On 11/30/2014 10:45 AM, Karlsson & Wang wrote: > I have been thinking about adding a square shaped voltage signal around 50 > kHz at 15 volt or with some margin for linear voltage regulator to supply > floating isolated power to the high side switches. There would be an initial > cost for generation but then it would be possible to tap of with as many > transformers as needed. I guess it need to be twisted pair to keep cable > inductance down, limited rise time and maybe some corner round off to keep > EMC problems down. Transformer should probably be optimized for low > capacitance since power is low and voltage fluctuations large. Basically it > would follow the same principle as the ordinary power grid although at higher > frequency and different shape. I did this on my first PWM servo amp. I used all sections of a 4069 inverter to drive the primary. I had these blowing up until I realized the capacitance of my fancy quadrifilar wire was HUGE, about 500 pF from one wire to the next. I got some bobbins with dividers in them, and it solved the problem.
I had 3 secondaries, one for each of the two high-side drivers, and one more for the high-side overcurrent sense circuit. > Unless there is need to run continuously at 100% duty cycle boot strap work > good enough, is easy to build and cheap. > You need to make sure your PWM modulator will obey duty cycle limits. If it will, then the bootstrap scheme is a lot simpler. if not, you get into some strange behavior when the bootstrap caps run down. if the FET driver doesn't have an undervoltage sensing circuit, then you could blow the FETs in this case, when they are partially on. Jon ------------------------------------------------------------------------------ Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server from Actuate! Instantly Supercharge Your Business Reports and Dashboards with Interactivity, Sharing, Native Excel Exports, App Integration & more Get technology previously reserved for billion-dollar corporations, FREE http://pubads.g.doubleclick.net/gampad/clk?id=157005751&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
