inductor ripple current boost converter

[badboy85]

Hello everyone,
I have a question for all you electronic experts. I'm sizing a DC-DC boost (for a maximum power point tracker MPPT controlled by a mic) and i would like to know how much it should be worth the inductor current ripple considering the fact that I should make a current and voltange input sensing! in simulation test deltaI (with an inductance of 2mH) is about 10% of the average value of current IL. Some online guides say that the the current variation deltaI, to avoid dangerous disruptions of IL, be chosen between 30% and 50% of the mean value of IL. Is it right? In my simulation circuit there is a block that allows me to calculate the average value of the current (average over the period of the PWM control of the Switch 16kHz IGBT) and send it to the circuit that controls the duty cycle of the Switch. So everything works fine, but now I have to pass to the real implementation and the ripple of IL causes me some doubts. In my simulation test i tried to insert a capacitor in the input but with the result that if it's small (10-100nF) does not change the situation, if large (50-200uF) slows the dynamic circuit for which the ripple remains, indeed in some instants worsens, and the control block does not work correctly, and then the whole tracking MPPT.
I hope you can give me some advice. Thanks to all :thumbsup:

 

[KlausST]

Hi,

the ripple current of a DCDC converter usually is no problem because the output capacitor will smoothen voltage.
Look for the voltage ripple at the output.

The lower the ripple current, the higher the inductance (or vice versa).
The higher th inductance, the bigger the inductance (often the more ohmic resistance = more power loss) and the more expensive.

Klaus

 

[badboy85]

Thank you for your answer.
The Vout ripple is ok, less then 2%. I just had some doubts about the inductor current ripple.

 

[BradtheRad]

The inductor is always conducting in a boost converter. As is the power supply (PV panel).

You can reduce inductor ripple by increasing the operating frequency.

Edit:

Gotta back-peddle...

There are conditions in a boost converter where the inductor may stop conducting. Example, when step-up ratio is high.

I'm running a simulation, charging a 12V battery from a PV panel putting out 11V. This is what your initial post suggests you are doing.

It is unlikely you will have conditions when the inductor is idle.