Logic level and Snubberless TRIACs

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Logic level and Snubberless TRIACs

2.1

Operation in Q1-Q2-Q3 quadrants

To make significant progress in the TRIAC technology is to essentially improve the turn-off

behaviour. In other words, the critical (dI/dt)c has to be improved.

To reach this aim, a different structure has been developed. In this structure, the different

active areas have been decoupled to separate the elementary thyristors and the gate area.

This improvement provides the gate triggering in the fourth quadrant. In practice this

modification does not lead to a problem because the gate drive circuits generally work in

Q1/Q3 or Q2/Q3. (see Figure 8)

Figure 8.

Basic gate drive circuits in Q1/Q3 or Q2/Q3 operations

For a given technology, the TRIACs commutation behaviour depends on the gate sensitivity.

The correlation between the critical (dI/dt)c and the triggering gate current for 12 A TRIACs

is represented in Figure 9. For a same current rating and gate sensitivity, Snubberless

TRIACs present a (dI/dt)c at least 2 times higher than for standard TRIACs.

Figure 9.

Correlation between commutation behavior and sensitivity

(measurement performed on several lots of 12 A TRIACs)

Diac

C

R

+V

cc

µC

+V

cc

Opto-triac

Q1/Q3 operation

Q2/Q3 operation

I

3rd quadrant

Critical

(dI/dt)c (A/ms)

Snubberless TRIACs

Standard TRIACs

I

3rd quadrant

Critical

(dI/dt)c (A/ms)

Snubberless Triacs

Standard Triacs

10

20

30

40

50

60

10

20

30

40

50

60

5

10

15

20

25

30

5

0

10

15

20

25

30