ACST8 Application information
Doc ID 7463 Rev 9 7/13
2.2 AC line transient voltage ruggedness
In comparison with standard Triacs, which are not robust against surge voltage, the ACST8
is self-protected against over-voltage, specified by the new parameter V
CL
. The ACST8
switch can safely withstand AC line transient voltages either by clamping the low energy
spikes, such as inductive spikes at switch off, or by switching to the on state (for less than 10
ms) to dissipate higher energy shocks through the load. This safety feature works even with
high turn-on current ramp up.
The test circuit of Figure 17 represents the ACST8 application, and is used to stress the
ACST switch according to the IEC 61000-4-5 standard conditions. With the additional effect
of the load which is limiting the current, the ACST switch withstands the voltage spikes up to
2 kV on top of the peak line voltage. The protection is based on an overvoltage crowbar
technology. The ACST8 folds back safely to the on state as shown in Figure 18. The ACST8
recovers its blocking voltage capability after the surge and the next zero current crossing.
Such a non repetitive test can be done at least 10 times on each AC line voltage polarity.
Figure 17. Overvoltage ruggedness test circuit for resistive and inductive loads for
IEC 61000-4-5 standards
AC Mains
R
Filtering unit
Rg
Model of the load
Rgene
Surge generator
ACST8
2kV surge
L
R = 13 , L = 2 µH, Vsurge = 2 kV
Rg = 82
Ω
Ω
