Explain the effect of the gate current on the forward breakover voltage
Answers
Forward break over voltage of SCR is the minimum forward voltage at which SCR starts conducting. Consider the VI characteristics of SCR in Fig above
SCR will not conduct up to certain value of forward voltage when it is in forward bias condition. It blocks the current up to this particular voltage. During this period the leakage current only flows through the device which is very less (negligible current). This region is called as forward blocking region. The voltage at which device starts conduction is called as forward break over voltage. In general, this voltage is in the range of 50 to 500 Volts.
If gate is supplied by a positive current then forward break over voltage occurs earlier than no gate current condition. By increasing the gate current, the forward break over voltage occurs for lower values of forward voltage.
Influence of gate current on forward voltage break:
• When we provide gate current then forward break over voltage is reduced in SCR.
• The magnitude of forward break voltage is contingent on the gate current. Higher gate currents let the current IA increase quicker, improve the regeneration process, and switch at lesser break overvoltages.
• If the gate is provided by a + current then forward break over voltage arises earlier than without gate current.