AP3029(2009) 查看數據表（PDF） - BCD Semiconductor
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AP3029 Datasheet PDF : 16 Pages
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Data Sheet
WHITE LED STEP-UP CONVERTER
AP3029
Application Information (Continued)
this PWM signal can be up to 2KHz. Please refer to
Figure 20.
AP3029
up to 2kHz
CTRL
Figure 20. Dimming Control
Using a PWM Signal in CTRL Pin
Secondly, adding a constant DC voltage through a
resistor divider to CTRL pin can control the dimming.
The FB voltage is indirectly adjusted when the CTRL
pin voltage is between 50mV to 1.8V, which can be
used as dimming control. Please refer Figure 21.
First, 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 Figure 23.
AP3029
VDC
FB
R3
R2
90K
5K
Effective
Feedback Voltage
R1
10Ω
R1
VDC
10k
0.1 to 3.6 V
AP3029
CTRL
R2
10k
Figure 23. Dimming Control
Using DC Voltage
Second, using a filtered PWM signal can do it. The
filtered PWM signal can be considered as a varying
and adjustable DC voltage.
Figure 21. Dimming Control
Using a DC Voltage in CTRL Pin
Thirdly, using a filtered PWM signal adding to CTRL
pin can achieve dimming control. The filtered PWM
signal can be considered as an adjustable DC voltage.
AP3029
FB
It will change the FB voltage indirectly and achieve PWM
dimming control. The circuit is shown in Figure 22.
R4
C R3
10K 0.1µF 90K
R2
5K
Effective
Feedback Voltage
R1
10Ω
PWM
Signal
R1
AP3029
5k
CTRL
C1
100nF
Figure 22. Dimming Control
Using a Filtered PWM Signal Voltage in CTRL Pin
(2). Changing the Effective Feedback Voltage
There are three methods to change the effective
feedback voltage.
Oct. 2009 Rev. 1. 8
Figure 24. Dimming Control
Using a Filtered PWM Voltage
Third, using a logic signal to change the feedback
voltage. For example, the FB pin is connected to the
GND through a mosFET and a resistor. And this
mosFET is controlled a logic signal. The luminous
intensity of LEDs will be changed when the mosFET
turns on or off.
BCD Semiconductor Manufacturing Limited
11
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