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Inverter Modifications

Discussion in 'General Electronics Discussion' started by Technician Tonny, Feb 19, 2017.

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  1. Technician Tonny

    Technician Tonny

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    Aug 31, 2015
    HI.... Is it posible to modify a dc inverter circuits which are inbuilt in crt television sets,
    The inverter output is soldered directly to the crt power filter capacitor,
    what if i remove the brigde, will it output stable 220VAC?!
     
  2. davenn

    davenn Moderator

    13,802
    1,941
    Sep 5, 2009
    hi

    you would have to tell us a lot more about the particular PSU
    a circuit diagram is going to be essential before any good suggestions could be given
     
    Technician Tonny likes this.
  3. Technician Tonny

    Technician Tonny

    34
    2
    Aug 31, 2015
    Davenn i tried googleling for the schematic but i found no matching circuit according to the one i have

    The inverter board uses two ic's ne555 and sg3524n, smp transformer and two fets....

    I tested its output with a d m meter and found 300 vdc, and at the transformer's output b4 the brigde, the meter shows high voltage....

    Such inverter circuits are found in CRT TV's which operate with both AC AND DC voltage

    I'm working on its schematic, i will provide it wen its done
     
    davenn likes this.
  4. Technician Tonny

    Technician Tonny

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    Aug 31, 2015
    20170315_163444.jpg INVERTER1.jpg 20170315_163534.jpg
     
  5. Aplicant

    Aplicant

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    Nov 16, 2016
    If you remove inverter output bridge diodes , inverter outputs
    310 vac 50 khz squarewave
    It never outputs 220vac 50 hz
     
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  6. duke37

    duke37

    5,364
    770
    Jan 9, 2011
    If it is a ferrite cored transformer, it will never be able to run at 50Hz.

    To get 50Hz you will need an iron cored tranformer and the SG362 modifying to generate the correct drive. frequency.
    This circuit produces square waves. The output can be filtered to give an approximate sine wave or a class D drive to generate a sine wave
     
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  7. Technician Tonny

    Technician Tonny

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    Aug 31, 2015
    duke37
    I have iron cored transformer's from old ups, hope it can work!

    and how can I modify the SG to change the frequency
     
  8. Audioguru

    Audioguru

    3,148
    698
    Sep 24, 2016
    The datasheet of the 555 and the SG tells you all about them.
    Your modified inverter output voltage will be too high when the load is light and will be too low when the load is heavy because it is missing voltage regulation.

    The heatsinks on the Mosfets are small so the Mosfets will melt if the inverter power is more than not much power.
     
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  9. duke37

    duke37

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    770
    Jan 9, 2011
    Look up the data sheet.
    Ct = 100nF, Rt = 280k should be about right.

    If you have a UPS, why not use that?
     
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  10. Aplicant

    Aplicant

    18
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    Nov 16, 2016
    If you want to take 220ac from your inverter in crt,you have to add this circuit. It converts 310vdc to 220ac
    Apply this
    [​IMG]
    You have 300vdc so you dont need ic1 and components around ic1
    [​IMG]
     
    Technician Tonny likes this.
  11. Technician Tonny

    Technician Tonny

    34
    2
    Aug 31, 2015
    Audioguru
    let me check the datasheets
    Thanks


    Duke 37
    I change the ct and the transformer ..ok let me do that now

    i don't use the ups because it used to drain the battery so quickly, it works for only 2 hours


    Aplicant
    I also remove R8 and D4 its like a feedback or comunication between the two ics!

    Thank you all for your assistance i really appreciate
     
  12. duke37

    duke37

    5,364
    770
    Jan 9, 2011
    Why do you think that you can make a more efficient power convertor than a commercial one?
     
  13. Technician Tonny

    Technician Tonny

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    Aug 31, 2015
    because ups a multpurpos... they charge, they work as automatic voltage regulator, power backup for computer sets.
    i think they where not designed to stay on for so long as inverters
     
  14. Technician Tonny

    Technician Tonny

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    2
    Aug 31, 2015
    your right now the inverter outputs
    __ 240vac without any load
    __ 130 vac when i connect a 100 wat bulb , and the 240 drops to 40 vac when i connect a crt tv,
    I tried another transformer and its output is 280 vac and drops to 180 when i connect a 100 watt bulb
    but am still wondering why it just increases the voltage to 300 vac when i connect a crt tv
    How to add the missing part of regulation,

    The heatsinks on the Mosfets are small so the Mosfets will melt if the inverter power is more than not much power

    The mosfets a still cool
     
    Last edited by a moderator: Feb 24, 2017
  15. Aplicant

    Aplicant

    18
    3
    Nov 16, 2016
    Upload your transformers
    Or use a much bigger transformer
    For example like this
    [​IMG]
     
    Technician Tonny likes this.
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