Hi,
Often made mistake: wrong (saturating) inductance.
--> So please post a link to the inductor's datasheet.
Next most often mistake: Unsuitable PCB layout.
--> Please post your PCB layout, where we can see the complete signal routing, especially the solid GND plane.
Btw: There are many similar threads here. (Different ICs). Read through them.
In more than 90% you see one if the above mistakes.
Klaus
i change the big resistor and put a film resistor but any change happenedHi,
Now we have:
* self made inductance.
We simply can't verify. There is a good chance that they are not suitable.
Besides the inductance value... the saturation behaviour is very important.
* No GND plane.
A couple of big copper areas is no "low impedance GND plane".
I assume there is no way around a redesign.
* big resistors:
Most probably "wire wound" which means "high series inductance".
If they are in the switching path (what we can't verfy, then they are completely unsuitable.
All informations for a reliably working SMPS are given in the datasheet and application notes provided by the IC manufacturer.
Read them and design the SMPS according this informations ... and it will work.
Btw: the part names in the schematic don't match to the PCB part names. It's a huge ammount of effort for us to find out which part is which part. I don't want to spend that much time...
Klaus
Hi,
What´s the benefit of using 4 diodes in parallel?
Did you do calculations?
In best case (Equal current distribution) you get a 18% improvement in power dissipation (which should not be much benefit)...but get the drawback of 4 times the capacitance (huge capacitance!)
But in reality I expect that the hottest diode will carry the most current and get even hotter. Maybe one diode carries 80% of the total current and the other diodes in total 20%.
--> Read application notes about paralleling diodes.
Klaus
As mentioned in your previous thread, I would expect a PI configuration instead of a low gain P controller.my big question is about voltage feedback.is that correct?
why did you simulate 8kHz..?
...
I see that 1nF, 22k on that chip gives about 60kHz ...
yes i use kevin sensing method but path length is about 4 centimeter. is that very bad?did you kelvin connect the sense resistor?
Did you put a gate series resistor to damp the fet switch on?
Hi,
I have to repeat what's written in post#2 and post#4 about GND plane.
Klaus
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