Page 4 of 4 FirstFirst ... 234
Results 31 to 32 of 32

Thread: TL494 halbridge like ATX problem

  1. #31
    Thanks for very informative reply!

    Regarding voltage drop:
    I observed very strange waveform on switching transistors, when converter is loaded about 50W.
    convertermeasurement.png
    This is how I connected scope, on the other transistor it's the same.
    1595832255.jpgconvertermeasurement2.jpg
    On the first screenshot when lighter load (few watts) the voltage on the collector is just fine, going from 325V to ground - very small voltage drop on transistors. But on the second screenshot, with higher load 50W there's smaller voltage swing - higher voltage drop on transistors? Is that becaouse of too small base current? Could this create voltage drop on the output and heat up transistors?
    I used a base drive transformer from old atx, maybe I should rewind it? Do You have some Idea for numbers of turns?

    And lastly, I changed number of turns of secondary to 2x10 and using 4x0,6 wire to fit it in window.

    Thanks, Fifi

  2. #32
    .... Silvio's Avatar
    Join Date
    Apr 2015
    Location
    Malta
    Posts
    887
    Blog Entries
    9
    Yes i can also see that the pulses are not symmetrical.
    This could be the highside i guess. Try to change the capacitor feeding the gate to correct. Try a different value and see for any changes. The task is to pulse the gate hard at all times. Try a higher aux supply like 15 or 17v feeding oscillator circuit and BDT primary. If gate is not drven hard enough then transistors enter linear mode and get hot.

Similar Threads

  1. TL494 Lab PSU
    By bogdan2011 in forum diysmps
    Replies: 27
    Last Post: 07-07-2019, 02:29 PM
  2. Tl494 smps
    By noorworkshop in forum Switching Power Supplies Informations
    Replies: 26
    Last Post: 06-13-2018, 06:59 PM
  3. TL494 Class D Amp
    By noorworkshop in forum Class D
    Replies: 1
    Last Post: 05-15-2018, 02:49 PM
  4. Replies: 7
    Last Post: 07-24-2014, 06:20 PM
  5. 1kW halbridge smps with PWM control
    By mych3 in forum diysmps
    Replies: 4
    Last Post: 07-22-2011, 09:37 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •