220VAC locales... ever used DC to feed switch mode power supples...and how many volts is generally okay?

[eccerr0r]

For those in 220V locales, anyone power their SMPS with DC, and how high of a voltage is okay?
What kind of PSU?
I suspect that 240V * sqrt(2) = 340V DC is probably fine because that would be about how much the the primary rectifier ends up with peak voltage. Just wondering, other than input capacitor voltages, can one go up above this 340V without damage? Will that input capacitor be the upper bound?
Wondering if exactly that, can I feed near 400VDC into bona fide specced at 220V SMPS without damage?

Currently have a 120/220V switchable SMPS I want to see if I can run with 400VDC (of course have to switch to 220V, the 120V range would probably kill a capacitor) and a 120V-220V universal wide input SMPS that I'll also want to feed 400VDC...

Will I just get ?

[stj]

it really depends on if the psu has a doubler i suspect.
but i would say 380v is a safe limit unless you want to remove the MOV's!!
it probably wont work with active PFC though.

lower limit is more interesting, people have powered stuff like Rygol/Siglent scopes with stuff like 60v battery packs!

[momaka]

I agree with stj.

360-380V DC should be about the acceptable range, at least for PSUs that use 2x 200V caps in series (most non-APFC PSUs.)

For PC PSUs with APFC ("full range" 100-240V AC input, no voltage selector switch), you could go even higher (up to 400V DC) if the primary cap is specced higher, like 420V or 450V. For 450V caps, I suspect up to 420V would be OK. Definitely wouldn't push it further, though, just so that there is some headroom for noise and voltage spikes on the input. And you might have to remove the MOV's, as sjt suggested. Otherwise I also suspect the PF of the PSU would also probably go down to non-APFC levels (i.e. ~60-70), since the APFC circuit likely either will turn Off or maybe just hardly work. Moreover, I don't know if APFC PSUs will be OK with being fed DC. From what I remember reading about the operation of APFC controllers (don't remember if that was from the CM6800/CM6802 PWM+APFC controller datasheet or elsewhere), most APFC ICs have an AC detection input. The AC input is used so that the APFC part of the controller can know when/how to pulse the APFC MOSFETs On/Off so that they always draw current proportionately through the APFC inductor. With no AC input, will the APFC controller stand still and do nothing or would it cause the rest of the PSU to shut down? Unfortunately, I haven't tried doing this type of test with any of my PSUs yet, so I can't tell you for sure. But there's a chance these PSUs may not want to work if they can't detect an AC input.

Wondering if exactly that, can I feed near 400VDC into bona fide specced at 220V SMPS without damage?

You'd have to check the voltage rating of the primary cap for that.
If the primary / input cap is rated for 200V or 250V, you'll definitely blow it
But if it's rated for 400/420/450V, then the answer is... *probably OK*

Having recently moved from the US to EU (230V AC), two LCD TVs that I took with me (one Samsung, one TCL) were both rated for 120V AC only. Opening them up revealed they both had APFC PSUs and input caps rated for 450V. So despite their label on the back explicitly saying "120V AC only", I had no problems plugging these in to EU 230V AC grid. No mods or anything - they just worked... which is what I expected.

Now you might be thinking: what if the primary cap is swapped with a higher voltage one?
And the answer to that is... I'm still trying to determine it for myself.
Long story short, I have a Panasonic surround sound system that's rated for 120V AC and has a 200V input primary cap. I'm trying to convert it to accept EU 230V AC and I already tried swapping the primary cap with a 400V one... but there are certainly more considerations to take into account in doing this, so my results are yet to be conclusive. Good news is, I haven't blown the PSU yet, but the primary side MOSFET is running quite a bit hotter, and I'm reluctant to test it under harder load, as I suspect things might overheat and blow up. I'll post the details in another thread, though.

and a 120V-220V universal wide input SMPS that I'll also want to feed 400VDC...

Will I just get ?

If the power SMPS / PSU is rated for 100-240V AC, it should be able to work with the equivalent DC of 240V AC (~340V DC) just fine. 400V might be a stretch, though. Again, check the voltage rating of the primary cap and the presence of any MOVs first (and if any, would they be able to take that kind of DC voltage.)
I've also noticed that some of my "universal input" (100-240V AC) power adapters run a little warmer at 230V AC than they do at 120V AC. Again, perhaps something similar going on like with the Panasonic SRS I have? IIRC, a technical guide I read a while back mentioned that higher input voltages = higher di/dt for the SMPS transformer... thus resulting in higher inductive "kickback" and need for a bigger snubber? If that's so, it would be interesting to know how much of a difference it would make when going from 340V DC (standard rectified 230/240V AC) to 380-390V DC.
Care to do the experiments for us?

[eccerr0r]

Currently trying ~250VDC on these PSUs and they're holding up as expected. Next step up is getting close to that 360ish volts at least theoretical. This is still part of my solar panel experiment - I just got four 90V+ OCV (but not at MPP) panels that I want to reduce the amount of wire so I'll have upwards 360VDC that I want to feed into these PSUs straight. Unfortunately I don't have space for 4 panels yet, so that is the limiting factor for the 360-400VDC experiment.

These PSUs are series connected and fed into my grid tie inverter. I figure this is the cheapest way to tie these high voltage panels into my GTI, though I might think about modding my GTI to take in a high voltage input directly as well as the low voltage input... so I don't have 20% loss from the PSUs...

Incidentally the 12V PSU I'm using at 250V DC is getting hot... at the output rectifier (130°F/55°C)! I think I may need to increase the heat sink, it was missing the heatsink when I got it (it wasn't even functional then...) Not sure if it has a schottky diode there or not, might improve efficiency/reduce need for heatsink. The PSU was intended for 100W so that diode does need to pass a good amount of current.

[sam_sam_sam]

This is an interesting topic I was wondering about weather or not you could inject dc voltage on a switching power supply and not burn something out because of doing something like this

I have one question and that is is there advantage doing this in dc current or wattage wise than just use ac voltage

[eccerr0r]

It's a risk I'm willing to take but it stresses two of the bridge diodes 100% duty cycle. Theoretically if I just swap the inputs of the psu every once in a while, it'd heat up the other two diodes and we're back at as if I was powering from AC.

Then again the 120/220 switchable psus the diodes already need to handle 2x current (usually) so it should be good to go.

I'm running DC because...that's all I've got... converting to AC to convert to DC to convert back to AC is kind of ridiculous actually lol....

[CapLeaker]

I've seen this high voltage DC thing on AC PSU's before, it's done because you can gain a few efficiency points, because you don't have to go from DC to AC and then from AC back to DC again. Matter effect I have done so on many other low voltage and higher voltage devices that had a bridge rectifier in its power supply. If you see a bridge rectifier you can use DC on most PSU's.

[sam_sam_sam]

If you see a bridge rectifier you can use DC on most PSU's.

This is nice to know because I was thinking the same thing but was not sure if that was the case or not but I have not had time to research it yet so that was catch my interest in this particular post

You made the comment on “Most” can you please elaborate more on this aspect of this comment —> which ones can not be made to work and what do you need to know about this statement

I do have a question about where do you exactly inject the dc voltage at the rectifier or at the filtering capacitor
I noticed that you mentioned that the rectifier needs to have the polarity reversed every once in awhile to keep it from overheating is there any reason why you could just inject the voltage at the filtering capacitor and remove the rectifier

The reason for this particular question was because I have seen higher voltage battery packs available at Battery Hookup before and I have a several 48 volt battery pack that would be very easily put together for high voltage battery pack to try this experiment on a switching power supply and was wondering if a switching power supply could be modified this way thanks for sharing your thoughts and ideas about this topic

The reason for testing this idea with battery power is that I have enough battery cells to make what ever voltage I need and if the testing goes well and I can get to a point of proof of concept then I will invest in some high voltage solar panels but that part will a ways off from now

[CapLeaker]

sam_sam_sam
yes, on the bridge rectifier getting hot if you feed a lot of current. Heat = wasted energy. That's where you take the rectifier out. But then you can't “reverse” polarity for example by accident. Where is the best access? The rectifier. Take it out and Bob is your uncle. Sure you could go directly to the cap too, just makes a mess and it's powering shit that's not used and then being blocked at the rectifier. Just take it out if you want direct DC access.
As for what PSU's you can't do it, you will see that on how complicated it is. There was one here on Badcaps that I even quit on after a while and that is rare for me as it was really a wing nut with tons of stages, transformers and so on.

[eccerr0r]

Yes I'm feeding it directly to the AC input (set to 220V if switchable because the doubler for 120V will not work when fed DC.) Diode loss will be less than 1% for me anyway, so I think that's fine - more loss in downstream components.