Speaking of high frequency transformer stuff...
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From: Joerg on 25 Feb 2010 21:58 Winfield Hill wrote: > Jon Elson wrote... >> Winfield Hill wrote: >>> Tim Williams wrote... >>>> How would you tackle the problem(?) of 1MHz, 100V common mode on >>>> transformers or whatever coupling you're using? Think high side >>>> drive. Is an ordinary gate drive transformer suitable ... >>> My favorite Intersil HIP4080 series of high-side/ >>> low-side driver ICs easily goes to 1MHz. Check 'em >>> out. No transformers, no optical couplers, nada. >>> Ahem, HIP4081A in stock at DigiKey. >>> >>> Rated at 80V (plus 15V swinging gate-drive), but hey, >>> go ahead and push it to 100V if necessary, or adjust >>> your turns ratio. >> I built a servo amp with the 4080 over a decade ago. The chip is rated >> for 80 V, but the applications manager eventually admitted to me "Oh, >> you're doing REALLY good to get them to run at 59 V, none of our other >> customers ever got them to last above 54 V!" Oh, that was a REAL NICE >> admission! So, I eventually redesigned the whole thing to use the >> IR2113 half-bridge driver chip. They have been VERY reliable, way above >> the voltages I normally run at. The one gotcha is that the common point >> between the two transistors cannot be allowed to go negative, so I had >> to put an ULTRA-fast diode across the low-side transistor. (The body >> diodes in the FETS are incredibly slow to turn on.) >> >> Unless the HIP4081A is on some improved process from the 4080 (I doubt >> it) you'll never get close to 80 V, even. Winfield, have you ever run >> the 4081A up above 40 V or so? > > Whoa, I've been a fan of the HIP4081A for more than 15 years. > The "A" variant, I must admit. In that time I never heard > anyone 'dis them. My own designs use the parts (purchased > repeatedly over a 7-year period) up to and over the maximum > voltage spec rating, 80, 90 and 100V, and to and over 1MHz. > > In my bench prototype testing I've had some ugly setups, > creating substantial V = L dI/dt voltages, that get out of > control in a real hurry (try 50nH*4A/10ns = 20V, be careful), > yet I only had one failure, during testing, which quickly > reverted to reliable operation after I tightened up critical > wiring to reduce the current-loop area. > > I have decades (OK, 1.5 decades) of successful 24-7 operation > of my designs (the guys leave everything running continuously) > using these parts at or near their limits. Recommended. > > BTW, I'm also a fan of the IR half-bridge drivers, but they > are relatively slow parts, meant for another kind of design. > Their slow speeds mean you won't so quickly run into wiring > issues, because for them L dI/dt has a much slower dt term. > I use these to make elegant 400V pulse generators (posted > on s.e.d.), but definitely not to run at MHz frequencies. > Just my 2ct: I haven't designed in Intersil parts since a couple years before I got my degree. And there's a reason ... -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |