On Wednesday 22 May 2013 15:56:55 Jon Elson did opine: > Gene Heskett wrote: > > Ultra fast, Si, or Schotkey? Si seems worthless but I have seen the > > amp or so rated Schotkey's make a difference. Their Vf is only about > > 2/3rds of a germanium diode, and a very low impedance once conduction > > starts. > > Ultrafast Silicon. It is a 200 V diode, so Schottky is out. There's so > much capacitance > already, I don't worry a whole lot about turn-off, the problem was to > get the diode > to turn ON fast enough. These are supposedly rated for 4 ns, the ES3D. > (I also use the ES1D in the high-side driver bootstrap circuit). So, > you have the situation the high-side transistor is on, sourcing 20 A > into the load through the 47 uH filter inductor. Then, the high-side > transistor shuts > off, and there is a couple hundred ns of dead-time before the low-side > transistor turns on. But, there's still 20 A flowing out through the > filter inductor, and you have to keep the node between the two > transistors from going below ground. I don't have to worry about small > negative voltages, the IR chips guarantee tolerance to -5 V, I have > seen them handle up to about -7 V without abnormal functioning. The > ES3D diode installed with suitably short traces solved the problem, and > held the worst-case negative spike to less than -4 V. > > Jon
Thats pretty decent Jon. Sounds like the best solution without depending on pure unobtainium parts too. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> $you = new YOU; honk() if $you->love(perl) -- Seen on Slashdot A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
