MAX16841ASA+T Maxim Integrated Products, MAX16841ASA+T Datasheet - Page 9

• Manufacturer Part Number: MAX16841ASA+T
• Description: LED Drivers Wide Input Offline LED Driver with Dim
• Manufacturer: Maxim Integrated Products

Circuit components R11, R12, C15, Q6, Q7, R13, and
R14 are used to control the input current. Q6 and Q7
are matched transistors. The voltage on C15 represents
the average input voltage. The average voltage is then
used to control the current in the current-mirror circuit
formed by R12, R13, R14, Q6, and Q7. The current
flowing into R12 is approximately proportional to the
Figure 1. Nonisolated (Buck) Topology
D3
AC1
AC2
18V
R6
DB-
DB+
R4
F1
Q5
G
Controller IC for Dimmable Offline LED Lamps
R26
R11
R12
R13
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Q6
DB+
C15
R14
REFI
Q7
L1
R1
R2
L2
C1
R10
R8
R9
DB+
C16
1
C3
R7
DB-
D1
R3
DB+
3
4
Q3
R16
R17
C4
L3
Q1
2
REFI
4
3
1
2
U1
D2
C2
R5
DIMOUT
TH
REFI
COMP
voltage across C15 and is now reflected on the collector
of Q6, and sinks the same amount of current from the
collector of Q7 that flows into R12. Inside the device is
a 50FA current source. The current flowing into R16 sets
the input current, or the average current flowing into R20.
The circuit tries to keep the input power over the line volt-
age almost constant.
MAX16841
R22
C14
D4
G
NDRV
GND
CS
IN
C9
Q2
8
7
6
5
R34
C8
IN
D6
15V
R18
R23
R24
C5
D12
R21
C13
D10
MAX16841
C10
Q4
L5
R20
C11
C12
LED+
LED-