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Any body build it? (12v to +35-35)

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arvinfx

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Hi,

I try to make power supply for car audio amp from this schematic:
**broken link removed**

Any body do this or some like this project?

It`s Work?
 
I see no reason why it wouldn't work, and the projects on that site are usually excellent - it's simply doing what all high power car amplifiers do. However, the low cost (and small size) of such units means it's not really financially viable to build your own.
 
I build it and not working but i have to try some problems...

It`s my fun and i now better to buy an amp pack about 30-50$ ;)

The step-up topology is not absolute work and in real it is very weak .
 
I build it and not working but i have to try some problems...

It`s my fun and i now better to buy an amp pack about 30-50$ ;)

The step-up topology is not absolute work and in real it is very weak .

It looks a pretty standard switch-mode design, assuming you've built it correctly I would imagine the problem is down to your transformer not been good enough? - did you use the specified core?.
 
It looks a pretty standard switch-mode design, assuming you've built it correctly I would imagine the problem is down to your transformer not been good enough? - did you use the specified core?.

right core? there is no "right core" at 60Hz. the circuit is a hobbyist grade AC inverter
 
Hi,

I try to make power supply for car audio amp from this schematic:
**broken link removed**

Any body do this or some like this project?

It`s Work?

you need to use a normal AC transformer rated for more than your expected load. to supply +/-35V@1A you would need an 80VA transformer (more actually) that costs $35 and weighs in at 4 pounds.
 
I suggest you look again, as you are completely 100% WRONG!!.

It's a high frequency switch-mode PSU for generating +/-30V or so for running high power amps in a car.

my bad ... i missed the units for one of the parts of the equation. 60KHz not 60Hz. MOST switching cores would work. it is more important that the inductance of the primary and saturation current be high enough.

having actually seen what they are doing as opposed to looking, it seems overkill... simple boost and inverter circuits would suffice at those conversion points. it does not make any sense to have an over complicated power transformer to save on silicon when two simple inductor switchers would suffice.
 
my bad ... i missed the units for one of the parts of the equation. 60KHz not 60Hz. MOST switching cores would work. it is more important that the inductance of the primary and saturation current be high enough.

having actually seen what they are doing as opposed to looking, it seems overkill... simple boost and inverter circuits would suffice at those conversion points. it does not make any sense to have an over complicated power transformer to save on silicon when two simple inductor switchers would suffice.

I suggest you study it further, and consult every single commercial unit I've ever seen or heard of - you need a transformer!.
 
I suggest you study it further, and consult every single commercial unit I've ever seen or heard of - you need a transformer!.

commercial units put profitability over everything including reliability. it is more profitable to do a warranty replacement on 5% of all shipped units when 50% will be repurchased in a 3 years than it is to build something that will last 10 years. it is also more profitable to have a custom transformer built, incurring thousands of dollars in NRE, to pay $3 for the transformer instead of $4 for 2 inductors.

on the other hand it makes no sense at all for a hobbyist to buy a $20 off the shelf switching transformer when 2 $4 inductors will do fine
 
commercial units put profitability over everything including reliability. it is more profitable to do a warranty replacement on 5% of all shipped units when 50% will be repurchased in a 3 years than it is to build something that will last 10 years. it is also more profitable to have a custom transformer built, incurring thousands of dollars in NRE, to pay $3 for the transformer instead of $4 for 2 inductors.

on the other hand it makes no sense at all for a hobbyist to buy a $20 off the shelf switching transformer when 2 $4 inductors will do fine

You can't have it both ways :D

The commercial manufacturer would be paying as LOT less for two inductors than he would for an expensive transformer - it's done with a transformer because it's by far the best way.
 
You can't have it both ways :D

The commercial manufacturer would be paying as LOT less for two inductors than he would for an expensive transformer - it's done with a transformer because it's by far the best way.

actually i can... what it costs for a mfg custom in the millions used in consumer goods is a huge difference from what a hobbyist would pay.

i can design and have a custom built for $2 (30W universal input) that would cost a hobbyist $20 if they could find it... $9 gets a basic versa-pac from coiltronics that will only handle low input voltages at i dont know with out actually working on it - maybe 20W at 500KHz
 
actually i can... what it costs for a mfg custom in the millions used in consumer goods is a huge difference from what a hobbyist would pay.

How does that affect the same manufacturer having a transformer custom made or a pair of inductors custom made - your point (as I read it) was that it would cost much more for the inductors. Particularly as the number of inductors would be double the number of transformers.
 
How does that affect the same manufacturer having a transformer custom made or a pair of inductors custom made - your point (as I read it) was that it would cost much more for the inductors. Particularly as the number of inductors would be double the number of transformers.

there is some confusion then... my points (multiple) were that it is much less for a hobbyist to build multiple inductor based converters and much less for a manufacturer to have a single transformer based multiple output converter.
 
there is some confusion then... my points (multiple) were that it is much less for a hobbyist to build multiple inductor based converters and much less for a manufacturer to have a single transformer based multiple output converter.

Right, I take your point - but even so, I don't think it's ever been done in that way - there's seems little point, and it wouldn't give isolated secondaries, even assuming you could generate split supplies in that way?.
 
Wow lads.

I've read that project page over and over a while back as I wanted to make a low voltage relatively high quality (and powerful) amp for monitor speakers. The power involved, and the fact the output is bipolar, really does mean a transformer is required (as opposed to simple boost converters). Although given the switching topology, its winding ratio can vary.

Another restriction (a BIG one) is its use for audio, so one must push the frequency up well out of the audio band, and even then beat frequencies betwen parts of the circuit can creep into the audio chain. The EMI from that circuit should be quite low, as relatively low conducted noise for a switched mode power supply. A flyback or boost would require so much filtering it could esily double the cost/size of the unit. Constant frequency PWM is mandatory for low noise applications, to ease filtering, at the cost of possibly most complex parts, and lower effiency at low power.

So, could it be built cheaper? if it was simply a quick and dirty 12V to +/-35V supply, at that power, its possible, but it wouldn't be any good for audio. That page is MADE for audio, perhaps not the finer points of SMPS, but I'm confident that schematic will work jstu fine for an amp. Ubergeek, if you feel you can knock up a schematic which the same noise output, efficiency, that uses less parts and is cheaper, go ahead! Its not the only way to do it, but I feel the designer, given all the variables (including parts availability, since the PWM chip is common) did an excellent job :)

Only ***** about SMPS, is winding your own transformer, getting any core gapping right etc.. really does require an oscilloscope.
 
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At first i build a boost circuit but the power is to low for my purpose about 70W (the boost topology can provide max power 150W in best design) and i find that webpage and assemble that with SG3524 . ( in the schematic is SG3525) and have both + and - 35 on output!
My problem in now is about current output it is about 50ma!!!!! and if i sink more current the input current extremely rise up about 5A.!
Some one say to me this problem is about feedback

The noise can reduce very acceptable with LC filter on both output, I say at my last post this is my hobby and i have perfect electronic laboratory ...
 
My problem in now is about current output it is about 50ma!!!!! and if i sink more current the input current extremely rise up about 5A.!
The power supply can supply 5A at 70V which is 350W. Ampliifiers get hot so their max output is about 200W and 150W is heat.
The battery must supply 350W and its current is 350/12= 29.2A. But the fuse is only 25A.
 
Have you measured the frequency of your PWM? also, any parts you have used that are different from the ones in the schematic, list them here or at least check they are compatible.. For example, using different MOSFET's, they might have larger gate capacitances, so they don't turn on/off very quickly. This will mean they will not conduct fully, and so have a larger voltage across them = power dissipation = heat. It would also drop your output voltage if you draw more current from it. Or perhaps they have a higher on resistance... or perhaps you're taking them past their rated voltage.

There are many things that could go wrong. But the most important components to check in this circuit are the switches, and the transformer.

The most obvious thing to check in this circuit, would be the transformer. At the very least, even if you used exactly the same core material and size, with the same windings, you should stillmeasure the inductance, and check for saturation when the circuit is active. It is likely that as you draw current from the output, the feedback loop changes the PWM duty cycle, and perhaps pushes YOUR transformer into saturation, making a nice heater!

As there are many different ferrite cores around, they can vary wildly with their properties, best way is to scope the transformer to see what the waveforms look like, and compare with common reference waveforms found all over the internet.
 
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