The holding current will depend on the NPN and PNP transistor I-V characteristics which, in-turn, depend on forward gain, forward emission coefficient, and ohmic resistances. The thyristor model also has an internal gate-cathode resistor which can have an effect if the external circuit resistor is higher than this integral value. Defining equations in our thyristor library block are the NPN and PNP bipolar transitor equations as defined in the reference pages:
plus equivalent circuit here:
However, finding holding current requires either simulation or writing an iterative equation solver given these defining equations as a starting point. You can explore impact of block parameters on holding current by opening our basic thyristor test harness model:
>> ee_thyristor
Click on the "Latch Current" hyperlink to enable hold current testing. You can then experiment with changing block parameters and how it impacts latching current. For example, try modifying V_GT as well as the overall gain.
You might find the system-level thyristor model in our library useful too: "Thyristor (Piecewise Linear)" - here you specify holding current directly plus on-state I-V characteristics.
I hope that helps
Best regards
Rick Hyde
