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Over driving a boost converter input

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ali_asadzadeh:
Hi,
I have designed a 91% efficiency Boost regulator based on UC3843, it would convert from 12V to 60V.

The circuit


The simulated output


Now for some reason I want to over drive the boost input over the 60V, say to 340V, I wanted the design to be able to survive and work ;) so the output should be around 340V in this case :D
The problem is that when I simulate it, it would generate some 650V overshoots, I need a way to clamp this overshoot.

I have changed the input voltage to 340V in here


We have a 650V overshoot, How should I clamp it?


Also I have built the above circuit and it works as expected with 12V input, I have not changed the Diode and MOSFET yet to be able to handle high voltages! so what part numbers for MOSFET and Diode do you suggest? I need them to be on the low cost side of things.

I have not tried to over drive the input yet, for now I wanted to make my calculations solid and then over drive it in real world. :) :)

OwO:
Inductor too small/on-time too long for 300V. dI/dt is proportional to voltage. Try probing the current on the mosfet.

Yansi:
Mosfet too wrong.

IRF540 for 340V input? lol. No way.

ali_asadzadeh:

--- Quote ---Mosfet too wrong.

IRF540 for 340V input? lol. No way.
--- End quote ---

Loool read the post completely! I said that I have plans for changing the MOSFET and diode!


--- Quote ---Inductor too small/on-time too long for 300V. dI/dt is proportional to voltage. Try probing the current on the mosfet.
--- End quote ---

I do not want to blow up things, So should I increase the inductor? to what value?

T3sl4co1l:
Actually now that you mention it, I'm very curious about what model TI used for the IRF540.  IIRC most I've seen, contain diodes that include BV (breakdown voltage).  That waveform shows it's clearly not using such a model!

Addressing the transient is easy:
a. Increase the source resistance to sqrt(30uH / 12uF) or greater, or
b. Set C1 initial voltage to 340V or enable DC operating point setting, or
c. Connect a TVS diode from GND to output, rated for say 400V.  (Use a 550V+ rated MOSFET.)

Tim

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