inverting dc-dc converter circuit
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From: E. Kappos on 30 Jan 2010 05:21 "Joerg" <invalid(a)invalid.invalid> wrote in message news:7sh55uFcm9U1(a)mid.individual.net... > John Larkin wrote: >> >> This afternoon we were talking with Phil Hobbs about an >> electro-optical thingie we're doing. The prime power is a +15 volt >> wall wart, and we need -30 internally to power some photodiodes and >> opamps and stuff, 30 mA maybe. Our design currently has a cute >> homebrew single-inductor flyback converter, which circuit I've posted >> here some time back. We are concerned about having such a potentially >> noisy gadget on the same small board with nanoamp signals. > > Two years ago I did the electronics for a super noise-sensitive > fiberoptics project. Late in the game a spec change came along (don't they > always?) and now we needed +40VDC and +210VDC. There was only 12VDC > available to make it from. So I did two homebrew converters, MIC4421's > driving FETs and I babied the shoot-through a bit. The 40V got one of > those Cooper Versa Pac transformers and the 210V an ordinary CCFL > transformer. The rectifiers were well muffled with the usual inductors. > > Not one wee whiff of noise. Ok, I had it on a PLL but even when I > unclutched that there was no noise. I love magnetics. > > >> I proposed a different circuit: imagine eight opto-SSRs and two >> capacitors. A low frequency clock, 400 Hz maybe, switches 4 of them on >> and 4 off, alternately. The arrangement connects the two caps in >> parallel to the +15 supply, charging them up. Then it disconnects them >> and then restacks them in series such as to make -30 to ground. The >> low frequency and fairly soft switching edges should make this pretty >> quiet. >> >> Phil named this the Groucho Marx Generator. >> > > Cool :-) > > -- > Regards, Joerg > > http://www.analogconsultants.com/ > > "gmail" domain blocked because of excessive spam. > Use another domain or send PM. Groucho apparently published it, under a pseudonym of course! :-) I've seen the the idea of charging in parallel and then connecting in series using BJTs in an article in Electronics magazine published in the early 70's: "Bootstrap circuit generates high-voltage pusle train" by Lawrence H. Bannister Center for Space Research, MIT, Cambridge, Mass. appearing in a collection of circuits published by McGraw Hill in 1977 "Circuits for Electronice Engineers", Electronics Magazine Book Series Edited by Samuel Weber (executive editor, Electronics) Of course the idea is so fundamental that it isn't impossible that its first application dates back to the time when capacitors were known as Leyden jars. Euthymios Kappos
From: John Larkin on 30 Jan 2010 09:38 On Fri, 29 Jan 2010 19:35:29 -0800 (PST), MooseFET <kensmith(a)rahul.net> wrote: >On Jan 28, 9:27�pm, John Larkin ><jjSNIPlar...(a)highTHISlandtechnology.com> wrote: >> This afternoon we were talking with Phil Hobbs about an >> electro-optical thingie we're doing. The prime power is a +15 volt >> wall wart, and we need -30 internally to power some photodiodes and >> opamps and stuff, 30 mA maybe. Our design currently has a cute >> homebrew single-inductor flyback converter, which circuit I've posted >> here some time back. We are concerned about having such a potentially >> noisy gadget on the same small board with nanoamp signals. >> >> I proposed a different circuit: imagine eight opto-SSRs and two >> capacitors. A low frequency clock, 400 Hz maybe, switches 4 of them on >> and 4 off, alternately. The arrangement connects the two caps in >> parallel to the +15 supply, charging them up. Then it disconnects them >> and then restacks them in series such as to make -30 to ground. The >> low frequency and fairly soft switching edges should make this pretty >> quiet. >> >> Phil named this the Groucho Marx Generator. >> >> John > >How about a couple of LTC1144s? They are only good for 18 volts, and their switch resistance is high, 120 ohms, so my 30 mA load would whack them. The Groucho circuit is just a homebrew equivalent. John
