120VAC to +V/-V devices?

I didn't read the whole thread so maybe somebody already mentioned it, but there is an article in this month's EDN Europe (10/2005) about transformer-less PSU

--DF

How about this way?

Thanks, Rich

On Fri, 21 Oct 2005 16:15:54 GMT, Rich Grise wrote:

--- If you don't already have it, get LTC's simulator at:

Without the regulators and the caps on their outputs, run this:

Version 4 SHEET 1 880 852 WIRE -592 176 -592 64 WIRE -592 352 -592 256 WIRE -464 64 -592 64 WIRE -464 752 -464 64 WIRE -416 352 -592 352 WIRE -416 464 -416 352 WIRE -336 64 -464 64 WIRE -336 352 -416 352 WIRE -336 464 -416 464 WIRE -336 752 -464 752 WIRE 160 64 -272 64 WIRE 160 272 160 128 WIRE 160 288 160 272 WIRE 160 352 -272 352 WIRE 160 464 -272 464 WIRE 160 672 160 528 WIRE 160 688 160 672 WIRE 160 752 -272 752 WIRE 272 64 160 64 WIRE 272 144 272 128 WIRE 272 288 272 144 WIRE 272 352 160 352 WIRE 272 464 160 464 WIRE 272 544 272 528 WIRE 272 688 272 544 WIRE 272 752 160 752 WIRE 384 144 272 144 WIRE 384 176 384 144 WIRE 384 272 160 272 WIRE 384 272 384 240 WIRE 384 544 272 544 WIRE 384 576 384 544 WIRE 384 672 160 672 WIRE 384 672 384 640 WIRE 496 144 384 144 WIRE 496 160 496 144 WIRE 496 272 384 272 WIRE 496 272 496 240 WIRE 496 400 496 272 WIRE 496 544 384 544 WIRE 496 544 496 400 WIRE 496 560 496 544 WIRE 496 672 384 672 WIRE 496 672 496 640 WIRE 576 400 496 400 WIRE 576 432 576 400 FLAG 576 432 0 SYMBOL voltage -592 160 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 3 -168 110 Left 0 SYMATTR InstName V1 SYMATTR Value SINE(0 350 60) SYMBOL cap -272 48 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 1000e-6 SYMBOL cap -272 336 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C2 SYMATTR Value 1000e-6 SYMBOL diode 176 128 R180 WINDOW 0 24 72 Left 0 WINDOW 3 39 33 Left 0 SYMATTR InstName D3 SYMATTR Value MUR460 SYMBOL cap 368 176 R0 SYMATTR InstName C3 SYMATTR Value 1E-6 SYMBOL res 480 144 R0 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL diode 288 352 R180 WINDOW 0 -19 62 Left 0 WINDOW 3 147 31 Left 0 SYMATTR InstName D1 SYMATTR Value MUR460 SYMBOL diode 144 288 R0 WINDOW 0 -27 0 Left 0 WINDOW 3 150 34 Left 0 SYMATTR InstName D2 SYMATTR Value MUR460 SYMBOL diode 256 64 R0 WINDOW 3 40 29 Left 0 SYMATTR Value MUR460 SYMATTR InstName D4 SYMBOL diode 176 528 R180 WINDOW 0 24 72 Left 0 WINDOW 3 39 33 Left 0 SYMATTR InstName D5 SYMATTR Value MUR460 SYMBOL cap 368 576 R0 SYMATTR InstName C4 SYMATTR Value 1E-6 SYMBOL res 480 544 R0 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL diode 288 752 R180 WINDOW 0 -19 62 Left 0 WINDOW 3 147 31 Left 0 SYMATTR InstName D6 SYMATTR Value MUR460 SYMBOL diode 144 688 R0 WINDOW 0 -27 0 Left 0 WINDOW 3 150 34 Left 0 SYMATTR InstName D7 SYMATTR Value MUR460 SYMBOL diode 256 464 R0 WINDOW 3 40 29 Left 0 SYMATTR Value MUR460 SYMATTR InstName D8 SYMBOL cap -272 448 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C5 SYMATTR Value 1000e-6 SYMBOL cap -272 736 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C6 SYMATTR Value 1000e-6 TEXT -210 834 Left 0 !.tran 1

-- John Fields Professional Circuit Designer

As long as the dielectric doesn't punch through as a result of transients !

Are you actually suggesting you could sell such a thing ?

I boggle sometimes at the creepage and clearance distances required for safety. Esp wrt margins in small transformers that may take up to 50% of the winding area.

Graham

Galvanic isolation requires the absence of a common current path IIRC.

Hence no - it's not true.

Graham

On Fri, 21 Oct 2005 16:51:03 +0100, Pooh Bear wrote:

--- Well, I've always considered that in order for a current path to be galvanic it must be ohmic, but I must admit that in this instance you may be right.

If you've got LTC's simulator, run this:

Version 4 SHEET 1 880 852 WIRE -832 352 -832 -320 WIRE -592 64 -592 -144 WIRE -592 176 -592 64 WIRE -592 352 -832 352 WIRE -592 352 -592 256 WIRE -464 64 -592 64 WIRE -464 752 -464 64 WIRE -416 352 -592 352 WIRE -416 464 -416 352 WIRE -384 -144 -592 -144 WIRE -368 -320 -832 -320 WIRE -336 64 -464 64 WIRE -336 352 -416 352 WIRE -336 464 -416 464 WIRE -336 752 -464 752 WIRE 160 64 -272 64 WIRE 160 272 160 128 WIRE 160 288 160 272 WIRE 160 352 -272 352 WIRE 160 464 -272 464 WIRE 160 672 160 528 WIRE 160 688 160 672 WIRE 160 752 -272 752 WIRE 272 64 160 64 WIRE 272 144 272 128 WIRE 272 288 272 144 WIRE 272 352 160 352 WIRE 272 464 160 464 WIRE 272 544 272 528 WIRE 272 688 272 544 WIRE 272 752 160 752 WIRE 384 144 272 144 WIRE 384 176 384 144 WIRE 384 272 160 272 WIRE 384 272 384 240 WIRE 384 544 272 544 WIRE 384 576 384 544 WIRE 384 672 160 672 WIRE 384 672 384 640 WIRE 496 -320 -288 -320 WIRE 496 -144 -304 -144 WIRE 496 -144 496 -320 WIRE 496 144 384 144 WIRE 496 144 496 -144 WIRE 496 160 496 144 WIRE 496 272 384 272 WIRE 496 272 496 240 WIRE 496 400 496 272 WIRE 496 544 384 544 WIRE 496 544 496 400 WIRE 496 560 496 544 WIRE 496 672 384 672 WIRE 496 672 496 640 WIRE 576 400 496 400 WIRE 576 432 576 400 FLAG 576 432 0 SYMBOL voltage -592 160 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 3 -168 110 Left 0 SYMATTR Value SINE(0 350 60) SYMATTR InstName V1 SYMBOL cap -272 48 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 1000e-6 SYMBOL cap -272 336 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C2 SYMATTR Value 1000e-6 SYMBOL diode 176 128 R180 WINDOW 0 24 72 Left 0 WINDOW 3 39 33 Left 0 SYMATTR InstName D3 SYMATTR Value MUR460 SYMBOL cap 368 176 R0 SYMATTR InstName C3 SYMATTR Value 1E-6 SYMBOL res 480 144 R0 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL diode 288 352 R180 WINDOW 0 -19 62 Left 0 WINDOW 3 147 31 Left 0 SYMATTR InstName D1 SYMATTR Value MUR460 SYMBOL diode 144 288 R0 WINDOW 0 -27 0 Left 0 WINDOW 3 150 34 Left 0 SYMATTR InstName D2 SYMATTR Value MUR460 SYMBOL diode 256 64 R0 WINDOW 3 40 29 Left 0 SYMATTR Value MUR460 SYMATTR InstName D4 SYMBOL diode 176 528 R180 WINDOW 0 24 72 Left 0 WINDOW 3 39 33 Left 0 SYMATTR InstName D5 SYMATTR Value MUR460 SYMBOL cap 368 576 R0 SYMATTR InstName C4 SYMATTR Value 1E-6 SYMBOL res 480 544 R0 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL diode 288 752 R180 WINDOW 0 -19 62 Left 0 WINDOW 3 147 31 Left 0 SYMATTR InstName D6 SYMATTR Value MUR460 SYMBOL diode 144 688 R0 WINDOW 0 -27 0 Left 0 WINDOW 3 150 34 Left 0 SYMATTR InstName D7 SYMATTR Value MUR460 SYMBOL diode 256 464 R0 WINDOW 3 40 29 Left 0 SYMATTR Value MUR460 SYMATTR InstName D8 SYMBOL cap -272 448 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C5 SYMATTR Value 1000e-6 SYMBOL cap -272 736 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C6 SYMATTR Value 1000e-6 SYMBOL res -272 -336 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL res -288 -160 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R4 SYMATTR Value 10k TEXT -210 834 Left 0 !.tran 1 TEXT -376 -384 Left 0 ;Human R TEXT -392 -208 Left 0 ;Human R

It seems that a human with 10k ohms of body resistance touching one side of the 120V mains on the mains side of the coupling caps and also touching the hot side of the load would get a nasty shock.

With a transformer isolating the mains from the load, that shouldn't be the case if the transformer is wound with the secondary wound away from the primary.

-- John Fields Professional Circuit Designer

Oh, silly me. I thought I might get an answer in English.

Thanks, Rich

Thanks, thats a great article. I was hoping NS or TI might have a bridge controller for operating with 120 VAC. Linear Tech does offer them but they aren't generally stocked locally.

I haven't worked with such high voltages but have a little experience with DC/DC converters.

JJ

Well, just from visualizing electrons sloshing around, it looks very much like a couple of full-wave voltage doublers, kind of interleaved. Is there some sneak path that's biting me in the ass, kind of like the two-bridges-on-a-CT-transformer dilemma?

Thanks, Rich

nice short ha! :)

On Sat, 22 Oct 2005 12:43:54 -0700, Jamie wrote: ...

Yabbut, I'm trying to ask, where, in this one where ALL of the inputs are capacitated, is the short? I never got past DC in school - I've just been faking it all of these years - please humour me, OK?

Thanks, Rich

That's what the capacitors are for: [C1], [C2], [C3], and [C4]. They block the DC path. Can you draw it again, but with the diodes? I tried, but my ASCII art sucks for stuff like that.

No, just mentioning that it was reminiscent of one. :-) And my intent was to just see if there's a capacitor in each side of the line, wouldn't that provide isolation? There's no DC path, after all.

Thanks! Rich

draw all the diodes. also don't forget that ground is connected at the fusebox to one of your AC inputs...

I think what you intended to invent is this, the voltage doubler. L ----+--------->|----+----> +V | | | [C] | | N ----)---------------+------> Chassis possibly, but not ground. | | | [C] | | `---------| -V

putting a capacitor big enough to pass useful amounts of current between the mains and earth will trip pretty much any earth leakage detector.

I've drawn the earth connection to the neutral line in too...

D1 -------+--[C1]---+------->|--+---+---- L | | D2 | | | | .---->|--+ | | | | D3 [C5] | +--(----||--+ | | | | D7 [C6] | +--(----|