LT1508_15 Datasheet, PDF (1/16 Pages) Linear Technology – Power Factor and PWM Controller

OBSOLETE:
FOR INFORMATION PURPOSES ONLY
Contact Linear Technology for Potential Replacement
FEATURES
I _{PFC and PWM Single Chip Solution}
I _{Synchronized Operation up to 300kHz}
I _{99% Power Factor Over 20:1 Load Current Range}
I _{Voltage Mode PWM}
I _{Instantaneous Overvoltage Protection}
I _{Dedicated Overvoltage Protection (OVP Pin)}
I _{Minimal Line Current Dead Zone}
I _{Typical 250µA Start-Up Supply Current}
I _{Line Switching Noise Filter}
I _{Low Quiescent Current: 13mA}
I _{Fast 1.5A Peak Current Gate Drivers}
I _{Separate Soft Start Control}
U
APPLICATIONS
I _{Universal Power Factor Corrected Power Supplies}
and Preregulators
LT1508
Power Factor and PWM
Controller (Voltage Mode)
DESCRIPTION
The LT ^®1508 is a complete solution for universal off-line
switching power supplies utilizing active power factor
correction. The PFC section is identical to the LT1248 PFC
controller except the EN/SYNC pin is removed because
PFC and PWM are synchronized internally.
The voltage mode PWM section (LT1509 is the current
mode counterpart) contains all the primary side functions
to convert the PFC preregulated high voltage output to an
isolated low voltage output. The PWM duty cycle is
internally limited to 47% (maximum 50%) to prevent
transformer saturation. PWM soft start begins when the
PFC output reaches the preset voltage. In the event of brief
line loss, PWM will be shut off when the PFC output
voltage drops below 73% of the preset value.
, LTC and LT are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRAM
V_CC
16V TO 10V
V_SENSE
14
7.5V
I_AC
9
7.9V
OVP
11
SS1
14µA
16
+
–
–
EA
+
+
–
14µA
SS2
13
PWMOK
VA_OUT
10
7.5V
V_REF
V_REF
12
M_OUT I_SENSE
8
7
RUN
7µA
2.2V +
M1
–
I_A
I_M
25k
I_B
I_M =
I_A2I_B
200µA²
–
CA
+
R
2R
+
1V
–
–
CL
+
7V TO
4.7V
+
–
NOTE: PWM PULSE IS DELAYED BY 55% DUTY CYCLE
AFTER PFC PULSE
19 I_LIM
V_C 18 ^50µA
CA_OUT
6
GND1
3
–
+
+
0.7V
–
R
RQ
RUN _S
OSC
4 C_SET
R_SET 15
55%
DELAY
S
RQ
R
200ns
BLANKING
PK_LIM V_CC
5 17
GTDR1
1
16V
GND2
2
GTDR2
20
16V
1508 BD
1