I'm trying to understand Buck Converters by designing & simulating a circuit in www.Falstad.com circuit simulation tool.
Here is the link to the circuit that I've Designed.
(Its a long link, copy paste it if it the hyperlink won't work)
The objective is to design a circuit that can accept 230V 50Hz AC supply from mains and output a DC supply with a Voltage limit of 60V and a Current limit of 30A.
I'm still in the initial stages and was only able to implement the Voltage limiting feature.
Few points to note regarding the design.
1.I have used a 555 timer IC to generate the PWM signal to switch the N-MOSFET as that was the only method of generating a variable PWM I could find on this simulator.
2.The values of the capacitors and the Inductors are not yet fixed as Its a work in progress.
3.Oa is an Op-amp that is used to amplify the 5V output signal from the 555 timer IC to 350V required to drive the N-MOSFET gate.
4.Ob is an Op-amp that is used to send a feedback signal of 5V by comparing the voltage at the load w.r.t a constant reference voltage of 60V.
5.I have created a scope of the voltage and current across the load.
If you reset and run the simulation, you'll see that the load voltage(Vl) shoots higher than 60V initially but after a certain time settles down and is correctly regulated at around 60V.
1) Why does it shoot up initially?
2) I suspect that the inductor is releasing its stored energy after the MOSFET is switched off and causing this voltage spike. Is this correct?
3) But going through several circuits on the internet I have come across similar circuits used to design a buck converters. If this circuit has all the parts for a voltage controlled buck converter, how do commercially available converters address this voltage spike issue?