the size of syntonic inductance to want balance after all sorts of elements reasonable choose, had better use saturated inductance, can move voice adjustment conveniently. (2) former edge is strung together lie between straight capacitance C5 without polarity. The transformer when complete bridge transformer works two-way excitation, existence solid some slants magnetism problem. The cause that cause is to losing pulse asymmetry, transformer voltage is put in dc heft, deflect magnetism is accumulated quickly to magnetism core saturation, bring about electric current to rise without limit, inversion fails. Join to lie between straight capacitance without polarity, can prevent dc effectively to slant magnetism. Additionally this system uses control of peak value electric current, one by one limits the peak value of pulse of every electric current, force losing pulse form semmetry. Both cooperate to use but from go up at all solve slant magnetism problem. (The diode of follow on current that 3) introduces to turn over paralell connection in output commutate part D7. In circumfluent phase, the load current that offers by Lf of filter wave inductance can pass D7 to form loop to undertake follow on current for the most part, can reduce the electric current of follow on current that reflexes former edge by transformer deputy edge effectively, reduce those who take sky comparing loss and circumfluent stage to guide thereby a loss. (4) is joined draw circuit. Because output the generation when rectification diode restores reversely,a taller voltage rushs too and high frequency concussion, easy attaint diode is calorific and serious. After joining what form by Rs and Cs to draw circuit, can improve rectification voltage weaveform apparently. If have,need additionally, advocate switch parts of an apparatus two end also but shunt-wound RCD network. 3 control circuit designs the characteristic curve that outside be being taken to inversion welder constant current is narrated before implementation, procrastinates, what this plan chooses UNTRODE company is special and compositive move photograph chip UC3879, cooperate periphery circuit, through much annulus section control method finishs control to ask. UC3879 is a kind of PWM that can undertake phasic modulation special and compositive chip. Can adjust independently the dead band time of pulse of two pairs of complementary output, for two bridges arm different syntonic process creates a condition. Its are phasic modulation principle is: Give command signal to carry an input by chip foot 3(EA) , classics interior outputs error signal Ve after error amplifier, undertake comparative with the toothed wave that by chip foot 19(RAMP) end inputs, output arteries and veins is wide adjustable PWM is undee, go changing the phasic relationship of two bridges arm. The peak value electricity that uses in this plan institute controls mode to fall, from transformer the commutate of sampling of voltaic signal classics of former edge gets the toothed wave signal that 19(RAMP) carries the foot. But because signal of former edge electric current is actually undee ascendant slope relatively delay, with give when comparing, because interference or burr shake movables,give birth to misoperation easily. When applying actually accordingly, be worth the sampling commutate of former edge electric current the overlay of toothed wave photograph on CT of as time as chip capacitance first, after be being compensated through brae, send a foot 19(RAMP) again end undertakes comparative controlling. If the graph is shown 4 times,peak value electric current controls a process. If the graph is shown 5 times,method of control of external characteristic section and circuit of chip periphery logic receive a standard. In graph 5(a) , 1 what electric current of transformer former edge abstains through: Sampling of transformer of 100 electric current gets Is after rectification, the overlay of toothed wave photograph that gets appropriate voltage signal go up with time capacitance CT through sampling resistor, input a foot 19(RAMP) end. Crural 4(CS) end has used as shed protection, when prep above of this foot voltage 2. Pulse outputs block when 5V. A dot receives what arise by graph 5(b) to appoint signal. Graph 5(b) realizes circuit for the external characteristic of welder namely. Include the following 3 parts. (Character of 1) constant current realizes peak value of electric current of theoretic former edge and deputy edge output to solder voltaic volume can be reflected each other, accordingly, need to give the peak value of electric current of pulse of transformer former edge only, let electric current of former edge pulse and the node that give peak value decide to move the size of photo corner, can realize constant current control. The Iref in graph 5(b) is set-point of voltaic peak value namely. (When characteristic implementation procrastinating to work normally outside 2) , set-point Vz procrastinates outside outputting voltage feedback to be worth Vfb to be more than, the output of comparator U3 is 0, do not have an influence to adder U4, solder electric current is decided by Iref of constant current set-point; When welding torch and workpiece adhesion short circuit, vfb is less than VZ, the output of comparator