Use laptop adapter. They usually works from DC mains.View attachment 142526

The maximum PV panel voltage is 125vdc.So a laptop charger 100vac-240vac would not work as it needs at least 140vdc.

You are going to have to use a switching regulator as you mentioned. Is there an AC component to the DC? Can you get to it? If so, you can use a step down transformer then just rectify it again or use a wall wart.

No AC component in PV panels.Unless the sunlight to it varies rapidly

I said put the DC straight across the DC smoothing capacitor, this would bypass the bridge....

As most laptop bricks run from 95 to 230V Ac

I tried this with an old Del inspron 65w laptop charger,I tried to trace the tracks from the diodes to the capacitors.I double checked the polarity of the capacitors before connecting them to the PV panels.
As a safety measure i connected a 1 amp fuse in between the PV panels and the capacitors .
As an experiment i didn't connect the full set so PV panels.I gave the capacitors about 60v from the panels.Immediately the fuse blew the moment i switched it on.I tried it a couple more times and got the same result!!

Also as a last resort to dissipate 15wats of heat,what kind of heat sink would be most suitable.Perhaps i can make one out of some Aluminum??

 

No AC component in PV panels.Unless the sunlight to it varies rapidly

Missed that. It was too early in the morning.

 

Is there a reason you have to use the high voltage source? A new power source of the correct voltage would be inexpensive and easy to find. OPPS-- I see, you need to use the solar panels. Can't these be re-configured to give you the proper voltage? Or maybe you need the high voltage somewhere else. Maybe I should think longer before I reply. Sorry.

 

Here is DC-DC step-down converter module 120-35v to 5V and 12V, 3A. Price: US $6,99
Maybe you can use it as is or rebuild (tune one component) to 15V output.
https://www.ebay.com/itm/DC-DC-Step...015786?hash=item2845d0fc2a:g:HGgAAOSwYeRaCxEx

 

As an experiment i didn't connect the full set so PV panels.I gave the capacitors about 60v from the panels.Immediately the fuse blew the moment i switched it on.I tried it a couple more times and got the same result!!

It should be so. Using incandescent bulb instead fuse permits to charge capacitor without short circuit. After it you can bypass bulb by some switch.

 

So many things wrong here.

A laptop supply converts AC to DC. Not DC to DC. Your mains are AC not DC.

The bridge rectifier converts the mains AC to DC, so there is a fair chance the laptop brick won't mind.

If it has a PFC front end, that could cause trouble. Its essentially a boost converter running on raw DC from the rectifier. The pulses of current draw should be more or less proportional to the amplitude of the sine wave going into the rectifier. It may not be able to control constant full amplitude.

 

My guess is that it is a typo on the photo that you posted. It does not look like a power inverter. And a car power invertor is not going to work. Cars are 12V not 750V.

And mains aren't DC. Well back in Tesla's day maybe.

There are plenty of power supplies that work with AC or DC high voltage input. Not at all unusual. I wasn't previously aware that some of the laptop brick adapters ran this way, but there's no reason to be suspicious of it.

 

There are plenty of power supplies that work with AC or DC high voltage input. Not at all unusual. I wasn't previously aware that some of the laptop brick adapters ran this way, but there's no reason to be suspicious of it.

Apart from items with a mains transformer, most will. Around the 80s there was a fad for SCR buck regulators - those would latch up and just pass through.

 

Try converting it to AC, stepping it down, then converting it to DC again.

 

Simulation shows that adapter in post #16 definitely will works with input voltage 85V DC.

 

15V seems to be a slightly unusual target, but here are a few hits on Digikey:
https://www.digikey.com/products/en...13&pv1525=216&pv1525=81&pv1525=150&pv1525=207

Here's a few more if you can make 12 or 24V work:
https://www.digikey.com/products/en...33&pv127=7716&pv127=7714&pv1525=44&pv1525=148

Neither of these searches is perfect or complete, but the point is that there are direct high voltage AC/DC to low voltage DC options available, and it's far simpler, and more efficient, than going through an inverter to create AC and then back through a rectifier to get DC again. That sounds crazy to me.

The searches above were only for units that accepted both AC and DC input, because there was much doubt in previous comments that such units existed. I assume there would be even more options if I looked at DC-only input, but maybe not - maybe that's where the lower input voltage limits become more common.

 

Try converting it to AC, stepping it down, then converting it to DC again.

That's more or less what a typical SMPSU does.

 

hi ak ,

I have a high DC source , string of PV panels.My open source voltage is aroung 120-125v.When connected to load it drops to around 98-100v.

I was looking for a quick and cheap way to stepdown this voltage to around 15v,to power some circuits.The current consumption would be 800mA to 1 amp.

. i am curious as to what type of load you connect "i am guessing unregulated" 100v to . Also , how will you power your circuits after the sun goes down or do you have a 96Volt battery system?. maybe you could tap into one of the panels with a cheap 12/24V regulator .
sorry if i am barking up the wrong tree here .

 

hi ak , . i am curious as to what type of load you connect "i am guessing unregulated" 100v to . Also , how will you power your circuits after the sun goes down or do you have a 96Volt battery system?. maybe you could tap into one of the panels with a cheap 12/24V regulator .
sorry if i am barking up the wrong tree here .

There is an automatic PV to battery bank change over.The PV panels are not easyly accessable so routing additional wires will be difficult.

It should be so. Using incandescent bulb instead fuse permits to charge capacitor without short circuit. After it you can bypass bulb by some switch.

I managed to get it working this morning.I bypassed the filter capacitor and gave the input after and it it was working.I think the capacitor was faulty from my first try.

Thanks for all your helps guys.

Wish you all a merry Christmas and a Hapy new year!

 

Hello, I'm trying to solve the same problem for the same reasons. My DC voltage is 200v @ 7.32amp. The problem I'm meeting is that people don't understand what they're talking about and also the dc voltages I'm working with are a lot lower than what I'm seeing being used in other resources.
Anyway I think I have a solution: Use a spark gap or rotary spark gap with a coil on the far side to hold amps and a capacitor matching the input(high voltage on the pre-side. I guess tesla actually came up with this along time ago because he was really into static charges. here's a working version of what I'm talking about.

 

Hello, I'm trying to solve the same problem for the same reasons. My DC voltage is 200v @ 7.32amp. The problem I'm meeting is that people don't understand what they're talking about and also the dc voltages I'm working with are a lot lower than what I'm seeing being used in other resources.
Anyway I think I have a solution: Use a spark gap or rotary spark gap with a coil on the far side to hold amps and a capacitor matching the input(high voltage on the pre-side. I guess tesla actually came up with this along time ago because he was really into static charges. here's a working version of what I'm talking about.

No bad for 1880's inefficient, high EMI/RFI technology in a necropost.

 

No bad for 1880's inefficient, high EMI/RFI technology in a necropost.

Ah, that's why I was getting all the static while listening to Thursday Night Mass on my AM radio a few hours ago.

 

Necropost. Thread closed.