power supply question

Discussion in 'General Electronics Chat' started by radetonator, Sep 2, 2011.

  1. radetonator

    Thread Starter Member

    Aug 1, 2011
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    Hi. If the circuit needs +5V and +15V power supply from a DC power supply, what is the best way to achieve? Using two voltage regulator or just one?
     
  2. ian123

    Member

    Aug 24, 2011
    73
    2
    depends on the circuit i f you need regulation of not and what is the output from the power supply before regulation.

    if the power supply is around 15 volts and the 15v circuit doesnt need regulation then one regulator will do for the 5 v
     
  3. tronicsrookie

    New Member

    Aug 22, 2011
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    0
    Why not use the optocoupler design with feedback regulation, that's used in most of the SMPS. Combined with high wattage and clean supply (Deviation less than 100th of output) that's the best you can ask for.

    Just visit any computer shop and pick up a faulty one for a few dollars and replace shorted diodes/FETs and use it in your project.

    Regds,
    TronicRookie.
     
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Where do you find a computer supply with a +15V output?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    With no current or ripple specifications, it's rather tough to give an accurate recommendation.

    If not overly concerned about ripple, you don't mind the bulk, and you can do with +12v instead of +15v an ATX-form-factor PC power supply can be converted to a "bench supply" rather inexpensively.

    If your current needs are quite low, you might do with 7815 and 7805 fixed regulators from a ~18v-20v DC supply, but power dissipation in the 7805 regulator will make it very inefficient; ~3/4 of the power in the 5v supply will be wasted as heat.

    To help us help you, tell us more about what your current requirements are at 15v and 5v.
     
  6. radetonator

    Thread Starter Member

    Aug 1, 2011
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    Thanks.

    +5V is for LT1721 and 74AHC08. +15V is for a RF mosfet driver. When Vcc=15V, power supply current of the driver is 10uA.
     
  7. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Most non-logic level Mosfets are fully turned on at 10V gate voltage, so a 12V level for the gate should be more than adequate. Since you don't give your Mosfet number or a data sheet link its hard to answer any better.
     
  8. radetonator

    Thread Starter Member

    Aug 1, 2011
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    I plan to buy a 15V 1.2A switch mode PSU. Should be ok?

    Mosfet driver: DEIC420
    http://www.ixysrf.com/pdf/driver_ics/deic420.pdf
    MOSFET: DE275-501N16A
    http://www.ixysrf.com/pdf/switch_mode/de275_501n16a.pdf

    I only need to use one pair.
    Thanks.:D
     
  9. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    You do realize that the components your using are SMD(surface mount device)? If a beginner their not the most friendly to work with.
     
  10. paulktreg

    Distinguished Member

    Jun 2, 2008
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    Don't know what specification you're after exactly but how about this?
     
  11. radetonator

    Thread Starter Member

    Aug 1, 2011
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    I think 1A for the whole circuit is enough. Input voltage for the driver is from 9V to 30V. According to the datasheet, the power supply current of the driver is 3mA. LT1721 needs 28mA and SN74AHC08 also does not consume much power.

    How you guys think about it?

    I found this PSU. looks nice
     
    Last edited: Sep 7, 2011
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