AIC1647

than the FB pin bias current. With a VDC ranging

from 0V to 5V, the selection of resistors in Figure

21 results in dimming control of LED current from

20mA to 0mA, respectively.

3. Using a Filtered PWM Signal

Filtered PWM signal can be considered as an

adjustable DC voltage. It can be used to replace

the variable DC voltage source in dimming

control. The circuit is shown in Figure 22.

L1

10

µH

D1

SW

VIN

SHDN

FB

GND

AIC1647

RFB

4.7

Ω

C1

1

µF

C2

1

µF

20mA

D2

R1

1K

RB512S-30

PWM

BZV55-B12

11.8V~12.2V

Fig. 19 Dimming Control Using a PWM Signal with Open-Circuit Protection

L1

10

µH

D1

SW

VIN

SHDN

FB

GND

AIC1647

RFB

4.7Ω

C1

1

µF

C2

1

µF

20mA

D2

R1

1K

RB512S-30

PWM

R2

BZV55-B12

11.8V~12.2V

51K

Fig. 20 Dimming Control Using a PWM Signal

9