UCD 25 watts to 1200 watts using 2 mosfets

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#581
hi dacuycoy,

i`m using ferrite toroid from car amp smps, its typically material 77 i think. this is the best so far for cheap cost i can get, sometimes i get it for free from electronic shops repair here. OD its about 1.3 inch or something i made about 15-18 turns awg 16, no hot at all no noise, big sound.

regards.
 
#588
IRFP250N work good, a lot of high power commercial class D amps have it in output stage ... powersoft too

but does somebody know Mosfet with 300 V ratings what is working class D ?

Crest use APT50Wxxxxx in Output stage but hard to get


IRFB Mosfets have only 150 V ratings, cant use for big output power
 
#590
Hi everyone,

Well, for reduce noice, I need good output coil, IRFP250 on output or IRF540 for low voltages. C10 of 100pF I change to 2.2nF, from pin 3 of LM311 i put 4.7nF to GND and 5.6K in serial to input. Output capacitor 1.5uF I change to 1uF if output coil is 40uH.

I have all components and tomorow I will build this amp, I plan to use PCB by Lycanlk, but on pcb I add two capacitors of 470uF near by out transistors.

Only problem are output transistors, because i dont have IRFP250, but I have IRFP240PBF, for test i hope they can work

Tell me, is this all corect about changes for reduce a noice what I wrote?

Thank you, Nikola
 
#591
Hello Dzony988,output inductance is too big i use 20uH with very good results
do not forget that this is selfoscilating amp and its oscilation is dependent off the output filter! iff you have a scope please check the oscillation frequency you'll see that the amp dos not run at 250Khz not even close iff you want 20hz-20Khz band is required to determine the oscillation frequency (the amp with 1,5uF+30uH oscilate at 150Khz)
 
#593
IONUTZXPO, thank you for replay. Its means I can use 20uH output coil and 1.5uF or smaller???

Is something else changes of componets to reduce the noice, like c10 of 100pF to 2.2nF, 4.7nF form pin 3 of LM311 to GND.....?

Can I use for output coil yellow core from PC ATX supplay. That coil have 20uH as I recall, since there are several different wires, use thickest I guess.

Thanks again, and please tell me about output capacitor that goes with 20uH, can I use PC coil and other changes to schematic to reduce the noice.

Thanks and Regards, Nikola
 
#594
hi Nikola,you can use 15-20uH +1uF for output filter ,i added 4.7nF over the 100pF (C10)and the noise is allmost gone
you can use pc coil but with gap otherwise the core will saturate and will heat up fast
i use Micrometals IronPowder cores T130-2 and litzwire
they are the best for output filter in class d amps
 
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#596
stewin said:
hi guys i've just found irfp260 in my country . and they do have a lower rds than irfp250 will they work better than irfp250 in this circuit i've heard about the 4227 but are not available . btw irfp360 are available too steve
Click to expand...

IRFP240 is lower than IRFP250.

I quite often use IRFB4019, low capacitance but can still manage 17 amps.
One bad side is it is to220 package so cant dissipate as much heat as the IRFP240.
 
#598
which fet can fit

hi guys the available fets are (irfp 240,250,260,360,450,460). irfb series or igbts are currently unavaillable here even the parts shop have no clue what they are. my question is which of the above fets can be used and is effecient . i thought that rds was the one that matters in class d. but thanks to this forum i learned that irf640 with a higher rds was superior compared to the irf540.
both irf540,irf640 are available but i wanted the TO247 package because of their voltage and current ability. stewin
 
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