AN871 Datasheet, PDF (4/13 Pages) STMicroelectronics – In power electronics the choice of the switch to be used is always very important

AN871 APPLICATION NOTE
Figure 4. Ignition circuit with SCR: storage capacitor connected across input voltage source
+V
D
(A)
+V
D
(B)
In these circuits the diode D acts as a freewheel diode to ensure the complete discharge of the energy
stored in the capacitor C.
The current through the transformer is oscillating in the cases 3A and 4A and unidirectional in the cases
4A and 4B.
Utilization of triac
The triac can be used as a very flexible unidirectional or bidirectional switch in such a circuit.
Moreover, it can be triggered with a negative gate current. This feature allows the use of standard buffer
circuit for the gate control (see Figure 5).
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