inverting dc-dc converter circuit
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From: miso on 2 Feb 2010 23:48 On Feb 2, 1:36 pm, Joerg <inva...(a)invalid.invalid> wrote: > m...(a)sushi.com wrote: > > On Feb 1, 9:00 pm, John Larkin > > <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Mon, 1 Feb 2010 20:43:39 -0800 (PST), "m...(a)sushi.com" > > >> <m...(a)sushi.com> wrote: > >>> On Feb 1, 11:34 am, John Larkin > >>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >>>> On Sun, 31 Jan 2010 16:30:19 -0800 (PST), MooseFET > >>>> <kensm...(a)rahul.net> wrote: > >>>>> On Jan 31, 3:03 pm, Jamie > >>>>> <jamie_ka1lpa_not_valid_after_ka1l...(a)charter.net> wrote: > >>>>>> MooseFET wrote: > >>>>>>> On Jan 31, 7:29 am, Glen Walpert <nos...(a)null.void> wrote: > >>>>>>>> On Sat, 30 Jan 2010 10:05:13 -0800, John Larkin wrote: > >>>>>>>>> On Sat, 30 Jan 2010 09:58:57 -0600, mook Johnson <m...(a)mook.net> wrote: > >>>>> If you want more efficient operation, you could do this: > >>>>> Version 4 > >>>>> SHEET 1 880 680 > >>>>> WIRE 240 -80 64 -80 > >>>>> WIRE 240 -64 240 -80 > >>>>> WIRE -320 -48 -448 -48 > >>>>> WIRE 64 -48 64 -80 > >>>>> WIRE 64 -48 -320 -48 > >>>>> WIRE 96 -16 80 -16 > >>>>> WIRE -320 48 -320 -48 > >>>>> WIRE -320 64 -320 48 > >>>>> WIRE -160 128 -320 128 > >>>>> WIRE 80 128 80 -16 > >>>>> WIRE 80 128 64 128 > >>>>> WIRE 240 128 240 32 > >>>>> WIRE 272 128 240 128 > >>>>> WIRE 400 128 336 128 > >>>>> WIRE 720 128 400 128 > >>>>> WIRE 240 144 240 128 > >>>>> WIRE 720 160 720 128 > >>>>> WIRE 400 176 400 128 > >>>>> WIRE -320 192 -320 128 > >>>>> WIRE -160 192 -320 192 > >>>>> WIRE 144 192 64 192 > >>>>> WIRE -448 256 -448 -48 > >>>>> WIRE -416 256 -448 256 > >>>>> WIRE -160 256 -416 256 > >>>>> WIRE 96 256 64 256 > >>>>> WIRE 240 256 240 224 > >>>>> WIRE 240 256 96 256 > >>>>> WIRE 400 256 400 240 > >>>>> WIRE 400 256 240 256 > >>>>> WIRE 512 256 400 256 > >>>>> WIRE 720 256 720 224 > >>>>> WIRE 720 256 592 256 > >>>>> WIRE 96 288 96 256 > >>>>> WIRE -416 304 -416 256 > >>>>> WIRE 848 304 784 304 > >>>>> WIRE -320 320 -320 272 > >>>>> WIRE -192 320 -320 320 > >>>>> WIRE 144 320 144 192 > >>>>> WIRE 144 320 -192 320 > >>>>> WIRE -320 336 -320 320 > >>>>> WIRE -192 336 -192 320 > >>>>> WIRE 720 352 400 352 > >>>>> WIRE 144 368 144 320 > >>>>> WIRE 400 368 400 352 > >>>>> WIRE 400 368 144 368 > >>>>> WIRE -416 400 -416 384 > >>>>> WIRE -192 400 -320 400 > >>>>> FLAG 96 288 0 > >>>>> FLAG -416 400 0 > >>>>> FLAG -320 400 0 > >>>>> FLAG 848 304 0 > >>>>> SYMBOL Misc\\NE555 -48 160 R180 > >>>>> SYMATTR InstName U1 > >>>>> SYMBOL voltage -416 288 R0 > >>>>> WINDOW 123 0 0 Left 0 > >>>>> WINDOW 39 24 132 Left 0 > >>>>> SYMATTR SpiceLine Rser=0 > >>>>> SYMATTR InstName V1 > >>>>> SYMATTR Value 15 > >>>>> SYMBOL res -336 32 R0 > >>>>> WINDOW 3 -64 71 Left 0 > >>>>> SYMATTR Value 2000 > >>>>> SYMATTR InstName R2 > >>>>> SYMBOL cap -208 336 R0 > >>>>> SYMATTR InstName C2 > >>>>> SYMATTR Value 0.01?f > >>>>> SYMBOL res -336 176 R0 > >>>>> WINDOW 3 -60 41 Left 0 > >>>>> SYMATTR Value 1500 > >>>>> SYMATTR InstName R1 > >>>>> SYMBOL ind 224 128 R0 > >>>>> SYMATTR InstName L1 > >>>>> SYMATTR Value 1mh > >>>>> SYMBOL schottky 336 112 R90 > >>>>> WINDOW 0 0 32 VBottom 0 > >>>>> WINDOW 3 32 32 VTop 0 > >>>>> SYMATTR InstName D2 > >>>>> SYMATTR Value 1N5819 > >>>>> SYMATTR Description Diode > >>>>> SYMATTR Type diode > >>>>> SYMBOL cap 384 176 R0 > >>>>> SYMATTR InstName C1 > >>>>> SYMATTR Value .5?f > >>>>> SYMBOL res 192 -32 R90 > >>>>> WINDOW 0 