I think it needs a larger value of C9, say 10nF, and a resistor, say 100k, between the pot wiper and the feedback pin.

 

Your schematic is still wrong. Review post #73

 

Your schematic is still wrong. Review post #73

Which part do you mean?
If you mean the potentiometer, I explained in the reposted post that in the real circuit, it didn't work that way at all.
If there is another part, please explain

 

I think it needs a larger value of C9, say 10nF, and a resistor, say 100k, between the pot wiper and the feedback pin.

I tested, there was no change
It's interesting, I used two software to simulate the circuits (both Buck and Buck Boost) and tested different values.
But variable resistance does not work in both software
This circuit has a secret

 

Which part do you mean?
If you mean the potentiometer, I explained in the reposted post that in the real circuit, it didn't work that way at all.
If there is another part, please explain

The variable resistor should have worked, so you probably wired it wrong.

You reconfigured the circuit to a boost topology. The FB network should resolve to 2.5v at the FB pin when the output is at the target voltage. So you need to stop guessing and recalculate the resistance values accordingly.

 

so you probably wired it wrong.

Thanks for your tips
I checked it several times, nothing was wrong

You reconfigured the circuit to a boost topology

In boost mode, the circuit is simpler and I can find its fault more easily

The FB network should resolve to 2.5v at the FB pin when the output is at the target voltage

The problem is when the load is placed on the circuit, in the no load state everything works perfectly
When the load is placed on the circuit, the circuit does not work properly as I explained earlier

 

The problem is when the load is placed on the circuit, in the no load state everything works perfectly
When the load is placed on the circuit, the circuit does not work properly as I explained earlier

What is the input voltage and What is the target output voltage and current?
What are you using for a load , and what is the load resistance?
Check the Inductor DCR. What shockley diode are you using?

 

What is the input voltage and What is the target output voltage and current?

The input voltage has been tested from 18 to 27 volts (15 amps).
The output voltage I need is from 5 to 50 volts.
In buck mode, I don't need more than 15 amps.(Boost 8 amps).

What are you using for a load , and what is the load resistance?

DC motor,Lamp,Battry,Resistor
In all of these the circuit operation is the same

Check the Inductor DCR

I dont get it
Do you mean inductance?

What shockley diode are you using?

MBR30100CT

 

What is "MOSFET protection"?
I have read about it. Is my problem not related to it?
Reverse polarity or overvoltage or...
Please look at the attached pictures

 

I dont get it
Do you mean inductance?

No...I mean DCR (DC resistance). But the inductance would be good to know also.
Any component in series with load has to pass the current delivered to the load.
It may be one of the components is limiting the required current.

 

No...I mean DCR (DC resistance). But the inductance would be good to know also.
Any component in series with load has to pass the current delivered to the load.
It may be one of the components is limiting the required current.

Do you mean the same resistance value that the LCR meter shows?

 

Do you mean the same resistance value that the LCR meter shows?

Yes

 

No...I mean DCR (DC resistance). But the inductance would be good to know also.
Any component in series with load has to pass the current delivered to the load.
It may be one of the components is limiting the required current.

What the LCR meter showed was 0.2 ohms

 

No...I mean DCR (DC resistance). But the inductance would be good to know also.
Any component in series with load has to pass the current delivered to the load.
It may be one of the components is limiting the required current.

Hello
I put the link of an oscilloscope
Please advise if it is suitable for what I want to do or not

https://www.amazon.com/DSO138-Oscilloscope-Digital-Handheld-Version/dp/B088FWHKZG

 

Does anyone have any ideas or suggestions?

 

No, further down - last but one item on page 8 "Operating supply current 17mA max"

Output current 63nC x 95kHz = 6mA

(30V - 12V)/(6mA+17mA+3mA) = 680Ω ½W

I have a question
According to your formula to calculate the resistance of IC pin 7, at 12V voltage without zener, the resistance should be 460 ohms, but in the schematic it is 4.7 ohms.
Is there another formula for calculating this resistance without a zener?

 

If you’re going to make any more switched-mode supplies, get an oscilloscope!

I bought an oscilloscope
If possible, tell me what to do now

 

I bought an oscilloscope
If possible, tell me what to do now

First, have a look at the clock waveform on pin 4. When you've got that nice and clear on the screen, you know you have the timebase set correctly.
Then have a look at the waveform on pin 6 (the gate drive waveform), which should be a rectangular wave of about 12V amplitude.
If everything looks OK so far, look at the waveform on the MOSFET drain, screenshot it, and post it for us all to discuss (i.e. argue about)

 

First, have a look at the clock waveform on pin 4. When you've got that nice and clear on the screen, you know you have the timebase set correctly.
Then have a look at the waveform on pin 6 (the gate drive waveform), which should be a rectangular wave of about 12V amplitude.
If everything looks OK so far, look at the waveform on the MOSFET drain, screenshot it, and post it for us all to discuss (i.e. argue about)

Thank you
The waveforms of pin 4 and 6 and drain should be taken under load or without load?

 

Pin 4 should not change with the load.
Pin 6 and the MOSFET drain will convey useful information both with and without the load.