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DI-74

更新时间: 2022-04-23 23:00:11
品牌 Logo 应用领域
帕沃英蒂格盛 - POWERINT 驱动器
页数 文件大小 规格书
2页 280K
描述
1.25 W Non-Isolated Constant Current LED Driver

DI-74 数据手册

 浏览型号DI-74的Datasheet PDF文件第2页 
Design Idea DI-74  
®
LinkSwitch-TN 1.25 W Non-Isolated  
Constant Current LED Driver  
Topology  
Device  
Power Output  
Output Voltage  
Application  
Input Voltage  
Buck-Boost  
LED Driver  
1.25 W  
85-265 VAC  
LNK304P  
12.5 V, 100 mA  
LinkSwitch-TN uses ON/OFF control to regulate the output  
current. When the current into the FEEDBACK (FB) pin  
exceeds 49 µA, MOSFET switching is disabled for the  
next switching cycle. The 49 µA threshold is specified at  
a pin voltage of 1.65 V (±7%), allowing it to be used as a  
reference.  
Design Highlights  
• Universal AC input range – single design worldwide  
• Accurate and stable constant current output  
• Small size and weight  
• Low cost, low component count solution replaces passive  
capacitor or resistor droppers  
• Fail safe topology – protects load  
• High efficiency (>60% at 85 VAC)  
• Scalable output power using larger LinkSwitch-TN devices  
• Meets EN55022 B EMI limits  
The voltage developed across R3, which is averaged by C4,  
represents the output current. When this voltage exceeds  
2 V, the voltage on the FB pin, via divider of R1 and R2,  
exceeds 1.65 V and >49 µA current is fed into the pin. The  
2 V across R3 sets an output current of 100 mA, or 25 mA  
for each string of LEDs. If the load is disconnected or the  
outputisshorted,nofeedbackisprovidedandLinkSwitch-TN  
enters auto-restart (5% on time). To prevent a high output  
voltage under no load the optional voltage feedback circuit  
can be included by adding VR1 and D4. The voltage of VR1  
is selected to be above the normal output voltage.  
Operation  
Using the Buck-Boost topology, the circuit shown in Figure 1  
generates a non-isolated constant current (CC) output for  
driving LEDs. Typical uses include night-lights, neon sign  
replacements, emergency exit signs or any application utilizing  
LEDs for lighting.  
Select the value of L1 following AN-37, LinkSwitch-TN  
Design Guide or using the PIXls design spreadsheet. Enter  
the output voltage as the voltage of the LED string and the  
output current as the total combined LED current.  
The AC input is rectified and filtered by D1, D2, C1, C2, RF1,  
and RF2. Two diodes improve both line surge withstand (2 kV)  
andconductedEMI. ResistorRF1shouldbeafusibleameproof  
type, whereas RF2 can be flameproof only.  
VR1  
R2  
300 Ω  
1%  
BZX79C18  
D4  
18 V, 500 mW UF4005  
R3  
20 Ω  
0.5 W  
1%  
R1  
RF2  
RF1  
C5  
2 kΩ  
D1  
47 , 0.5 W  
LED 1-20  
25 mA per String  
8.2 , 1 W  
Fusible  
1 uF, 50 V  
low ESR  
1%  
FB  
BP  
S
1N4007 Flame Proof  
D
C3  
D3  
0.1 uF  
50 V  
UF4005  
1 A, 600 V  
Ultrafast  
LinkSwitch-TN  
U1  
C4  
47 uF  
10 V  
LNK304P  
C1  
4.7 uF  
400 V  
C2  
4.7 uF  
400 V  
L1  
12.5 V,  
100 mA  
85-265  
VAC  
1.2 mH  
220 mA  
D2  
1N4007  
PI-3846-062106  
Figure 1. Schematic of a 1.25 W, 12.5 V, 100 mA constant current LED Driver, Using a Non-Isolated Buck-Boost Topology.  
June 2006  
DI-74  
www.powerint.com  

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