0 56 VBottom 0 > >>>>> WINDOW 3 32 56 VTop 0 > >>>>> SYMATTR InstName R3 > >>>>> SYMATTR Value 1k > >>>>> SYMBOL pnp 176 32 M180 > >>>>> SYMATTR InstName Q1 > >>>>> SYMATTR Value BCW68F > >>>>> SYMBOL zener 704 160 R0 > >>>>> SYMATTR InstName D1 > >>>>> SYMATTR Value DFLZ33 > >>>>> SYMATTR Description Diode > >>>>> SYMATTR Type diode > >>>>> SYMBOL npn 784 352 R180 > >>>>> SYMATTR InstName Q2 > >>>>> SYMATTR Value 2N3904 > >>>>> SYMBOL res 608 240 R90 > >>>>> WINDOW 0 0 56 VBottom 0 > >>>>> WINDOW 3 32 56 VTop 0 > >>>>> SYMATTR InstName R4 > >>>>> SYMATTR Value 10k > >>>>> TEXT 416 408 Left 0 !.tran 0 0.010 0 1 startup > >>>> Here's my inverter, sort of similar. > >>>>ftp://jjlarkin.lmi.net/Inverter.jpg > >>>> The thevenin impedance seen by the emitter determines loop gain. I > >>>> needed the ESR of the tantalum in the output to get good loop > >>>> stability; startup dV/dT is low enough that a tantalum appears safe > >>>> here. > >>>> Load regulation is surprisingly good, about a tenth of a volt from 80 > >>>> to 500 mA. > >>>> John > >>> I see a start up problem here. Look at the UVL of the LM5112. Won't > >>> this circuit whack the inductor while starting up? > >> It's designed to start up at about 70% duty cycle. When the output > >> gets close to -12, the transistor turns on and backs off the duty > >> cycle to whatever it needs, which should be a bit over 50%. > > >> John > > > I'm talking about the first pulse. The P-fet will be on because of the > > UVL being designed with a N-fet in mind. You should be able to see > > this on a storage scope. > > > I see a lot of people rolling their own converters and have read the > > justifications, but seriously, controller chips have (or should have > > if done well) every contingency in mind. ... > > No, often they haven't. By far the biggest conceptual mistake is running > the internal VCC regulator at around 7.5V. Pretty much none of the FETs > above 200V Vds are guaranteed at less than 10V gate drive. Don't they > _read_ datasheets? What are they thinking? So you end up with some > external sauerkraut to correct that mistake with discrete parts. BTDT. > Great. > > <banging head on table> > > Then there's more, for example a lack of a 2nd FB input to > current-limit. So, more sauerkraut externally. At some point you might > as well roll the whole thing your self, and I often do. > > I could go on. But the final clincher is the old $$$. A chip that costs > $2 or more in qties just doesn't fly in many designs. What the world > needs is a MC34063 in FET technology and running at up to a MHz. And a > similar TL494. Whoever brings that to market at reasonable pricing will > rake in tons of sales. > > [...] > > -- > Regards, Joerg > > http://www.analogconsultants.com/ > > "gmail" domain blocked because of excessive spam. > Use another domain or send PM. Have you contacted the apps engineer and complained about the lack of high voltage FET drive? Specs have to start someplace. Now generally the product definer does some tear downs and tries to find common ground between a few products on the market already. Often the designer gets a project like do the blah blah blah chip, but make it do blah blah blah voltage, or some other spec. The task comes from a customer that liked a certain part, but needed a better spec. Price is always negotiable, especially if you buy other parts from the same manufacturer. If you buy from disty, well, I guess that isn't an option. Is LTC so big you can't talk to someone?
