The overhaul train of thought of transducer switch power source and overhaul method

  • Time:
  • Click:290
  • source:ZIEG CNC Machining
The circuit of switch power source of transducer can simplify completely to pursue to go up circuit model, the crucial essential factor in circuit is included inside. And any complex switch power source, after eliminate branches and tendrils, also can remain on graph such main force. It is actually in the overhaul, should have pair of complex circuit " change brief " ability, should looking be like desultorily in circuit extend, pick up give these a few main sequence of thought. Want to kitchen to what solve an ox Dingxue reviews, before train oneself the circuit of switch power source of nonexistent what whole, the trend that has each part sequence of thought and vein only -- oscillation loop, stabilized voltage loop, protection loop and laden loop. There are a few veins in seeing circuit 1, oscillation loop: Of switch transformer advocate the leakage of winding N1, Q1- - the access that source pole, R4 is electric current of power source job; R1 provided the electricity that start; N2 of self-confessed report winding, D1, C1 forms the power supply voltage of oscillation chip. Of these 3 link move normally, it is power source can the precondition that oscillation rises. Of course, time component R2, C2 and PC1 chip itself are received outside the 4 feet of PC1, also made the one part of oscillation loop. 2, stabilized voltage loop: N3, D3, C4 + 5V power source, r7, the component such as R10, PC3, R5, R6 formed stabilized voltage to dominate return circuit. Of course, PC1 chip and 1, R3 of component of 2 feet periphery, C3, also be the one part of stabilized voltage loop. 3, protect loop: R4 has formed PC1 chip itself and component of 3 feet periphery to shed protective loop; Component of the shunt-wound D2 on N1 winding, R6, C4 made the protective circuit of IGBT; The voltage feedback signal of loop of substantial stabilized voltage -- stabilized voltage signal, also can be being regarded is all the way voltage protects signal. But the content that protects circuit is not itself of circuit of protection of bureau be confined to only, those who protect circuit case because the unusual place of laden circuit is caused,accusing often is. 4, laden loop: Sub winding of N3, N4 reachs follow-up circuit, all be laden loop. Of laden loop unusual, meeting drag in is mixed to protective loop stabilized voltage loop, make two loop make protect and adjust a movement accordingly. Before oscillation chip itself is participated in and was being formed 3 loop, chip attaint, 3 loop can go on strike simultaneously. Be opposite 3 or the overhaul of 4 loop, undertake below the premise with chip normal itself. Additional, like wanting to resemble playing chess, will undertake breakdown is judged with global idea and systematic train of thought, see essence through the phenomenon. If stop brace up breakdown, perhaps be not damage by oscillation loop component place is caused, it is breakdown of stabilized voltage loop or laden loop likely unusual, brought about chip interior to protect accuse since circuit, and the output that halted PWM pulse. Not can will isolate completely with each loop rise undertake the overhaul, the occurrence of some breakdown component is shown probably " pull one hair and move all over " the effect. Constant expression is circuit of switch power source the following phenomenon of 3 kinds of typical breakdown: One, voltage of sub and laden power supply is 0V. Reaction is not had after transducer electrify, the operation shows face plate does not have a directive, the 24V that measures control terminal and 10V voltage are 0V. Examination main circuit charges resistor or charge beforehand return is whole, can judge for breakdown of switch power source. Overhaul move is as follows: 1, measure a law to measure switch to be in charge of Q1 to have with resistor first without phenomenon of puncture short circuit, r4 of voltaic sampling resistor has without open circuit. Component of circuit easy attaint is switch to be in charge of, after its damage, r4 is pounded because of sufferring and block value greatens or open circuit. The G of Q1 extremely PC1 of chip of series connection resistor, oscillation often suffers strong report to pound and damage, must change at the same time; Check laden loop to have without short circuit phenomenon, eliminate. 2, change attaint, or there is short circuit element in detecting, can undertake electrify is checked, farther judgement breakdown is to go out in oscillation loop or stabilized voltage loop. Check a method: A, check R1 of the resistor that start to have first without open circuit. Normal hind, send UC3844 directly with 18V direct current source 7, 5 feet, for oscillating circuit alone electrify. Measure 8 feet due 5V voltage output; 6 feet are due the voltage output that 1V controls. Explain oscillation loop is basic and normal, breakdown is in stabilized voltage loop; If measure 8 feet to have 5V voltage output, but 6 feet voltage is 0V, check 8, time component of R, C is received outside 4 feet, circuit of 6 feet periphery; If measure voltage of 8 feet, 6 feet to be 0V, UC3844 oscillation chip is broken, change. B, alone to UC3844 electrify, short receive PC2 to input side, if circuit rises brace up, explain breakdown inputs side periphery circuit in PC2; Circuit still does not rise brace up, check PC2 to output side circuit. 