Hi everyone > *It seems to me that if you wired it as an autotransformer, you'd get a > 1:6 unit.* > Hmm you're probably right, since the inductor discharges through both the primary and secondary winding.
*Are you thinking of operating in flyback mode? * Yes, this is based on a modified boost converter, so energy will be transferred to the secondary only during (1-D). It seems that forward converters are more common than flyback converters but I would like to avoid the extra inductor and rectifier. *Looks like all it involves is a couple of capacitors, a FET, and a diode. > Should be something you could add to an existing design, although it > might be a technique that only applies to forward converters (I need to do > more reading, apparently). * Active clamps can be used in any topology that use inductors with more than one winding, but the controllers with built-in driver for the auxiliary FET are meant for forward converters according to their data sheets. This is actually something I have been wondering about: *Is there a substantial difference in controllers meant for flyback or forward conversion? Or can such controller be used for in any topology? * It is indeed possible to implement the auxiliary driver with discrete components, but I don't think it is a good idea, since the dead-band in between must be controlled extremely carefully. Otherwise the dissipation in the switch will be extreme. *but I'm unsure why ringing would be a problem.* When the switch closes the current in the leakage inductance (which is in series with the switch) don't have anywhere to go. Instead the voltage will increase which just might destroy the switch completely, or at least shorten its life time. A more detailed analysis reveals that the leakage inductance will actually resonate with the output capacitance of the (closed) switch. By adding an RC snubber network in parallel the ringing can be damped in several different ways (under-, critical- and overdamped). This type of snubber will however consume som energy which will reduce efficiency. Another bad effect of the ringing is that the transfer of energy from the magnetizing inductance to the secondary will not start until the potential at the midpoint of the coupled inductor (transformer) has reached the reflected output voltage. In simpler words this means that the energy will not be transferred efficiently until the ringing has ended. Also the ringing will be a good source of EMI. This might not be a huge issue in hobby electronics, but now that I know about it I can just not forget about it =) * * > > *There's a nice discussion of snubbers here: > > http://softsolder.com/2009/03/06/rc-snubber-resonant-design/* This was a great reference, and that is the way I would proceed with the design of an RC snubber network, at least when it comes to the measurements. I do think that the text lacks a bit of the details, and I would probably do an analysis in the laplace-domain, see how the poles move when R and C is changed (root locus method) and choose their values based on that. If the RC snubber don't catch the peak voltage I might need to put an RCD snubber across the primary winding, but I think simulation in Spice will reveal that. As you see this is actually a quite advanced procedure; with active clamp there is just one clamping capacitor that I need to choose. I also think that the size of the clamp capacitor is not as dependent on stray capacitance either. Best Regards Anton -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/SzB6R8iwUh8J. For more options, visit https://groups.google.com/groups/opt_out.
