Thank you all for your replies especially Coffee & WSJ
So I place two 470 ohms resistors at the base of mosfet's drivers and now the output signal looks way better than before
Also there was already two resistors between the drivers' emitter with center connected to the output and I just drew the schematic wrong. (Sorry about that)
I tried to increase the output power but no matter what I did I couldn't get more than 50 Volts rms in the output, and above that point I get clipping even with no load connected to the output.
my power supply voltage is above +-82V rms at 600W output power
So what am I missing here??
Here's the new output signal and the schematic :
IMG_20190408_002749.jpg - Google Drive
New.png - Google Drive
So I place two 470 ohms resistors at the base of mosfet's drivers and now the output signal looks way better than before
Also there was already two resistors between the drivers' emitter with center connected to the output and I just drew the schematic wrong. (Sorry about that)
I tried to increase the output power but no matter what I did I couldn't get more than 50 Volts rms in the output, and above that point I get clipping even with no load connected to the output.
my power supply voltage is above +-82V rms at 600W output power
So what am I missing here??
Here's the new output signal and the schematic :
IMG_20190408_002749.jpg - Google Drive
New.png - Google Drive
Yes there is still a bit of oscillation
I could get about 70V to 75V peak at full load but after that clipping start
Here's come voltage measurements at CE of transistors (Without load and at the point the clipping starts):
Q5 >> 86V
Q2 >> 91V
Q3 >> 90V
Q7 >> 89V
Q6 & Q9 >> 89V
Q12 & Q14 >> 92V
you could see the rails at the Drain of mosfets
and about those 1n4148 application could you explain more?
thank you in advance
The 2x470ohm for R17, R18 is a was too high value to close the output devices fast enough. Try to reduce them to 220, or even 100 ohms, but You need to change the drivers, because they are weak for this high amout of MOSFETs, and for this power. MJE1532/33 of 15034/35 is much better.
Sajti
Which means 350W/8ohms, or 700W/4ohms depending what dummy load You use.
The 15V loss is little bit high, I would say, that less than 10V would be normal.
Sajti
I use 25 * 3.9 Ohms 10W resistors in series and parallel configuration to make a 250W 3.9 Ohms dummy load
I also put the whole thing in the water to cool them down
What is the resistance in the base of the drivers? What is iB for the drivers and what voltage drop does this create?
On the 1n914 diodes for the "input" rail, these are low current devices and not really meant for surge currents that will be seen charging those caps on the input rail. I would either simply use a 100R resistor or if you feel a serious need for diodes, stick in a 1n4004 or similar.
On the 1n914 diodes for the "input" rail, these are low current devices and not really meant for surge currents that will be seen charging those caps on the input rail. I would either simply use a 100R resistor or if you feel a serious need for diodes, stick in a 1n4004 or similar.
470 ohms
without any input signal the voltage drop is about 5 mV, but at full output power it goes to about 140 mV
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