AP3033 查看數據表（PDF） - BCD Semiconductor

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AP3033

BOOST CONTROLLER

BCD Semiconductor 

Preliminary Datasheet

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.

(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.

PWM

R4

AP3033

FB

R3

R2

C

Effective

Feedback Voltage

R1

AP3033

FB

VDC

R3

R2

Effective

Feedback Voltage

R1

Figure 16. Dimming Control

Using Filtered PWM Voltage

Figure 15. Dimming Control

Using DC Voltage

Jan. 2010 Rev. 1. 0

BCD Semiconductor Manufacturing Limited

10

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