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Old 25th July 2013, 07:18 AM   #3591
stewin is offline stewin  Kenya
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Join Date: Jul 2007
thanks exflaco i am modifying and i will go back to tlo71 +/-5v6 and use +/-15 for the preamp tlo74.
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Old 25th July 2013, 10:23 PM   #3592
stewin is offline stewin  Kenya
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hi all photos of my project. detex irs900 , thienchay irs900, my smps version of lukas design but with ocp protecton , and my 24db 4way crossover with high pass and low pass on all 4 channels 33hz o 22khz

>>>after mounting the amps and smps i will resume the new simple amp i posted on #3587
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Last edited by stewin; 25th July 2013 at 10:28 PM.
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Old 27th July 2013, 09:58 AM   #3593
stewin is offline stewin  Kenya
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hi all i have a few questions

>>> is it o.k technically to use one aux 12vlts 2 amps to power the ir2110 and cd4049 for four channels of irs900 or irs4k5. or does it need a 12vlts aux power supply for each channel.?

>>> has anyone else experienced this challenge , when you have irs900 4 channels and same power supply in my case "
(+\-40vts, outputs irfp250n,gate resistor 100ohms, output inductor 22turns eei 35, aux 12voltage each channel with its own 12vlts dropping the voltage from 0-40vlts by a small fet irf640 ) "

if i do not connect a speaker to any channel . it drains a lot of current and cuts the fuse . but if all channels have a load i.e speaker connected everything is o.k and works perfectly provided i do not disconnect a speaker from any of the 4 channels. what is the solution?
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Old 27th July 2013, 11:02 AM   #3594
CPX is offline CPX  Romania
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"is it o.k technically to use one aux 12vlts 2 amps to power the ir2110 and cd4049 for four channels of irs900 or irs4k5. or does it need a 12vlts aux power supply for each channel.?"
Yes,provided you use filtering on each module.

"if i do not connect a speaker to any channel . it drains a lot of current and cuts the fuse "
Try a 1 kohm load and see what it does..

Please post a ground connection diagram (for power and signal paths).
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Old 27th July 2013, 11:08 AM   #3595
paskal9 is offline paskal9  Malaysia
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Quote:
Originally Posted by jlester87 View Post
When you bridge your amp, there is less sag based on your experience but will it overload the transformer more and have heat problems? compared to halfbridge configuration?
it minimizes the voltage sag to a point that it only drops 1-2 volts during huge bass hits. this is to a sealed 15" sub with only 86 dB sensitivity.

since it's bridged, power supply voltage are kept low. thus allowing for added rail capacitance without using high voltage caps. i have about 40,000uf for each channel.

with bridged configuration for subwoofer use, the sub only handle bass signal which will never be continuous. put enough rail capacitance and transformer load will be reduced as the current will be sourced from the caps. i've put 10A fuse from the trafo line to the cap bank to see if the current draw will surge past 10A and it didn't burn no matter how loud i went.
from the cap bank to the amp modules, current surge is more than 5A during heavy bass hits at high volume. 10A fuse don't burn. 40,000uf in the bank (for each module), another 8,000uf reservoir in the module itself.

my trafo don't even get warm after movies playback. it's only rated for 500VA driving 2 bridged modules with about ~1.2kW each. following the general opinion in here, i need at least 2kW transformer to get full capability.

Quote:
Originally Posted by stewin View Post
hi all i have a few questions

>>> is it o.k technically to use one aux 12vlts 2 amps to power the ir2110 and cd4049 for four channels of irs900 or irs4k5. or does it need a 12vlts aux power supply for each channel.?
in theory you could power all the channels with the same 12V line, provided the 12V could handle the current. but in reality, you'll be dealing with lots of heat output which will be hard for the mosfet to manage. if your circuit doesn't draw much current, or if the voltage drop isn't as much, leading to less heat output then it should work.

(feel free to correct me)

Quote:
Originally Posted by stewin View Post
>>> has anyone else experienced this challenge , when you have irs900 4 channels and same power supply in my case "
(+\-40vts, outputs irfp250n,gate resistor 100ohms, output inductor 22turns eei 35, aux 12voltage each channel with its own 12vlts dropping the voltage from 0-40vlts by a small fet irf640 ) "

if i do not connect a speaker to any channel . it drains a lot of current and cuts the fuse . but if all channels have a load i.e speaker connected everything is o.k and works perfectly provided i do not disconnect a speaker from any of the 4 channels. what is the solution?
sounds like it's unstable without a load. if you have a scope, check the output to confirm that the amp is still oscillating without a load connected to it.
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Old 27th July 2013, 11:49 AM   #3596
manojtm is offline manojtm  India
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Quote:
if i do not connect a speaker to any channel . it drains a lot of current and cuts the fuse . but if all channels have a load i.e speaker connected everything is o.k and works perfectly provided i do not disconnect a speaker from any of the 4 channels. what is the solution?
Hi stewin,

Without load(speaker) amp will not oscillate.Provide a dummy load use 1K5/2W or 2K2/2W resistor.

