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FAN4803CP-1 Datasheet(数据表) 7 Page - Fairchild Semiconductor

部件型号  FAN4803CP-1
说明  8-Pin PFC and PWM Controller Combo
下载  12 Pages
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制造商  FAIRCHILD [Fairchild Semiconductor]
网页  http://www.fairchildsemi.com
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FAN4803CP-1 Datasheet(HTML) 7 Page - Fairchild Semiconductor

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PRODUCT SPECIFICATION
FAN4803
REV. 1.2.3 11/2/04
7
Internal Voltage Ramp
The internal ramp current source is programmed by way of
the VEAO pin voltage. Figure 7 displays the internal ramp
current vs. the VEAO voltage. This current source is used to
develop the internal ramp by charging the internal 30pF +12/
–10% capacitor. See Figures 10 and 11. The frequency of the
internal programming ramp is set internally to 67kHz.
PFC Current Sense Filtering
In DCM, the input current wave shaping technique used by
the FAN4803 could cause the input current to run away.
In order for this technique to be able to operate properly
under DCM, the programming ramp must meet the boost
inductor current down-slope at zero amps. Assuming the
programming ramp is zero under light load, the OFF-time
will be terminated once the inductor current reaches zero.
R
f
× C
COMP
COMP
1
(3)
(4)
2
× π ×
R
Hz
× nF
k
COMP
1
62 8
× 30
16
330
.
C
f
R
ZERO
COMP
1
2
× π ××
10
C
Hz
×
k
µF
ZERO
1
628
× 3
330
016
.
.
=
==
=
=
=
Figure 4. Voltage Control Loop
FAN4803
FAN4803
IVEAO
34
µA
IOUT
VO
220
µF
RLOAD
667
330k
11.3M
0.15
µF
15nF
POWER
STAGE
COMPENSATION
VEAO
∆VEAO +
Figure 5. Voltage Loop Gain
60
40
20
0
–20
–40
–60
FREQUENCY (Hz)
0.1
10
1000
1
100
Power Stage
Overall Gain
Compensation
Network Gain
Figure 6. Voltage Loop Phase
0
50
100
150
200
FREQUENCY (Hz)
0.1
1
10
1000
100
Power Stage
Overall
Compensation
Network
Figure 7. Internal Ramp Current vs. VEAO
50
40
30
20
10
0
VEAO (V)
02
7
5
13
6
4
FF @ –55ºC
TYP @ –55ºC
TYP @ 155ºC
SS @ 155ºC
TYP @ ROOM TEMP




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