Hello Forum,
Some electronic devices specify a certain, specific voltage that they need to work properly. Some other devices specify a specific current. Why don't they all specify the voltage or the current?
If the voltage is specified, the current will be automatically fixed by the internal impedance of the device. At the end of the day all devices require power, which is the product P=IV.
As a beginner, I am familiar with two types of sources: constant voltage sources and constant current sources. Regardless of the type of load and its impedance, a constant voltage source always applies the same voltage across the device. The constant current source, instead, makes the device draw the same amount of current, regardless of its impedance.
I am asking these questions because I have a small, basic personal project: power, using a small solar cell (max two connected in series) an electronic device like a smart phone.
a) I am not sure if the solar cell behaves more like a current source or voltage source.
b) The voltage from the solar cell(s) is usually much smaller that the electronic device required voltage. We can get, using a couple of cells (I don't want to use many) about 1 or 2V. A USB device I think needs 5V.
I guess I will need a DC-DC converter between the cell and the device....Is that all I need to trickle charge the phone, for example?
For a fixed solar illumination, I wonder how I can transfer the most power from the cell to the phone. I am familiar with impedance matching but I don't know if I need to worry about it and where in the circuit. So far I have the cells, the phone and I need to get the small DC-DC converter which I don't think does the impedance matching between the solar cell and the phone...
How should I look at this situation?
thanks,
Kavan