Opinions please -- 200V, 70mA from 3.2V

The efficiency of all of these schemes depend greatly on model values for MOSFETs, transformers (or inductors), and various parasitic elements. Inductor flybacks have no leakage-inductance loss issues, and do well on many other accounts. With a Schottky diode working at the 15V intermediate level, its inefficiency could be below 2.7%. The HV diode loss should be much less. The other losses are a matter of picking the right parts.

I keep mine updated, and, whadda ya know, there was a 2N7002 right there. I only put it in so that the efficiency calculation would take the gate drive into account--it works fine without it.

Cheers

Phil Hobbs

No idea why they used another symbol for that, it makes no sense. But yeah, updating might be needed soon on my side because people use lib parts a lot. I am a bit hesitant though because in the past that also caused older parts to get dropped from the libraries and then my own sims would no longer run.

No kidding, a car company did that. A teeny amount of brake power fed a teeny battery and they boasted about recuperating brake energy and all that.

I always try to furnish >10V in gate drive.

Yes, winning is simulation is just the semifinals. Getting close to what you simulated is what makes for the real win.

There is no 2N7002 in my copy of LTSpice (OS X version, just updated).

There is only a hole with three wires ending in empty. Which way was your transistor connected?

Weird. It's connected as a source follower. Alternatively just connect the pulse source to the gate resistor of the main FET.

Cheers

Phil Hobbs

last few updates of LT have excluded that model.

Why? who knows.. I used to use it much for basic concept testing.

Jamie

On Sunday, 24 January 2016 23:37:16 UTC+11, Bill Sloman wrote:

ringing immediately after switch-over - but relying on L3 as the smoothing inductor works fine, and emboldened me to increase C2 to 3.3uF - in fact a high voltage electrolytic would make even more sense.

output.

I've had another poke around.

Version 4 SHEET 1 1820 776 WIRE 1008 -32 -160 -32 WIRE 1136 -32 1008 -32 WIRE 1632 -32 1456 -32 WIRE 1136 0 1136 -32 WIRE 1456 0 1456 -32 WIRE 1632 0 1632 -32 WIRE -160 96 -160 -32 WIRE -112 96 -160 96 WIRE 848 96 -32 96 WIRE 1280 96 848 96 WIRE 1456 112 1456 80 WIRE 1632 112 1632 80 WIRE 1632 112 1456 112 WIRE 1280 144 1280 96 WIRE -128 192 -160 192 WIRE -32 192 -128 192 WIRE 128 192 48 192 WIRE 256 192 128 192 WIRE 608 192 336 192 WIRE 1136 240 1136 64 WIRE 1280 240 1280 208 WIRE 1280 240 1136 240 WIRE -368 256 -464 256 WIRE -208 256 -288 256 WIRE 128 256 128 192 WIRE 128 256 -208 256 WIRE -464 336 -464 256 WIRE -160 432 -160 192 WIRE -64 432 -160 432 WIRE 112 432 16 432 WIRE 240 432 192 432 WIRE 368 432 240 432 WIRE 1008 448 1008 -32 WIRE 1280 464 1280 240 WIRE 1616 464 1280 464 WIRE 1632 464 1616 464 WIRE 1728 464 1632 464 WIRE 848 496 848 96 WIRE 0 544 -48 544 WIRE 128 544 80 544 WIRE 304 544 208 544 WIRE 400 544 304 544 WIRE 560 544 480 544 WIRE 608 544 608 192 WIRE 608 544 560 544 WIRE -160 560 -160 432 WIRE 608 560 608 544 WIRE 1632 560 1632 464 WIRE 1728 560 1728 464 WIRE 240 592 240 432 WIRE 304 592 304 544 WIRE -48 640 -48 544 WIRE -48 640 -112 640 WIRE 368 640 368 432 WIRE 448 640 368 640 WIRE 560 640 528 640 WIRE -464 704 -464 416 WIRE -160 704 -160 656 WIRE -160 704 -464 704 WIRE 240 704 240 656 WIRE 240 704 -160 704 WIRE 304 704 304 656 WIRE 304 704 240 704 WIRE 608 704 608 656 WIRE 608 704 304 704 WIRE 848 704 848 560 WIRE 848 704 608 704 WIRE 1008 704 1008 512 WIRE 1008 704 848 704 WIRE 1456 704 1456 112 WIRE 1456 704 1008 704 WIRE 1632 704 1632 624 WIRE 1632 704 1456 704 WIRE 1728 704 1728 640 WIRE 1728 704 1632 704 WIRE -464 736 -464 704 FLAG -208 256 Vct FLAG 1616 464 Vout+ FLAG -128 192 tank- FLAG 560 544 tank+ FLAG -464 736 0 SYMBOL ind2 -48 208 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 4 56 VBottom 2 SYMATTR InstName L1 SYMATTR Value 0.054m SYMATTR Type ind SYMATTR SpiceLine Rser=0.00012 Cpar=1p SYMBOL ind2 240 208 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 4 56 VBottom 2 SYMATTR InstName L2 SYMATTR Value 0.054m SYMATTR Type ind SYMATTR SpiceLine Rser=0.00012 SYMBOL nmos 560 560 R0 SYMATTR InstName M1 SYMATTR Value FDS6680A SYMBOL nmos -112 560 M0 SYMATTR InstName M2 SYMATTR Value FDS6680A SYMBOL ind -384 272 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L3 SYMATTR Value 0.064m SYMATTR SpiceLine Rser=0.0001 Cpar=100p SYMBOL voltage -464 320 R0 WINDOW 123 0 0 Left 2 WINDOW 39 24 132 Left 2 SYMATTR SpiceLine Rser=0.001 SYMATTR InstName V1 SYMATTR Value 3.2 SYMBOL res 544 624 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 56 SYMBOL res 96 528 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 180 SYMBOL ind2 -128 112 R270 WINDOW 0 44 45 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L4 SYMATTR Value 223.5m SYMATTR Type ind SYMATTR SpiceLine Rser=7.2 Cpar=100pF SYMBOL schottky 1120 0 R0 SYMATTR InstName D2 SYMATTR Value UPSC600 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1712 544 R0 SYMATTR InstName R4 SYMATTR Value 2.84k SYMBOL schottky 864 560 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D1 SYMATTR Value UPSC600 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 1024 512 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D4 SYMATTR Value UPSC600 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 1264 144 R0 SYMATTR InstName D3 SYMATTR Value UPSC600 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 1616 560 R0 SYMATTR InstName C2

SYMBOL ind2 1440 -16 R0 SYMATTR InstName L6 SYMATTR Value 0.006m SYMATTR Type ind SYMBOL res 1616 -16 R0 SYMATTR InstName R6 SYMATTR Value 36 SYMBOL cap 288 592 R0 SYMATTR InstName C1 SYMATTR Value 27n SYMBOL res 496 528 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 56 SYMBOL res 32 416 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R5 SYMATTR Value 180 SYMBOL cap 224 592 R0 SYMATTR InstName C3 SYMATTR Value 27n SYMBOL ind 96 448 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L5

SYMATTR SpiceLine Rser=0.035 Cpar=1.2p SYMBOL ind 112 560 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L7

SYMATTR SpiceLine Rser=0.035 Cpar=1.2p TEXT -416 760 Left 2 !.tran 0 30m 1u 10n startup TEXT -448 8 Left 2 !K1 L1 L2 L4 L6 0.99

The extra components in the gate drives are designed to kill the high-frequ ency ringing while slowing the switching transitions less than the single r esistors did. R1 and R3 damp direct drain-to-gate feedback, while the LCR n etwork is designed to block feed-back through the transformer.

I can't help thinking that a more complicated gate-drive structure, with mo re active components, such as you might buy form Linear Technology, could g ive you cleaner switching, while blocking ringing but I don't known enough about them to have any bright ideas, and in a context where everybody wants to use only off-the-shelf transformers (no matter how unsuitable for the j ob) it wouldn't make sense to learn more.

Okay, I put in a normal NMOS symbol and included a Zetex 2N7002 model, so it should just work.

I'll post this again with an attachment for all you Windows folks.

Cheers

Phil Hobbs

It still can't find the RFU diode but that is probably because I didn't update. Otherwise works fine with Windows 7 Pro.

It's a 450 PIV fast recovery diode. There should be another suitable one in the standard library.

Cheers

Phil Hobbs

Must be a boutique part. Even findchips.com can't find it.

I just picked it out of the "choose new diode" dialogue box.

Some people are just hard to please. ;) I replaced them with DA2JF81, for which I could find a model.

So one more time--with feelin'--

Cheers

Phil Hobbs

Thanks, but that wasn't my intention, I could have just picked another one from my list as well. Was just wondering about such an exotic diode.

I am still in a bit of disbelief that Vladimir is gone.