The most recent circuit you posted is not the same as your original and as Gene pointed out, you have now made a series resonant circuit between the 220nF cap and the 200uH primary inductance.
In the simulation, the source resistance is zero, the ESR of the cap is zero and there is only 0.25R series R and a bit over 500R parallel R (admittedly highly nonlinear) to damp the resonance. This is why the output voltage is so high. The value of output voltages you see in simulation may depend somewhat on exactly how the simulator is set up (and which simulator you use). Gnucap, LTspice and QUCS show rectified output voltages of around 180V for the 500k side output and 153V for the 500R side. I haven't run this in ngspice. A real transformer would have a K < 1 but for this level of simulation setting K to 1 instead of 0.999 will significantly speed up the simulation with negligible effect on the output. Setting K to <1 introduces some leakage inductance but at 0.999 this is very small so it has a high resonant frequency with the 220nF input cap. The nonlinearity of the load switching between 500R and 500k through the diodes kicks this into ringing so the simulator spends ages calculating each ring. As Wojciech suggested, if you use an inductor with a much higher value then the resonance drops to well below your band of interest and the output voltages are about where you'd expect. The primary currents also fall dramatically. In your circuit, with an ideal inductor they are about 4.1A rms. Your little pulse transformer probably saturates some way below that current. With a 2mH primary inductance this falls to about 108mA rms. Of course, you then lose the bandpass filter effect of the resonance at 23kHz. The same general discussion applies to if you use a single inductor instead of a 1:1 transformer except of course there is no leakage inductance to worry about. What were the scales on the scope traces you sent? Cheers, Andy. signality.co.uk On 27 June 2011 01:27, Wojciech Kazubski <w...@o2.pl> wrote: > Dnia piątek 24 czerwca 2011 o 13:10:35 myken napisał(a): >> This is strange in my simulation the attached circuit works fine. In >> real life it kinda works but the signals are distorted like you can see. >> I think that has something to do with the fact we used a pulse >> transformer to try the circuit. If we disconnect Vx the signals stay the >> same, so the distortion is in the transformer. If you say it doesn't >> work then why doesn't it work? >> > Probably the transformer has too low inductance for that frequency, it should > be in mH range. Magnetizing current I=Uin/(2*pi*f*L) is high and > saturates the core so waveforms are not sinusoidal. > > Wojciech Kazubski > > > > _______________________________________________ > geda-user mailing list > geda-user@moria.seul.org > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user