AL9902

Document number: DS37878 Rev. 1 - 2

10 of 18

www.diodes.com

July 2015

© Diodes Incorporated

AL9902

Applications Information

DC-DC and Offline LED Driver

The AL9902 is a cost-effective offline buck LED driver-converter specifically designed for driving LED strings. It is suitable for being used with

either rectified AC line or any DC voltage between 5-500V. See Figure 1 for typical circuit.

C1

C2

C3

Rsense

Rosc

D1

AL9902

L1

3

HD06

1

2

4

Z1

602V

AC+

AC-

GND

VIN

PWM

VDD

LD

CS

SW

SO

Rosc

Figure 1 Typical Application Circuit (without PFC)

Buck Design Equations:



D

IN

LEDs

V

V

osc

ON

f

D

t





L

LED

ON

LEDs

IN

I

3

.

0

t

)

V

V

(









SENSE

R

))

3

.

0

I

(

5

.

0

(

I

25

.

0

LED

LED







Design Example

can be determined:

The value of the inductor is determined as follows: