STMicroelectronics STEVAL-IHT008V1 User Manual page 30

Triacs and AC switches insulated control
the NPN transistor collector-emitter, I
triggering voltage.
The collector resistor (R
being the NPN transistor resistor filter, VCC_AC the power supply to provide the gate
current to the AC switch, VCE(SAT)
I the TRIAC gate current, ß
GT
transistor base-emitter.
Given the optocoupler and the R
defined by the equation below.
in our example, with the IS127 optocoupler and the 2N2222 NPN transistor, the following
resistor values should therefore be chosen.
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the TRIAC gate current and V
GT
) of the NPN transistor is defined in the next equation, with R40
18
the transistor collector-emitter of the optocoupler,
Opto
is the NPN transistor gain and VBE(SAT)
NPN
resistor value, the LED resistor R
28
DocID029048 Rev 1
UM2027
is the TRIAC gate
GT
is the NPN
NPN
of the optocoupler is
29