Freind has a car audio 'demo board'.
Has been running it off car batteries (with charger) for a while.
I don't believe this is the best idea as he goes through two batteries a year.
He needs a supply (12-14VDC) capable of around 30-50 amps.
I'm thinking a simple unregulated (transformer, bridge rectifier, filter cap) would be fine.
Yes a regulated supply would be better, but at those currents suitable transistor arrays would be expensive.
Is a regulated supply feasible for this current demand ?
No I don't want a switched supply (output noise).
Your thoughts are welcome.
Has been running it off car batteries (with charger) for a while.
I don't believe this is the best idea as he goes through two batteries a year.
He needs a supply (12-14VDC) capable of around 30-50 amps.
I'm thinking a simple unregulated (transformer, bridge rectifier, filter cap) would be fine.
Yes a regulated supply would be better, but at those currents suitable transistor arrays would be expensive.
Is a regulated supply feasible for this current demand ?
No I don't want a switched supply (output noise).
Your thoughts are welcome.
I agree, cars are extremely noisy (electrically).
Hadn't thought of the motor driven alt.
Power wastage doesn't appeal to me though.
He does have one high current (15 A cont.) supply.
It was 'built' by someone with not many brain cells though.
It runs ultra hot and is not really protected at all.
17VAC trans --> bridge --> 10,000uf --> LM317 with two pass transistors.
The design is lifted straight from an application sheet.
So the reg/pass section is dissipating 12 volts to start with.
At a draw of 10A (normal drain) the poor thing is frying in it's tiny case.
The heatsink is barely big enough to mount the three TO3 trannies.
Hence why I'm trying to get him to let me build a proper supply.
I can design/build a regulated supply if he springs the $$$.
Just wondering if anyone has a better sugestion.
Must be as close to short term abuse proof as possible.
He aint always considerate of equipment
Hadn't thought of the motor driven alt.
Power wastage doesn't appeal to me though.
He does have one high current (15 A cont.) supply.
It was 'built' by someone with not many brain cells though.
It runs ultra hot and is not really protected at all.
17VAC trans --> bridge --> 10,000uf --> LM317 with two pass transistors.
The design is lifted straight from an application sheet.
So the reg/pass section is dissipating 12 volts to start with.
At a draw of 10A (normal drain) the poor thing is frying in it's tiny case.
The heatsink is barely big enough to mount the three TO3 trannies.
Hence why I'm trying to get him to let me build a proper supply.
I can design/build a regulated supply if he springs the $$$.
Just wondering if anyone has a better sugestion.
Must be as close to short term abuse proof as possible.
He aint always considerate of equipment
This is taken directly from National's LM338 data sheet.
This might be worth consideration. It's modular design
lends itself well to scaling.
Anything worth doing, is worth overdoing.
Cut to shape, file to size, pound to fit.
This might be worth consideration. It's modular design
lends itself well to scaling.
Anything worth doing, is worth overdoing.
An externally hosted image should be here but it was not working when we last tested it.
Cut to shape, file to size, pound to fit.
MadMutt said:
No I don't want a switched supply (output noise).
hi,
a filter is not a problem.
car audio amps already have suppressors.
star882 said:Output noise shouldn't be a problem. An automotive electrical system is very noisy.
indeed!..the alternator itself is noisy..
check this out: http://www.meanwellusa.com/search/usp-500/default.htm
i have a mean well rated @ 25A running my car amp for almost 2yrs now w/o any probs..
perhaps 2 supplies
Is this supply used for both head units and amplifiers?
Perhaps using the regulated unit for the cd decks. Likely more sensitive to 12v noise.
use the dirty unregulated for the big amps. My supply is unregulated but has 30,000uf in caps to supply power to an amp. For really big amps, a battery is a must to handle the peak amps.
I like the alternator idea. You can get alot of amps cheaper.
Is this supply used for both head units and amplifiers?
Perhaps using the regulated unit for the cd decks. Likely more sensitive to 12v noise.
use the dirty unregulated for the big amps. My supply is unregulated but has 30,000uf in caps to supply power to an amp. For really big amps, a battery is a must to handle the peak amps.
I like the alternator idea. You can get alot of amps cheaper.
cheapest...
...probably a 50amp car charger/starter with a battery in parallel, huge peak current capacity, but will supply 10-15 amps all day, total cost < $100.
If more average current is needed, parallel another charger. The only obvious drawback is the physical space required to hold the equipment.
HTH
Stuart
...probably a 50amp car charger/starter with a battery in parallel, huge peak current capacity, but will supply 10-15 amps all day, total cost < $100.
If more average current is needed, parallel another charger. The only obvious drawback is the physical space required to hold the equipment.
HTH
Stuart
big caps, more transistors
correction, my 12v 20amp unregulated has 200,000uf capacitance. I added a few cans a few years ago.
It is built from a collection of old spare parts. amazing the transformers they used in the computer power supplies in the 80's
the heatsink was littered with t0-3 pass transistors and 2-3 feet tall.
The initial design is not bad. Add a bigger heatsink and more pass transistors of the same type (2x). Parallel the voltage drop and current load to more transistors (basically make a bigger amp like the 1.5kw wonder on elliots projects). this will keep it cooler and increase current capacity.
then add cooling fan.
if the voltage sags, use a higher current transformer.
correction, my 12v 20amp unregulated has 200,000uf capacitance. I added a few cans a few years ago.
It is built from a collection of old spare parts. amazing the transformers they used in the computer power supplies in the 80's
the heatsink was littered with t0-3 pass transistors and 2-3 feet tall.
