I an buy a 12V solar panel, but I want 6V (which I will then limit to 5.2V using a zener diode). How do I drop the voltage to 6V, without just using a resistor? The resistor just uses up power – making the solar cells less effective. It would be better if I could somehow use the extra voltage to boost the current (the power output would be the same).
Thanks! I looked up http://en.wikipedia.org/wiki/78xx – this seems to be the best solution — but there is no way to change the extra voltage into current (aside from an AC transformer).
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3 Comments
Randy G
on 24th Jun, 10 07:06pm
The only way that I know of would be to convert the DC output of the solar panel to AC [using an inverter], and then use a step down transformer to cut the voltage in half (then you would need a rectifier circuit to change the power back to DC).
You will still lose some power in the conversion, but not nearly as much.
lare
on 24th Jun, 10 08:06pm
if it were me, i would drop the zener and go with a 3 term regulator. First the “12 volt” panel has a swing in its actual output voltage. It is a good enough source for the 7805 though. Second, a zener “regulates” by insuring the maximum power is being drawn at all times, this is about as wasteful as possible. And third, this allows putting a battery for storage ahead of the regulator to help with cloudy days. use the battery on the 12 volt side, not the 5 volt side.
roderick_young
on 24th Jun, 10 08:06pm
The only way to not throw away more than half the power is to use a switching regulator.
There might be off-the-shelf 12V to 5V DC-DC converters, intended for use on motherboards. Certainly, there are 12V to 3.3V ones made.
If you wanted to design your own, you would find a part like the AP34063 or the LM5020, and build your regulator around that. This is a non-trivial exercise, though. Email me if you need more information.