I have a problem with the output indictor, it gets so hot that the smps trafo resin it was dipped in melted and ended up as a blob on the board.
The module runs on about 300KHz and the coil was originally 24 turns but i reduced it to 15 turns, but it ran hot so i reduced it with one turn and it got better, it still runt hot but i dunno if i should decrease it or increase it.
I tried with a unmodified coil with 24 turns on it but with that the amp would not work at all, it just beeped and got hot fast.
Now it runs with a subwoofer, it does degrade in sound quality and has to be ran into overmodulation to get any descent volume with a sub but with speakers it performs well. As it does better with a sub now compared to before it seem like the decreased coil and upped switching freq was a step in the right direction.
When does the coil get hot, if the switching freq is below its resonating freq or above ?
High side driver, thats after the bootstrap diode, right ? The bootstrap cap was chosen so it would not blow up, its a 0.47µF 250v one.
The module runs on about 300KHz and the coil was originally 24 turns but i reduced it to 15 turns, but it ran hot so i reduced it with one turn and it got better, it still runt hot but i dunno if i should decrease it or increase it.
I tried with a unmodified coil with 24 turns on it but with that the amp would not work at all, it just beeped and got hot fast.
Now it runs with a subwoofer, it does degrade in sound quality and has to be ran into overmodulation to get any descent volume with a sub but with speakers it performs well. As it does better with a sub now compared to before it seem like the decreased coil and upped switching freq was a step in the right direction.
When does the coil get hot, if the switching freq is below its resonating freq or above ?
High side driver, thats after the bootstrap diode, right ? The bootstrap cap was chosen so it would not blow up, its a 0.47µF 250v one.
fredos/Eva, wake up!
What is causing the output filter to heat up ? Too high/low inductance ?
The amp runs @ about 300khz and the coil is 14 turns on a T106-26 core, with 15 turns it was almost worse and with 24 turns the amp dident even work, the fets just heated quickly while the coil beeped and crackled.
What is causing the output filter to heat up ? Too high/low inductance ?
The amp runs @ about 300khz and the coil is 14 turns on a T106-26 core, with 15 turns it was almost worse and with 24 turns the amp dident even work, the fets just heated quickly while the coil beeped and crackled.
I'm using T106-52 (green-blue) cores from old computer power supplies and my amplifier with TDA8920BJ works good. I wound 15 turns for 22uH (for 4 ohm speakers).
Here you have a link to a very useful program: http://www.dl5swb.de/html/mini_ring_core_calculator.htm
Here you have a link to a very useful program: http://www.dl5swb.de/html/mini_ring_core_calculator.htm
Tekko,
Did you read my post? You may not have the right inductor, but something else is going on the T106-2 with 15-24 turns will have some inductance (impedance) at 300KHz, so even if it isn't the right value, it is not the root cause of your trouble.
BTW, the T106-2 is not a tape core, it is a powder core.
Rick
Did you read my post? You may not have the right inductor, but something else is going on the T106-2 with 15-24 turns will have some inductance (impedance) at 300KHz, so even if it isn't the right value, it is not the root cause of your trouble.
BTW, the T106-2 is not a tape core, it is a powder core.
Rick
I have tried 10, 13, 14, 15, 16, 17 and 24 turns on a T106-26 (iron toroid from output of puter ps) and 15-30 turns on a T157-52 core with the same results, heated coil and same ugly sine on the output.
The less turns, the hotter the coil became but no dufference in the amps behaviour.
I know the T106-2 is a powder core, so is T106-26.
My cores is apparently not T106-26, as they are made out of solid iron
The less turns, the hotter the coil became but no dufference in the amps behaviour.
I know the T106-2 is a powder core, so is T106-26.
My cores is apparently not T106-26, as they are made out of solid iron
Tekko said:
How are the mosfets, nice and cool? Can you keep your finger on em? Just a little, few seconds, not at all? Have you run it open loop off a clock to allow you to tune/tweak the gate waveforms?
Dead time good?
Then close the feedback loop, observe and tweak.
Core still hot? Ditch it, use air for now, that rules out saturation at least.
Take measurements.... test.... reread Eva's and Fred's advice to you..... good stuff! If you just keep swapping cores and adding/removing windings.... you're going to stay stuck in a rutt.
The fets yesterday only got about 30-35deg when i ran the amp for hours on its maximum power into a 4ohm subwoofer with a 2ohm resistive load (a big chunky tube) in parallel.
How to i close the feedback loop ? it is connected from the output, via a pot and then visa a 22k resistor and then it goes to the audio input, in audio input is AC coupled to the cinch jack with a 4.7µF cap and a 2.2k resistor. Isent it closed already ?
The cores get hot no matter the turns ratio, but it gets hotter the less turns there is on it, and cooler the more turns.
How to i close the feedback loop ? it is connected from the output, via a pot and then visa a 22k resistor and then it goes to the audio input, in audio input is AC coupled to the cinch jack with a 4.7µF cap and a 2.2k resistor. Isent it closed already ?
The cores get hot no matter the turns ratio, but it gets hotter the less turns there is on it, and cooler the more turns.
Tekko, ounce again FIRST: Change the material of your toroide core, use the -2 or -6 from micrometal, or some MPP or sendust, THAT'S THE ONLY WORKING MATERIAL FOR CLASS D AMPLIFIER!!! I have try over 500 differents materials and I can told you you, thats even perfect spec, that's the only working material for class d power amp.
Second
Another thing that will help your circuit: CHANGE THE WAY YOU DO YOUR FEEDBACK LOOP!!!
Now I will help you more when you follow these 2 basic thing.
Fredos
www.d-amp.com
PS I dont sell already made coil as you ask me. Go to micro metal website and order it.
At least you can find some sendust core here:
http://www.coilws.com/Powder Core Inductor/HF_Thru_hole.php
http://www.cwsbytemark.com/prices/sendust.php
And learn more about material there:
http://www.coilws.com/Powder Core Inductor/PowderCore_Guide.php
Second
Another thing that will help your circuit: CHANGE THE WAY YOU DO YOUR FEEDBACK LOOP!!!
Now I will help you more when you follow these 2 basic thing.
Fredos
www.d-amp.com
PS I dont sell already made coil as you ask me. Go to micro metal website and order it.
At least you can find some sendust core here:
http://www.coilws.com/Powder Core Inductor/HF_Thru_hole.php
http://www.cwsbytemark.com/prices/sendust.php
And learn more about material there:
http://www.coilws.com/Powder Core Inductor/PowderCore_Guide.php
I was only @ the ptotoboard stage back then, one change rendered the whole thing useless and had to be redone on a new board. Now when i have a real board i can make every change u/i want without messing up anything.
I ahve already soldered/desoldered around 10-20 coils if u count every time i have changed cores or rewound, as well as added/removed/moved caps.
how mutch is shipping for a http://www.coilws.com/Powder Core Inductor/HF Series PN/HF229-200M-15A.pdf ?
Btw, u´d need to tell me what the change should be. I could email u the circuit and u could plot the changes on it.
Actually u should blame ledmania, its his circuit, all i did was removing the currlim cir and replacing the resistor voltage splitters with pots.
I ahve already soldered/desoldered around 10-20 coils if u count every time i have changed cores or rewound, as well as added/removed/moved caps.
how mutch is shipping for a http://www.coilws.com/Powder Core Inductor/HF Series PN/HF229-200M-15A.pdf ?
Btw, u´d need to tell me what the change should be. I could email u the circuit and u could plot the changes on it.
Actually u should blame ledmania, its his circuit, all i did was removing the currlim cir and replacing the resistor voltage splitters with pots.
Tekko said:
That's a big part of the problem I hope you realize? Did you even simulate this at all or know what to expect? How do you know enough to be able to take measurements and troubleshoot it intelligently then? Test and measure, observe the effects, compare with the ideal and take action as required. I don't see ledmania here complaining about it not working... he must have done his homework!
I don´t think he have either simulated or built it. hes still away working and left this @ home.
As he sounded i was the first one even trying his class d idea.
But yea, a simulator containing these IC´s would be interesting.
Who suggested that i should use an air coil to get rid of saturation ? I tried a air coil, highest ac voltage out yet, off the scale on the scope, i think 200v
shortly after something fizzeled and the amp went neg rail on the op.
The boot diode measures almost dead short, as well as one fet but which one thats busted i dunno until i desolder one of them.
Hopefully i havent lost my last gate driver. If i have, i´ll
Btw classd4sure, could i add u on msn ?
As he sounded i was the first one even trying his class d idea.
But yea, a simulator containing these IC´s would be interesting.
