You do know that op amps and 555s are ICs(?).

The feedback loop for your circuit needs compensation to be stable due to the phase-shift of the L1C2 output.
Here are some articles on that.

Below is the LTspice sim of a simple hysteretic type (bang-bang) buck-converter using a comparator, which does not require feedback compensation:
The output is shown for battery voltages of 16V, 20V, and 24V.
The output has ≤50mV of ripple at 0.5A load current:

View attachment 346208

Hi sir I've been trying to emulate your buck converter in order to use it for a wireless power transfer project that I am working on. I do not understand how I can get a steady 5V output. I basically want to keep a fixed 12V input, and the coupling varies as we vary the distance of the receiving and transmitting coils(0.25-0.35 even a wider range would be great). Would you mind pointing me in the right direction as to how I can modify your circuit? I attached an image of my circuit as well as the ltspice file. Thanks in advance!

 

Hello again,

One of the things that comes to mind is that using the 555 timer as a switching controller with feedback means relying on the linearity of the device via the control voltage input. It is most likely only linear over a certain range, and then it can be very nonlinear. The consequence of being too nonlinear is the loop gain can vary too much over the entire operating range of the converter which could lead to gross instability.
Something to be aware of and check out once the circuit is built and/or study using a simulator.

 

Hijacking someone else's thread is not allowed so now you have a thread of your very own. This was split from:
https://forum.allaboutcircuits.com/...regulated-buck-converter-using-no-ics.206145/

 

Where did you get that two-MOSFET multivibrator circuit design from?

 

Hijacking someone else's thread is not allowed so now you have a thread of your very own. This was split from:
https://forum.allaboutcircuits.com/...regulated-buck-converter-using-no-ics.206145/

Hi there,

This is interesting. It appears that the first post in this new thread may have been a so-called hijacking, but the post right after that was not a reply for that first post it was a reply for the original thread which used a 555 timer IC. What do we do in that case. If the whole thread after that (first post here) is moved, then the replies that were meant for the original thread do not apply to the new thread (ha ha) because the new thread starts out with an entirely different concept.