i havent tried that schematic with the schmitt triggers yet, i only have a simple thing on a breadboard going so far with a TC4422 as output device.
Schematic of that: http://diymania.hv4all.com/selfosc classd/d-amp.PNG
I can add a jumper in the eagle design to allow trying either with or without the comparator.
Schematic of that: http://diymania.hv4all.com/selfosc classd/d-amp.PNG
I can add a jumper in the eagle design to allow trying either with or without the comparator.
And here is the board, just finished cadding.
http://diymania.hv4all.com/selfosc classd/D-Amp2brd.png
http://diymania.hv4all.com/selfosc classd/D-Amp2brd.png
I dreamt up a new class d yesterday based on pieces plucked from different schems found around the forum and inet.
Heres the result: http://diymania.hv4all.com/selfosc classd/new/selfoscdamp.PNG
Its built on a breadboard, runs alittle hot with no heatsinks but it sounds suprisingly good.
It took some tinkering to get it to work.
What kind of class d is this, non discrete UcD, hysteresis ?
Heres the result: http://diymania.hv4all.com/selfosc classd/new/selfoscdamp.PNG
Its built on a breadboard, runs alittle hot with no heatsinks but it sounds suprisingly good.
It took some tinkering to get it to work.
What kind of class d is this, non discrete UcD, hysteresis ?
This amp is now greatly improved, despite having no voltage regulators, its almost hum free.
The fets rise in temperature to around 60-70 degs with no heatsink on idle, and it seem independent to volume.
Heres the schemo of what i have on my breadboard:
http://diymania.hv4all.com/selfosc classd/new/selfoscdampsimple.PNG
As a last note, i think it sounds very good for beeing what it is.
The fets rise in temperature to around 60-70 degs with no heatsink on idle, and it seem independent to volume.
Heres the schemo of what i have on my breadboard:
http://diymania.hv4all.com/selfosc classd/new/selfoscdampsimple.PNG
As a last note, i think it sounds very good for beeing what it is.
I bet that the switching transistors on Behringer class D powered consoless don't heat to 70ºC when idle with just +/-12V supplies... This is probably because at least the designer knew enough electronics to place the gate diodes in the right direction 
Tip: If your circuit was working properly, it could play full volume music with +/-35V rails into 8 ohms without the bare IRF540 reaching 70ºC.
Tip: If your circuit was working properly, it could play full volume music with +/-35V rails into 8 ohms without the bare IRF540 reaching 70ºC.
Well this is on a breadboard and its self oscillating, probobly at a frequency higher than the behringer = shoot through with the stock behringer gate resistor values. Tho they used IRF640 and 9640, and i use IRF540 and 9540. also the behringer D-Amp doesent operate without a heatsink like my D-amp does, if i slap on a chunk of alu, i bet to you that it stays cool.
I placed my gate diodes in the same dir as behringer did, and my circuit seem to be working properly, i just havent started working on tweaking deadtime yet, gotta wait till i get my new scope first so i can see whats really up here.
Would it be a good idea to make a real board to this before starting to really tweak it or should i tweak away the fet heating before making the boards ?
I placed my gate diodes in the same dir as behringer did, and my circuit seem to be working properly, i just havent started working on tweaking deadtime yet, gotta wait till i get my new scope first so i can see whats really up here.
Would it be a good idea to make a real board to this before starting to really tweak it or should i tweak away the fet heating before making the boards ?
I have no way of checking idle freq, yet.
The diodes may be reversed in schemo (i did this to see if anything changed in sim) but on breadboard they remain in the same directions as in behringer schem.
Fet heating is most likely deadtime, its very rarely anything else, unless one is faulty. IWhen i make the read boards, i gonna put some superfast diodes across the fets, i may even include the overload stuff as its just a few components.
Atm the amp is fed from a 2x9V 20VA transformer, that stays cool so the amp is not pulling any excess current which suggest i just have a light deadtime issue.
When i make the real boards there may even be so well that the fets won´t heat anymore, it could be just the breadboard screwing things up, their not intended for rf stuff since they have quite high stray capacitance and stray induictance and things like that.
The diodes may be reversed in schemo (i did this to see if anything changed in sim) but on breadboard they remain in the same directions as in behringer schem.
Fet heating is most likely deadtime, its very rarely anything else, unless one is faulty. IWhen i make the read boards, i gonna put some superfast diodes across the fets, i may even include the overload stuff as its just a few components.
Atm the amp is fed from a 2x9V 20VA transformer, that stays cool so the amp is not pulling any excess current which suggest i just have a light deadtime issue.
When i make the real boards there may even be so well that the fets won´t heat anymore, it could be just the breadboard screwing things up, their not intended for rf stuff since they have quite high stray capacitance and stray induictance and things like that.
Hey eva, you know what i did ? I forgot i used 22 ohm resistors when i made the power stage instead of 56 ohms, no wonder the fets are heating!
Anyways i got a preliminary board laid out.
http://diymania.hv4all.com/selfosc classd/new/selfoscdampbrd.png
Anyways i got a preliminary board laid out.
http://diymania.hv4all.com/selfosc classd/new/selfoscdampbrd.png
The first PCB version is terrible, the second has substantial improvements, the third is not much better than the second. You seem to be finally getting some points about PCB layout anyway.
The second LC filter will disturb the self oscillating loop unless you make it resonate well above the idle oscillating frequecy. Then it won't provide any carrier attenuation. Don't worry about carrier residuals.
The second LC filter will disturb the self oscillating loop unless you make it resonate well above the idle oscillating frequecy. Then it won't provide any carrier attenuation. Don't worry about carrier residuals.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.