Gate pulse circuit for thyristor triggering - has two winding impulse transformers through which capacitor discharges providing long enough pulse to prevent faulty triggering

摘要

The circuit produces a pulse of sufficient length to prevent faulty triggering whilst still using a simple capacitor discharge circuit. The impulse transformer (6) has single primary and secondary windings. A tap (10) on the primary is connected to the positive terminal of the impulse capacitor (9) through a diode (11). This winding is separated from the reference voltage rail (2) by a switch (12). The capacitor is connected to a dc voltage source (3) by a limiting resistor (7) and diode (8). - When an impulse is required the switch (12) is closed and the capacitor discharges into the primary winding, and a peak voltage appears on the secondary side. At the same time the diode (13) at the other end of the primary becomes forward biased and current from the dc source (3) flows through the whole winding thus lengthening the tail of the pulse. A bypass circuit (14) may be used to prevent immediate recharging of the capacitor (9). The switch (12) is typically a solid state electronic device.