100 volt dc to 0-24 volt dc circuit design with SCR ????????

[arnould]

Hello everyone. Thanx for reading this.I couldnt design it well and i am new at this so if you can design this circuit it will make me so happy.

I wanna make a buck converter which can convert 100 volt dc to between 0-24 volt dc.
and This buck converter is gonna work with SCR.   is switching frequency effecting to output voltage and current? ? think yes but
How does switching frequency effect to output voltage and current?

[Alex30]

If you could provide a quick sketch or example on what you were thinking of doing that would help us work out how to help you. Also why 100V DC? Why not 28V or 26V? Does it have to be 100V DC?

[arnould]

it is gonna help me so much. because it is one of my power electronics lectures final exams question.
the proffesor gave us one question of exam for searching for it.
I hope someone help this newbie.and oneday I hope with years of working experience ? will design it myself but its gonna be so late for now

[c4757p]

If it's an exam question, surely they taught you something about it?

[Seekonk]

If you want to take credit for another persons work, a career change to management would be appropriate.

[oldway]

This technology is almost outdated for low voltage and low power buck converter.
Use Mosfet switching devices and not fast SCR's.
It has great benefits:
- higher switching frequencies: up to 500Khz for Mosfet's, only 6 Khz (more of less) for fast scr's.
- lower dc loss: more or less 2V for fast scr's , less than 2V for Mosfet.
- lower cost: need 2 scr's, switching inductor and high quality capacitor, not needed with Mosfet.
- simpliest schematic.
As scr's can't be turned off by gate pulse, you need provide "forced comutation" who let the anode current stay 0 for a time longer than the the Turn - off time of the scr before reapply direct voltage.
Basic esquematic and explanation of scr chopper (buck converter) can be found here:

https://www.pantechsolutions.net/power-electronics/introduction-of-dc-chopper-using-scr

You need to add an inductor to use it as an DC-DC converter.

http://www4.hcmut.edu.vn/~nvnho/Download/EngPE/Chapter1_Switching%20Power%20Supply.pdf

More explanations about scr chopper:

http://www4.hcmut.edu.vn/~nvnho/Download/EngPE/Chapter1_Switching%20Power%20Supply.pdf

You must choose fast scr with Toff between 5 and 50µs.