Heloo.
I bulit a SMPS, ( the A-AND-T-LABS) www.a-and-t-labs.com
but when connecting the supply to the load a noise can be heard form the output TRANSFORMER ETD-49. (ssshhhshshh)
remove the load sound dissappears!
that noise can be heared clearly at the amplifier when connected.
Transformer winding.
Primary 28 Turns --> 1mm
Secondary 14,CT,14 Turns --> 1.6mm
I am not that professional into transformers, so i dont know why i hear this nois, and does this nois makes my driving MOSFETS gets hot quickly?
Any help will be more than appreciated.
Thanks all
I bulit a SMPS, ( the A-AND-T-LABS) www.a-and-t-labs.com
but when connecting the supply to the load a noise can be heard form the output TRANSFORMER ETD-49. (ssshhhshshh)
remove the load sound dissappears!
that noise can be heared clearly at the amplifier when connected.
Transformer winding.
Primary 28 Turns --> 1mm
Secondary 14,CT,14 Turns --> 1.6mm
I am not that professional into transformers, so i dont know why i hear this nois, and does this nois makes my driving MOSFETS gets hot quickly?
Any help will be more than appreciated.
Thanks all
Hi
Like Eva says. These PS outputs need light loads for stability/ and or duty cycle control. Should not be a problem if connected to a class AB amp with quiescent current. Otherwise use a couple of dummy loads... 10 Watts or so until your amp is connected and biased.
edit > read the manual on testing 4.2 http://www.a-and-t-labs.com/K6_Sw_Amp/Amp_assembly_manual_wfigs.pdf
Like Eva says. These PS outputs need light loads for stability/ and or duty cycle control. Should not be a problem if connected to a class AB amp with quiescent current. Otherwise use a couple of dummy loads... 10 Watts or so until your amp is connected and biased.
edit > read the manual on testing 4.2 http://www.a-and-t-labs.com/K6_Sw_Amp/Amp_assembly_manual_wfigs.pdf
SMPS
hi.
The SMPS is running with the SG3525
putting any load at the output will not solve the problem, even 10K resistor.
Mesure the wave at the gates with no loads, wave looks nice,
put the load , the wave gets very ugly and jumping, distorted.
I spent houres trying to find the problem, i failed.
is the gate drive transformer a problem?
the mosfets gets very hot at 33Ohm load per rail + / -
hi.
The SMPS is running with the SG3525
putting any load at the output will not solve the problem, even 10K resistor.
Mesure the wave at the gates with no loads, wave looks nice,
put the load , the wave gets very ugly and jumping, distorted.
I spent houres trying to find the problem, i failed.
is the gate drive transformer a problem?
the mosfets gets very hot at 33Ohm load per rail + / -
Re: SMPS
This is indicating parasitic resonances.
Also the lot of RC-dampers in the schematic are looking like the R&D guys where struggling with undesired resonances. IMHO this topic is the most difficult part of designing power switch mode circuits.
How to fight it? Layout, component selection, dampers.
Not funny if a professionally sold design shows massive issues with that. As a first uncritical modification you could try to place a RC(L) snubber directly at the MosFets across the rail.
This RCL has to be adjusted to the frequency of the undesired resonance. If not adjusted properly it will be worthless.
The same sort of snubbers (but with small caps: May be 100pF + 10 Ohms + parasitic L) you can apply from drain to source of each MosFet. BUT take care - at these voltage levels you may get quite high losses in these drain-source snubbers. Which switching frequency do you have? Schematic is indicating values which lead to 80kHz. If you have 80kHz, then 100pF will already give you 0.8W losses in each 10 Ohms resistor.
Also sometimes it already helps to place fast & low inductive ceramic caps accross the rail, but you should choose a LOSSY ceramic type (large tan delta in the data sheet).
All other mods which come to my mind, would directly go into critical circuit and layout parts...
Good luck!
microsim444 said:
This is indicating parasitic resonances.
Also the lot of RC-dampers in the schematic are looking like the R&D guys where struggling with undesired resonances. IMHO this topic is the most difficult part of designing power switch mode circuits.
How to fight it? Layout, component selection, dampers.
Not funny if a professionally sold design shows massive issues with that. As a first uncritical modification you could try to place a RC(L) snubber directly at the MosFets across the rail.
This RCL has to be adjusted to the frequency of the undesired resonance. If not adjusted properly it will be worthless.
