LT1508CSW Linear Technology, LT1508CSW Datasheet - Page 14

IC PWM/POWER FACTOR CNTRLR20SOIC

LT1508CSW

Manufacturer Part Number
LT1508CSW
Description
IC PWM/POWER FACTOR CNTRLR20SOIC
Manufacturer
Linear Technology
Datasheet

Specifications of LT1508CSW

Mode
Average Current
Frequency - Switching
100kHz
Voltage - Supply
27V
Operating Temperature
0°C ~ 100°C
Mounting Type
Surface Mount
Package / Case
20-SOIC (7.5mm Width)
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Current - Startup
-
14
LT1508
APPLICATIONS
An LT1431 reference/amplifier coupled to a low cost
optoisolator closes the loop from secondary side to pri-
mary side. Efficiency versus power and line voltage is
shown in Figure 10. The PFC preregulator alone has
efficiency numbers between 90% and 97% over line and
load.
A 3-turn secondary added to the 70-turn primary of T1
bootstraps V
requirement as well as about 39mA to cover the gate
current of the three FETs and high side transformer. A
0.15 sense resistor is used to sense input current and
CC
to about 15V supplying the chip’s 13mA
U
INFORMATION
U
W
90
85
80
75
70
90
U
132
Figure 10
V
RMS
180
servo to the command created by the outer voltage and
multiplier. Thus the input current follows the input line
voltage, and changes as necessary, in order to maintain
constant bank voltage. The forward converter sees a
voltage input of 382VDC unless the line voltage drops out,
in which case the 330 F main capacitor discharges to
240VDC before the PWM stage is shut down. Compared to
a typical off-line converter, the effective input voltage
range of the forward converter is much smaller, simplify-
ing the design. Additionally, the higher bus voltage pro-
vides greater hold-up times for given capacitor size.
200W/300W
100W
30W
1508 • F1O
250

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