Texas Instruments LM3448 Evaluation Board LM3448-EDSNEV/NOPB LM3448-EDSNEV/NOPB Datenbogen
Produktcode
LM3448-EDSNEV/NOPB
BRIGHT
DIM
MAINS AC
R1
250 kÖ
DIAC
LOAD
R2
3.3 kÖ
C1
100 nF
TRIAC
LM3448
7.2V
V
CC
UVLO
S
R
Q
PWM
I-LIM
1.27V
ISNS
ASNS
COFF
MOSFET
DRIVER
GND
FLTR1
FLTR2
DIM
VCC
ANGLE DETECT
BLEEDER
DIM DECODER
1.276V
4.9V
RAMP
0V to 4V
THERMAL
SHUTDOWN
50k
370k
1k
RAMP GEN.
5.9 kHz
3V
1V
1V
INTERNAL
REGULATORS
750 mV
33
:
125 ns
LEADING EDGE BLANKING
Tri-State
COFF
LATCH
CONTROLLER
START
4
P
s
BLDR
230
SW
SNOSB51C – SEPTEMBER 2011 – REVISED MAY 2013
SIMPLIFIED INTERNAL BLOCK DIAGRAM
Figure 14. Simplified Block Diagram
THEORY OF OPERATION
The LM3448 contains all the necessary circuitry to build a line-powered (mains powered) constant current LED
driver whose output current can be controlled with a conventional TRIAC dimmer.
driver whose output current can be controlled with a conventional TRIAC dimmer.
OVERVIEW OF PHASE CONTROL DIMMING
A basic "phase controlled" TRIAC dimmer circuit is shown in
.
Figure 15. Basic TRIAC Dimmer
8
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