ACST2 Просмотр технического описания (PDF) - STMicroelectronics

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ACST2

AC Switch family Alternating current switch

STMicroelectronics 

AC line switch basic application

2

AC line switch basic application

ACST2 Series

The ACST2 device has been designed to switch on and off highly inductive or resistive loads

such as pump, valve, fan, or bulb lamp. Thanks to its high sensitivity (IGT max = 10 mA), the

ACST2 can be driven directly by logic level circuits through a resistor as shown on the

typical application diagram. Thanks to its thermal and turn-off commutation performances,

the ACST2 switch can drive, without any additional snubber, an inductive load up to 2 A.

Figure 15. Typical application diagram

Line

AC Mains

L

AC LOAD

R

ACST2

Rg

Power supply

MCU

2.1

Protection against overvoltage: the best choice is ACST

In comparison with standard triacs, which are not robust against surge voltages, the ACST2

is over-voltage self-protected, specified by the new parameter VCL. In addition, ACST2 is a

sensitive device (IGT = 10mA), but provides a high noise immunity level against fast

transients.

The ACST2 switch is able to sustain safely the AC line transient voltages either by clamping

the low energy spikes or by breaking over under high energy shocks, even with fast turn-on

current rises.

The test circuit of the Figure 16 is representative of the final ACST2 application, and is also

used to stress the ACST switch according to the IEC 61000-4-5 standard conditions. Thanks

to the load limiting the current, the ACST switch sustains the voltage spikes up to 2 kV

above the peak line voltage. The protection is based on an overvoltage crowbar technology.

Actually, the ACST2 will break over safely as shown on Figure 17. The ACST is recovering

its blocking voltage capability at the next zero current crossing point. Such non repetitive test

can be done 10 times on each AC line voltage polarity.

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