Regards
MANOJ
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Old 27th July 2013, 02:50 PM   #3597
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Hi Steve,
your schematic does not show any start up path for the upper gate drive supply.
==> A self oscillating amp without such start up path is likely to lock up, especially during turning on.
You can try a 33k (at least 0.5W) resistor from positive power rail to the VB pin of the IR chip.

Your obseravtion of high current draw and blowing fuse is a little bit making me afraid, that you are also struggling with some parasitic effects which provide some uncontrolled gate drive to the upper MosFets even without driver supply.
This is adding the unpleasant risk of a heavy defect when experimenting with the additional resistor. To reduce this risk, you should put serial light bulbs (i.e 230V/100W) in the pos and neg supply wires before experimenting.


Good luck
Markus




P.S.
Just adding my safety hint from the other thread, because I see the same pictures here.

1. My honest congrats.
2. In the region of the wide isolation barrier, please scratch away the thin copper lines at the sides of the PCB. In the moment this copper line effectively jumpers most of the creepage distance, because it is a conductor which is very close to the primary and also very close to the secondary.
3. Take care with the creepages also in the transformer.
4. Check if the blue cap across the barrier has Y1 rating.
5. Enjoy your build! Great to see your walk of success.

...ohps just seeing now, the tape around the ferrite core should be wider.
Again the same topic - the ferrite comes close the primary and the secondary PCB.
My proposal: Make the tape much wider than the transformer (i.e. 6mm on each side) and have it 3 layers at least. I know that's looking ugly.


Keeping fingers crossed that the inside transformer construction provides sufficient isolation, cannot judge this from the distance.
Fundamental rule for you to check:
Imagine the currents wants to creep from primary to secondary along any surface.
Also indirect path which incorporate conductive parts like unconnected copper or ferrite are critical. I.e. Primary ==> core ==> secondary.
Distances along the surface of conductive material are no creepage, because the conductive material jumpers this distance.
Whereever you find a path which has less than 5-8mm creepage over isolating material, you should think how to enlarge.
[/B]

Disclaimer:
My safety hints are based on my best personal knowledge, but I cannot
guarantee regarding potential errors.
Also there is no way to give full information about safety standards by a few posts. Also there is no way to notice all short comings.
It is just an attempt to reduce potential safety issues, which I noticed while zapping through the forum.
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Old 27th July 2013, 05:52 PM   #3598
stewin is offline stewin  Kenya
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thanks all i will do as you posted and will post my feedback. GOD bless you all
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Old 28th July 2013, 02:48 AM   #3599
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Location: Quezon City
Quote:
Originally Posted by stewin View Post
hi all i have a few questions

>>> is it o.k technically to use one aux 12vlts 2 amps to power the ir2110 and cd4049 for four channels of irs900 or irs4k5. or does it need a 12vlts aux power supply for each channel.?

>>> has anyone else experienced this challenge , when you have irs900 4 channels and same power supply in my case "
(+\-40vts, outputs irfp250n,gate resistor 100ohms, output inductor 22turns eei 35, aux 12voltage each channel with its own 12vlts dropping the voltage from 0-40vlts by a small fet irf640 ) "

if i do not connect a speaker to any channel . it drains a lot of current and cuts the fuse . but if all channels have a load i.e speaker connected everything is o.k and works perfectly provided i do not disconnect a speaker from any of the 4 channels. what is the solution?
You're using IRFP250 which has a high Qg, provide at least 1A aux supply per module.

Looks like the amp is unstable and the mosfets are slightly turning on when the amp is not oscillating. Does each of the irf640 aux supply too far away from the modules?

Quick and dirty solution is to make sure that the amp is oscillating without speakers connected. IRS900 already has a 1.5k 2W dummy load.
Connect a preamp with "turn on pop" so that the amp will oscillate at startup. Just use a speaker protect with delay so that you won't hear it.
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Old 28th July 2013, 02:57 AM   #3600
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Location: Quezon City
Quote:
Originally Posted by paskal9 View Post
it minimizes the voltage sag to a point that it only drops 1-2 volts during huge bass hits. this is to a sealed 15" sub with only 86 dB sensitivity.

since it's bridged, power supply voltage are kept low. thus allowing for added rail capacitance without using high voltage caps. i have about 40,000uf for each channel.

with bridged configuration for subwoofer use, the sub only handle bass signal which will never be continuous. put enough rail capacitance and transformer load will be reduced as the current will be sourced from the caps. i've put 10A fuse from the trafo line to the cap bank to see if the current draw will surge past 10A and it didn't burn no matter how loud i went.
from the cap bank to the amp modules, current surge is more than 5A during heavy bass hits at high volume. 10A fuse don't burn. 40,000uf in the bank (for each module), another 8,000uf reservoir in the module itself.

my trafo don't even get warm after movies playback. it's only rated for 500VA driving 2 bridged modules with about ~1.2kW each. following the general opinion in here, i need at least 2kW transformer to get full capability.
Did you test it with pure sine wave input signal? Music signal's average power is only 1/8 of sine wave, it might be the reason why your fuses didn't burn and your'e only getting 5A current surge.

Anyway as you said since the bass signal will never be continuous, smaller transformer will suffice specially if you put a lot of capacitance.

Last edited by jlester87; 28th July 2013 at 03:04 AM.
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