well i'm thinking about rectifing the main line and getting 170V and using PWM with a few MOSFETs straight through a filter to get 14.4V at 50+ amps. no transformer, just PWM and a filter. will it work?
If you like danger and death, yes. Otherwise, NO!!!!!!!!!!!!!!! This is potentially lethal, and we like to keep the Forum members alive.
Aaaaaaaaaaaaahhhhhh ...
That is why they call 'em Isolation Transformers .... so that stupid DIY types won't stick their fingers into the box and kill themselves.
(FYI: anyone older than the age of 55 already knows this: one hand on the "rail" and one hand on the "ground" makes Jack a very, very dull boy.
)
I am a long time electrician and can assure you that I have taken enough jolts from the light sockets that the next one will probably kill me for sure ... No kidding. ... and my insurance would probably call it suicide and cut my wife outta da bennies.
That is why they call 'em Isolation Transformers .... so that stupid DIY types won't stick their fingers into the box and kill themselves.
(FYI: anyone older than the age of 55 already knows this: one hand on the "rail" and one hand on the "ground" makes Jack a very, very dull boy.
)I am a long time electrician and can assure you that I have taken enough jolts from the light sockets that the next one will probably kill me for sure ... No kidding. ... and my insurance would probably call it suicide and cut my wife outta da bennies.
There is a way ...
... to do this, but you should use a one to one torrid transformer and quick blow fuses and/or circuit breakers ... for no other reason than the results will be vastly improved, audio wise, and ... who knows, you might actually live through the experience.
(Most of the States' building codes insist that any alternating current voltage greater than 70.7 VAC be enclosed with shielding or at least 600 Volt resistant insulation ... cause that's usually the "threshold of death". ... and another thing: for DC volts, the "threshold of burn" is just over 28 VDC, ... ~30 VDC = nasty burns.)
... to do this, but you should use a one to one torrid transformer and quick blow fuses and/or circuit breakers ... for no other reason than the results will be vastly improved, audio wise, and ... who knows, you might actually live through the experience.
(Most of the States' building codes insist that any alternating current voltage greater than 70.7 VAC be enclosed with shielding or at least 600 Volt resistant insulation ... cause that's usually the "threshold of death". ... and another thing: for DC volts, the "threshold of burn" is just over 28 VDC, ... ~30 VDC = nasty burns.)
a 170V to 14.4V buck converter? please don't.
- safety, isolation, death, blah blah blah
- your input FET will have to switch 170V at 50A.
- your input capacitors will have to handle 50A of ripple too.
- you'll need a hell of a lot of input filtering to keep switching noise from heading back your AC cord.
- at 8.5% duty cycle, your output inductor will be massive. Have fun winding a gate drive transformer for that too.
etc.
- safety, isolation, death, blah blah blah
- your input FET will have to switch 170V at 50A.
- your input capacitors will have to handle 50A of ripple too.
- you'll need a hell of a lot of input filtering to keep switching noise from heading back your AC cord.
- at 8.5% duty cycle, your output inductor will be massive. Have fun winding a gate drive transformer for that too.
etc.
astouffer said:
More specifically, though, I meant why try this approach?
For simplicity's sake, there are plenty of off the shelf AC/DC modules that will give you a nice clean multi-hundred watt DC output with minimal external circuitry available. That would definitely be easier then what is mentioned above.
Internally, all of the isolation and filtering is in, but all the user sees (and has to work with) is a brick with some posts sticking out.
There's a much direct (and safe!) way to use a car amplifier at home.
Why using a smps to reduce line ac to 14.4V and, internally, a smps which raises the supply to 35-50V?
Let bypass the supply section of your car ampli. In this way you don't need a huge 50A psu!! ..only few Amperes!
Why using a smps to reduce line ac to 14.4V and, internally, a smps which raises the supply to 35-50V?
Let bypass the supply section of your car ampli. In this way you don't need a huge 50A psu!! ..only few Amperes!
Lyons-
Performing a search of the Power Supply forum would have turned up this thread, to which I humbly refer you:
http://www.diyaudio.com/forums/showthread.php?s=&postid=1005388#post1005388
Please read the entire thread before you do anything else to see why some have gone this route, and why it is so UNWISE (not to mention UNSAFE) to do so. I'm sure EVA, poobah, jackinnj, anatech or any of the other power supply gurus will chime in here and agree with this.
Regards,
Steve
Performing a search of the Power Supply forum would have turned up this thread, to which I humbly refer you:
http://www.diyaudio.com/forums/showthread.php?s=&postid=1005388#post1005388
Please read the entire thread before you do anything else to see why some have gone this route, and why it is so UNWISE (not to mention UNSAFE) to do so. I'm sure EVA, poobah, jackinnj, anatech or any of the other power supply gurus will chime in here and agree with this.
Regards,
Steve
The truth about switchers... you can't build one or two for what you could BUY one for... magnetics are the obstacle. Switcher magnetics are just about never "off the shelf". Besides, line direct apps here are taboo. Your idea is not that nuts, but for 700 Watts or so... you will choose a full bridge convertor and wind up with load isolation anyway (which is not taboo).
Here this top of the line with wide input and PFC... about $900.
You can find cheaper stuff that has certs.
If you are doing this to power car amps... consider the wisdom of knocking down all this voltage with PWM just to have the car amp boost it back up again.
$900 bucks will build a nice amp or 4 from scratch... and you won't need 700 Watts.
🙂
Here this top of the line with wide input and PFC... about $900.
You can find cheaper stuff that has certs.
If you are doing this to power car amps... consider the wisdom of knocking down all this voltage with PWM just to have the car amp boost it back up again.
$900 bucks will build a nice amp or 4 from scratch... and you won't need 700 Watts.
🙂
sounds like i need to explain myself a little. I do have a good bit of experience with electronics, I have been doing comercial electical work for a middle school that past few years and have just recently become interested in audio and power supplys. i have caught a hold of 277 and 115 and have even seen a survivor who has caught a leg off of 480. I know lethal voltages and i know 170V DC so please no more comments on that. Now since it sounds like this idea is a waste of time, would it be possible to bypass the car amps supply with a supply from the mains and have the amp work?
uh probably, but why?
by the time you futz around with all the mods to power supply etc, etc, you could probably build a much better sounding SS amp with far fewer parts
If your goal is numerous hundreds of watts of output power at which larger car audio amps are rated, you're in for quite a chore designing a stable and low impedance power supply.
However, if you're looking for musicality, I'd wager most of the better NIGC or digital amp projects/ kits out there would sound more nimble, articulate and refined than virtually any repurposed car audio product.
(notice I didn't even mention vacuum tubes )
Yourself and buddies who've survived shocks have just been lucky with the Telsa Roulette - one of these days the chamber will not be empty, and neither will the casket.
by the time you futz around with all the mods to power supply etc, etc, you could probably build a much better sounding SS amp with far fewer parts
If your goal is numerous hundreds of watts of output power at which larger car audio amps are rated, you're in for quite a chore designing a stable and low impedance power supply.
However, if you're looking for musicality, I'd wager most of the better NIGC or digital amp projects/ kits out there would sound more nimble, articulate and refined than virtually any repurposed car audio product.
(notice I didn't even mention vacuum tubes )
Yourself and buddies who've survived shocks have just been lucky with the Telsa Roulette - one of these days the chamber will not be empty, and neither will the casket.
lyons5959 said:
Just because the first five chambers were empty is no reason to explain to others that Russian Roulette is OK. Mains-driven circuitry is DEADLY DANGEROUS and discussion is against forum policy. Cease and desist.
First off...for safety sake use a isolated circuit as suggested...
This type of SMPS is fairly simple to make....
I would use a Push-Pull converter with passive driven synronous FETS on the secondary side....
You can wind your own transformer and inductor......
That way it would be isloated....
One misconception is that you get 170V DC when you are rectified from 120V AC.... that would be with vertually no load and massive filtering caps... As your load increases, then your ripple increases and your rectified DC is jumping around.... Most text books first order equations don't apply when you are feeding a switcher.... The switcher will have a negative input impedance...this means that as the ripple will take on a different waveform than a resistive load to the rectifier... The duty cycle will get bigger as the DC voltage swings lower with ripple, thus causing the voltage to decrease even faster with rise in input current, up until the duty cycle is limited.....
If your worried about EMC...you could put a input filter on the front end, it just needs to be well designed...
If you need assisatnce in doing this SAFELY.....let me know...
Chris
This type of SMPS is fairly simple to make....
I would use a Push-Pull converter with passive driven synronous FETS on the secondary side....
You can wind your own transformer and inductor......
That way it would be isloated....
One misconception is that you get 170V DC when you are rectified from 120V AC.... that would be with vertually no load and massive filtering caps... As your load increases, then your ripple increases and your rectified DC is jumping around.... Most text books first order equations don't apply when you are feeding a switcher.... The switcher will have a negative input impedance...this means that as the ripple will take on a different waveform than a resistive load to the rectifier... The duty cycle will get bigger as the DC voltage swings lower with ripple, thus causing the voltage to decrease even faster with rise in input current, up until the duty cycle is limited.....
If your worried about EMC...you could put a input filter on the front end, it just needs to be well designed...
If you need assisatnce in doing this SAFELY.....let me know...
Chris
lyons5959 said:
This is what mrjam was suggesting and it is easy enough to do. One big transformer, rectifier, a few capacitors and you are done.
**BE SAFE** PC powersupply
I've set up a 350w computer power supply on a 1000w SPL car amp for use indoors at my cousins.He's been booming for a month.I was round there yesturday and its still running happily.It puts out bout 9amps at 12volts if I remember right. The fan keeps it cool as if in a PC and its safe. I connect a resistor from +5v to gnd.There is a reason for it but I can't remember what(its past my bedtime) hot:
BE SAFEBE SAFE BE SENSIBLE THINK OF OTHERS AROUND YOU !!
I've set up a 350w computer power supply on a 1000w SPL car amp for use indoors at my cousins.He's been booming for a month.I was round there yesturday and its still running happily.It puts out bout 9amps at 12volts if I remember right. The fan keeps it cool as if in a PC and its safe. I connect a resistor from +5v to gnd.There is a reason for it but I can't remember what(its past my bedtime) hot:
BE SAFEBE SAFE BE SENSIBLE THINK OF OTHERS AROUND YOU !!
Re: **BE SAFE** PC powersupply
Hmmm, Let's see.... 12V x 9 Amps = 108W available for the "1000W" amp. I'm just a little curious: where do the other 892 watts come from? I'm no expert here, but I sure would like to know how 108W can power a 1kw AMP? I'd like to use his energy conversion methods. 😉
mikee55 said:I've set up a 350w computer power supply on a 1000w SPL car amp for use indoors at my cousins.He's been booming for a month.I was round there yesturday and its still running happily.It puts out bout 9amps at 12volts if I remember right. The fan keeps it cool as if in a PC and its safe. I connect a resistor from +5v to gnd.There is a reason for it but I can't remember what(its past my bedtime) hot:
BE SAFEBE SAFE BE SENSIBLE THINK OF OTHERS AROUND YOU !!
Hmmm, Let's see.... 12V x 9 Amps = 108W available for the "1000W" amp. I'm just a little curious: where do the other 892 watts come from? I'm no expert here, but I sure would like to know how 108W can power a 1kw AMP? I'd like to use his energy conversion methods. 😉
- Status
- Not open for further replies.