off line 400 volt supply

Discussion in 'The Projects Forum' started by themotorman, Nov 10, 2010.

  1. themotorman

    Thread Starter Member

    Jun 13, 2009
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    I need a battery charger capable of 400 volts 5 amps constant current then constant voltage when battery has reached 400 volts. I need a few suggestions as to the IC for the controller, my old choice would be the UC3825 but I think that newer better choices might be out there. This will be a buck converter as I will double the 240 volt 60 hz . Ideas please. Thank you.
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Bear in mind that you would be doubling 230*1.414 = 325V, not 230V.
    Generally speaking, that will be pretty hard to achive, as the power required is 2kW, which is not small. According to the usual SMPS design guides, you will need a flyback converter with half-bridge primary and preferably center-tapped secondary. Or a whole bunch of smaller ones.

    Just look at schematics of the higher-wattage computer PSUs like 500W+ and you should see how it should be done. Maybe except for the voltage doubling option on the primary side when used at 120V, which you certainly don´t need.
     
    Last edited: Nov 10, 2010
  3. SgtWookie

    Expert

    Jul 17, 2007
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    Even if you're 85% efficient (about the going rate for reasonably well-thought-out hobbyist circuits) with 240VAC in, you'll be drawing nearly 10 amps on the supply, which is not inconsequential - and at 85% efficiency, you'll be dissipating roughly 350W of power in the supply alone. :eek:

    Did you look at TI's page for related products?
    http://focus.ti.com/docs/prod/folders/print/uc3825.html#relatedproducts
     
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  4. themotorman

    Thread Starter Member

    Jun 13, 2009
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    I am doubling the 240 volt input so I will have about 650 volts peak so a buck converter seems like the simpler approach. I know it's a lot of power since it will be used to charge my EV batteries. The UC3825 does have pulse by pulse current limiting and I have used it before. Since the UC3825 was designed so long ago I thought that some of the newer BiCMOS chips might be better. I will run at around 20 Khz to make sure that my IGBT losses are reasonable. It is not an easy challenge and I just wondered if anyone had done anything similar, hence my call for help.
    More ideas ?? Thank you.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Well, if you're going to try to switch it slowly, you will need LARGE inductors that will need to store & release that energy efficiently - which will be a LARGE problem.

    You're going to have to find the best trade-off between switching speed and inductor size.

    If you want to switch it at 20kHz, I predict that you will need a large inductor that will have to sustain a good deal of power dissipation; therefore expensive.

    Look into better gate drivers instead. Don't worry too much about turn-ON times if you are in discontinuous mode; it's the OFF times that will kill you. If you're in continuous mode, the turn-ON times will kill you as well.
     
  6. themotorman

    Thread Starter Member

    Jun 13, 2009
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    Thanks again. I wanted to use IGBT's because they are reliable and rated for high voltages and not expensive. IGBT's are not good for high frequencies hence my choice. Yes, the inductor will be pretty large but my current of 5 A is not very high so I think I will be OK. The UC3843 looks like an IC that might work well. I was planning on using the IR high side drivers as they have more than adequate energy/pulse for my app. An alternate approach is to use SCR's but then I am limited to a phase control high voltage system. with all the energy stored in high capacitance high voltage caps.
    An area that might be a challenge is that when nearly all the cells are all at max voltage it is necessary to trickle charge at around a few hundred mA so that all cells are full together. That means the supply must jump from 5 A to 0.2A . I haven't worked my way thru that yet. Ideas ?
     
  7. SgtWookie

    Expert

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    Well, I don't have a clue what kind of batteries you're planning on using - or are using.

    Li-Ion? SLA? What?

    Do a search for "synchronous buck controller", and start learning about them. The idea here is that a MOSFET can be used as an "ideal diode" to avoid the power losses that a typical diode would have.
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Unless the voltage you are using to charge the batteries is INSANELY higher than the battery voltage, the battery itself will limit current going in to a much lower amount (close to your .2 amp figure) as it gets close to a full charge.

    If the battery pack is 240 volt and you are using 400 volts to charge with then you MUST limit current. If you are using 260 volts to charge with then the battery will self limit the current it draws when nearly fully charged.

    Without more info on the batteries(type and size) it would be impossible to give more accurate help.
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
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  10. SgtWookie

    Expert

    Jul 17, 2007
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    You might also want to look at the UC2906 and UC2909 battery charge controllers. These were specifically made for charging batteries.

    Another option might be to use a microcontroller to monitor the bulk charge/absorption/float/equalization phases, depending on what batteries you're going to use.
     
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