The same sort of snubbers (but with small caps: May be 100pF + 10 Ohms + parasitic L) you can apply from drain to source of each MosFet. BUT take care - at these voltage levels you may get quite high losses in these drain-source snubbers. Which switching frequency do you have? Schematic is indicating values which lead to 80kHz. If you have 80kHz, then 100pF will already give you 0.8W losses in each 10 Ohms resistor.
Also sometimes it already helps to place fast & low inductive ceramic caps accross the rail, but you should choose a LOSSY ceramic type (large tan delta in the data sheet).
All other mods which come to my mind, would directly go into critical circuit and layout parts...
Good luck!
I am referring to this schematic:
http://www.a-and-t-labs.com/K6_Sw_Amp/art_schematic/k6pwr.pdf
http://www.a-and-t-labs.com/K6_Sw_Amp/art_schematic/k6pwr.pdf
New SMPS
Heloo.
I am not that pro into switching power supply.
please can you give me more details about expected values for the RCL?
There is a 1.8mh coils at the 220V Input,!
If this circuit will fail to operate, I will make a new one, SG3525 and IR 2110 ,4 IGBT HGTG30N60A4D.
It belong to an professional audio amplifiers maker, its not an easy one.
but spending time at that one, is better than spending time at the K6 Supply!!
Thanks all.
Heloo.
I am not that pro into switching power supply.
please can you give me more details about expected values for the RCL?
There is a 1.8mh coils at the 220V Input,!
If this circuit will fail to operate, I will make a new one, SG3525 and IR 2110 ,4 IGBT HGTG30N60A4D.
It belong to an professional audio amplifiers maker, its not an easy one.
but spending time at that one, is better than spending time at the K6 Supply!!
Thanks all.
Hi Micro,
I am sorry without really seeing all details and doing detail measurements it is not possible to give more clear values.
The 100pF in series with 10 Ohm from drain to source is a standard approach to start with, normally its good to keep the geometric loop of this RC small in order to get a low L. Usually this is already better than nothing.
Most desings need larger C, which does unfortunately cause more losses in the R.
So the most practical way is to put this snubber and compare the wave forms vs. the wave forms without snubber.
And then change step by step to larger C and find the optimum.
If you have access to another SMPS, then it is worth a trial and see if it is showing less headache.
One or multiple coils and capacitors at the 220V input is usually the EMI filter. Probably not the source of your headache.
I am sorry without really seeing all details and doing detail measurements it is not possible to give more clear values.
The 100pF in series with 10 Ohm from drain to source is a standard approach to start with, normally its good to keep the geometric loop of this RC small in order to get a low L. Usually this is already better than nothing.
Most desings need larger C, which does unfortunately cause more losses in the R.
So the most practical way is to put this snubber and compare the wave forms vs. the wave forms without snubber.
And then change step by step to larger C and find the optimum.
If you have access to another SMPS, then it is worth a trial and see if it is showing less headache.
One or multiple coils and capacitors at the 220V input is usually the EMI filter. Probably not the source of your headache.
Mosfets Burn
After serious tests at the Switching suppply i built.
I have noticed that the mosfets will blow up suddenly for no reason.
specially after 2.5 AMP drawn from the mosfets.( connect the amplifier, and play some music at 4 ohm load,)
Those Mosfets IRFP450 must be stable with at least 10 AMPS!
I don't know if any one may advice why they blow that fast, at low current draw.
K6 power supply can be viewed at www.a-and-t-labs.com
Please advice your notes abuot my new SMPS above
After serious tests at the Switching suppply i built.
I have noticed that the mosfets will blow up suddenly for no reason.
specially after 2.5 AMP drawn from the mosfets.( connect the amplifier, and play some music at 4 ohm load,)
Those Mosfets IRFP450 must be stable with at least 10 AMPS!
I don't know if any one may advice why they blow that fast, at low current draw.
K6 power supply can be viewed at www.a-and-t-labs.com
Please advice your notes abuot my new SMPS above
Yes, I mean the voltage across gate-source (Ugs) and across drain-source (Uds) and the current into the drain (Id).
In first you might run at low power, which the circuit can handle even in its current set up.
Oil or vacuum varnish impregnation etc of course do help to reduce noise, but they do not correct any electrical issue.
In first you might run at low power, which the circuit can handle even in its current set up.
Oil or vacuum varnish impregnation etc of course do help to reduce noise, but they do not correct any electrical issue.
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