Page 3 of 10 FirstFirst 12345678910 LastLast
Results 21 to 30 of 94

Thread: My new Sproggy style power supply

  1. #21
    Variable Bitrate
    Join Date
    Jul 2000
    Location
    Ottawa, Canada
    Posts
    422

    Post

    couple quick questions
    1- these LT1083/LT1084/LT1085 7.5A, 5A, 3A Low Dropout Positive Adjustable Regulators
    have they been tried, other then heat whats the pros/cons of these (they are a much simpler setup the the maxim chips and offer better current)
    2- sample from these guys ?
    3- looking for samples i found ON semiconducter had some of the stuff i needed for my sproggy hybrid (still in works nearly a year later, i just about done laying out the board design.)
    [SIZE=1]'91 Nissan Stanza

    [XXXXXXXXXXXXXXXXXXXX] XX% Completed -
    Car Totaled and i bought a 20G mp3 player

    http://machs-fuel.tk
    a DIY video projector page

  2. #22
    Maximum Bitrate
    Join Date
    Oct 2001
    Location
    Ontario, Canada
    Posts
    845

    Post

    Hey Machs where you from in Canada?

    Care to share the board design that you're working on?

    The general reason that we want to avoid the linear regulators is the heat and the power wastage. for 5V 5A you're wasting 35W and for 3.3V 5A you're wasting 43.5W! So for 41.5W of output you're wasting 78.5W, requiring 120W of input, giving 35% efficiency! If you then use that for the 12V rail out for 5A (at 16V input) then you're adding another 20W wastage. And if you think radiating 110W of power is *easy*, you've got something else coming to you ;P Switched regulated power supplies generate enough heat already, never mind tripling it.

    If you don't care about wasting power, just go for an invertor and use a normal power supply, much much easier.

    [ 11-21-2001: Message edited by: Telek ]
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

  3. #23
    Maximum Bitrate
    Join Date
    Oct 2001
    Location
    Ontario, Canada
    Posts
    845

    Post

    I was checking for some component for the 12v rail which can give more than 3amps .. i think LM2587-12 yup the same one can give us 5amps but in boost mode .... yup go to the national site they have the spec im woking on the converstion ! to - v
    I just reread the spec sheet again, and the problem isn't the LM2587-12 at all, it's the T6 that can only output 1.3A, so that will need to be replaced as well, regardless of HOW we increase the 12V output (Skinnyboy might also want to take note of this).

    I think we're pretty much stuck to 1.2A until we figure out how to switch the T6 to something else. That's where the problem lies, and if we can replace that with something else can can do 5A, then we're all set and don't need to change anything else.

    Isn't this ironic that since the car itself runs on 12V, this is the output that we are having the most trouble with??
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

  4. #24
    Maximum Bitrate
    Join Date
    Nov 1999
    Location
    Sydney NSW Australia
    Posts
    581

    Post

    Actually LM2587-12 wont give you 5Amps at 12v input working in flyback mode!
    So its not only the transformer that is the problem its the regulator itself.
    Fosgate

    System Comp V3 - In progress.
    Low power MB with C7 CPU, DC-DC PSU, car ECU link, USB TV, GPS, 7" TFT, Wireless, Voice.

  5. #25
    Newbie
    Join Date
    Jul 2001
    Posts
    4

    Post

    I just reread the spec sheet again, and the problem isn't the LM2587-12 at all, it's the T6 that can only output 1.3A, so that will need to be replaced as well, regardless of HOW we increase the 12V output (Skinnyboy might also want to take note of this).
    WELL DUH!!!!!!!!
    we have an alternative...
    It is most commonly known as T3 and has about 2.5 times the output current of T6, but is about 4 times bigger, I have 2 of them, but chose not to use them...

  6. #26
    Maximum Bitrate
    Join Date
    Oct 2001
    Location
    Ontario, Canada
    Posts
    845

    Post

    Actually LM2587-12 wont give you 5Amps at 12v input working in flyback mode!
    So its not only the transformer that is the problem its the regulator itself.
    All I know is that I read the spec sheet again, and got an email back from the makers and they both indicated that it could output 5A at 12V.

    So what do you plan to do Skinny if you don't want to use the T3s? and the design that you showed me doesn't work because you put components in the middle of the heatsink!
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

  7. #27
    Maximum Bitrate
    Join Date
    Nov 1999
    Location
    Sydney NSW Australia
    Posts
    581

    Post

    Originally posted by Telek:
    <STRONG>

    All I know is that I read the spec sheet again, and got an email back from the makers and they both indicated that it could output 5A at 12V.

    </STRONG>
    NOT in the Flyback mode and not with the input voltage at 12V!!!
    Fosgate

    System Comp V3 - In progress.
    Low power MB with C7 CPU, DC-DC PSU, car ECU link, USB TV, GPS, 7" TFT, Wireless, Voice.

  8. #28
    Maximum Bitrate
    Join Date
    Oct 2001
    Location
    Ontario, Canada
    Posts
    845

    Post

    Where do you see this??

    I see absolutely nothing that indicates that the "5A Flyback regulator" would be limited to 1.2A at 12V. Can you please explain?
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

  9. #29
    Maximum Bitrate
    Join Date
    Nov 1999
    Location
    Sydney NSW Australia
    Posts
    581

    Post

    Years back when i was designing my PSU I did a full reseach on LM2587-12 regulator. It is true that it can produce 5Amps with 12V output however this possible using other mode of operation for this regulator...
    I dont remember if it was step-pu mode or some other but using a flyback design it can only produce around 2Amps max...
    The input voltage also plays a big role in this issue.
    If i remember corectly on the datasheet there are few graphs that represent this...
    Few months back we had a long dicussion here regarding this same issue (Im sure some poeple remember it) The conclusion was that using flyback technology with the current companents we cant get more then 2 amps on the +12v rail.
    What will happen if you put the biger transformer on the output of the regulator... you might end up over loading the regulator and buring it out (if you put it under a heavy load) or if you lucky messing up the operation of the flyback mode.

    [ 11-22-2001: Message edited by: Fosgate ]
    Fosgate

    System Comp V3 - In progress.
    Low power MB with C7 CPU, DC-DC PSU, car ECU link, USB TV, GPS, 7" TFT, Wireless, Voice.

  10. #30
    Newbie
    Join Date
    Jul 2001
    Posts
    4

    Post

    I have some research to post..
    Okay, here it is..

    My car is a 6cylinder family car with a 550CCA battery, when you start the car, the voltage drops to around 11, and when the car is idling it is about 14, so, I am not going to even bother with a buck-boost supply, I am just going to use a low dropout high current regulator to prevent over voltage...

    Okay
    here is some more stuff, that is FACT!!!

    LM2587-12:

    5-6volt input - 1.6amps out
    6-16volt input - 1.2amps out - I think we chose the wrong one
    11-12volt input - 3.7amps out
    11-16volt input - 2.2amps out
    16-40volt input - 5amps out

    As you can see, it would probably be better to pre-regulate the car supply to 5volts..
    But, you can actually get more power out of it than we thought because that was worked out as the minimum, which was with a 6volt input..

    Also, the cars alternator can give spikes of upto 100volts, so, go fry your HD by connecting it straight to the battery if you wish, feel free to argue..

    [ 11-23-2001: Message edited by: SkinnyBoy ]

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •