Nenad Grujic

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  1. UC3842 SMPS 500W

    Hi all Can some one give me answer on few next question : I have EE4215 core who work on 62 kHz frequency and material for core is ZP40 (need be similar like N84 or PC40 ) , max power on 62 kHz is something like 690W and I'm test is on 500W , but my core or transformers is so hot on long work time , with fan that is 85 degree , without is 117 degree , have you idea why have that allot heating on transformer ? Secondary side coil is make it with Cu foil 23 mm width and 2x5 turns , that foil is ok for constant 21A and work on 62 kHz ? Primary side is 24 turn , 4 x 0.5 mm wire , that is ok if we are measure that input current is 2.26A ? Thanks for help
  2. UC3842 SMPS 500W

    Hi folks I'm redesign circuit diagram for my smps , now look me that signal is ok , have only one problems with secondary side control voltage , need invert principle , on this moment when optocoupler is not active then signal have bigger delay , and when is active then delay is low , but on real need invert that , need have low delay when optocoupler is active . Have you idea how I can do that on PWM IC side , not on secondary side , or maybe can on secondary side but need be stable in work ? First image (DSC_0123.jpg) is with not active optocoupler on secondary voltage regulation , second image (DSC_0124.jpg) is with active optocoupler but like you can see need invert that . SG3525-500W-SMPS-V4.1-schematic.pdf
  3. UC3842 SMPS 500W

    Today I m try run voltage regulation on secondary side and again allot problems . For voltage regulation I m use TL431 , and plane is have regulation from 15V to 24V . I m calculate voltage with formula Uout=(1+R1/R2)*Vref , and if you look my circuit diagram then R10 is 43 k , R14 is 8,2k and R15 is 25k (all so try with 50k but same ) and have only 4V difference with max. and min. position for R15 , can say that not work how I m plane , and that is from 15V to 24V . All so second problems is nex. , plane is that for start SMPS first voltage for run will be come from capacitors (310V ) through R6 , on this test 10 k resistor 3W , and after start SMPS use supplay from transformers on switcher and have rectifier with fast diode , when supply come from resistor 10 k then voltage is 10V , enough for first run and when supply come from transformers then have 18V and then current not need come from 10 k resistor or if will be then will be small , but on real work that not work correct , have you idea how do that ?
  4. UC3842 SMPS 500W

    Today I m replace damage FET and put new , and all so connect LOAD direct to secondary side on smps , after few min work FET is total cold and LOAD is very hot , that look me like good way . I m see that signal on FET is not total quadratic , maybe because now power come from 310V from capacitor and 10 k resistor for start and after when smps start work come from transformers secondary coil who is wind only for power PWM part , and I have in serial connection 45R resistor on power network ? First image is signal wave from PWM part to Q2 FET and second is voltage wave on secondary side with 15R resistor like LOAD . Have you idea why have that wave deformation and if you better look you can see some oscillation on dead time , that is wrong snuber or ?
  5. UC3842 SMPS 500W

    "Тут картина как раз наоборот, В сварочниках чаще ставят обычные диоды в паралель поскольку на токи сварочника проще поставить пачку обычных чем искать шотки на такие токи." Hepo , can you please explain me this , I'm not sure that I m understand what you won say ?
  6. UC3842 SMPS 500W

    o_l_e_g , I think that 100V will be ok ? I have use some old version software for transformers calculation and then is not write me pik voltage , that is ExcellentIT 7100 , but after I m see when click to secondary voltage information then write me all so pik voltage , that is 46.8V , for that I think that 100V diode will be nice , what you think ?
  7. UC3842 SMPS 500W

    Hero , I have few supply for PC and all diode is 4045 or 3040 no one is 30100 or 40100 , tomorrow I will try found it or I will buy new . I'm little look what is problems and have few question , on HB supply frequency on secondary side is 2x frequency on one FET , my frequency is 87kHz and then on diode 174 kHz frequency , that is right ? Can not found information what is max frequency for MBR 3040 or similar diode , can you give me that info , or max time for close diode ? On my smps not have storage inductor , and now see that is big mistake , I will add it , how I can calculate it ? I m see that on my smps in diode ( 2 diode in one package ) only is damage A1 to K and every time A2 is ok , have some reason for that ?
  8. UC3842 SMPS 500W

    Today I m run smps and after few second problems , first is damage diode D7 on secondary side (short connection between A1 and K ) and after that is all so damage FET . I not understand why is that happen because before I m connect load then voltage on secondary side after diode is be 28V and I m use MBR4045 , that is 45 V , all so current is with 3R something like 9.6A but diode is 40A , can some one explain me why that is happen ? Transformers is EE42/21/15 core with 4x0.5 mm wire on primary side , 19 turn , secondary is 2x5 turn with 5x0.8 mm wire , for supply PWM module I m use 1x0.5 mm wire , 4 turn . Frequency is now 87 kHz with 1.5 uS duty time .
  9. UC3842 SMPS 500W

    Yurkin2015 , I m need bee I am or with ' but when type then not look and make type mistake , sorry for that . I'm attach circuit diagram , this is with true value , all so need say that I'm not put transformers , on primary side I'm connect bulb 60W . SG3525-500W-SMPS.pdf
  10. UC3842 SMPS 500W

    I m total confuse UVV , I m change frequency from 25 kHz to 80 kHz , connect smps , and then is first blow me IR2110 , then all so FET-s and SG3525 and fast diode D3 , D4 . On image have how look PWM signal on SG3525 output , like we can see that have enough delay between signal , and that need be enough for discharge Gate on FET and close FET . Need say that on transformers primary side I m connect bulb , not have transformers , and for that all is strange me .
  11. UC3842 SMPS 500W

    Hepo , today I m assembly smps , circuit similar like up circuit , and I see that have few not understandable problems . First is that with R6 100 k not have enough power for run SG3525 and IR2110 , have only 2V , need recalculate that resistor , but I not know how much is min, current that I need have for run FET , that is for first run , when smps will be start then is plane use power from transformers for run SG3525 and IR2110 ? Second is , I m connect bulb to transformers place ( primary side ) , and with firs measure that all look nice , but think that have problems because FET will be hot after few minute ( current on testing is only 270 mA ) , have you idea what can fake me ? I won measure all before put transformers that I m sure that all work fine .
  12. UC3842 SMPS 500W

    I m add IR2110 in circuit diagram , now will be usable for half bridge ? How I can calculate C8 , have some rules for that , I know that max current is limited with capacitor value and frequency , it is same with high frequency ? All so wan quest for Q1 and Q2 , some circuit have snubber on that FET , some one use diode and also some one not use nothing , what is the best options for long and stable work ?
  13. UC3842 SMPS 500W

    Yes 2300 , my type mistake , sorry . This is with new setting for core calculation for half bridge principle , that is ok now ?
  14. UC3842 SMPS 500W

    Yes you have right , flux density is 4700 and permeability is 2600 , need change that .
  15. UC3842 SMPS 500W

    Can you please look this :