This application note describes the design of an RC snubber circuit that improves the turn-off characteristics of a TRIAC
When a TRIAC controls inductive loads, the mains voltage and load current are not in phase. To limit the slope of the reapplied voltage and ensure proper TRIAC turn-off, designers usually use a snubber circuit connected in parallel with the TRIAC. This document analyzes snubber circuit functions to improve turn-off commutation.
The note details how to design an RC snubber circuit as a trade-off between limiting the critical slope of reapplied voltage ((dV/dt)c), managing overvoltage at turn-off, and controlling turn-on stress due to capacitor discharge. It provides equations for step response analysis in RLC series circuits.
The snubber circuit reduces the static dV/dt at a lower level than the dV/dt specified in the datasheet, thereby avoiding spurious triggering caused by electrical noise.
The circuit is used to limit the slope of the reapplied voltage and ensure proper TRIAC turn-off, while also improving immunity to fast transient voltages.
The example uses a capacitance of 10 nF and a resistance of 2.7 kΩ.