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Old 17th May 2011, 12:59 PM   #1121
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Quote:
Originally Posted by fibko View Post
This is my first prototype of UCD. 400W/4ohm sin @ +-60V
Nice PCB

----------------------------------------------------------------------

Testing my prototype at +-60 vdc .
Input Signal at 1KHz , less than 1Vpp.

I got these results.

Before the inductor Im getting a nice square signal,after the inductor i dont know why the signal its like cutted/. I got less tha 5W

What do you think?
a inductor problem?,high side mosfet driver problem?

ty
Attached Images
File Type: png Oscilacion_60vcd_1024x749.png (105.2 KB, 1056 views)
File Type: png Salida_menos_de_1vpp_in_60vcd_1024x749.png (127.4 KB, 979 views)

Last edited by electroconico; 17th May 2011 at 01:21 PM.
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Old 17th May 2011, 01:50 PM   #1122
luka is offline luka  Slovenia
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only 116kHz???? that should be more then 220k
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Old 17th May 2011, 09:23 PM   #1123
fibko is offline fibko  Slovakia
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Quote:
Originally Posted by electroconico View Post
Nice PCB

----------------------------------------------------------------------

Testing my prototype at +-60 vdc .
Input Signal at 1KHz , less than 1Vpp.

I got these results.

Before the inductor Im getting a nice square signal,after the inductor i dont know why the signal its like cutted/. I got less tha 5W

What do you think?
a inductor problem?,high side mosfet driver problem?

ty
Hello, try change these components. R5 change amplifier gain and R9, C17 change oscilation frequency to 250Khz.
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Old 18th May 2011, 12:06 AM   #1124
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@fibko
For modern fets with fast diode (or older like IRFP250N +bypass with MUR120) you can change gate resistor from 27Rto 22R for better gate charge and C15 to 100uF for beter reproduction of low frequency because 47uf is lower limit in feedback for low frequency (like 70Hz or lower)

Do you measure swich freq with this satup? Do you exceed 240KHz without noice?
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Old 18th May 2011, 10:45 AM   #1125
fibko is offline fibko  Slovakia
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Quote:
Originally Posted by Dzony988 View Post
@fibko
For modern fets with fast diode (or older like IRFP250N +bypass with MUR120) you can change gate resistor from 27Rto 22R for better gate charge and C15 to 100uF for beter reproduction of low frequency because 47uf is lower limit in feedback for low frequency (like 70Hz or lower)

Do you measure swich freq with this satup? Do you exceed 240KHz without noice?
Amplifier run approximately on 250Khz with small noise. How I can start oscillate amplifier without signal? Because when I turn on, amplifier not oscillate.
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Old 18th May 2011, 02:32 PM   #1126
opor is offline opor  Thailand
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Quote:
Originally Posted by Dzony988 View Post
@fibko
For modern fets with fast diode (or older like IRFP250N +bypass with MUR120) you can change gate resistor from 27Rto 22R for better gate charge and C15 to 100uF for beter reproduction of low frequency because 47uf is lower limit in feedback for low frequency (like 70Hz or lower)

Do you measure swich freq with this satup? Do you exceed 240KHz without noice?
Can I change gate resistor to 22R with 1N4148 bypass diode?
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Old 18th May 2011, 02:59 PM   #1127
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Ask pafi, luka and lorilaci, but I think you cant. MUR120 is better, substitute for MUR is EGP20G. Both has 2A curent 400V and 50nS.

I'm not sure for mur with big powers.
Can anyone tell us.
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Old 18th May 2011, 04:57 PM   #1128
luka is offline luka  Slovenia
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Quote:
Originally Posted by opor View Post
Can I change gate resistor to 22R with 1N4148 bypass diode?
well yes, 4148, 4448 and such diode work great, ultra fast
while they are not any high current ones, they are great pulse diodes, since gates are discharged fast and in short time
Its also should be WANTED to use fets not like 250's, but the ones with small gate capacitance and so on, those are much better on audio and in working of the amp itself
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Old 18th May 2011, 09:01 PM   #1129
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I used a 100pF cap instead 330pF.
Mosfet irfp250N with bypass dione mur120.
Power supply +-60vdc

Input signal less than 0.6vpp

Is it a saturation problem ??

I can't go up more than that.
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Old 18th May 2011, 09:03 PM   #1130
luka is offline luka  Slovenia
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does the coil get hot?
why do you use such small signal?
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