In practical thyristor circuits, an RC series network is often connected in parallel across its terminals. This network is commonly referred to as an RC snubber circuit.

We know that a crucial characteristic parameter of a thyristor is its critical rate of rise of the off-state voltage (dlv/dlt). This indicates the minimum voltage rise rate required for the thyristor to transition from the off-state to the on-state under rated junction temperature and gate open-circuit conditions. If the voltage rise rate is too high, exceeding the thyristor's voltage rise rate value, it will turn on even without a gate signal. This can occur even if the forward voltage applied to the thyristor is lower than its anode peak voltage. This is because a thyristor can be considered as consisting of three PN junctions.

When the thyristor is in the blocking state, because the layers are very close together, the junction surface of its J2 junction is equivalent to a capacitor C0. When the anode voltage of the thyristor changes, a charging current flows through capacitor C0 and through junction J3. This current acts as the gate trigger current. If the anode voltage rises too quickly when the thyristor is turned off, the charging current of capacitor C0 will be too large. This could potentially cause the thyristor to falsely turn on even without a trigger signal, a phenomenon commonly known as hard turn-on, which is unacceptable. Therefore, the rate of rise of the anode voltage applied to the thyristor should be limited.

To limit the rate of voltage rise in the circuit and ensure the safe operation of the thyristor, an RC snubber network is often connected in parallel across the thyristor. This utilizes the characteristic that the voltage across a capacitor cannot change abruptly to limit the rate of voltage rise. Because the circuit always has inductance (transformer leakage inductance or load inductance), the resistor R connected in series with capacitor C can act as a damper. It can prevent overvoltage damage to the thyristor caused by oscillations across the capacitor during the transition process of the R-L-C circuit. Simultaneously, it avoids excessive discharge current through the capacitor through the thyristor, which could cause overcurrent damage. Since thyristors have very poor overcurrent and overvoltage capabilities, they cannot function properly without reliable protection measures. The RC snubber network is one of the commonly used protection methods.