80V DC supply from a 12 or 24 Volt Battery ?

Discussion in 'General Electronics Chat' started by Joster, Dec 5, 2013.

  1. Joster

    Thread Starter Member

    Jun 12, 2013
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    Hi all,

    I'm wondering if it's possible to build some kind of DC to DC converter to get 80V from a 12V battery or maybe two in series. I'm trying to build an audio amp that will give me an 80 V peak to peak signal and run it off of a battery. Obviously at 80V my current supply will be limited bit I'm not sure what it would be limited too.

    Any tips would be awesome!

    Thanks,

    Joe
     
  2. tcmtech

    Well-Known Member

    Nov 4, 2013
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    At and 80 VDC rail voltage you are likely pushing a good deal of power so to be honest the easiest cheat would be to take an off the shelf power inverter and tweak the DC - DC power supply side to put out 80 volts.

    Given that most common 120 VAC output inverters have a 160 - 170 VDC high side rail voltage redoing the main power transformer to have half the secondary windings and changing the voltage feedback circuit to read at half the normal DC voltage should give you a pretty solid and reliable 80 VDC high capacity power supply.

    Of course the high side rectifiers will need to be changed if you are drawing more amps than they are rated for.
     
  3. Joster

    Thread Starter Member

    Jun 12, 2013
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    Thanks!

    That is a great idea but I don't think I'm savy enough to tackle that hack. What about if I used 4 12v batteries. 2 in series for a +24V supply and 2 in series for a -24 V supply. And then used some kind if doubling circuit for at total potential difference of 96V ?
     
  4. tcmtech

    Well-Known Member

    Nov 4, 2013
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    If you can't handle that hack you probably can't handle making a DIY high current voltage doubler system either.
     
  5. ian field

    Distinguished Member

    Oct 27, 2012
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    There's a *LOT* of stuff for in car audio freaks if you look in the right places.

    56V - 0 - 56V inverters are common - I'd be surprised if a bit of shopping around didn't find the voltage you want.
     
  6. Jony130

    AAC Fanatic!

    Feb 17, 2009
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  7. tcmtech

    Well-Known Member

    Nov 4, 2013
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    The whole problem with building any car audio amplifier is the same as building your own power inverter.

    By the time you buy all the parts and put them together, assuming you have the skills to do so in the first place, you could go out and buy two or more mass produced ones that would out perform your DIY unit in all rational measure and performance.

    As a person who spent way too much time in the car audio world in my late teens to mid 20's I can assure you that when I wanted to design my own stuff I started with off the shelf mid range quality amplifiers and modified them to perform as I wanted.

    No point in spending countless hours and amounts of money building a amplifier when I could buy a factory built one and modify that for far less time and money invested. ;)
     
  8. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    I built one back in the day. You need what's called a push-pull forward converter. Probably a lot cheaper to buy one these days.
     
  9. MrSoftware

    Member

    Oct 29, 2013
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    Just for my own education; Could the voltage be raised by using a group of capacitors instead of a transformer? This way the power can remain DC, no need to create an inverter. For example, a circuit which can switch a group of capacitors to parallel wiring while they charge to 12V, then quickly switch them to series wiring to multiply the voltage. Use the high voltage to maintain charge on a larger capacitor that feeds the high voltage rails. Continue switching them between parallel and series to keep the flow going. Aside from most probably creating very noisy DC power, what are the other technical reasons that no one does it this way?
     
  10. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Not for your application. capacitor (charge pump) boosting is for low current applications only.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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  12. ian field

    Distinguished Member

    Oct 27, 2012
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    If you mean a Cockroft & Walton diode capacitor voltage multiplier - its quite difficult to get much power out the other end, you either have to use very large capacitors or high frequency, and very large electrolytics tend to have issues with ESR and parasitic inductance.

    Having said that - I think one of the Philips car radio audio amplifiers uses a charge pump voltage doubler (+ & -rails) to break the 17.5W barrier.
     
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