buck converter in proteus simulation

Thread Starter

mah

Joined Mar 15, 2010
393
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
 

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Ian0

Joined Aug 7, 2020
2,728
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.
 

Thread Starter

mah

Joined Mar 15, 2010
393
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.?
 

Papabravo

Joined Feb 24, 2006
16,523
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
 

Thread Starter

mah

Joined Mar 15, 2010
393
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
 
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Ian0

Joined Aug 7, 2020
2,728
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)
 
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