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■APPLICATION INFORMATION (Continued)

<Dimming Control (Continued)>

3. Using DC Voltage

If in an application it is necessary to control the LED current by a variable DC voltage, illumination control of LED is

achieved by connecting R1 and R2 and applying a direct-current voltage to R2, as shown below.

Ex.1) When R1 = 10k

(LED current) varies between 20mA to 0mA.

<Prevent Emission Caused by White LEDs Leakage>

If this

happens, please connect a transistor to between the LED and the FB pin.

By driving the CE signal in-phase and cutting

the pass to current, the minimum illumination can be prevented.

Ex.2) When R1 = 10k

C1 = 0.1

μF, RLED = 10Ω, the average LED current will

be 10mA by inputting a PWM signal of CE ‘H’ level:

2.2V, CE ’L’ level: 0V, duty cycle: 50%, oscillation

frequency: 100Hz.

As well as the way of dimming

control by applying the PWM signal to the CE pin, the

average LED current increases proportionally with the

positive duty cycle of the PWM signal.

Figure : Circuit using DC voltage

Figure : Circuit inputting a PWM signal to the FB pin

XC9116

FB

VDC

R2

R1

RLED

ILED

ZD

(

)

PWM

XC9116

FB

RLED

R1

R2

R3

ILED

ZD

(

)

C1

VIN

Lx

CE

FB

GND

L:22uH

VLF3010A

VIN

CL

0.22uF

(base)

SD

XB0ASB03A1B

20mA

RLED

10

Ω

3.6V

(3.2V~6.0V)

CIN

4.7uF

XP151A21A2