The initial design is not bad. Add a bigger heatsink and more pass transistors of the same type (2x). Parallel the voltage drop and current load to more transistors (basically make a bigger amp like the 1.5kw wonder on elliots projects). this will keep it cooler and increase current capacity.
then add cooling fan.
if the voltage sags, use a higher current transformer.
power supply
http://www.apexjr.com/images/bigtranny2.jpg
this transformer would make a great power supply.
Has multiple inputs and outputs....
http://www.apexjr.com/images/bigtranny2.jpg
this transformer would make a great power supply.
Has multiple inputs and outputs....
cheapest way
As the amp needs 50A at 12V, the economic way is using old stuff like 2n3055, these outdated stuff doesn't cost that much. Also lower the tranny voltage to AC12V, after rectification will get 16V. 4V at 50A need to dissipate 200W of power, computer cooling fan is suitable for minimize the size. If one tr. carries 5 Amps, 10 would do the job. consider this way. good luck.
gmphadte said:
As the amp needs 50A at 12V, the economic way is using old stuff like 2n3055, these outdated stuff doesn't cost that much. Also lower the tranny voltage to AC12V, after rectification will get 16V. 4V at 50A need to dissipate 200W of power, computer cooling fan is suitable for minimize the size. If one tr. carries 5 Amps, 10 would do the job. consider this way. good luck.
A switching regulator is not that hard to build nowadays. You could even build one capable of dropping 20V-50V DC (from some trafo and capacitors) to 13.8V DC at 50A-100A without producing too much heat with parts taken from junk car amplifiers. Conceptually this is called a "buck converter" and is one of the simplest posible SMPS.
Re: Re: Simple BIG 12VDC supply ideas wanted
Every Car amp over 25W/Ch has a switched-mode DC-DC Converter. Uhhhh, looks like Eva stole my thunder....
.....and almost everyone of those is controlled by the ubitiquous TL494 PWM IC. Oh, so is almost every AT/ATX computer psu....
With today's filtering techniques, most, if not all of detectable noise can be eliminated at the output, and you won't have to waste hundreds of watts of power in dissipated heat.
Also, with 200,000mF of capacitance, I hope you have some very heavy-duty rectifiers. They will have to supply all 30-50A of current to both the filter caps and the load during the 15-30 degrees of rotation near the peak of the haversine wave, enough to last for all 360 degrees of the unfiltered DC.
The resultant non-linear current waveform in F with the voltage waveform, yields an extremely poor Power Factor (PF). This can be mitigated by using an SMPS, with possible Active PFC front end.
Just a few ideas...................
Steve
MadMutt said:
Every Car amp over 25W/Ch has a switched-mode DC-DC Converter. Uhhhh, looks like Eva stole my thunder....
Eva said:
.....and almost everyone of those is controlled by the ubitiquous TL494 PWM IC. Oh, so is almost every AT/ATX computer psu....
With today's filtering techniques, most, if not all of detectable noise can be eliminated at the output, and you won't have to waste hundreds of watts of power in dissipated heat.
Also, with 200,000mF of capacitance, I hope you have some very heavy-duty rectifiers. They will have to supply all 30-50A of current to both the filter caps and the load during the 15-30 degrees of rotation near the peak of the haversine wave, enough to last for all 360 degrees of the unfiltered DC.
The resultant non-linear current waveform in F with the voltage waveform, yields an extremely poor Power Factor (PF). This can be mitigated by using an SMPS, with possible Active PFC front end.
Just a few ideas...................
Steve
Over the top brute force passive LC approach. But hey, its car audio.
1400VA toroid, kit available here.
4 parallel #9 center tapped 32 turn secondaries.
2 45V 60A or better Schottky rectifiers configured full wave, heat sinked.
Hammond 195G75 choke. 5mH, .01R. 75 amps. Rather expensive to buy new. Others could be substituted for saving at cost of performance and/or more bleeder current needed.
At least a Farad of capacitor bank, this is needed to keep transient behavior acceptable with extremely high Q choke. More would be better, say 4F+ a smaller low Z cap. Source resistance should keep diodes within surge ratings on start.
4.7 ohm bleeder resistor or bank, 100 watt+, eats ~40w.
Simulated: 13.9VDC @ idle, 12.6VDC @ 50A. 12VDC @70A. With 117V RMS mains.
1400VA toroid, kit available here.
4 parallel #9 center tapped 32 turn secondaries.
2 45V 60A or better Schottky rectifiers configured full wave, heat sinked.
Hammond 195G75 choke. 5mH, .01R. 75 amps. Rather expensive to buy new. Others could be substituted for saving at cost of performance and/or more bleeder current needed.
At least a Farad of capacitor bank, this is needed to keep transient behavior acceptable with extremely high Q choke. More would be better, say 4F+ a smaller low Z cap. Source resistance should keep diodes within surge ratings on start.
4.7 ohm bleeder resistor or bank, 100 watt+, eats ~40w.
Simulated: 13.9VDC @ idle, 12.6VDC @ 50A. 12VDC @70A. With 117V RMS mains.
As mentioned, the DC-DC converter in the amp renders my exercise silly for this application. Its tough, but the iron is just too expensive, and its heavier than even car batteries.
You might end up somewhere similar if you needed a filament supply for a very large direct heated tube amplifier. Here it would be a smaller part of your total capitol outlay...
You might end up somewhere similar if you needed a filament supply for a very large direct heated tube amplifier. Here it would be a smaller part of your total capitol outlay...
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