> Let me clarify my position on the cap charge question. > Neglecting pawer factor and efficiency the power source > can deliver 12 watts. If 12 V is converted to 300 V, the > original stated voltage, the maximum available current is > limited to 40 mA. 300 V X 40 mA = 12 watts. > The current, I = dQ/ dt. Q = CE so I = C dE/ dt and > I dt = C dE. Integrating both sides, It = CE and t = CE/I > The time t = 160uF X 300 V / .04 A = 1.2 Seconds. You are off by a factor of two because you assume the current into the cap is constant over the whole charge time. There is no reason this needs to be true, especially since we were talking about the minimum time for a theoretically perfect converter. However, even real world converters can, and most would, have higher current when the cap is at lower voltage. > This time was confirmed on Ansoft's program "Serenade" Oh, a computer said it was true. We can all go home now! What a sorry state of affairs things are in when a computer simulation is used to answer a theoretical question instead of applying a little theory. This is a great example of the dangers of relying too much on simulation. You get such a nice neat authorotative answer that it distracts you from realizing you asked the wrong question to begin with. Real engineering isn't about cranking thru numbers. Even a computer can be programmed to do that. It is about understanding the problem, then using creativity, intuition, experience, and intelligence to apply science to solve the problem. Computers can be useful tools for number crunching and keeping track of things, but they can't do real engineering. Not by a long shot. ***************************************************************** Olin Lathrop, embedded systems consultant in Devens Massachusetts (978) 772-3129, olin@embedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics