Ac Switch Gate Control Dimensioning; Figure 41. T1635T-8Fp Datasheet Extract - STMicroelectronics STEVAL-GLA001V1 User Manual

9

AC switch gate control dimensioning

Gate current I
G
current I given in the AC switch datasheet. This parameter is temperature dependent, so recalculation is
GT
required if a parameter like ambient temperature changes.
The STEVAL-GLA001V1
calculated to ensure turn-on for ambient temperature from 0 to 60 °C. It also takes into account fluctuation on
VCC_AC voltage (non-regulated auxiliary voltage referenced to mains voltage) from approximatively 13 V to 21 V.
In case of schematic use in another design, you must recalculate the gate control circuit, especially the R
resistor (R103 or R106 or R115+R117 pair). Refer to the formulas below to adjust R
X101 Triac
X101 is a T1635T-8FP Triac. The figure below gives the I
temperature
At 0 °C ambient temperature I
VCC_AC minimum voltage, the gate resistors calculation is:
R115 + R117 =
The nearest normalized value is 150 Ω.
You can calculate maximum power in the resistors considering VCC_AC maximum voltage:
Therefore, R115 and R117 are 150 Ω/2 W resistors.
Note: Use the above formulas to recalculate resistor values in case of schematic use in another design with a different
ambient temperature.
X102 AC switch
X102 is an ACST310-8B AC switch. The figure below gives the I
temperature.
UM2304 - Rev 3
is required to switch an AC switch ON. This I
evaluation board embeds three AC switches and all gate control circuits have been
Figure 41.
* 1.26 = 44 mA is needed to ensure Triac activation. Considering this current and
GT
V R115 + R117
I G min
V R115 + R117 V CC_AC min + V GT max − V CEsat
I G max = =
R115 + R117
P R115 = R115 × I G max
current should be higher than the triggering gate
G
parameter value and its variation versus the
GT
T1635T-8FP datasheet extract
V CC_AC min + V GT max − V CEsat
=
I G min
R115 + R117
2
= 0.8 W
parameter value and its variation against
GT
UM2304
AC switch gate control dimensioning
resistor values.
G
13 + 1.3 − 0.5
= = 313 Ω
44 × 10 −3
21 + 1.3 − 0.5
= = 73 mA
300
G
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