AN439

TRIAC turn-off description

7/16

For an underdamped oscillating circuit (0

TRIAC is defined by:

Equation 8

With damped natural resonance:

Equation 9

In the case of pure inductive load (R = 0, worst case), the circuit is undamped. The

Equation 10

without snubber will be limited to about 60 V/µs for 100 – 220 V applications. Thus, it is not

necessary to get the (dI/dt)c values for (dV/dt)c above 100 V/µs .

t

p

p

0

p

T

0

e

)

t

sin(

)

t

cos(

·

E

E

)

t

(

V

·

·

-

·

·

·

·

·

-

ω

ξ

ω

ω

ω

ξ

ω

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

+

=

2

0

p

1

ξ

ω

ω

-

·

=

0

6

)

F

(

T

)

H

(

)

V

(

RMS

)

s

/

V

(

OFF

2

t

at

10

.

C

.

L

2

V

dt

/

dV

ω

π

µ

.

.

-

=

=