dc-dc general question

[analogLow]

If I have a solar cell from which I always want to extract the maximum power, I understand that I need to dynamically adjust the impedance which it sees (e.g. as temperature changes). The load it sees is the regulator.

Lets say I have a simple buck LC converter:
Buck converter - Wikipedia, the free encyclopedia
I need to adjust the impedance of the dc-dc regulator to be give the MPP. Is the impedance of the dc-dc regulator adjusted by only the duty cycle? Im just trying to get a more intuitive feel for this. Is the impedance big or small for a low duty cycle?:lol::lol:

Thanks,
analogLow

 

[leo_o2]

Yes. Impendance is bigger under low duty cycle.

 

[analogLow]

thanks. so a lower duty cycle means that there is less current IL from the input going through the inductor over a given time ... so if you want the same output voltage Vo, then impedance increases since Z=Vout/IL as IL decreases. right?

 

[leo_o2]

In CCM, though duty cycle affect the current IL, the influence is still very small.
For ideal CCM, the influence will be zero.
For ideal CCM, D=Vout/VIN.
However, in DCM, duty cycle will influence the IL much.