Who suggested that i should use an air coil to get rid of saturation ? I tried a air coil, highest ac voltage out yet, off the scale on the scope, i think 200v
shortly after something fizzeled and the amp went neg rail on the op. The boot diode measures almost dead short, as well as one fet but which one thats busted i dunno until i desolder one of them. Hopefully i havent lost my last gate driver. If i have, i´llBtw classd4sure, could i add u on msn ?
No, I don't think you should give up.
Actually I think it's liberating to read threads about DIY'ing it all from start to finish, and not "just" moding a fabricated module, though there is of course room for both
Building a class-d amp is though not that easy .... not at all .... it takes knowledge, skills, time and effort. You have to know electronics well, and you have to be able to do simulations and calculations. You also have to have som practical experience in building, measuring and fault finding, to reach your goal.
I think you are bessically trying to make a lot of things work at the same time, not isolating your problems.
It would seem easy to take the TL494 as a starting point, but you have to know it's internal workings in depth first. Otherwise it might actually be easier to build your modulator from a comperator and some discrete components, instead.
As someone sugested at first, start with getting the modulator working properly on a bread board at first. On a bread board it's easy to change components, and make sure that waveforms from the modulator is correct before adding the power stage.
Also starting with a post filter amp in your first shot might be a bit unwise, as you cant make it work step by step, but only when every stage of the amp is build!
Therefore maybe modity the circuit to run as a pre filter amp first.
Build the modulator first taking the feedback from it's output and get it running well.
I would also skip the PC-PSU and use a linear PSU at first, based on a trafo, a diode bridge ome capacitors and a regulator e.g. LM7812, just to make sure this is not the cause of your problems. Don't use the PC-PSU before the whole amp is running well on a regular PSU!
If your coil heated up while running idle but with a reasonable load, it's pretty sure it's not suitable for your amp. Order some Micrometal T106-2 or T200-2.
When you reach the point of having a workable modulator, start just adding the power stage without taking the feedback from it's output. Make sure it works before you change the feedback point. At this point you could still be working on a breadboard.
Ad an appropiate output filter. Calculate the needed values, and do measure the coil to make sure it has the right value.
Try the amp running with an easy load (old 8 ohm speaker that you are prepared to lose), measure and listen to some music. It must sound correct, otherwise something is not working correctly!
Step by step, don't try running the amp at full power for hours until you know it is running correctly in all aspects!
Only then, you should start experimenting with the feedback.
..... and then make the first PCB.
Yes it's a long slow process, but I think that is what it takes
........ but don't give up
Actually I think it's liberating to read threads about DIY'ing it all from start to finish, and not "just" moding a fabricated module, though there is of course room for both
Building a class-d amp is though not that easy .... not at all .... it takes knowledge, skills, time and effort. You have to know electronics well, and you have to be able to do simulations and calculations. You also have to have som practical experience in building, measuring and fault finding, to reach your goal.
I think you are bessically trying to make a lot of things work at the same time, not isolating your problems.
It would seem easy to take the TL494 as a starting point, but you have to know it's internal workings in depth first. Otherwise it might actually be easier to build your modulator from a comperator and some discrete components, instead.
As someone sugested at first, start with getting the modulator working properly on a bread board at first. On a bread board it's easy to change components, and make sure that waveforms from the modulator is correct before adding the power stage.
Also starting with a post filter amp in your first shot might be a bit unwise, as you cant make it work step by step, but only when every stage of the amp is build!
Therefore maybe modity the circuit to run as a pre filter amp first.
Build the modulator first taking the feedback from it's output and get it running well.
I would also skip the PC-PSU and use a linear PSU at first, based on a trafo, a diode bridge ome capacitors and a regulator e.g. LM7812, just to make sure this is not the cause of your problems. Don't use the PC-PSU before the whole amp is running well on a regular PSU!
If your coil heated up while running idle but with a reasonable load, it's pretty sure it's not suitable for your amp. Order some Micrometal T106-2 or T200-2.
When you reach the point of having a workable modulator, start just adding the power stage without taking the feedback from it's output. Make sure it works before you change the feedback point. At this point you could still be working on a breadboard.
Ad an appropiate output filter. Calculate the needed values, and do measure the coil to make sure it has the right value.
Try the amp running with an easy load (old 8 ohm speaker that you are prepared to lose
), measure and listen to some music. It must sound correct, otherwise something is not working correctly!Step by step, don't try running the amp at full power for hours until you know it is running correctly in all aspects!
Only then, you should start experimenting with the feedback.
..... and then make the first PCB.
Yes it's a long slow process, but I think that is what it takes
........ but don't give up
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