LT1248_15 Datasheet, PDF (1/12 Pages) Linear Technology – Power Factor Controller

FEATURES
s _{High Power Factor Over Wide Load Range}
with Line Current Averaging
s _{International Operation Without Switches}
s _{Instantaneous Overvoltage Protection}
s _{Minimal Line Current Dead Zone}
s _{Typical 250µA Start-Up Supply Current}
s _{Rejects Line Switching Noise}
s _{Synchronization Capability}
s _{Low Quiescent Current: 9mA}
s _{Fast 1.5A Peak Current Gate Driver}
U
APPLICATIO S
s _{Universal Power Factor Corrected Power Supplies}
s _{Preregulators Up To 1500W}
LT1248
Power Factor Controller
DESCRIPTIO
The LT^®1248 provides active power factor correction for
universal off-line power systems. By using fixed high
frequency PWM current averaging, without the need for
slope compensation, the LT1248 achieves far lower line
current distortion with a smaller magnetic element than
systems that use either peak-current detection or zero
current switching approaches in both continuous and
discontinuous modes of operation.
The LT1248 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 LT1248 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 LT1248 provides many protection features including
peak current limiting and overvoltage protection, and can
be operated at frequencies as high as 300kHz.
, LTC and LT are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRA
VA_OUT
7
V_REF
9
M_OUT I_SENSE
54
CA_OUT PK_LIM
3
2
V_CC +
16V TO 10V –
2.6V/
EN/SYNC 2.2V
–
10
+
V_SENSE
11
–
EA
I_AC
7.5V
+
6
OVP
7.9V
+
8
–
SS
12µA
5V
13
7.5V
V_REF
RUN
2.2V ₊
7µA
M1
–
I_A
32k
I_B
I_M
=
I_A² I_B
200µA²
I_M
–
ONE SHOT
+
200ns
–
+
–
CA
+
+
–
–
+
0.7V
SYNC
RUN
OSC
R
RQ
S
14
C_SET
12
R_SET
GND
V_CC
1
15
1 6V
16
GTDR
1248 BD
1