inverting dc-dc converter circuit
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From: Hammy on 2 Feb 2010 18:09 On Tue, 2 Feb 2010 16:27:45 -0600, "Tim Williams" <tmoranwms(a)charter.net> wrote: >"Joerg" <invalid(a)invalid.invalid> wrote in message > >Yeah, I was recently looking for forward controllers... now, there's >millions of flyback sorts of devices, and (usually with slope compensation) >these can be built into half wave forward converters too. But TL494 and >TL598 (totem pole output, cf. SG3524 and 3525) are the only push-pull >forward controllers I've seen. I was shocked to see there is well and >truely nothing new in this market, where the old, slow bipolar devices still >rule. > >I would love to have one with beefy CMOS output (0.2 to 2A gate drive). >CMOS is more than capable of implementing the internal circuitry. A speed >upgrade besides and you've got a lovely IC. > >What is LT doing? I know they've made lots of single-chip and HF sorts of >devices, but I never find anything from LT in searches like this. > >Tim 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 http://canada.newark.com/texas-instruments/ucc25600d/pulse-width-modulation-pwm-controller/dp/34P6588 Coilcraft has the gate drive transformer. I have a couple they are tiny. http://www.coilcraft.com/ha3858.cfm
From: John Larkin on 2 Feb 2010 18:49 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. John
From: Joerg on 2 Feb 2010 18:54 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? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 2 Feb 2010 19:14 On Tue, 2 Feb 2010 12:02:27 -0800 (PST), "miso(a)sushi.com" <miso(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
From: Tim Williams on 2 Feb 2010 19:15
"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. ;-) Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms |