Issue with FlyBack AC/DC Converter - Output 5V, 500mA

Discussion in 'General Electronics Chat' started by morethegr8, Mar 20, 2016.

  1. morethegr8

    Thread Starter Member

    Feb 14, 2011
    27
    0
    Hello,

    Im using LinkSwitch II - LNK615DG for my design.

    Problems:

    When i connect this circuit to AC mains - 230VAC. Bridge diode and fuse Blows.
    I replaced MB8S with General purpose diodes 1N4007 and i started circuit with series test lamp setup.
    Now the circuit shows output of 1.8 ~ 2.45 VDC and is not stable.

    Kindly help me debug the circuit as i don't have Variac and working at 230VAC is highly dangerous.

    Thanks in advance.

    Design Reference:
    3.25 W CV/CC Charger Using LinkSwitchTM-II
    That Meets New 2011 European Standards.


    upload_2016-3-20_21-48-50.png
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,974
    744
    Its a Transformerless psu, so unless you want to have it closed down stick a transformer on the input first,

    So what is the chip T1 doing, is it a smpsu type, also U1?
     
  3. morethegr8

    Thread Starter Member

    Feb 14, 2011
    27
    0

    Its custom made Hi freq Transformer . with specs same as given in design data.
    T1 is EE16 Transformer.
    U1 is LNK605/615DG

    Design is same as shown in image below.

    upload_2016-3-20_22-18-21.png
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,974
    744
    So if the output voltage is low it will be set by the reference fb pin, or bpm have you replaced the chip as well?
     
  5. morethegr8

    Thread Starter Member

    Feb 14, 2011
    27
    0

    Yes, I did.
    I have built two same modules.
    One gives no output at all while other gives low voltage.
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,974
    744
    Check D5,6
     
  7. morethegr8

    Thread Starter Member

    Feb 14, 2011
    27
    0
    Hi, Dodgydave.

    I changed my transformers. Now the issue is output goes upto 8V.

    I think i have problems with feedback loop of the transformer.
     
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