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Thread: Basic UPS Circuit for DC-DC converter

  1. #1
    Join Date
    Nov 2003

    Basic UPS Circuit for DC-DC converter(alternative solution)

    Original posted from

    Circuit : Andy Collinson
    Email: [email protected] ( I didnt design the circuit)


    I have been looking for the alternative solution for the OPUS 150 Watt power supply since they told me to wait for three weeks.

    I think alot of people want a UPS or PSU in their cars, that way we dunt need a shutdown controller for the computer and we dunt even have to wory about the ciritcal low voltage (8 ~10 volt) during the ignition.

    So , this is what i have found on line, a Basic UPS circuit.

    and here is my plan:

    1)I will remove the western bridge since we only use that for AC inverter.

    2)input is from the cigrate lighter (12 ~14Volt)

    3)insert a 12 Volt UPS battery (from Ebay) at B1

    4) add a DC-DC ITX or ATX power supply at V2

    That way, if the power from cigrate lighter failed, 12 volt battery will keep supplying the power.

    The good thing about this project is we dunt have to hook our power supply to the car battery and we dunt have to worry about the ciritcal voltage during the ignitation , and it is cheap

    The down side about this project is I am not too sure how long will it take to fully charge the battery from the cigrate lighter, and there is no sign to tell you that the remaning left in the battery. I might be able to design an alarm circuit with LED indicator. And the most important thing. Since we are dealing with 5 amp or 6 amp current for our computers, I am not sure the current will heat up the component and burn the circuit.

    I have been tested my circuit on the Pspice and it works on the simulation. Unfortuantely, I really dunt have any real hand experience and I'm wondering if any one can give me some advice here, thank you
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  2. #2
    Join Date
    Nov 2003
    U can check the original URL for the voltage and the current calculation.

  3. #3
    Join Date
    Nov 2003
    Another Soluton:

    12 V car battery (8 v ~14 v)---> 120 V 150~450 w inverter ----> UPS w/ LED indicator(from fry's)---->regular computer power supply.

    not to efficent, but it is the cheapest way since the inverter only cost me 29 dolars and 35 dollars for UPS, and I already have my power supply from my old computer.

  4. #4
    Raw Wave
    Join Date
    Jun 2003
    VP2 only outputs 5V throught 7805.

    You can get 7812 with maximum current of 2A at 12V and no more. But with this regulator you need about 14V minimum for it to output 12V...check the datasheet as I cant remember.

    The charging current is quite low, youll find it take a day or so before your backup charge to 100%...of course it depend on the capacity.

  5. #5
    Low Bitrate pc832's Avatar
    Join Date
    Nov 2003
    San Diego
    I just posted this in another thread.

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