12VDC (Or 5VDC direct from HV PV?

XRinger

I'm looking at these little switching power supplies,


And have seen 12Vdc (and some +5 units) on Ebay that use AC input voltages of 100-240V AC 50/60 Hz.
http://www.ebay.com/itm/370435334398

It seems to me, these little Ebay Switchers might also run on DC from 100 to up to 240 volts DC..

Meaning one could use a high voltage output PV source to power small low voltage DC devices..

Anyone here ever try it?

And since 1.414 * 240 = 339, could these things run off of a 339vdc PV array?

Thanks,
Rich

BB.

Re: 12VDC (Or 5VDC direct from HV PV?

Yes, you can put ~370 volts or so into the high voltage section of a "simple" switching power supply (120/240 vac switchable).

Or, if you find power factor corrected supplies, you might be able to feed 100 VAC - 264 VAC or even 100-264 VDC directly into those types of switching power supplies.

Either you will have to purchase some "cheap" supplies and do a smoke test, or contact the designers and see if they will give you the information (everyone is afraid of lawsuits).

-Bill

niel

Re: 12VDC (Or 5VDC direct from HV PV?

now isn't this a coincidence as i was just pming nsaspook about my little switchers. you are showing the same ones i have. they work good, but in a high rf environment they blow out.

XRinger

Re: 12VDC (Or 5VDC direct from HV PV?

The vendor was selling that same 12V PS for $3, so I ordered one to try on my 145vdc array, unloaded or 115.6v at MPP.

If this works (I think it might), I'll use it to simplify a little MPPT project I'm planing to build.
Instead of using a resistor and Zener diode to make a logic supply, I'll just use a plug-n-play Power supply. 8)

For now, I can test the transistor & heat-sink setup I plan to use, with a function generator.
While I wait a 2 or 3 weeks for delivery..

RCinFLA

Re: 12VDC (Or 5VDC direct from HV PV?

PV panels are current sources, not a voltage source.

If you have much more PV power being generated then the wall wart needs and there is a mppt charge controller already loading the panels it will likely work.

I would not consider it a reliable setup and if the wall wart oscillates coming in or out of some heavy shade occurance it could screw up your MPPT controller's operating point causing it to lose a lot of power harvest.

XRinger

Re: 12VDC (Or 5VDC direct from HV PV?

RCinFLA wrote: »

PV panels are current sources, not a voltage source.

If you have much more PV power being generated then the wall wart needs and there is a mppt charge controller already loading the panels it will likely work.

I would not consider it a reliable setup and if the wall wart oscillates coming in or out of some heavy shade occurance it could screw up your MPPT controller's operating point causing it to lose a lot of power harvest.

I'm not worried about the PS failing to supply reliable +12v, since the load
to my DIY MPPT circuit will likely only be 5 to 10 ma, and the PV array will put out
80 to 100 volts no-load during overcast conditions.

The source is four CS6P-200 (200w Canadian Solar Vmp 28.9 & Voc 36.2), in series.
The project circuit looks a bit like the one below, but with the FET, C1 & C3 rated at 200 to 250v.

I would use the power supply, in place of R1 C4 & Z3.



Theory of operation:
When the voltage on pin 2 the of LM311 exceeds 5V, Q1 will fire, discharging C1.
Then the process will repeat, rapidly when it's sunny.
R3 will be adjusted so pin 2 only sees 5V when the array is => 115.6 volts. (MPP).