2 AC line switch - basic application
ACS102-6T
2
AC line switch - basic application
The ACS102-6T switch is triggered by a negative gate current flowing from the gate pin G. The
switch can be driven directly by the digital controller through a resistor as shown in Figure 13.
Thanks to its overvoltage protection and turn-off commutation performance, the ACS102-6T
switch can drive a small power high inductive load with neither varistor nor additional turn-off
snubber.
Figure 13. Typical application program
Valve
AC Mains
V
MCU
ss
Rg
ACS102-6T
Power supply
V
dd
2.1
Protection against overvoltage: the best choice is ACS
In comparison with standard triacs, which are not robust against surge voltage, the ACS102-6T
is over-voltage self-protected, specified by the new parameter VCL. This feature is useful in two
operating conditions: in case of turn-off of very inductive load, and in case of surge voltage that
can occur on the electrical network.
2.1.1 High inductive load switch-off: turn-off overvoltage clamping
With high inductive and low RMS current loads the rate of decrease of the current is very low.
An overvoltage can occur when the gate current is removed and the OUT current is lower than
IH.
As shown in Figure 14 and Figure 15, at the end of the last conduction half-cycle, the load
current decreases (1). The load current reaches the holding current level IH (2), and the ACS
turns off (3). The water valve, as an inductive load (up to 15 H), reacts as a current generator
and an overvoltage is created, which is clamped by the ACS (4). The current flows through the
ACS avalanche and decreases linearly to zero. During this time, the voltage across the switch is
limited to the clamping voltage VCL. The energy stored in the inductance of the load is
dissipated in the clamping section that is designed for this purpose. When the energy has been
dissipated, the ACS voltage falls back to the mains voltage value (5).
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STMICROELECTRONICS [ ST ]
