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Thread: 12v 12A regulator with only one chip!!!!!

  1. #1
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    Cool 12v 12A regulator with only one chip!!!!!

    Hi everyone, im spanish and i have spended a considerly amount of money in my car-pc without making it works properly. i have a p4 in an atx motherboard and a bought the m2-atx to power it, the problem came later when this power supply arrived to my house. The pc couldnt start becouse there werent enough power on the 12v rail (atx12v connector, needed---> 7A minimum only for the celeron).

    Then i thought i could connect to this connector another power supply only for regulate the 12v, but this was a hard task. i found very unefficient and big circuits but finally i found the LTC3780 chip that was specified to drop about 5A on the 12v with the buck-boost metod with the 6-30Vin. Searching for a made circuit to build it i discovered that there is a circuit called dsx12v with only this chip that could drop 12A at 12v!!!! wow, with the chip designed only for 5A.

    I have looked for this way of configuration for that current but i found nothing nothing. The only things i know is that they used the IRLR7833 power mosfet this chip and some caps.

    I would like to recieve some help from someone who know something about electronics to build my circuit. Please i have to do it work

    Here are some notes for the LTC3780 chip. that can be ordered as sample in www.linear.com. i have 2 of them
    Datasheet
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    Thanks for your attention

  2. #2
    Newbie didiet78's Avatar
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    Change rsense and mosfet. Read datasheet 5 times, you'll find the answer
    - Will work for Bandwith -

  3. #3
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    You will need to lower the value of the Rsense so the current limit is increased. The MOSFETs can be paralleled to handle the increased current.

    Watch out for the inductors values and Peak/RMS current rating. You will also need to get better capacitors, one with lower ESR. Again paralleling them will do but will obviously increase the board size.

    If you only need around 10A one off PSU, then you can just use those power module, search the forum. Parallel them to get the required current rating. You can get free samples of them.

  4. #4
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    Quote Originally Posted by didiet78
    Change rsense and mosfet. Read datasheet 5 times, you'll find the answer
    5 times? I read it 50 times

    Some of the stuff in there are not so clear, there are a few conflicts as well.

  5. #5
    Newbie didiet78's Avatar
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    Quote Originally Posted by Chris31
    You will need to lower the value of the Rsense so the current limit is increased. The MOSFETs can be paralleled to handle the increased current.

    Watch out for the inductors values and Peak/RMS current rating. You will also need to get better capacitors, one with lower ESR. Again paralleling them will do but will obviously increase the board size.

    If you only need around 10A one off PSU, then you can just use those power module, search the forum. Parallel them to get the required current rating. You can get free samples of them.


    For mosfet, i thing IRLR7833 will do. You don't have to paralleled.

    For 10A 2 paralled ltc3780 (at 5A like in Datasheet) like mastero psu did
    - Will work for Bandwith -

  6. #6
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    Question confused

    Thanks very much but i dont understand on what depend the inductor. In this desing the value is diferent.
    And are there any other values to change, resistors and values of caps or others?
    how can i get the low esr caps? and how low they have to be?
    Thanks
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  7. #7
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    Quote Originally Posted by Chris31
    If you only need around 10A one off PSU, then you can just use those power module, search the forum. Parallel them to get the required current rating. You can get free samples of them.
    How can i do this?

  8. #8
    FLAC
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    Quote Originally Posted by zaccaro

    Then i thought i could connect to this connector another power supply only for regulate the 12v, but this was a hard task. i found very unefficient and big circuits but finally i found the LTC3780 chip that was specified to drop about 5A on the 12v with the buck-boost metod with the 6-30Vin. Searching for a made circuit to build it i discovered that there is a circuit called dsx12v with only this chip that could drop 12A at 12v!!!! wow, with the chip designed only for 5A.
    Do you just want a DSX12V power supply rather than going through all the trouble?

    Jeff
    MPEGBOX - Plexiglass Computer
    www.mpegbox.com

  9. #9
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    Quote Originally Posted by zootjeff
    Do you just want a DSX12V power supply rather than going through all the trouble?

    Jeff
    I know that this is easier but I have spent 100€ (120$) in one psu and the money doesnt rain. I prefer to look for another solution. In case it cannot, it will buy it.

    By the way zoojef, are you the man who designed the dsx12v circuit?

  10. #10
    FLAC
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    Quote Originally Posted by zaccaro
    I know that this is easier but I have spent 100€ (120$) in one psu and the money doesnt rain. I prefer to look for another solution. In case it cannot, it will buy it.

    By the way zootjeff, are you the man who designed the dsx12v circuit?
    Yes I am the designer, www.mpegbox.com is my website. I designed the DSX12V DSX12VD and the DSATX as well as the uSDC20D and MPBS1.

    You'll spend much more than 120$ in building your own board. Even if you get most of the parts for free..

    The DSX12V is like 75 dollars.

    -Jeff
    MPEGBOX - Plexiglass Computer
    www.mpegbox.com

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