U3 is tall, be equivalent to giving increased Iref, the output Ve of amplifier of UC3879 in-house error also increases, solder electric current increases subsequently, outside coming true thereby, procrastinate. (3) sky carries voltage to if,be restricted only appearance undertakes losing feedbacking controlling to electric current, so empty the UC3879 when carrying will from beginning to end with wide output of the biggest arteries and veins, create needless waste and security is reduced. Design the voltage conditioner that makes by comparator U1 all the way alone, carry voltage to undertake losing feedbacking controlling to the sky of welder, be more than when Vfb carry voltage set-point for nothing when Vk, u1 outputs a taller n to block C nods output, make UC3879 outputs pulse to move photo corner is 180 ° , namely effective arteries and veins is wide for 0 ° , make output voltage is reduced. Such, UC3879 outputs those who control signal to move photo corner is mixed in 0 ° change alternately between 180 ° , obtain constant sky to carry voltage not only, and reduced record loss for nothing. 4 drive segregation designs this plan to design frequency to be 100kHz, advocate switch canal is in status of high frequency action, the requirement shortens as far as possible the rise time of voltage of M0SFET bar source and decay time, reduce switch loss. Because this drive circuit wants to have bigger drive electricity, at the same time drive circuit wants to the down-lead of main circuit as far as possible short, reduce the impedance of grid drive circuit. The circuit of high frequency drive that this plan institute uses is shown 6 times like the graph. Among them IN is received self-invited the output pulse signal at UC3879, CND1 receives signal of control circuit ground, GND2 is received by the source of drive MOS-FET extremely. 6N137 is smooth Ou of a high speed, transmission defer time is only 40 Ns. The signal that from control circuit comes to passes smooth Ou to keep apart evacuation to come drive circuit, the electric segregation that makes control circuit and drive circuit to have better, remove the 10 trouble to dominating circuit. MAX4426 is a chip of high frequency drive that is used technically at M0SFET, its interior has two drive circuit, can easily paralell connection in order to provide greater output power. The model rises, decay time is 20ns only, defer time is little be more than 40ns, can work at 1MHz, offer 1. The peak value of 5A exports electricity. 5 experiments weaveform confirms border result for check, trial-produce prototype of power source of solder of an inversion arc. Design capacity is 6kW; Switch frequency 100kHz; Input voltage of 220V communication electrified wire netting, input filter wave capacitance to use 450V of ／ of F of 4 470 μ electroanalysis capacitance; MOSFET advocate the IXFK48N50 that switch canal chooses IXYS company, its parameter is 48A ／ 500V, output capacitance 600pF, considering voltaic capacity, use means of double-barreled paralell connection; High frequency transformer designs capacity 10kW, choose EE85 magnetism core, change than for 3, former edge leakage feels 2. 5 μ H; Lie between straight capacitance to choose 2. The CBB capacitance of 500V of ／ of 2 μ F; Outputting what rectification part chooses is denotative model fast restore rectification diode DSEI one 2x101) of one 02A(IXYS company; H of μ of LO of filter wave inductance, filter wave capacitance 220 μ F. Graph 7 compensate weaveform for voltaic brae. Passageway 3 for weaveform of sampling of original electric current; Passageway 1 to be used at compensatory toothed wave; Passageway the 2 weaveform after be compensation. Bright silicon increases the slope after compensation. The graph is not former edge voltage 8 times (electric current of passageway 3) , former edge (passageway 2) and output commutate voltage (passageway 1) is undee. From the graph 8 in can see clearly take sky comparing loss. Graph the 9 weaveform that for lag arm tubal pressing falls and its drive artery develops. Among them passageway L and passageway 2 it is weaveform of former edge electric current, voltage respectively; Passageway 3 for lag arm tubal pressing falls, passageway 4 for its drive weaveform. Graph 10 it is a graph the local spreading of 9 is undee. Can see when lag arm tubal pressing falls apparently from which already syntonic to 0 hind, drive artery develops ability by low become tall, make its guide below 0 voltage, realize soft switch. The article designed 6 epilogue a kind of complete bridge that is based on peak value electric current to control mode moves power source of solder of arc of syntonic inversion. Successful trial-produce the prototype of power source of solder of arc of high frequency inversion of 6kW of a 100kHz ／ . Experimental result makes clear, make with UC3879 give priority to the external characteristic that dominate chip and uses the design in article to dominate circuit, can the job of welder of inversion of better land implementation is characteristic, two bridges arm can realize soft switch inside wider range, systematic work is steady, overall efficiency is tall. Introduce control of peak value electric current, good, trends answers control function of the system faster. CNC Milling