From: Stefan Jahn <stefan@gr...>  20060801 07:30:05

Am Mo, 31.07.2006, 23:02, schrieb Mike Kost: > Hi there, Hello Mike, > I've been simulating models of analog PWM modulators. I've noticed that if > I > do not have a sufficient number of points per ms of simulation time, the > results will start to diverge (wildly) from the expected result. As I add > simulation points, it converges on the expected result. This is not > unreasonable since PWM systems have very large transients (depending on > how > the simulator handles such transients). The downside is that I end up with > much more simulation data than is necessary for review/analysis, and qucs > gets a little chunky when it has a 1.5 GB memory footprint. I noticed that > the transient simulation has a MinStep property that expresses the minimum > time step size to be used in simulation, but that there isn't a MaxStep > property. My interpretation is that the MaxStep is defined as (Stop  > Start)/Points. If this interpretation is correct, is there a way to > specify > a MaxStep equivalent that's independent of the number of data points > captured? Yep. Your interpretation is right. > If not, any suggestions for better accuracy with fewer points? > I've already manipulated the integration method and gotten large > improvements over the 2nd order trapezoidal (I'm on a 4th order Gear at > the > moment). In your case you would like to limit the "maxstep" to a smaller value to get better accuracy, but few points only. Did I understand you correctly? Stefan. 