On Wed, 18 Jan 2017 18:09:41 -0800 (PST), dagmargoodboat@yahoo.com wrote:>On Wednesday, January 18, 2017 at 12:42:37 PM UTC-5, John Larkin wrote: >> On Wed, 18 Jan 2017 08:57:52 -0800 (PST), dagmargoodboat@yahoo.com >> wrote: >> >> >On Tuesday, January 17, 2017 at 9:26:46 PM UTC-5, John Larkin wrote: >> > >> >> This worked without tricks, somehow: >> >> >> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/HV/28S840A.pdf >> >> >> >> 1400 volts out at the top, with a 1:1 autotransformer. This may >> >> current-limit for a few cycles at startup, but it works its way up. >> > >> >Are those low-duty 350V spikes any problem for your inductor's >> >200Vac-rated insulation? I eliminated several magnetics options because >> >I was uncomfortable with their inter-winding insulation specs. >> >> Well, it seems to work. I once took a twisted pair of #30 magnet wire >> and applied voltage; it arced at about 1500 volts. >> >> I don't think I've ever observed voltage breakdown in an inductor. It >> would be interesting to test a DRQ127 to destruction. >> >> > >> >My supply takes feedback from the bleeder chain to regulate the HV output. >> >Being able to make regulated HV from +12v in a couple square inches is cool. >> >> Yeah, I seldom do HV, so it's always interesting. PCB surface creepage >> limits are confusing. >> >> Here's my board: >> >> https://dl.dropboxusercontent.com/u/53724080/PCBs/T840_E1.jpg >> >> >> The layout is uglified by the clearance complications. I did that >> layout myself, which doesn't help either. > >Looks decent to me. > >I fretted the clearances until I noted the creepage on a 1kV D-PAK >switching FET elsewhere--20V/mil. I think I'm under 8 volts/mil on >the board, worst-case. Then we're coating, which will cover all the >bare metal.I noticed the same thing. High-voltage dpak fets have off-the-chart gradients between their leads. So does that IR gate driver.> >> Note the heat sinking on T1! > >Neat. Curiously, my inductor doesn't get warm. I expected it would, but >it doesn't. > >Cheers, >James Arthur-- John Larkin Highland Technology, Inc lunatic fringe electronics
Removing voltage-multiplier-related flyback SMPS switching glitches
Started by ●January 17, 2017
Reply by ●January 19, 20172017-01-19
Reply by ●January 19, 20172017-01-19
dagmargoodboat@yahoo.com wrote...> > Curiously, my inductor doesn't get warm. > I expected it would, but it doesn't.What's your output voltage and load current? -- Thanks, - Win
Reply by ●January 19, 20172017-01-19
<dagmargoodboat@yahoo.com> wrote in message news:429e5f24-49e9-4bc7-a052-ea00f692e9f2@googlegroups.com...>> https://www.seventransistorlabs.com/Images/Deadbug_Sch.png > > Have you considered positive feedback to turn your switch transistor off > faster, rather than passively? That would save you some dissipation. > A small capacitor from the switch's collector to the base of your > current-sensor transistor would make the whole thing snap off.Hmm. It's been *years* since I played with that circuit -- but that sounds plausible. Can't do too much, lest it interfere with the current-sinking behavior. (It would only be able to make a better VCCS, not a negative-resistance one. Or, erm, negative capacitance?) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●January 19, 20172017-01-19
On Thursday, January 19, 2017 at 7:40:58 AM UTC-5, Winfield Hill wrote:> dagmargoodboat@yahoo.com wrote... > > > > Curiously, my inductor doesn't get warm. > > I expected it would, but it doesn't. > > What's your output voltage and load current? > > > -- > Thanks, > - Win50-600V, 4mA. It should be good for twice that current, but is intentionally limited right now, for fault tolerance. Cheers, James Arthur