From: miso on 2 Feb 2010 23:52 On Feb 2, 4:14 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Tue, 2 Feb 2010 12:02:27 -0800 (PST), "m...(a)sushi.com" > > > > <m...(a)sushi.com> wrote: > > >> >> Here's my inverter, sort of similar. > > >> >>ftp://jjlarkin.lmi.net/Inverter.jpg > > >> >> The thevenin impedance seen by the emitter determines loop gain. I > >> >> needed the ESR of the tantalum in the output to get good loop > >> >> stability; startup dV/dT is low enough that a tantalum appears safe > >> >> here. > > >> >> Load regulation is surprisingly good, about a tenth of a volt from 80 > >> >> to 500 mA. > > >> >> John > > >> >I see a start up problem here. Look at the UVL of the LM5112. Won't > >> >this circuit whack the inductor while starting up? > > >> It's designed to start up at about 70% duty cycle. When the output > >> gets close to -12, the transistor turns on and backs off the duty > >> cycle to whatever it needs, which should be a bit over 50%. > > >> John > > >I'm talking about the first pulse. The P-fet will be on because of the > >UVL being designed with a N-fet in mind. You should be able to see > >this on a storage scope. > > Good point, except that it seems to work fine, even from a > current-limited bench supply. The UVLO is typically 3 volts, and that > klunky old NDT2955 has a 2.6 volt threshold, so it's barely on before > the oscillator starts. > > But "storage scope"? Is there any other kind? > > >I see a lot of people rolling their own converters and have read the > >justifications, but seriously, controller chips have (or should have > >if done well) every contingency in mind. The first pulse, the initial > >ramp up (soft start), etc. Linear Tech, Maxim, etc parts have been > >tied to the whipping post and flogged without mercy. If you sell > >millions of a component, even problems with 1% of them is a total > >disaster. > > There aren't many inverting switchers around. The trick of having a > regular buck wind its own "ground" rail negative is OK, but usually > gets into trouble at higher output voltages. This circuit soft-starts > because the +5 reference comes up fairly slowly, by design. That > protects the tantalum on the output. > > And designing circuits is fun. > > But we've had a lot of problems with LDOs and switchers, way more than > 1% of the various parts we've used. > > National did this to us, LM3102: > > ftp://jjlarkin.lmi.net/SwitcherRise.JPG > > which cost a whole board spin. > > John Well yeah, but that's National. ;-) TI is a good jelly bean company. You can whack a power supply once and most customers won't notice and probably no harm done, especially in your proprietary product. For a stand alone chip, somebody would spot the thunk and complain.
From: Jim Thompson on 3 Feb 2010 00:03 On Tue, 02 Feb 2010 16:21:27 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Tim Williams wrote: >> "Hammy" <spam(a)spam.com> wrote in message >> news:kpbhm5tdt8aeu5dp1cofgu395583h2r0ju(a)4ax.com... >>> Have you seen the UCC25600 LLC Resonant mode controller.Can only sink >>> source 0.4A-0.8A . The absolute minimum guaranteed gate drive output >>> is 9V >>> >>> http://focus.ti.com/docs/prod/folders/print/ucc25600.html >> >> Ooh, I should revise my induction heater design with one of those. That's >> basically what I'm doing, except the transformer secondary is a hunk of >> metal. ;-) >> > >And next time you demo it with a piece of tube held upwards into the >coil at least wear welders gloves :-) > >Man, just looking at the video scared me. A guy in the army told me >about a similar experiment except that in his case a chunk of white-hot >metal decided to follow gravity. Missed his hands but landed right onto >one of his shoes ... phssssss ... through the shoe ... Back in '64, my best electronics technician student, Jim Foster, told of having aluminum poured _in_ his shoe when he worked in a foundry in Michigan. When he got out of hospital he came to Arizona, and my class. Naturally, when he graduated, I hired him. Except for some moving hiccups, where he worked for Widlar for almost a year, he worked for me from 1964-1989... he is the secretary of my extensive design notes over all those years :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Michael A. Terrell on 3 Feb 2010 08:36 Joerg wrote: > > John Larkin wrote: > > On Tue, 2 Feb 2010 16:27:45 -0600, "Tim Williams" > > <tmoranwms(a)charter.net> wrote: > > > >> "Joerg" <invalid(a)invalid.invalid> wrote in message > >> news:7srk6kFk53U1(a)mid.individual.net... > > > > > > I'm not seeing Joerg's posts lately. I wonder why. > > > > Hmm, I've use the spambot evade address the provider suggested but put a > fully legit (a.k.a. working) reply-to in the header. Shouldn't be > filtered away by any ISP. Or is it? Spammers and trolls use that fake address, along with thieves as a reply too address when they are phishing and want you to visit a website to give them your personal information. A lot of people filter it out. I do, on some other newsgroups. -- Greed is the root of all eBay.
From: John Larkin on 3 Feb 2010 09:50
On Wed, 03 Feb 2010 08:36:54 -0500, "Michael A. Terrell" <mike.terrell(a)earthlink.net> wrote: > >Joerg wrote: >> >> John Larkin wrote: >> > On Tue, 2 Feb 2010 16:27:45 -0600, "Tim Williams" >> > <tmoranwms(a)charter.net> wrote: >> > >> >> "Joerg" <invalid(a)invalid.invalid> wrote in message >> >> news:7srk6kFk53U1(a)mid.individual.net... >> > >> > >> > I'm not seeing Joerg's posts lately. I wonder why. >> > >> >> Hmm, I've use the spambot evade address the provider suggested but put a >> fully legit (a.k.a. working) reply-to in the header. Shouldn't be >> filtered away by any ISP. Or is it? > > > Spammers and trolls use that fake address, along with thieves as a >reply too address when they are phishing and want you to visit a website >to give them your personal information. A lot of people filter it out. >I do, on some other newsgroups. It's not in my filter file, but maybe Supernews rejects it. John |