Need some help designing an SMPS for a car amp - diyAudio
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Old 24th June 2010, 05:15 AM   #1
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Default Need some help designing an SMPS for a car amp

I'm working on a project using 4x TDA8950 modules in BTL (midwoofers) and 2x TDA8950 (mid/tweeter) modules in SE for a car stereo project.

Since its for audio I'm guessing I'll need +/-35V at no more than 12-15A or so. Theoretically this beast will be capable of 200x4 + 100x4 RMS but in practice it will be less and as such the PSU need not provide the full 1200W. The amp is being purposely overbuilt for dynamic headroom. (clipping? what's that? )

I'm working with a friend on the PSU and were debating on what topology to use. We have decided on some sort of push pull converter but there are a few similar topologies as well and we're not quite sure which is best.

Also, what control system should we use? I was thinking a TL494 and a comparator for the overload protection although I'm unsure how it all goes together. My friend suggested a 556 and a handful of logic and comparators.....although I think that may open Pandora's Box even further. (He graduated with his EE degree a short while back and likes to build EVERYTHING from scratch.)

Do I wind my own transformer or is there some place I can get one? Some of the homebrew SMPSes I see on here look like they have prefabricated transformers and they look *good*.

SMPSes are new to me and my friend....this is an ambitious project as a first SMPS for sure! Once the topology is locked in, we can figure out the little details that make it tick.

If someone has a *tested* design (SPICE testing is OK too!) they'd like to point out or share, Im all ears.
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Old 3rd August 2010, 09:59 AM   #2
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Well, if this isn't coming in too late... The TL494 will be fine for a first project. However the 555 + comparator approach is viable (not a 556, you only need one), but only for single-ended applications such as flyback or 2-transistor forward. To get it to output signals suitable for a push-pull would require too much external circuitry IMO.

And just so you know, i'm only 19 and i got the 555 approach working all by myself on a boost converter and now on an off-line 2-transistor forward (yes, i use a 555 to drive a mains-powered circuit!) so it isn't really THAT hard. My main reference is "Switching Power Supply Design, Third Edition", it's a great book.
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Old 3rd August 2010, 10:11 AM   #3
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I don't see why you couldn't do several 100w smps, I used SG3525, buffers, irfz44's
and it has no problem driving 4x 400w amps, 2 of the channels are 800w @ 2R
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