In my applications, I simply used a resistor in series with the transformer secondary. With the particular thyristors I used, it worked well with 3.3 ohms. In retrospect, a diode or two would probably work better. The goal is to restrict the current flowing back OUT of the inductor to less than what's needed to retrigger it on the next phase.

This problem is most often seen when using TRIACs, since an SCR only conducts on alternate 1/2 cycles and the stored energy is released when each SCR is reverse biased. (But if you share a pulse transformer this is a problem even with SCRs, and reverse current must be shunted to avoid malfunction.)

I drove my pulse transformers with LM311 as the power driver device. (I had a box of them.)