AN4350 datasheet(16/34 Pages) STMICROELECTRONICS

16 / 34 page

Circuit description and design guidelines

AN4350

16/34

DocID025181 Rev 1

Equation 38

A capacitor between the COMP pin and ground can be also added to remove the high

frequency voltage ripple without impacting on the transfer function (i.e. adding a small

capacitor in the range of few nF).

Figure 6. Transfer function

2.7

System design tips

Starting from the estimated value using Equation 11, Equation 15, Equation 17, Equation 20,

Equation 37 and Equation 38, further fine tuning on the real LED driver board could be

necessary and it can be easily done considering that:



Decreasing the RPF resistor value, the power factor effect increases



Decreasing the ROS resistor value, the input current close to zero decreases



Decreasing the RSENSE resistor value, the maximum deliverable output current

increases



Increasing the CC compensation capacitor, the system phase margin increases and

voltage loop bandwidth decreases.



Decreasing the RC compensation resistor, the voltage loop gain/bandwidth decreases

and also the ripples on the COMP pin.

RC 4  BWCV







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



220

 4  5Hz





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

F

AN4350 Datasheet(PDF) 16 Page - STMicroelectronics