2, oscillation of occurrence intermittence of switch power source, can hear " belch " sound or " Zhi, Zhi " sound, or do not listen " belch " sound, but the extinguish when when the operation shows face plate, shining. Because laden circuit is unusual,this is, bring about power source overload, had caused the typical breakdown feature that sheds protective circuit movement. Of load current unusual rise, rise what cause primary winding magnetizing current substantially, the voltage signal of 1V above is formed in R4 of voltaic sampling resistor, make UC3844 in-house electric current detects accuse since circuit, circuit stops brace up; Signal flows to disappear too on R4, circuit rises afresh again brace up, such loop move back and forth, oscillation of power source occurrence intermittence. Check a method: A, measure two end of C4 of power supply circuit, C5 resistance, if have short circuit direct phenomenon, the likelihood is rectification diode D3, D4 has short circuit; Exterior of observation C4, C5 has wait for a phenomenon without fluid of bosomy top, gush, tear open next detecting when necessary; As good as of power supply circuit constant, the likelihood has element of short circuit breakdown for laden circuit; As good as of circuit of power supply of B, examination constant, electrify, use a division, undertake to each power supply one by one eliminates. If unplug,issue terminal of fan power supply, job of switch power source is regular, the operation shows face plate shows normally, come loose for 24V sirocco fan has damaged; Unplug below + 5V power supply is received child or cut off power supply Copper Foil, switch power source works normally, it is + 5V laden circuit has attaint element. 3, exorbitant or the power supply voltage of laden circuit is too low. The oscillation loop of switch power source is normal, the problem goes in stabilized voltage loop. Output voltage is exorbitant, the component attaint of stabilized voltage loop or small effect, make feedback voltage extent insufficient. Check a method: A, end is outputted in PC2 and receive 10k resistor, output voltage fall after a rise. Explain circuit of stabilized voltage of PC2 output side is normal, breakdown reachs input side circuit in PC2 itself; B, shunt-wound on R7 500 Ω resistor, output voltage has remarkable fall after a rise. Explain photoelectricity coupler PC2 is good, breakdown is worth to resistor component is received to change outside PC3 small effect or PC3. Conversely, for PC2 undesirable. Voltage of laden power supply is too low, have 3 trouble likelihood: 1, laden and overweight, make output voltage to drop; 2, component of stabilized voltage loop is bad, cause tension feedback signal is too big; 3, switch provides small effect, make circuit (switch transformer) change can insufficient. Examination and repair method: The A, laden circuit one by one power supply spur track removes (attention! Do not come with the means that commutate of this power supply provides open a way circuit of come away load, receive those who have signal of stabilized voltage feedback especially + circuit of 5V power supply! Turn over what feed presses signal to disappear, can bring about each output voltage is unusually elevatory, and will laden circuit is big burn down! ) judgement whether to because load is overweight,cause voltage fall after a rise; If cut off some power supply hind, circuit picks up to be worth normally, explain itself of switch power source is normal, check laden circuit; Output electric depress, check stabilized voltage return. The B, resistor component R5 that checks stabilized voltage return, R10, without change value phenomenon; Generation of one by one changes PC2, PC3, it is normal to be like, explain era changes component small effect, guide connect internal resistance to greaten. If disable,C, generation changes PC2, PC3, breakdown may provide small effect for switch, or switch and incentive circuit have a problem, also do not eliminate UC3844 interior to output circuit small effect. Change canal of high grade switch, UC3844. To run-of-mill breakdown, it is effective that afore-mentioned breakdown platoons examine a way, but not certain 100 percent spirit is smooth. If check oscillation loop, stabilized voltage loop, laden return,do not have unusual, circuit or output voltage are low, or intermittent oscillation, or flat be without reaction, this this case appears likely. Do not want be anxious first, let the account that we analyse circuit breakdown in past development, in order to help as soon as possible failure isolation component. The intermittent oscillation of circuit or stop brace up the reason is not rising brace up when loop and stabilized voltage loop, what reason still can bring about circuit not to rise brace up? (1) advocate circuit of the R with two shunt-wound end of winding N1, D, C, absorb a network for aiguille voltage, during offerring switch canal to end, store the release access of energy of the magnetic field in existence transformer (the) of passageway of retrorse electric current that switch is in charge of, protected switch canal to be not passed to press puncture. When serious leakage of electricity of D2 or C4 or puncture short circuit, power source was equivalent to increasing a very heavy load, make output voltage severe regain to fall, u3844 power supply is