This Application Note explains in detail why adding a gate to cathode capacitor between the gate terminal and the reference terminal of the thyristor does not efficiently improve the thyristor immunity to fast voltage transients, especially for non-sensitive devices.
This document investigates the use of capacitors connected between the gate and cathode terminals of Triacs and SCRs. While such components are often added to stabilize control terminal potential and filter noise from line disturbances, this analysis demonstrates their limitations in improving immunity to fast voltage transients (dV/dt).
The study reveals that for non-sensitive devices, adding a gate-to-cathode capacitor does not significantly improve dV/dt immunity and may actually increase the risk of failure under repetitive or accidental high di/dt conditions. The note provides test results comparing sensitive and less sensitive Triac models to illustrate these effects.
| Document Revision | Rev 1 |
|---|---|
| Test Temperature | 125 °C |
It is not efficient for non-sensitive devices and can increase the risk of failure for repetitive or accidentally high di/dt.
It may be useful only for sensitive devices, but it improves immunity during tests for only half the time in AC voltage applications.