solar cell powered portable devices

[jszair]

I have a question regarding solar cell powered portable devices.

Typical solar cell output voltage is 400mV, and I'd like to convert that to ~5V to power portable device. I looked up IC datasheets and found these two DC/DC converter might be useful.
http://focus.ti.com/lit/ds/symlink/tps61202.pdf
http://cds.linear.com/docs/Datasheet/3105p.pdf

My question: maximum output current for 400mV input and 5V output is pretty low, ~150mA. Does that mean the maximum power provided by the converter is 5V*150mA = 0.75W?

 

[Resqueline]

The TI chip requires up to 0.5V input to start up so that might require two cells in series for reliable operation. At 0.4V in it seems to manage only about 80mA out.
The Linear chip starts reliably at 0.4V in but it manages only 15mA out at 0.4V input.
Yes, your calculation is correct, except I don't know where you found the 150mA figure.

 

[(*steve*)]

Given the way solar panels work, it would be far more efficient to have 12 solar cells, each 1/12th the size, connected in series and using a simple shunt regulator to keep the open circuit voltage down.

Of course, nothing will prevent the output voltage falling if there is insufficient light to maintain the output current you require..