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Old 20th May 2003, 11:42 AM   #1
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Default Car Audio PSU Ideas

I've been looking at this for a while now and still have no idea whick way to go.
Output ripple isn't really a large factor in the design since alternators give out a large amount anyway so ruling out linear reg's is a good idea, there power disapation also leads to alot of wasted money on heatsinks and whatnot.
Switching regs are the next option and probly the best. But all have similar effiency figures at high currents.
My question is which type is more suitable to the application (Buck, boost, half wave, full wave)?
Mains voltage switchers arn't really for the DIY'er so there ruled out.
I'm going to attemp to learn PIC programming so this might be a first project (with alot of practice).
Prefered stats - ~40amp , 9-16v
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Old 23rd May 2003, 01:41 AM   #2
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Hi,

Do you mean a power supply for in the car, or on the bench? If you're talking about building a switcher for in the car, your only realy option is push-pull. It's the only topology that will get enough power from the low (12v) input.

-Dan
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Old 23rd May 2003, 03:11 AM   #3
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Quote:
Do you mean a power supply for in the car, or on the bench?
Bench supply, for testing/home usage of car amps.
Probly a 25v supply but I havn't got any transformers yet
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Old 24th May 2003, 02:49 AM   #4
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Quote:
Originally posted by fr0st

Bench supply, for testing/home usage of car amps.
Probly a 25v supply but I havn't got any transformers yet
fr0st,

I wouldn't bother trying to come up with an AC powered supply. Use a deep cycle battery, and small DC supply to float charge the battery when not in use.

In all honesty, I have both, a large (85 Amp) 12 volt supply, and a deep cycle battery. I prefer the battery. Current capacity is much higher than the supply. (about 10 times). Also, I have run into problems using the supply to power amplifiers. Sort of a zero beat problem between the two swithing frequencies (the supply, and the amp).

Oh, yeah, a battery will be much much cheaper...

-Dan

P.S. If you're still looking for large torroid cores, I may be willing to let one of mine go... ...in all reality I'm probably not going to use them all...
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Old 24th May 2003, 03:03 AM   #5
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Default push pull is where you are headed

there are some switcher experts on these pages --

a 400 to 800 watt switching power supply is by no means a trivial excercise. with the push pull format you can design the windings of the transformer secondary to deliver the rail voltages you need. I highly recommend that you take a look at the ARRL Handbook section on switching supplies (or the equivalent RSGB book).

there really seems to be a demand for a high power switcher PCB! If no one else does it, I will design it, but will fix it for one of the chips I like,
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Old 24th May 2003, 11:24 AM   #6
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I've considered a battery I'd rather a power supply for the main reason that it would be used for alot fo other testing not just car audio.
The float charge for a battery is about 13-14v anyway so there still the posibility of scaling it down and use it as a charger.
Linear regs are a good option in elimitating beat frequency between power supplys but the inefficiency of it makes it an expensive option.
Quote:
a 400 to 800 watt switching power supply is by no means a trivial excercise. with the push pull format you can design the windings of the transformer secondary to deliver the rail voltages you need.
A design like the ESP car SMPS is possible but you would be limited by core size. Parallel transformers is out for DIY as I've tried before it near impossible to get the voltage just right and for them to stay that way.
Is it possible to use chips like the tl494 and 3524/3525 in a switching regulator (buck)?
Although inductors arn't cheap many could be paralleled for higher current.
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Old 26th May 2003, 04:45 PM   #7
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Quote:
Originally posted by fr0st

The float charge for a battery is about 13-14v anyway so there still the posibility of scaling it down and use it as a charger.
Linear regs are a good option in elimitating beat frequency between power supplys but the inefficiency of it makes it an expensive option.

Is it possible to use chips like the tl494 and 3524/3525 in a switching regulator (buck)?

I usually float charge my battey with 12.8 volt supply. I have an 8 amp supply doing that, with a constant 1 amp load (piece of equipment that always needs to run...) You don't want to float charge a battery with much more than it's normal terminal voltage, at least for long term.

As for linear regs... ...it can be done that way, but for the current you'd need, you'll need some really really big components. Even then, you'll probably have difficulty getting to the required current. I'm not saying that it can't be done... ...it can, but it may be more trouble than it's worth. What exactly are your requirements/design goals?

-Dan

P.S. There's a pic of a 2Kw DIY switcher.
Attached Images
File Type: jpg supply.jpg (87.8 KB, 1255 views)
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Old 26th May 2003, 05:01 PM   #8
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Default note the liberal use of hot-melt adhesive!

do well all use Hot-Melt for keeping caps in their place -- I do too!
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Old 26th May 2003, 07:34 PM   #9
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Quote:
Originally posted by dkemppai
If you're talking about building a switcher for in the car, your only realy option is push-pull. It's the only topology that will get enough power from the low (12v) input.
H-bridge (aka full-bridge) is even better, especially from a reliability standpoint.
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Old 27th May 2003, 01:37 AM   #10
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Default Re: note the liberal use of hot-melt adhesive!

Quote:
Originally posted by jackinnj
do well all use Hot-Melt for keeping caps in their place -- I do too!
I have a friend who's said that "With a hot glue gun and a soldering iron, you can make anythying!" Sometimes I think he's right! It's great for prototypes!

Quote:
Originally posted by RobM
H-bridge (aka full-bridge) is even better, especially from a reliability standpoint.
Problem with H-bridge is that you have two pairs of switching devices in series with each other, on each side of the transformer. Therefore conduction losses double, so it's not as efficient. H-Bridge is great at high input voltages, where currents are small, and conduction losses are minimal.

Push-pull can be as reilable as H-bridge... ...it's all in the design, not the topology...

-Dan
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