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TRIAC turn-off description

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Figure 3.

dI/dt and dV/dt at turn-off

1.2

(dI/dt)c versus (dV/dt)c characterization

To characterize the turn-off TRIAC behavior, we consider a circuit in which the slope of the

decreasing current can be adjusted. In addition, the slope of the reapplied voltage can be

controlled by using, a circuit of resistors and capacitors connected across the TRIAC. For a

the (dI/dt)c in TRIAC datasheets. This is also the way to trace the curve of the TRIAC

commutation behavior (see TRIAC datasheet curve “Relative variation of critical rate of

decrease of main current (dI/dt)c versus reapplied (dV/dt)c”).

In TRIAC datasheets, the commutation behavior is specified in different way according to

the TRIAC technologies. For standard TRIAC, a minimum (dV/dt)c is specified for a given

(dI/dt)c. For logic level TRIACs, a minimum (dI/dt)c is specified for two given (dV/dt)c (0.1

V/µs and 10 V/µs). For Snubberless TRIACs, a minimum (dI/dt)c is specified without

(dV/dt)c limitation.

Figure 4 represents the curve of the commutation behavior obtained with a standard 4 A

TRIAC. This TRIAC is available with different sensitivities:

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●

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For lower sensitive gate TRIACs (Z0409 and Z0410), the (dI/dt)c is slightly modified

according to the (dV/dt)c. For sensitive gate TRIACs (Z0402 and Z0405), this parameter

noticeably decreases when the slope of the reapplied voltage increases.

I

G

OUT

G

I

T

COM

V

T

I

T

t

V

T

I

G

t

t

V

Mains

dI/dt

OFF

dV/dt

OFF