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UCY2G150MPD PDF预览

UCY2G150MPD

更新时间: 2024-11-04 12:22:59
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美台 - DIODES /
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描述
High Power Factor LED Replacement T8 Fluorescent Tube

UCY2G150MPD 数据手册

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AN75  
AN75  
High Power Factor LED Replacement T8 Fluorescent Tube  
using the AL9910 High Voltage LED Controller  
Yong Ang, Diodes Inc.  
Introduction  
This application note describes the principles and design equations required for the design of a high  
brightness LED lamp using the AL9910. The equations are then used to demonstrate the design of a  
universal, offline, high power factor (PF), 13W LED lamp suitable for use as the replacement for T8  
fluorescent tube. A complete design including the electrical diagram, component list and performance  
measurements are provided.  
AL9910 high power factor buck LED driver  
Figure 1 Electrical schematic of a high power factor 13W LED lamp  
Figure 1 shows the electrical diagram of an offline 13W LED driver.  
On the input side, CX1, CX2, CX3, CX4, L1 and L2 provide sufficient filtering for both differential mode  
and common mode EMI noise which are generated by the switching converter circuit.  
The rectified AC line voltage from the bridge rectifier DB1 is then fed into a passive power factor  
correction or valley fill circuit which consists of 3 diodes and 2 capacitors. D1, D2, D3, C1, C2 improve  
the input line current distortion in order to achieve PF greater than 0.9 for the AC line input.  
The constant current regulator section consists of a buck converter driven by the AL9910. Normally,  
the buck regulator is used in fixed frequency mode but its duty cycle limitation of 50% is not practical  
for offline lamp. This problem can be overcome by changing the control method to a fixed off-time  
operation.  
The design of the internal oscillator in the AL9910 allows the IC to be configured for either fixed  
frequency or fixed off-time based on how resistor RT is connected. For fixed off-time operation, the  
resistor RT is connected between the Gate and ROSC pins, as shown in Figure 1. This converter has  
now a constant off-time when the power MOSFET is turned off. The on-time is based on the current  
Issue 1 – January 2011  
1
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