ACST12 Application information
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Figure 17. Universal drum motor control – typical diagram
2.2 AC line transient voltage ruggedness
In comparison with standard TRIACs, which are not robust against surge voltage, the
ACST12 is self-protected against over-voltage, specified by the new parameter V
CL
. The
ACST12 switch can safely withstand AC line transient voltages either by clamping the low
energy spikes 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 rises.
The test circuit of Figure 18 represents the ACST12 application, and is used to stress the
ACST switch according to the IEC 61000-4-5 standard conditions. Thanks to the load which
is limiting the current, the ACST switch withstands the voltage spikes up to 2 kV above the
peak line voltage. The protection is based on an overvoltage crowbar technology. The
ACST12 switches safely to the on state as shown in Figure 19. The ACST12 recovers its
blocking voltage capability after the surge. Such a non repetitive test can be done at least 10
times on each AC line voltage polarity.
Universal motor
Motor direction
setting
Speed motor
regulation
Rg
AC Mains
Stator
MCU
Vcc
12V
ACST
Rotor
MCU
