Datasheet

HVLED815PF Device description
Doc ID 023409 Rev 4 29/36
Equation 18
Where V
OS_TYP
is the desired voltage across C
OS
capacitor applying the V
IN_TYP
typical
input voltage (i.e. VIN_TYP=220 V for 176/264 Vac input range); F
sw
is the switching
frequency and can be estimated using the following formula, where f
T
and f
R
are the
transition and resonant frequency respectively:
Equation 19
Equation 20
Equation 21
where CD is the total equivalent capacitor afferent at the drain node.
Based on the desired voltage across C
OS
capacitor and calculated R
OS
resistor, then the
sum of R
A
and R
B
can then calculated as a results of partitioning divider:
Equation 22
Using the previous R
OS
resistor value the R
PF
resistor can be estimated using the following
formula:
Equation 23
Finally the current sense resistor R
SENSE
can be estimated in order to select the
desiderated average output current value:
π