AL8820

Document number: DS37369 Rev. 1 - 2

10 of 15

www.diodes.com

December 2014

© Diodes Incorporated

AL8820

Low switching frequency can decrease the switching loss but need to choose higher inductor values that will result in larger size in order to meet

the saturation current. For example, the relationship between switching frequency and inductor value is shown as below Table 1 in the same

application system. Considering these factors, 500kHz switching frequency is recommended in typical application.

Operation Frequency of SW1 at Peak Voltage of Vac

10µH

637kHz

15µH

500kHz

27µH

373kHz

Table 1

LED Current Control

Connected between VIN pin and CS2 pin, the nominal average output current in the LED(s) is defined as:

2

100

LED

SET

mV

I

R



Buck Converter Inductor Selection

FET, and component parameter. The inductance L3 is calculated according to the following equation:

2

2

2

1

)

(

3

SW

IN

LED

LED

LED

COIL

DSON

SET

LED

IN

f

V

V

I

I

R

R

R

V

V

L



















Where:

lower efficiency. Higher switching frequency can choose smaller inductor value that has smaller size in order to meet the saturation current but will

increase the switching loss. For example, the relationship between switching frequency and inductor value is shown as below Table 2 in the same

application system. Considering these factors, about 300kHz switching frequency is recommended in typical application.