the best design for a <15A linear regulator for solar power supply
Hi all. I've got a tk2050-based board from sure electronics (4x100W at 4ohm), and i want to power it with solar cells. It needs 30Vdc and about 500W of power (so, let's say 15Amps).
I'll use photovoltaic cells as power source: 12V modules in series/parallel. This will give me a 35/40V unregulated bias voltage, and i have to control it in the best way.
There's some stuff I already have:
-10x lm317 in T case
-5x lm338 in T case
-2x TIP142 (NPN darlington pair)
-2x 2N3055 in K package (quite old, don't even know if they still work)
-other smaller seemiconductors like TIP31, TIP32
-4x 22000uF 50V electrolytic capacitors, (and many smaller others)
Yes, i've looked for some schematics. lm338's datasheet suggests some circuits but they use a (discontinued) op-amp to drive 3xlm338 in parallel. But this shouldn't give me 15A due to high voltages and T pakage, and i wouldn't like to use and op-amp. I've looked at some schematics with a lm317 and a power transistor like tip142, but they don't go over 10A. I would like to parallel 2 of this big darlington but i don't know what's the right thing to do.
And before someone asks, yes, I still don't have 500W solar cells, at the moment I've got around 300W (stable and continuous), but I could get more power soon, and eventually use the regulator with a switching power supply. So I would design this for full-power use.
I think you need to go SMPS if you want to take all available energy out from your panels.
I know this is not the answer you are looking for.
But with linear regulation you will waste most of the energy to heat and losses.
Agreed about the losses with a linear supply and the recommendation for a SMPS.
However, don't get scared away by a switching supply. You can run a pretty simple Buck-type switching supply to regulate and drop the 35-40V down to a regulated 30V. You can probably even use the bipolar devices and filter caps you have.
Look at http://www.ti.com/lit/ds/symlink/tl2575hv-adj.pdf This may do just what you need and you will only need an appropriate inductor and switching diode. Plus, you can likely order a free sample from TI/National.
With this type SMPS, you can achieve 90% efficiency or better, have good regulation, and keep the circuit fairly simple.
I think this isn't the best application for solar cells. If you're listening to music, not continuous sine waves or pink noise, the average power consumption will be something like 1/10 of the peaks. If you had some storage (battery or capacitor bank) that could supply the peak current, you could get away with a much smaller solar array.
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