Hi all. I am working on a small step-up converter for a battery operated project and I discovered a little problem (LTSpice file and picture below).
The circuit works as follows: The primary's swing is limited by the 30V Zener diode (which also protects the transistor). After passing through the 1:10 transformer, the energy is stored in C4. The expected voltage on the VOUT node would be 300V minus one diode drop, but it only gets to about 270V. Probing the VPULSE node shows that the output pulses dip below 0 quite a bit. Why is this occuring? Is this negative component normal for the flyback topology or am I doing something wrong?