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AP3029 Datasheet(PDF) 11 Page - BCD Semiconductor Manufacturing Limited |
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AP3029 Datasheet(HTML) 11 Page - BCD Semiconductor Manufacturing Limited |
11 / 16 page 11 Oct. 2009 Rev. 1. 8 BCD Semiconductor Manufacturing Limited Data Sheet WHITE LED STEP-UP CONVERTER AP3029 Application Information (Continued) this PWM signal can be up to 2KHz. Please refer to Figure 20. 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. 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. It will change the FB voltage indirectly and achieve dimming control. The circuit is shown in Figure 22. 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. 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. 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 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. AP3029 CTRL up to 2kHz AP3029 CTRL R1 10k R2 10k V DC 0.1 to 3.6 V AP3029 CTRL R1 5k C1 100nF PWM Signal R1 10 Ω FB AP3029 R2 5K R3 90K V DC Effective Feedback Voltage R1 10 Ω FB AP3029 R2 5K R3 90K PWM R4 10K C 0.1 µF Effective Feedback Voltage |
Similar Part No. - AP3029_09 |
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Similar Description - AP3029_09 |
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