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 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