Texas Instruments LM3448 Evaluation Board LM3448-EDSNEV/NOPB LM3448-EDSNEV/NOPB Datenbogen
Produktcode
LM3448-EDSNEV/NOPB
R16
R10
Linear R
HOLD
insertion circuit
Valley-fill triac holding current
circuit
Triac edge
detect
Reverse phase holding
current
Forward phase
holding current
holding current
C16
R19
Q6
R17
R18
Q4
C11
R11
C3
R6
R7
Q2
R5
C2
D4A
R8
C9
R9
Q3
Q8
R23
D4B
V
CC
V
CC
BLDR
DIM
V
CC
BLDR
V+
V
VF
4
6
R3
BLDR
VCC
LM3448
C7
C8
V+
Q1
D1
R4
V
CC
D3
SNOSB51C – SEPTEMBER 2011 – REVISED MAY 2013
Figure 28. Basic holding current circuit
OPTIMIZING THE HOLDING CURRENT
For optimal system performance and efficiency, only enough holding current should be applied at the right time in
the cycle to keep the TRIAC operating properly. This will ensure no variation or ‘flicker’ is seen in the LED light
output while improving the circuit efficiency. Circuits that do this are outlined individually as blocks in Figure 15.
These circuits are designed to identify the type of phase dimmer in-line with the LM3448, add holding current for
different dimming conditions, or to discharge parasitic capacitances. The objective is to only add enough holding
current as needed regardless if the dimmer is of a forward or reverse phase type. This allows the lighting
manufacturer to optimize efficiency and gain Energy Star approval if desired.
the cycle to keep the TRIAC operating properly. This will ensure no variation or ‘flicker’ is seen in the LED light
output while improving the circuit efficiency. Circuits that do this are outlined individually as blocks in Figure 15.
These circuits are designed to identify the type of phase dimmer in-line with the LM3448, add holding current for
different dimming conditions, or to discharge parasitic capacitances. The objective is to only add enough holding
current as needed regardless if the dimmer is of a forward or reverse phase type. This allows the lighting
manufacturer to optimize efficiency and gain Energy Star approval if desired.
Figure 29. TRIAC Holding Current Circuits
18
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