Application information

L6599

28/36

Figure 32. Line sensing function: internal block diagram and timing diagram

With reference to Figure 32 the following relationships can be established for the ON

supplied by another source) continuously oscillates between the start-up and the UVLO

thresholds, as shown in the timing diagram of Figure 32.

As an additional measure of safety (e.g. in case the low-side resistor is open or missing, or

in non-power factor corrected systems in case of abnormally high input voltage) if the

Vin

ON

1.25

–

R

H

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

15

10

6

–

1.25

R

H

-----------

+

⋅

=

Vin

OFF

1.25

–

R

H

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

1.25

R

H

-----------

=

R

H

Vin

ON

Vin

OFF

–

15

10

6

–

⋅

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

=

R

L

R

H

1.25

Vin

OFF

1.25

–

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

⋅

=