From: Fred Bartoli on 30 Jan 2010 09:55 John Larkin a �crit : > On Fri, 29 Jan 2010 19:35:29 -0800 (PST), MooseFET > <kensmith(a)rahul.net> wrote: > >> On Jan 28, 9:27 pm, John Larkin >> <jjSNIPlar...(a)highTHISlandtechnology.com> wrote: >>> This afternoon we were talking with Phil Hobbs about an >>> electro-optical thingie we're doing. The prime power is a +15 volt >>> wall wart, and we need -30 internally to power some photodiodes and >>> opamps and stuff, 30 mA maybe. Our design currently has a cute >>> homebrew single-inductor flyback converter, which circuit I've posted >>> here some time back. We are concerned about having such a potentially >>> noisy gadget on the same small board with nanoamp signals. >>> >>> I proposed a different circuit: imagine eight opto-SSRs and two >>> capacitors. A low frequency clock, 400 Hz maybe, switches 4 of them on >>> and 4 off, alternately. The arrangement connects the two caps in >>> parallel to the +15 supply, charging them up. Then it disconnects them >>> and then restacks them in series such as to make -30 to ground. The >>> low frequency and fairly soft switching edges should make this pretty >>> quiet. >>> >>> Phil named this the Groucho Marx Generator. >>> >>> John >> How about a couple of LTC1144s? > > They are only good for 18 volts, and their switch resistance is high, > 120 ohms, so my 30 mA load would whack them. The Groucho circuit is > just a homebrew equivalent. > > John > The real Groucho Marx generator uses relays. -- Thanks, Fred.
From: mook Johnson on 30 Jan 2010 10:58 On 1/28/2010 11:27 PM, John Larkin wrote: > > > This afternoon we were talking with Phil Hobbs about an > electro-optical thingie we're doing. The prime power is a +15 volt > wall wart, and we need -30 internally to power some photodiodes and > opamps and stuff, 30 mA maybe. Our design currently has a cute > homebrew single-inductor flyback converter, which circuit I've posted > here some time back. We are concerned about having such a potentially > noisy gadget on the same small board with nanoamp signals. > > I proposed a different circuit: imagine eight opto-SSRs and two > capacitors. A low frequency clock, 400 Hz maybe, switches 4 of them on > and 4 off, alternately. The arrangement connects the two caps in > parallel to the +15 supply, charging them up. Then it disconnects them > and then restacks them in series such as to make -30 to ground. The > low frequency and fairly soft switching edges should make this pretty > quiet. > > Phil named this the Groucho Marx Generator. > > > John > What kind of regulation do you need on the -30V? Is that 30mA constant or does it move around a lot between 0 and 30mA?
From: Michael A. Terrell on 30 Jan 2010 11:59
Fred Bartoli wrote: > > John Larkin a �crit : > > On Fri, 29 Jan 2010 19:35:29 -0800 (PST), MooseFET > > <kensmith(a)rahul.net> wrote: > > > >> On Jan 28, 9:27 pm, John Larkin > >> <jjSNIPlar...(a)highTHISlandtechnology.com> wrote: > >>> This afternoon we were talking with Phil Hobbs about an > >>> electro-optical thingie we're doing. The prime power is a +15 volt > >>> wall wart, and we need -30 internally to power some photodiodes and > >>> opamps and stuff, 30 mA maybe. Our design currently has a cute > >>> homebrew single-inductor flyback converter, which circuit I've posted > >>> here some time back. We are concerned about having such a potentially > >>> noisy gadget on the same small board with nanoamp signals. > >>> > >>> I proposed a different circuit: imagine eight opto-SSRs and two > >>> capacitors. A low frequency clock, 400 Hz maybe, switches 4 of them on > >>> and 4 off, alternately. The arrangement connects the two caps in > >>> parallel to the +15 supply, charging them up. Then it disconnects them > >>> and then restacks them in series such as to make -30 to ground. The > >>> low frequency and fairly soft switching edges should make this pretty > >>> quiet. > >>> > >>> Phil named this the Groucho Marx Generator. > >>> > >>> John > >> How about a couple of LTC1144s? > > > > They are only good for 18 volts, and their switch resistance is high, > > 120 ohms, so my 30 mA load would whack them. The Groucho circuit is > > just a homebrew equivalent. > > > > John > > > > The real Groucho Marx generator uses relays. And a doorbell button. ;-) -- Greed is the root of all eBay. |