can i replace D304X with 2sc3991

Discussion in 'The Projects Forum' started by sunshine, Nov 21, 2008.

  1. sunshine

    Thread Starter Member

    Jun 18, 2008
    13
    0
    hi


    i have a smps and i wanted to increase it's power. the choppers are a couple of this NPN power transistor http://www.china-ate.com/PDF/AUDION/D304X.pdf and the driver transistors are c945 and this transistor http://www.fairchildsemi.com/ds/KS/KSC5027.pdf. now what i want to do is replace the choppers with a couple of this transistor http://www.semiconductor-sanyo.com/ds_e/ENN2836.pdf. the smps topology is push-pull.

    i'm aware of the basic topologies and theory of operation, but i don't know about the calculations this is why i'am asking.


    thanx
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The transformer is going to be the limiting device in any switcher. It can only handle so much energy, so driving the primary harder may only cause it to overheat.
     
  3. sunshine

    Thread Starter Member

    Jun 18, 2008
    13
    0
    hi beenthere, thanx for your tips on my other thread.

    well the transformer is big enough i guess, and i have good air flow inside the box.

    also by the way, about the ic identification, should i really read all or big sum of the material provided by datasheets/books to know about how the nomenclature work? i mean this isn't a work of nature to decipher, this is man made thing. doesn't the jedec have anything to say about that subject?
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Well, some devices, such as those in logic families are standardized and easily recognized. About the only thing to know is that Motorola prefixes the 4000 series CMOS logic with a "1". For some time, semiconductors all had 1N and 2N designations, but now you can find many variations on individual device numbers. Standardizations seems to be gone.

    For almost everything else, it's apparently up to the manufacturer. Some manufacturers had stansard prefixes, like National's "LM". but now everybody makes equivalents with the same prefix.

    You're not likely to sit down and commit this stuff to memory. But after some exposure, numbers will stay with you, as well as functions. Everybody operates off a personally learned set of devices that are comfortable to work with. If a design won't work with the old stuff, then it's time to hit the old parametric search and find something new.
     
  5. sunshine

    Thread Starter Member

    Jun 18, 2008
    13
    0
    and about the replacement transistors? will they work, could there be any conflict with the existing peripheral components and the new transistors? or hfe problem?
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    I get a DNS lookup error on the Sanyo transistor.

    If the voltage and current ratings are equal or better, and the gain + rated bandwidth are as good or better, then they should substitute in. No idea about pushing more power, though.
     
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