TNY266 flyback switcher

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  • Khron
    Badcaps Legend
    • Sep 2006
    • 1350
    • Finland
    #1

    TNY266 flyback switcher

    Hello again,

    I'm in the process of putting together a "UV exposer" with a MAX1698A led driver, and i've decided to supply it from a 5vsb section "grafted" from an HP power supply, based on a TNY266 chip.

    The schematic i'm using is attached below. Now, the switcher is definitely working (scoped it out), and on the 220u filter cap, from the aux primary winding, i'm getting 14-17v. Trouble is, for some reason, the chip is on minimum duty cycle, and on the secondary, i'm getting some tiny blips (which i'm not even sure are enough to open the rectifier schottky). I also changed the optocoupler, same thing.

    I wonder if the coil i'm using is a bit too big (180uH), but... Should / could that affect things quite like that? Secondary caps are two 1500uH/6.3v Nichicon HD. I also tacked on a 51ohm resistor as a ~100mA minimum load. Nothing else is mounted on the board (so just supply-related components).

    Could the TL431 be bad?
    Attached Files
    Last edited by Khron; 11-10-2010, 06:09 AM.
    Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans
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    • stj
      Great Sage 齊天大聖
      • Dec 2009
      • 31015
      • Albion
      #2
      Re: TNY266 flyback switcher

      wouldnt it be a lot simpler to use a clockwork switch?
      i know it's like archialogical period tech, but it's designed for what your after.

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