Datasheet

Device description HVLED815PF

28/34 DocID023409 Rev 5

The R

, R

resistors are selected to add a positive offset on CS pin in order to keep

a good line regulation over the input voltage range and cab be selected using Equation 18:

Equation 18

Where V

OS_TYP

is the desired voltage across C

capacitor applying the V

IN_TYP

typical

input voltage (i.e. V

IN_TYP

= 220 V for 176/264 Vac input range); F

is the switching

frequency and can be estimated using Equation 19, where f

and f

are the transition and

resonant frequency respectively:

Equation 19

Equation 20

Equation 21

where C

is the total equivalent capacitor afferent at the drain node.

Based on the desired voltage across the C

capacitor and calculated R

resistor, then

the sum of R

and R

can then calculated as a results of partitioning divider:

Equation 22

Using the previous R

resistor value the R

resistor can be estimated using Equation 23:

Equation 23

