FAN4803 Fairchild Semiconductor, FAN4803 Datasheet - Page 9

• Manufacturer Part Number: FAN4803
• Description: To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to continuously decrease the switching frequency at light-load conditions
• Manufacturer: Fairchild Semiconductor

PRODUCT SPECIFICATION
V
V
output voltage, typically a bootstrap winding off the boost
inductor. The V
age exceeds 16V, and terminates the PFC output drive while
disabling the VEAO current sink. Once the VEAO current
sink is disabled, the VEAO voltage will charge unabated,
except for a diode clamp to V
width. Once the V
VEAO sink will be enabled, discharging external VEAO
compensation components until the steady state voltage is
reached. Given that 15V on V
the PFC output, 16V on V
426V.
REV. 1.2.3 11/2/04
CC
CC
is assumed to be a voltage proportional to the PFC
OVP
CC
CC
OVP comparator senses when this volt-
rail has decreased to below 16.2V the
C ZERO
R COMP
CC
V OUT = 400V
corresponds to an OVP level of
CC
CC
, reducing the PFC pulse
corresponds to 400V on
C COMP
RP
Figure 10. Typical Peak Current Mode Waveforms
4
3
I SENSE
VEAO
Figure 11. FAN4803 PFC Control
35 A
Component Reduction
Components associated with the V
typical PFC controller such as the ML4824 have been elimi-
nated. The PFC power limit and bandwidth does vary with
line voltage. Double the power can be delivered from a 220
V AC line versus a 110 V AC line. Since this is a combina-
tion PFC/PWM, the power to the load is limited by the PWM
stage.
R1
V ISENSE
OUTPUT
V C1 RAMP
DRIVE
GATE
5V
–4
C 1
30pF
V I SENSE
V C1
+
–
COMP
RMS
GATE
OUTPUT
and I
RMS
pins of a
FAN4803
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