How about just open sourcing the design? I'd like my cap expert to take a l= ook at it and see what he thinks -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of= Sean Breheny Sent: Friday, February 16, 2018 8:30 AM To: Microcontroller discussion list - Public. Subject: Re: [EE] 7-16V to 350-400V SMPS boost IC? Hi David, The thought crossed my mind but I really built it for my own use. The desig= n presently was optimized for whatever parts I had laying around and is mad= e using a veroboard. I would have to do a PCB layout. I'll think about it. Sean On Thu, Feb 15, 2018 at 3:25 PM, Van Horn, David < david.vanhorn@backcountr= yaccess.com> wrote: > Is this something you'll be selling? > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On=20 > Behalf Of Sean Breheny > Sent: Thursday, February 15, 2018 1:19 PM > To: Microcontroller discussion list - Public. > Subject: Re: [EE] 7-16V to 350-400V SMPS boost IC? > > Thanks! > > I have used MLCCs for bulk decoupling on some motor drives. They have=20 > three big advantages over aluminum electrolytics: > 1) much longer life at high temperatures > 2) very low ESR/ESL which can be distributed around the board to=20 > provide an overall very low impedance between any point on the power=20 > plane to any point on the ground plane, which comes in very handy to=20 > prevent ground bounce effects when switching FETs on and off hard at=20 > high currents > 3) much better specs on internal heating from ripple current (by=20 > better specs, I don't necessarily mean that the MLCCs can handle more=20 > ripple current but rather that the electrolytic caps' ability to=20 > handle high frequency ripple depends on the details of internal heat=20 > transfer which are not characterized or controlled well by most=20 > manufacturers) > > The big disadvantages are higher cost, infancy reliability problems=20 > due to flex cracking, and capacitance change with voltage. > > I would often get requests to evaluate additional possible suppliers=20 > for these caps and I often had to check the dC/dV myself because many=20 > manufacturers do not provide that data, although the situation is=20 > getting better and most do provide it now. > > I was bitten by this the first time I used them - I was shocked to=20 > find that the voltage ripple on the motor drive bus was twice what I=20 > had calculated it should be, which I then traced back to the caps=20 > having roughly half their nominal capacitance at 50% bias (DC bias=20 > equal to half the rated max working voltage). At that time, Taiyo=20 > Yuden (where I was getting the caps) did not provide this info in=20 > their datasheets. I think they now do provide it. I got lucky because=20 > I had overspec'd the quantity of capacitance by about a factor of 2=20 > because of uncertainties so it just worked out (with no additional margin= ). > > The device I built to perform this test works by simply connecting a=20 > very accurate low-value current source, with a compliance to at least=20 > 100V, to the capacitor under test. A microcontroller (NXP ARM, not=20 > PIC) watches the voltage rise, computes the slope at various points=20 > along the rise and computes the capacitance from the slope and the=20 > known current. The micro also has the task of stopping the current=20 > flow when the desired max voltage is reached. It reports the data over=20 > a USB-based virtual COM port in a text-based format. It can handle a=20 > range of 100pF to 100uF accurately (typically I get about 0.3% and I=20 > am still tweaking the firmware to use various techniques to try to be=20 > able to guarantee 0.5% at all times) > > Sean > > > -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .