Is there a formula for calculating the latching current of a thyristor and the resistance of the thyristor after it forward conducts and I_gate becomes 0? I couldn't find anything online; the tutorials just describe how it works.
Thanks in advance!
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\$\begingroup\$ Don't mix peaches and apples. Latching current is a parameter, nothing to calculate. You can calculate the equivalent resistance from forward voltage drop. \$\endgroup\$– Marko BuršičCommented Oct 6, 2021 at 16:18
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No there is no formula, it's a characteristic of the device and some guidance can be found in the datasheet (eg. 2N5064 datasheet).
As always, there can be considerable variation from unit to unit, as well as with temperature.
Also note that the temperature curve is normalized and no typical number is given at all, so a holding current of (say) 0.2mA would meet the specifications. This can have consequences to your design. It's probably of the order of the gate trigger current.
Thyristors do not have on resistance per se, they have a voltage drop which depends (in a very nonlinear way) on current. Again, the device datasheet is your reference. For many purposes you could assume the 'on' voltage drop is constant at around a volt. You could convert that into a "resistance" but it would have little meaning and less utility since it would only be valid at a single current.
answered Oct 6, 2021 at 16:07