The Gate Triggering Circuit means a signal is applied between the gate and the cathode of SCR. These are three types,
- DC Signals
- AC Signals
- Pulse signals.
The Pulse Triggering is the most popular method for triggering the SCR. In this type the gate circuit can produce a single pulse appearing periodically or a sequence of high frequency pulses. Pulse transformer is used for isolation.
In this circuit NE555 IC is used as astable multivibrator mode to give square wave output. This output is given to transistor T Aand T2, When one transistor is ON other transistor is OFF vice versa. The Pulse transformers are commonly used in firing circuit for SCR’s and GTO’s. pulse transformer have one primary winding and can have one or more secondary windings. This output of pulse transformer is given to drive circuit of SCR or TRIAC and MOSFET.
How to connect :
- Pulse Transformer output G1 (To SCR gate-1)
- Pulse Transformer output K1 (To SCR Cathode-1)
- Pulse Transformer output G2 (To SCR gate-2)
- Pulse Transformer output K2 (To SCR Cathode-2)
The commonly used pulse transformers are 1:1 or 1:1:1 and are designed to have low winding resistance, low leakage reactance and low inter-winding capacitance.