Boost converter help

Discussion in 'The Projects Forum' started by sumanth724, Apr 9, 2012.

  1. sumanth724

    Thread Starter New Member

    Apr 9, 2012
    6
    0
    hiii guys I am working on boost controller using 555 timer my circuit as below

    but I am not getting any boosted output, the out is almost same as my input
    so I removed the feed back network and changed the pico farad capacitor at input to 0.1uF capacitor then I am getting around 100v for 6v input, but I don't need such huge boosting.

    my requirement is i should get around 15v for 5 v input and around 35v for 15v input, my range of operation is only between 5v to 15v and my range of output is 15v to 35v.

    Please help me in this regard and also give me other circuits if it suits my requirements..
     
  2. #12

    Expert

    Nov 30, 2010
    16,322
    6,818
    555 timers don't work at 90 MEGA hz!
    Even the new and improved TLC555 only claims 2 Mhz.

    You have the right idea though. Slow the oscillator down and reconnect the FB circuit. Be sure to re-math the inductor so you don't saturate it at the lower speed.
     
  3. yourownfree

    Active Member

    Jul 16, 2008
    89
    0
    It looks like the cap in the drawing is wrong. With the values given the frequency is way too high. it shows it to be 48 MHz. But with a .01 uF it would be 48 KHz. I think the cap was suppose to be 10 nF or .01 uF is the same size. Change it to .01uF and see how it goes.duty cycle is 66% high according to the 555 calculator here
     
  4. sumanth724

    Thread Starter New Member

    Apr 9, 2012
    6
    0
    even I tried with 0.01uf but no satisfactory output
     
  5. #12

    Expert

    Nov 30, 2010
    16,322
    6,818
    Time to troubleshoot.
    Perhaps you smoked the 470uf capacitor when you put 100 volts on it?
    Can you measure an oscillation on the output of the 555 chip?
    The IRF540 has a death limit at 100 volts, too.
     
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