LM5117: DCM Ring in SW node

Thank you for yout reply.

When the inductor current drops to 0, I think the energy stored in the inductor has been released, where does the AC or residual current come from? Is the energy stored in the inductor not released?

I think when the inductive current drops to 0, the energy stored in inductor has been released. At this time, the output Cout provides energy, discharges the inductor , and LC oscillation is formed by L and Coss(MOS/diode).

I've done the simulation.

Thank you for your reply.

As is shown in the picture below, I think：at the t1 moment (instant) , the inductor current drops to 0 and the energy stored in inductor has been released completely. After t1, the capacitor discharges and charges the inductor in reverse, at which point the current is also negative. Between t1 and t2, start LC damped concussion. Until time t2, the energy saving capacity of the body diode in the loop and the energy stored in the inductor L are exhausted.

Do I understand correctly? 

I think at the t1 moment when the inductive current drops to 0,the inductor's energy has been released exactly . At t1, there is no residual AC current in the inductor. So the first one below is false. Also, there's no a little bit of current in L.The second one below is right.

Jiang Long said:

In the answer to this question(Link as follows), mention that"there's still a little bit of current in L".But at this point the current in L has dropped to zero, where does the current come from?

I asked the other engineers, and there were two possible explanations:

① maybe the residual AC current in the inductor；(But I don't understand the AC current)

② maybe that the Output Cout reverse discharge。 Vout(Cout)，L，Coss(MOS LS) constitutes LC resonant circuit。Vout(Cout) is equivalent to a constant Voltage source.