When I made a reverse current protection circuit in a buck converter?

[mssong]

I am aware of a technique to turn off the low-side MOS with zero current sensing to prevent reverse current in a buck converter.

Where will the reverse current that would not have flowed without this technique flow when the reverse current protection circuit is added? Will it flow to the output load or stay in the inductor?

Or does the inductor current decrease so that there is no reverse current?

I don't quite understand, can you show me the current waveform when the reverse current protection circuit is added?

 

[BradtheRad]

MN mosfet is an advance to improve efficiency over the plain diode (although using a diode makes design and construction easier).

The simple buck converter design has a diode pointing upward in the place of Mn. It conducts to let the inductor discharge for the second portion of the cycle. (The inductor may discharge til it generates no more current (known as Discontinuous Current Mode).)

At that moment the diode then performs the role of preventing reverse flow, same as Mn is supposed to do. However the diode shuts off by itself, thus making life easier when we build a buck converter. The mosfet needs bias to control it when a new cycle begins, or else it needs to be monitored for reverse current flow so it can be shut off.

 

[Easy peasy]

@mssong - have a think to yourself - if there is a small reverse current in the lower mosfet - and your controller latches the mosfet off until the next cycle - where will the mosfet current go ? - remember it is small

Do you know about DCM CrCM & CCM ? time for some reading