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LM3445-120VFLBK/NOPBDatasheet PDF
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Application Report
SNVA429C–August 2010–Revised May 2013
AN-2034 LM3445 -120VAC, 8W Isolated Flyback
LED Driver
.....................................................................................................................................................
ABSTRACT
This demonstration board highlights the performance of a LM3445 based Flyback LED driver solution that
can be used to power a single LED string consisting of 4 to 8 series connected LEDs from an 90 V
RMS
to
135 V
RMS
, 60 Hz input power supply. The key performance characteristics under typical operating
conditions are summarized in this application report.
Contents
1 Introduction .................................................................................................................. 3
2 Key Features ................................................................................................................ 3
3 Applications .................................................................................................................. 3
4 Performance Specifications ................................................................................................ 3
5 LM3445 120VAC, 8W Isolated Flyback LED Driver Demo Board Schematic ...................................... 5
6 LM3445 Device Pin-Out .................................................................................................... 7
7 Bill of Materials .............................................................................................................. 7
8 Demo Board Wiring Overview ............................................................................................. 9
9 Demo Board Assembly ................................................................................................... 10
10 Typical Performance Characteristics .................................................................................... 11
11 PCB Layout ................................................................................................................. 14
12 Transformer Design ....................................................................................................... 15
13 Experimental Results ..................................................................................................... 16
13.1 Non-Dimming Performance ..................................................................................... 16
13.2 Dimming Performance ........................................................................................... 17
13.3 Power Factor Performance ...................................................................................... 19
14 Circuit Operation With Rotary Forward Phase TRIAC Dimmer ..................................................... 20
15 Circuit Operation With Reverse Phase TRIAC Dimmer .............................................................. 21
16 Electromagnetic Interference (EMI) ..................................................................................... 22
17 Thermal Analysis .......................................................................................................... 24
18 Circuit Analysis and Explanations ....................................................................................... 26
18.1 Injecting Line Voltage into Filter-2 (Achieving PFC > 0.95) ................................................. 26
List of Figures
1 Demo Board ................................................................................................................. 4
2 LED Current vs. Input Voltage (using Dimmer)......................................................................... 4
3 Demo Board Schematic.................................................................................................... 6
4 LM3445 Device Pin-Out.................................................................................................... 7
5 Wiring Connection Diagram ............................................................................................... 9
6 Top View.................................................................................................................... 10
7 Bottom View................................................................................................................ 10
8 Efficiency vs. Line Voltage Original Circuit............................................................................. 11
9 Efficiency vs. Line Voltage Modified Circuits .......................................................................... 11
10 LED Current vs. Line Voltage Original Circuit ......................................................................... 11
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SNVA429C–August 2010–Revised May 2013 AN-2034 LM3445 -120VAC, 8W Isolated Flyback LED Driver
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