Why need discharge circuit between SW and GND in buck converter?

BobTPH

Joined Jun 5, 2013
3,825
During the on part of the cycle, the inductor is connected to V+. During the off cycle, you cannot simply disconnect it, you need a path for current to continue flowing. Normally, this is simply a diode to ground, but it could be a MOSFET as well.

Bob
 

Ian0

Joined Aug 7, 2020
3,525
I thought it was to make sure that the charge pump that provides the gate voltage for the upper FET can operate.
But I note that the upper FET is drawn wrongly. The source appears to go to V+, but it is drawn as an N channel FET, but the diode is the right way round for a P channel FET.
 
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