never seen problem (IR2110 + CRO)

Discussion in 'The Projects Forum' started by onlyvinod56, Mar 14, 2011.

  1. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    362
    1
    Hello

    1.This is an smps project. see the pdf file.
    2. The pulses from SG3525 are OK.
    3. When i checked the pulses at pin1 of IR2110 w.r.t pin2(ground), CRO is displaying the pulses.
    4. similarly when i checked the pulses at pin7 w.r.t pin5 (high side), CRO is not displaying anything.
    5. When i connect the two channels of CRO simultaneously, then both the pulse sequences are displayed.

    What is this effect??? (for schematic see the first fig attaached)
    Note that i didnt connect the mosfets yet. just im checking the output of IR2110.


    For another project - SPWM inverter.
    see the second figure attached.
    I compared a sinusoidal with triangular using LM339. And then the pulses are given to the IR2110. At this time i did not faced any problems. Individually and simultaneously also the CRO is displayed the pulses.

    How can i rectify the problem for the SMPS.???
     
    Last edited: Mar 15, 2011
  2. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,031
    Only a hunch/speculation: You've got some problem with ground, and the fact that the CRO and your circuit don't share ground.
     
  3. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    362
    1
    Does it mean my circuit is correct?
    can i connect the mosfets?
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,031
    Don't base your answer on my opinion! I don't see an obvious error but I'm not an expert on these devices.

    There's not a lot of risk in merely connecting your FETs - it's the current they are switching that could cause damage. You might experiment with switching a few LEDs or something that won't risk overheating the FETs.
     
  5. observativetiger

    New Member

    Jul 12, 2012
    1
    0
    I had to figure this one out too, and the answer is; If you want to see the "high side signal output" when the MOSFETs are out or not powered, you need to ground the VS pin(s). In other words wayneh is correct, you have a ground problem.

    I had a little help from this doc; http://www.irf.com/technical-info/designtp/dt97-3.pdf, and Tahmid. I am only posting this on such an old thread because I can only find this answer in one other place on the net...and I hope this helps someone...even though the IR2110 is now at EOL and you should be using a newer driver IC as recommended by IR.

    Cheers,
    observativetiger
     
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