why can't i get more than 8 voltage in proteus for buck converter?. i increased duty cycle up to 100% however the output is constant at 8v

 

hi mah,
Can you post an image of the Gate to Source waveform.?
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hi mah,
This is what I see in LTS, same result [ check my circuit accuracy.
Using 95%
E

Update:
Your Gate to Source drive is too low, now 18v Source

 

gate signal on channel A and source on channel B

 

Your MOSFET is connected common-drain (a source-follower), so the gate voltage must go to at least 5V above the positive supply to switch it on fully. The gate must be at least 5V above the source to switch it on, and when it is switched fully on the source will be at the positive supply.

 

Your MOSFET is connected common-drain (a source-follower), so the gate voltage must go to at least 5V above the positive supply to switch it on fully. The gate must be at least 5V above the source to switch it on, and when it is switched fully on the source will be at the positive supply.

this configuration limits the output of the buck converter so how to make the VGs independent of the power supply on drain.?

 

Either:
1) Use a P-channel MOSFET
or:
2) Use a high-side driver IC

 

this configuration limits the output of the buck converter so how to make the VGs independent of the power supply on drain.?

Generally speaking a P-channel MOSFET has a larger die area with slower switching characteristics and slower switching.
A high-side driver IC will boost an existing logic control voltage to a higher level so that an N-channel FET can be used in this application. Of course sin this is a buck converter you could easily derive the gate voltage from the input voltage. Be careful not to exceed any limitations on Vgs listed in the datasheet

 

Either:
1) Use a P-channel MOSFET
or:
2) Use a high-side driver IC

I have already used high side driver 2110 and the same problem exists. The driver supply must be higher than the mosfet drain supply .which mean that if the buck input is 100 v the ic driver VCC should be higher than 100v

 

hi mah,
Check out this video, he has other SMPS videos.
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I have already used high side driver 2110 and the same problem exists. The driver supply must be higher than the mosfet drain supply .which mean that if the buck input is 100 v the ic driver VCC should be higher than 100v

The IR2110 contains a charge pump which lifts the gate voltage above the VCC supply. (The Vb voltage)

 

The IR2110 contains a charge pump which lifts the gate voltage above the VCC supply. (The Vb voltage)

I used ir2110 in proteus and the same problem exists

 

I used ir2110 in proteus and the same problem exists

Did you remember to put the diode in?
I've used that type of device in real life, and it does actually work.