insufficient, in-house under-voltage accuses since protective circuit, and bring about circuit to enter intermittent oscillation. Because component paralell connection is on N1 winding, short circuit hind is measured not easily piece, often by oversight; (Power source of 2) some switch has voltage of input power supply (voltage is exorbitant) protect circuit, once circuit itself breakdown, make circuit appears to press protective action too by accident, circuit stops brace up; (Resistor of sampling of 3) electric current is undesirable, when if cite a base,oxidation, carbonization or block value greaten, bring about pressure fall rise, appear to shed protection too by accident, make circuit enters intermittent oscillation state; (The rectification diode of winding of 4) self-confessed report D1 small effect, guide connects internal resistance to greaten, circuit cannot rise brace up, change experiment; (5) switch transformer because winding mildewy, be affected with damp be affected with damp, quality factor is reduced, with archetypal date transformer era changes an experiment; (Since 6)R1 brace up circuit parameter mutates, but do not measure piece unusual, or switch provides small effect, all over right now check circuit as good as constant, but do not rise namely brace up. Repair a method: Change circuit has parameter and state already, make breakdown cruel be shown! Try the resistance that reduces R1 (unfavorable under 200k Ω the following) , circuit can rise brace up. This law also can repair one of methods as lash-up. Invalid, change transformer of switch canal, UC3844, switch experiments. Outputting voltage always is on the high side or on the low side a bit, short of is worth normally. What the examination does not give circuit and component is unusual, changed almost all component in circuit, the output voltage of circuit is worth or be in " reluctance and patchy " condition, be like sometimes can " regular job " , but let do not be free from anxiety in popular feeling, seem jumpy like, do not know when to can come " unusual display " . Do not want to abandon, adjust circuit parameter, make output circuit to reach normal value, achieve its job status, let us " be at ease " degree. The mutation of circuit parameter, have the following kinds of reasons: 1, transistor small effect, if dynatron magnifies multiple is reduced, or guide connect internal resistance to greaten, diode is greatening to resistor, retrorse resistor decrescent; 2, loss of the relevant dielectric loss that cannot measure the electric capacity that give with avometer, frequency; 3, the ageing of parts of an apparatus of transistor, chip and parameter drift, if the light of photoelectricity coupler delivers efficiency to become low; 4, inductance component, if the Q value of switch transformer is reduced,wait; 5, the block of resistor component is worth mutation, but not remarkable. 6, know exactly about sth of afore-mentioned 5 kinds of reasons are planted ginseng at among them, form " integrated action " . Of the circuit that forms by all sorts of reasons " present " this kind of condition, be a kind " clammy " , perhaps we must change overhaul train of thought, the doctor of traditional Chinese medicine has " differentiate card is applied treat " academic, we also should be used, next prescription, not be to be aimed at which component, however will whole circuit " recuperate " , make by " clammy " tend " normal " . so " ambiguous muddleheaded move " , give disease treated. Repair a method (the light fine tuning of component numerical value rectifies) : 1, output voltage on the low side: A, increase R5 or reduce R6 resistance; B, reduce R7, R8 resistance or increase R9 resistance. 2, output voltage on the high side: A, reduce R5 or increase R6 resistance; B, increase R7, R8 resistance or reduce R9 resistance. The purpose that afore-mentioned adjustment, be undertaking canvass to circuit, change after small effect component, undertake. The purpose is the relevant gain that adjusts circuit of stabilized voltage feedback, the pulse that makes oscillation chip is outputted takes sky comparing change, of switch transformer store can change, make the output voltage of sub winding reachs normal value, circuit enters new " normal balance " condition. A lot of look be like not repairable difficulty breakdown, pass so one, the adjustment of two resistance, billows does not have Jing ground rehabilitate. Watchful issue needs in the overhaul: 1, in examination of switch power source and repair process, should cut off three-phase to output the power supply of circuit IGBT module, in order to prevent drive power supply unusual, cause the damage of IGBT module; 2, when repairing the trouble with output exorbitant voltage, should cut off more + 5V is right CPU advocate board power supply, lest unusual or tall voltage damages CPU, cause CPU advocate board discard as useless. 3, cannot make stabilized voltage loop is interrupted, will bring about output voltage is unusually elevatory! 4, the diode of circuit of switch power source, use those who be used at protection at rectification to mix, be high speed diode or diode of Xiao Ji spy, diode of commutate of series of not usable and common IN4000 substitutes. 4, after switch provides damage, had better change those who use archetypal name, now network so develop, goods origin is unchallenged, can be bought commonly. CNC Milling CNC Machining