On Tuesday 21 May 2013 21:53:39 Jon Elson did opine: > Gene Heskett wrote: > > Humm, is there an IC that will function as the switch driver, and > > whose output could be controlled with a PWM mode? Something that > > would start at 15% duty and taper to 100% when the applied voltage > > had dropped to say 20 volts. Then the Q is how fast can these be > > switched, I get the impression I'm still looking at hexfets I can > > steal out of dead computer PSU's. These things speed (lack thereof) > > will cause their own SOA self destruction I expect. > > I use the IR2113 and similar chips to drive FETs. You'd need some op > amps and/or comparators to generate the PWM. Lack of speed? The > IRFB31N20D was so fast it caused problems with the dV/dT (and dI/dT) > affecting the rest of the > circuitry. Easily 100 ns turn-on/turn-off times, even with resistors in > the gate circuit.
Those are problems you should like Jon, they are telling you that your ground & power planes need to be wider, and need more bypassing. Both of those translate to reduced switching losses & cooler devices. Often you will need both a .05 ceramic on very short leads or better yet, surface mount, AND a 10uf in order to get enough bypassing. Of course I'm far enough away its not worth getting in the car to come and beat some manners into me. :) I think. FWIW, resistors in the gate to slow the rise & fall times will raise the switching losses, in some cases enough to destroy the device long before your finger says its even getting warm. But you knew all that. > Jon > > ------------------------------------------------------------------------ > ------ 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users 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> Questionable day. Ask somebody something. 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
