Need Help


Old 09-04-05, 02:26 AM
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Need Help

Hi guys I have a final project at the college and I want to design a converter for DC 12 volts which in the car to AC 220 volts and I need help
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Old 09-04-05, 09:17 AM
Join Date: Nov 2004
Location: CA
Posts: 2,041
Well, for $29 you can buy one at Radio Shack! But if you need to design, first you have to have a circuit which will create and alternating waveform, (i.e. multivibrator), and then something to smooth out the waveform ( transformeres don't like square waves.) Then you would use a transformer to step up to a higher voltage. If you are an EE student, you can figure out what step up ratio you need to take possibly ~12 volts Peak to Peak, step it up, and end up with 220 RMS. Naturally, you would want to include overcurrent protection and some voltage regulation. You would also have to specify the load current you are designing for. This will establish the necessary wire size for the DC end, the battery size, and the transformer primary current rating.
Old 09-04-05, 12:38 PM
Join Date: Aug 2004
Location: USA
Posts: 539
I'm not an expert,

but I think that the only waveform a transformer doesn't like is pure DC.

The transformer should operate from a sine, square or sawtooth waveform just fine-with some possible loss of efficiency.

You may want to search various chip maker's websites, I think they have developed some single-chip solutions to designing a switching type power supply-which is essentially what you're doing. The reference designs (including a block diagram of the chip itself) may give you a good starting point and some ideas on how to proceed.

For lower ouput current applications, you may be able to run two standard power supply transformer backwards, with the inputs and outputs in series-or maybe convert to 120V, then us another transformer for the final step up.

You may be to salvage transformers from old car battery chargers-or a welder if you can find one. These are usually heavy duty-high current tranformers, one or two of these may work well for you. Just design and add a oscillator, variable drive (PWM?), and feedback/error correction. Fuses/breakers for safety too-on both the inputs and outputs!

I hope this helped!

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