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"Burning off" 9V at 6A

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by truenoteno, Aug 11, 2003.

  1. truenoteno

    truenoteno New Member

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    I have a 312 watt switchmode power supply that i would like to make use of.

    It supplies upto 48V at 6amps.
    I would lke to use an LM338 voltage regulator but the max input voltage is 40v. How could I chew up about 9V at 6amps ?
    I could only think of having about 13 6A rectifiers but that is too expensive, takes up room and leaves more room for error.

    thanks
     
  2. stevez

    stevez Active Member

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    Do the power regulation in steps - take the 48 to 40 volts or so then go from there. My recollection is that the 338 is limited to 5 amps max - as long as you don't exceed power dissapation ratings. It would seem that you could "wrap" a power transistor or two around an LM317 - see datasheet for ideas on that.
     
  3. bogdanfirst

    bogdanfirst New Member

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    how about using a 2n3055 transistor hooked with a zenner diode and another transistor. since the regulation is done with the LM then you dont need to have 40V regulated.
    i guess that another solution is to buy 13 diodes rated at 6 amps, or 7 bridge rectifiers.....wich might be cheaper than the diodes.....
    i think that the first solution is the best.....
    what do you think?
     
  4. dave

    Dave New Member

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  5. Sebi

    Sebi New Member

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    Use L4970 SMPS from ST. It can deliver 10A, but the input also 40V.
     
  6. Mosfet

    Mosfet New Member

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    Pre-regulator
    Transistor Q1 can be any power NPN similar to a 2N3055 or MJE3055.
    Transistors Q2 & Q3 could be TIP31C's, I happen to have a lot of them.
    Or Q1 & Q2 could be a power Darlington instead.
    Resistor R1 should be a 2 watt package.
    Zener diode D1 sets the output voltage and could be lower.
    Mount the transistors close by on the same heatsink as your LM338 [electrically insulated].
    That way the thermal overload circuit in the LM338 will protect them also.
     

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  7. truenoteno

    truenoteno New Member

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    thanks for your help
     

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