inverting dc-dc converter circuit
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From: John Larkin on 29 Jan 2010 14:00 On Fri, 29 Jan 2010 08:13:04 -0700, don <don> wrote: >John Larkin wrote: > >>>>> John Larkin wrote: >>>>> >>>>>> homebrew single-inductor flyback converter, which circuit I've posted >>>>>> here some time back. > >If you still have this circuit handy, please re-post. > >don Here it is: ftp://jjlarkin.lmi.net/Inverter.jpg John
From: John Larkin on 29 Jan 2010 14:09 On Fri, 29 Jan 2010 06:39:14 -0500, legg <legg(a)nospam.magma.ca> wrote: >On Thu, 28 Jan 2010 21:27:10 -0800, John Larkin ><jjSNIPlarkin(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 >> >At least one more cap to keep droop below 10% ppk. 25uF Sure, it needs an output cap. >The switched caps would have to be 5 or 10x multiples of this to >maintain anywhere near 30V after the transfer. I'd just use huge aluminum electrolytics. 1000 uF caps would be no problem. > >With half the energy transfer lost in switching, thats 120mA drawn >from the 15V rail. No. A charge pump like this can approach 100% efficiency. > >Not small anymore. > >There are quieter conversion methods than flyback or switched caps. The nice thing about the Groucho circuit is how slowly it runs, ballpark 400 Hz, with soft switching edges. And no magnetics. John
From: Joerg on 29 Jan 2010 17:18 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.
From: Bill Sloman on 29 Jan 2010 17:35 On Jan 29, 3:57 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- Web-Site.com> wrote: > On Thu, 28 Jan 2010 22:32:10 -0800, Muzaffer Kal <k...(a)dspia.com> > wrote: > > >On Thu, 28 Jan 2010 22:05:37 -0800, John Larkin > ><jjSNIPlar...(a)highTHISlandtechnology.com> wrote: > > >>On Thu, 28 Jan 2010 23:56:41 -0600, Vladimir Vassilevsky > >><nos...(a)nowhere.com> wrote: > > >>>John Larkin wrote: <snip> > >>It's incredible that you think it might. Stick to digital. > > >>John > > >You mean this doesn't work:http://www.csgnetwork.com/ne555c1.html? > >Give it a try. > > Larkin and Obama are out of the same mold... mediocre talent, yet > excessive ego ;-) Whereas Jim's egomania is justified by his stellar reputation amongst integrated circuit designers? Bob Widlar, Barry Gilbert and Hans Camenzind recognised him as comparable talent? Had every actually heard of him? -- Bill Sloman, Nijmegen
From: MooseFET on 29 Jan 2010 22:35
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? |