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Switching Supply — Parallax Forums

Switching Supply

bennettdanbennettdan Posts: 614
edited 2006-06-14 22:56 in General Discussion
Hello
···· I have a battery pack that has 120vdc comming out of it and want ot drop it down to about 30vdc so I can then use a linear regulator to get voltage needed to run my stamp circuit. Does anyone know of a way to drop it down say like a switching power supply circuit? I need atleast 10 amps.

Post Edited (bennettdan) : 6/13/2006 9:21:54 PM GMT

Comments

  • stamptrolstamptrol Posts: 1,731
    edited 2006-06-13 19:18
    Bennettdan,

    This will be a pretty serious design project if you need a reliable unit. I've used some packaged units from Melcher which will certainly do the job. They are efficient switching units and are bulletproof.

    If you decide to build your own, it goes without saying that your battery bank can inflict damage and injury if it gets away from you. The crudest designs will have short pulses at 120 VDC with an average of 30 VDC. Without proper filtering and regulation, your downstream equipment will be exposed to peaks many times over its rating.

    Is there any other way to feed your system?
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2006-06-13 19:39
    www.vicr.com/documents/datasheets/ds_vi-200.pdf
  • bennettdanbennettdan Posts: 614
    edited 2006-06-13 20:54
    I have an electric truck conversion I am building and have built the controller for it I have tested it on smaller voltages like 48 vdc and I am ready to go higher I will still need 24vdc off of my battery pack so I plan to build a swicth mode supply to operate my drive curcuit. I have some really nice isotp IGBT transistors I plan to chop the voltage to about 30vdc as you suggested then use a comaparator curcuit for protection and then use linear regulators to produce the 24vdc out.
  • stamptrolstamptrol Posts: 1,731
    edited 2006-06-14 12:09
    Bennettdan,

    I was involved with electric vehicles back in the 80's and had a great time experimenting. Did some early work on a 400 Amp chopper for main motor control. It was an early use of MOSFETS where I put 40 in parallel. A real monster but really demonstrated that the MOSFET was easy to control and would load-share reasonably well.

    PJ's suggestion will work as well as the Melcher I suggested and will allow you to keep going without getting bogged down in a design project!

    Cheers
  • bennettdanbennettdan Posts: 614
    edited 2006-06-14 20:38
    I have a drive that is working and I am using a dual pack IGBT modual that is rated for 600A it is made by powerx its in an isotop design and is quite compact.
  • stamptrolstamptrol Posts: 1,731
    edited 2006-06-14 22:11
    Sounds like you're well on your way and seem aware of the pit-falls.

    If you decide to build your own, why not use a spare IGBT even though it will be over-kill.....you'll always have a spare drive transistor with you!

    To drive the Gate of the IGBT, you could probably use something like the PWMPAL from Parallax and use a Stamp to monitor the output voltage and adjust the PWM level to keep the average voltage within range. Would still need lots of filtering, but shouldn't be too hard.

    Any pics of your truck?

    Cheers,
    Tom
    www.siskconsult.com
  • bennettdanbennettdan Posts: 614
    edited 2006-06-14 22:56
    well I have a small curcuit I have been testing with 48v off of 4 batteries the only problem I have is when the battery voltage drops when I engage my traction motor. I dont know if a a/d and stamp combo will keep up I thought about having a comparator curcuit setup to belooking for 29v and 31v then I can use my curcuit with a digital pot and pulse the pot up and down to keep it close to 30v I think this will be faster than the a/d, what do you think?
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