Setting up FOT control with the L6562

AN1895

8/16

7.

selected according to:

to-base forward drop of T. Substituting:

in this case a 1.5k

Ω resistor will be chosen

8.

Cs will be selected according to the relationship:

;

a standard value Cs=330 pF will be used.

Figure 4.

Diagrams for the design of the circuit of Figure 3 (valid for wide-range

mains operation).

Rs

V

GDx

V

ZCDclamp

–

V

F

–

I

ZCDx

V

V

ZCDclamp

V

MULTpkmax

V

BE

–

–

()R1

+

R1R2

----------------------------------------------------------------------------------------------------------------------------------------------------

+

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------

>

Rs

15

5.7

–

0.5

–

10 10

3

–

5.7 1500

5.7

3

–

0.55

–

() 12000

⋅

+

⋅

1500 12000

⋅

----------------------------------------------------------------------------------------------

+

⋅

----------------------------------------------------------------------------------------------------------------------------

>

739

Ω

=

Cs

C

V

ZCDclamp

V

GDx

V

ZCDclamp

–

V

F

–

----------------------------------------------------------------

<

560 10

12

–

5.7

15

5.7

–

0.5

–

-----------------------------------

⋅

363pF

==