How to design an Uninterruptible Power Supply (UPS)?

Discussion in 'The Projects Forum' started by mdzhdhaka, Sep 13, 2008.

  1. mdzhdhaka

    Thread Starter New Member

    Sep 13, 2008
    Hello there!
    To build an UPS (off-line or on-line) is my BSc. Engg. project topic and tried a lot to collect the circuit diagram of UPS around 600VA (for supply voltage of 220V AC) but didn't find any good one to construct it.
    It will be a great help to give any information about the circuit diagram of UPS or its major components such as inverter (pure sine wave or modified sine wave inverter, anyway, it will be great to find the multilevel inverter circuit), battery charger, control circuit.
    I'll be ever grateful if any can give any reference.
    asif16119 likes this.
  2. SgtWookie


    Jul 17, 2007
    I have yet to see a decent schematic published on the Internet for a UPS.

    This is an area that's only marginally profitable for the manufacturers, and they jealously guard their schematics and theories of operation.

    There are different types of UPS's. True UPS systems are continually online, generating the required output while their battery or batteries are constantly being recharged. There is a sacrifice of efficiency for this truly uninterrupible power supply.

    The other type is a standby UPS; these keep the batteries charged, and constantly monitor the status of the line voltage. If there are power surges, sags, "brownouts" or other anomalies, the inverter section is brought online and the mains disconnected. There is a small time delay between the mains power anomaly and the inverter "kicking in". Some loads can tolerate this lag, and some loads cannot.

    A typical mainframe computer installation would use a "true" UPS. They have better than 99.99% "up" time.
    A typical home computer installation would use a "standby" UPS. They aren't as stable.
  3. iONic

    AAC Fanatic!

    Nov 16, 2007
  4. Tahmid

    Active Member

    Jul 2, 2008
    If you are planning to make a square wave offline UPS, the circuit would be pretty easy with discrete parts, but if it has to be modified sine or pure sine, use of microcontroller is necessary.
    If you can give more details, I may be able to help.

  5. karthik_dm


    Oct 16, 2008
    thankz for sharing
  6. rajmehta

    New Member

    Oct 17, 2008

    Yes, Exactly I completely agree with Tahmid. As per he said i made square wave UPS and believe me it was successful project from my school time.
    Bye the share your experienced after complete it...
  7. scubasteve_911

    Senior Member

    Dec 27, 2007

    The problem with that schematic is that it lacks source code for the micro, also, i couldn't find information on some of the transformers used.

  8. karthik_dm


    Oct 16, 2008

    check out this inverter circuits,they produce square wave AC output from the 12v DC input from battery, to increase the wattage u hav to increase the transformer and driver transistor/mosfet current rating..the basic oscillator is common for all inverters u can also vary the output freq. by changing the sq.wave oscillator freq..set it to 50Hz..
  9. jblueink


    May 27, 2008
    pls can you help with the source code and the transformer rating of the inverter circuit you provide,atlist that will make the circuit more useful and helpful
  10. karthik_dm


    Oct 16, 2008
    thanks for your interest...
    the circuits i have given are simple inverters. They are square wave oscillators. The square wave output feeds the driver transistors and switches them alternatively. i.e.,during +ve cycle the upper pair of transistor conducts and vice an alternate switching of transformer winding(primary) takes place. Then the 12v AC at primary is stepped up to 220v AC at secondary. They don't need any programming. If you prefer microcontrollers for switching in inverter then you have to write a program for generating square wave;some use PWM.....Transformer ratings depends on the wattage you need. for ex. if P=500 watts, then P=V x I. since V=220 volts, I=P/V
    i.e, I=500/220.then the current I=2.27Amps. so you need a step up transformer with ratings of 220V/3amps at secondary end for 500W.There are transformers readily available. Or u take one from older UPs. for testing you may use a 12V-0-12v/8A step-down T/F by using its secondary as primary and pri. as secondary..