LT1249
Power Factor Controller
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
Standard 8-Pin Packages
High Power Factor Over Wide Load Range
with Line Current Averaging
International Operation Without Switches
Instantaneous Overvoltage Protection
Minimal Line Current Dead Zone
Typical 250碌A Start-Up Supply Current
Rejects Line Switching Noise
Synchronization Capability
Low Quiescent Current: 9mA
Fast 1.5A Peak Current Gate Driver
The 8-pin LT
廬
1249 provides active power factor correc-
tion for universal offline power systems with very few
external parts. By using fixed high frequency PWM current
averaging without the need for slope compensation, the
LT1249 achieves far lower line current distortion, with a
smaller magnetic element than systems that use either peak
current detection or zero current switching approach, in
both continuous and discontinuous modes of operation.
The LT1249 uses a multiplier containing a square gain
function from the voltage amplifier to reduce the AC gain
at light output load and thus maintains low line current
distortion and high system stability. The LT1249 also
provides filtering capability to reject line switching noise
which can cause instability when fed into the multiplier.
Line current dead zone is minimized with low bias voltage
at the current input to the multiplier.
The LT1249 provides many protection features including
peak current limiting and overvoltage protection. The
switching frequency is internally set at 100kHz.
While the LT1249 simplifies PFC design with minimal
parts count, the LT1248 provides flexibilities in switching
frequency, overvoltage and current limit.
APPLICATIO S
s
s
Universal Power Factor Corrected Power Supplies
Preregulators up to 1500W
, LTC and LT are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRA
VA
OUT
5
V
SENSE
7.5V
6
I
AC
4
+
M
OUT
3
R
MOUT
4k
I
A
I
B
32k
MULTIPLIER
I I
I
M
=
A B
2
200碌A
15碌A
1V
+
2
CA
OUT
2
EA
鈥?/div>
V
CC
16V/10V
+
鈥?/div>
鈥?/div>
I
M
250碌A MAX
+
CA
鈥?/div>
+
+
g
m
= 1/3k
RUN
0.7V
M1
鈥?/div>
+
SYNC
OSC
20碌A
35pF
1249 BD
44碌A
22碌A
4k
鈥?/div>
U
GND
1
7.5V
V
REF
RUN
V
CC
7
R
S
Q
GTDR
8
16V
W
U
1
LT1249IS8 產品屬性
LT1249
100
集成電路 (IC)
PMIC - PFC（功率因數修正）
-
平均電流
100kHz
250µA
15.5 V ~ 27 V
-40°C ~ 125°C
表面貼裝
8-SOIC（0.154"，3.90mm 寬）
8-SOIC
管件
LT1249IS8相關型號PDF文件下載
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