HS gate drive transformer?
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From: Joerg on 28 Apr 2010 17:54 Grant wrote: > On Wed, 28 Apr 2010 08:08:06 -0700, Joerg <invalid(a)invalid.invalid> wrote: > >> JosephKK wrote: >>> On Fri, 23 Apr 2010 10:48:28 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> Hammy wrote: >>>>> On Fri, 23 Apr 2010 09:24:53 -0700, Joerg <invalid(a)invalid.invalid> >>>>> wrote: >>>>> >>>>> >>>>>> With a flying source that's a problem because the Instek connects the >>>>>> probe shield to PE. So you get ground loops and tons of ringing. Plus >>>>>> you neighbors listening to AM radio won't be very happy about that. You >>>>>> can get battery packs for many Instek models but it's very expensive. I >>>>>> never checked whether one can hack into this and connect one's own >>>>>> battery. Even then you'd at least need to wrap the probe through a nice >>>>>> big ferrite a few times. >>>>> Yep they defiantly aren't giving the battery option away. >>>>> >>>> Another old trick is to use a car battery and inverter. Mine just >>>> croaked. Couldn't believe it, half a year ago it was showing slight >>>> signs of weakness but would still crank a 2.6l gasoline engine alright. >>>> So I replaced the one in the car. When I needed it for isolation >>>> purposes a month ago ... nada, zip, zilch. It was totally hi-Z, charger >>>> went to 17V and shut off, and the battery wouldn't even light a 1W bulb. >>>> Puzzling how it could have gone so fast. >>>> >>> Sounds like electrolyte dry out. See if you can find a way to "juice" >>> the cells again. >> >> Strange thing is, the fluid level inside is ok. It's one of those >> supposedly maintenance-free ones but one can pry off the lid assembly to >> peek inside. > > Sulphation, do the plates look white? High impedance batteries due to > sulphation can be recovered, hardly worth the effort though as the success > rate has been reported as low as 30%. Leave it at 17V for a long time, > or get one of those pulse/spike units that are supposed to break down the > sulphate. > They look the usual dull silvery color. But the battery does slightly bulge at both ends so you may be right, there could be sulphation further down inside of the cells. > Car batteries often are used in a chronically undercharged state due > to short trips, and if you happen to have a regulator at low end of the > loose spec auto range. > > Since you took the lid off, try adding some battery restorer? Try some > phosphoric acid -- some web searching will hint at the dosage. I've only > read about this acid, not tried it. I think I'll give it to the recyclers. But it may have to wait until I buy a replacement. Because there is a high tax on batteries in California and you only get it back if you hand over the old one. If you just bring a battery without buying a new one that refund is lost. I made that mistake once. >> Why is it that this brand name battery is dead after 5-6 years, the gel >> cell in my StatPower emergency kit also died after 5-6 years, while the >> gel cell in my over 10 year old big $10 Chinese flashlamp is still fine? > > 5-6 years is an okay life for car battery, design life is 4 years. > > Poor charging techniques, old fashioned charging regimes that didn't get > updated with the newer battery technology? > Has the technology change that much on car batteries? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Grant on 28 Apr 2010 18:52 On Wed, 28 Apr 2010 14:54:51 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Grant wrote: .... >> 5-6 years is an okay life for car battery, design life is 4 years. >> >> Poor charging techniques, old fashioned charging regimes that didn't get >> updated with the newer battery technology? >> > >Has the technology change that much on car batteries? Not a lot, calcium and silver additives? But the car has changed heaps, more standby loads but still the crappy 13.5V to 14.5V or so constant voltage charging regime that usually under or over charges the poor battery. Short trips like the high voltage, long trips the low -- then there's battery temperature compensation done by ambient but rarely at the battery. Sloppy, battery will last the warranty period... Grant. -- http://bugs.id.au/
From: Joerg on 28 Apr 2010 19:21 Grant wrote: > On Wed, 28 Apr 2010 14:54:51 -0700, Joerg <invalid(a)invalid.invalid> wrote: > >> Grant wrote: > ... >>> 5-6 years is an okay life for car battery, design life is 4 years. >>> >>> Poor charging techniques, old fashioned charging regimes that didn't get >>> updated with the newer battery technology? >>> >> Has the technology change that much on car batteries? > > Not a lot, calcium and silver additives? But the car has changed heaps, > more standby loads but still the crappy 13.5V to 14.5V or so constant > voltage charging regime that usually under or over charges the poor > battery. Short trips like the high voltage, long trips the low -- then > there's battery temperature compensation done by ambient but rarely at > the battery. Sloppy, battery will last the warranty period... > Mine's a run-of-the-mills battery, maybe Sam's Club. The car is also a rather mundane SUV. Since I do not trust electronics in cars much I purposely bought a vehicle that has no electric this, that and the other thing. No power windows, not even central-lock. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: legg on 28 Apr 2010 22:25 On Thu, 22 Apr 2010 20:44:03 -0400, Hammy <spam(a)spam.com> wrote: > > >I wound a toroid to use as a HS gate drive transformer for a 100W two >switch flyback. I'm using the typical DC restore technique AC couple >the transformer. > >Here's my schematic; > >http://i42.tinypic.com/9gvyow.png > >I'm using a PIC and a FET driver to simulate the extremes of the PWM >controller duty cycle and drive level and it works well with the >exception of Burst Mode. Burst mode is when the controller modulates >the original gate signal at light load for anyone who doesn't know. > >A picture is worth a thousand words. > >Here's my gate waveform at 90kHz 70% duty. A little sloping but >acceptable. > >http://i39.tinypic.com/25kieyq.jpg > >Now here's where the fun begins I'm modulating the 90kHz to simulate >burst mode. > >http://i44.tinypic.com/qy5l69.jpg > >Here's a zoom of one of the burst. > >http://i43.tinypic.com/2eumxbk.jpg > >My primary and secondary are 1:1 ; inductance of 1.5mH. > > Is there anyway to clean this up? In reality, a burst controller would be 'bursting' at a minimal duty cycle - not as is programed in your PIC here. This is more a power-limit/hiccup type of simulation; the symptoms at the gate drive will be similar, but are unlikely to repeat as frequently. To avoid backswing effects on discontinuous drive trains; C1 must not be large enough to support saturating voltseconds. Reduce C2 to ~ 10xCgs. Reduce Rgs to produce 30% gate voltage droop under full load low line conditions. Tailor D2 characteristics (as ~ back to back zeners) for a few voltes of 'off' bias. For lowest power loss in bipolar ouput drive circuits, schottkies should be applied from drive output to both rails, to recover mag energy. Rc is probably mislocated here. RL
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