AN871 Datasheet, PDF (5/13 Pages) STMicroelectronics – In power electronics the choice of the switch to be used is always very important

AN871 APPLICATION NOTE
Figure 5. Ignition circuit with Triac: In case B the Triac is triggered by a negative gate current. In
case A, no freewheel diode is needed
+V(400V)
Conv.
DC/DC
(A)
SPARK PLUG
Vcc
DRIVER
IG
(B)
DRIVER
+V(400V)
IG
+Vbat
SPARK PLUG
Safety equipment. The discharge of capacitor is also widely used in safety equipment which sets powder
trigger mechanism in action: Air bag, belt pretensionner, etc...
In such a system, SCR’s are generally the best choice to provide high energy pulse with less than one
microsecond response time. Usually, the gate trigger drive of the SCR circuit is very simple and therefore
provides a high reliability (see Figure 6).
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