Olin Lathrop wrote... [snip] >Unless I messed up, the L3 current will always >reach 0 before the C4 voltage reaches the low switching limit. There = are >some more details, but this is the general gist of the argument. > The simulation results I got support that. At maximum load, and with input voltage varied from 11 to 20 volts, the dead time (time between cessation of inductor current flow at the end of one cycle and switch turn-on at the beginning of the next) looks like it should go from a minimum of 40 microseconds (at 11V in) to more than a hundred microseconds at 20 volts. =20 In no case did I see the switch turn on while current was still flowing in the catch diode, making diode Trr a non-issue. >> Buck convertersa re usually best run in continuous current mode ... > >I see nothing inherent to buck converters to support that statement. > Back in the days when a switching regulator like this might be designed with a PNP Darlington transistor as the switch, the relatively high peak current levels associated with intermittent-mode operation would have caused I * Vce(sat) losses that could constitute a significant efficiency issue; but with modern MOSFETs as switches this is hardly a problem anymore. Dave -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu