inverting dc-dc converter circuit
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From: John Larkin on 29 Jan 2010 00:27 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
From: Vladimir Vassilevsky on 29 Jan 2010 00:56 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. Incredible. Why a 555 with a trivial diode-capacitor voltage multiplier won't work? VLV
From: John Larkin on 29 Jan 2010 01:05 On Thu, 28 Jan 2010 23:56:41 -0600, Vladimir Vassilevsky <nospam(a)nowhere.com> wrote: > > >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. > >Incredible. > >Why a 555 with a trivial diode-capacitor voltage multiplier won't work? > > >VLV It's incredible that you think it might. Stick to digital. John
From: Muzaffer Kal on 29 Jan 2010 01:32 On Thu, 28 Jan 2010 22:05:37 -0800, John Larkin <jjSNIPlarkin(a)highTHISlandtechnology.com> wrote: >On Thu, 28 Jan 2010 23:56:41 -0600, Vladimir Vassilevsky ><nospam(a)nowhere.com> wrote: > >> >> >>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. >> >>Incredible. >> >>Why a 555 with a trivial diode-capacitor voltage multiplier won't work? >> >> >>VLV > > >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. -- Muzaffer Kal DSPIA INC. ASIC/FPGA Design Services http://www.dspia.com
From: Sylvia Else on 29 Jan 2010 01:54
John Larkin wrote: > On Thu, 28 Jan 2010 23:56:41 -0600, Vladimir Vassilevsky > <nospam(a)nowhere.com> wrote: > >> >> 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. >> Incredible. >> >> Why a 555 with a trivial diode-capacitor voltage multiplier won't work? >> >> >> VLV > > > It's incredible that you think it might. Stick to digital. Diode forward drops would be an issue if you really need -30 and are trying to use a doubler circuit. Otherwise, for the benefit of the rest of us, why wouldn't it work? Sylvia. |