How can depletion layer be broken?

At this point, a small increase in reverse voltage causes sudden rise in reverse current. This sudden rise of reverse current destroys the depletion region or p-n junction. The strong electric field of the narrow depletion region, which causes the junction breakdown or depletion breakdown, is called zener breakdown.

What is gate triggering of SCR?

Gate triggering: This form of SCR triggering is the one that is most commonly seen in the different circuits used. To turn-on of an SCR, a positive gate voltage between gate and cathode. This gives rise to a gate current where charges are injected into the inner p layer of the device.

What is gate pulse?

Thyristors are silicon-controlled rectifiers (SCRs) commonly used as switching elements; they can be driven by electronic control circuits to activate and de-activate high-power devices such as lamps, motors and heating systems.

Why is pulse triggering preferred to other triggers?

Pulse triggering is preferred higher than RC triggering because of its following advantages: The SCR has small turn ON time ie, upto 5uS. The DC gate voltage and current increases losses in the SCR. Pulsed gate drive has reduced losses.

Why do we use pulse transformer for SCR triggering?

Pulse transformers are most frequently used for this purpose. These can transmit both the trigger signal and the required control power. Opto-couplers are also used; however, the control power at cathode potential of the thyristor must be generated by a separate power supply or recovered from the anode voltage.

What are gate triggering schemes?

Gate triggering is an efficient and most commonly used method to trigger the thyristor or SCR. As the thyristor is in forward biased, then an ample voltage on the gate terminal adds some electrons to the J2 junction.

Why is pulse triggering preferred over DC triggering?

For thyristors pulse triggering is preferred than dc triggering because: The DC gate voltage and current increase losses in the SCR. Pulsed triggering is to reduce gate losses. The pulsed gate drive can easily be passed through isolation transformers to isolate SCR and the trigger circuit.