Snubber circuits are used with thyristors in order to:
- Protect the gate circuit
- Limit the rate of rise of voltage dv/dt
- Limit the rate of rise of current di/dt
- None of these
Correct answer: 2. Limit the rate of rise of voltage dv/dt
Explanation: The dv/dt rating of thyristor implies the maximum rate of rise of anode voltage that will not trigger device without any gate signal. A snubber circuit is used in order to control this limit.
Also read: 10 Types of Power Electronics converters
An example application of snubber circuits is in case of Shockley diode.
Note that Shockley diodes may be fired in a way other than breakover: excessive voltage rise, or dv/dt. If the applied voltage across the diode increases at a high rate of change, it may trigger. This is able to cause latching (turning on) of the diode due to inherent junction capacitances within the transistors. Capacitors, as you may recall, oppose changes in voltage by drawing or supplying current. If the applied voltage across a Shockley diode rises at too fast a rate, those tiny capacitances will draw enough current during that time to activate the transistor pair, turning them both on. Usually, this form of latching is undesirable, and can be minimized by filtering high-frequency (fast voltage rises) from the diode with series inductors and parallel resistor-capacitor networks called snubbers: (Figure below)
Above text is from Article extracted from Tony Kuphaldt’s Lesson in Electric circuits Volume III Semiconductors under the terms and conditions of Design Science License. Read complete article here.