photo-voltaic dc-dc boost converter

[seunatoki]

Hi All,
please I JUST built photo-voltaic boost a converter, boosting from 12V to 30V but immediately i connected load or even small LED, the voltage would go down 12V or 11V without going up again. Then I discovered that it takes about 5 to 8 seconds before it get to maximum voltage What could be the reason for this ?
Cheers

 

[vinodstanur]

Hi All,
please I JUST built photo-voltaic boost a converter, boosting from 12V to 30V but immediately i connected load or even small LED, the voltage would go down 12V or 11V without going up again. Then I discovered that it takes about 5 to 8 seconds before it get to maximum voltage What could be the reason for this ?
Cheers

In simple words, the reason is the high internal resistance of the 12v source.

When boost converter trying to take more current, internal voltage drop in the cell increases and this decreases the input voltage for the boost converter. When no load is connected, the capacitor at o/p of converter gets charged slowly to 30v but when load is connected it decreases and boost converter is not able to boost it because of less voltage at input.


In other words,
According to maximum power transfer theorem, your cell can deliver (V^2)/(4R) where V is cell voltage, R is internal resistance of cell. So in real time you cannot expect more than this even if the boost regulator is considered to be ideal. Now you can compare the power consumption by an LED and the maximum of the cell, if it is not enough, boost regulator will also become helpless in real time.

 

[Audioguru]

Why not use a 12V solar panel with a current rating high enough to drive your loaded voltage boost converter? The solar panel might be very large and very expensive.

 

[seunatoki]

Thanks Vinodstanur, I really appreciate this and am happy. I have written program for MPPT which I think it will take of this, but there is alot of sense in what you said. Please can I do to improve this ?
Cheers