Diodes AP3033 Manuel d'utilisateur télécharger pdf (Page 10)

Preliminary Datasheet

Jan. 2010 Rev. 1. 0 BCD Semiconductor Manufacturing Limited

WHITE LED STEP-UP CONVERTER AP3033

Application Information (Continued)

Two other typical types of dimming control circuit are

presented as below.

(1) Using DC Voltage to Change the Effective Feed-

back Voltage

Adding a constant DC voltage through a resistor

divider to FB pin can control the dimming. Changing

the DC voltage or resistor between the FB Pin and the

DC voltage can get appropriate luminous intensity.

Comparing with all kinds of PWM signal control, this

method features a stable output voltage and LEDs

current. Please refer to Figure 15.

Figure 15. Dimming Control

Using DC Voltage

(2) Using Filtered PWM Signal to Change the Effec-

tive Feedback Voltage

The filtered PWM signal can be considered as a

varying and adjustable DC voltage, please refer to Fig-

ure 16.

Figure 16. Dimming Control

Using Filtered PWM

Voltage

PWM

Effective

Feedback Voltage

AP3033

R2R3

Effective

Feedback Voltage

1 2 ... 5 6 7 8 9 10 11 12 13

Pas de commentaire

Diodes AP3033 Manuel d'utilisateur Page 10