FA5502PM Fuji Electric holdings CO.,Ltd, FA5502PM Datasheet - Page 15

• Manufacturer Part Number: FA5502PM
• Description: Power Factor Correction
• Manufacturer: Fuji Electric holdings CO.,Ltd

(4) PWM comparator
FA5502P/M
Oscillator output V
V
comparator output goes High and OUT pin also goes
High. Note that, during the oscillator discharge period,
OUT pin is forced to be Low, thereby determining the
maximum duty cycle. (see characteristics curve).
internal
capacitor C4 for soft start. Priority is given to V
V
comparator timing chart.
IFB
IFB
Fig.9 shows the configuration of PWM comparator.
G1
CS pin (pin 11) is a soft start pin. When start up, an
are compared. While V
whichever
C4
Fig.8 Voltage gain of CUR.AMP
constant
CS
Fig.9 PWM comparator circuit
11
7.5V
V
CS
CT
is
current
and current error amplifier output
lower.
V
V
Z
PWM.COMP
IFB
CT
11µA
(11µA
Fig.10
CUR.AMP output
(IFB pin)
Oscillator output
(CT pin)
CT
(typ.))
< V
P
Output
circuit
shows
IFB
frequency
,
charges
PWM
CS
PWM
or
(5) Multiplier
15
OUT
pin
OUT
pin
V
V
V
V
V
V
The rectified line voltage is divided down by resistor
and monitored by VDET pin (pin 3). Considering the
dynamic range of multiplier, design the R6 and R7 in
Fig.11 so that the peak voltage at VDET pin within a
range from 0.65V to 2.4V over the entire range of line
voltage. VFB pin is normally above 1.55V and, at this
status, multiplier output voltage Vm is approximately
expressed by:
Where
circuit for light load operates.
11 k
CUR.
multiplier, see characteristics curve.)
IFB
CT
CS
CS
IFB
CT
The multiplier generates a current reference signal.
When VFB pin is lower than 1.55V, compensation
As shown in Fig.7, Vm is applied via a resistor of
Normal operation
Vm
K: Output voltage factor (multiplier section)
R7
R6
Operation with Dmax
Fig.10 PWM comparator timing chart
to inverting input (IIN-) of current error amplifier
AMP.
V
. 1
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IN
25
3
(For
VDET
Fig.11 Multiplier circuit
K
(
V
V
VDET
VFB
input/output
V
VFB
. 1
MUL
55
)
V
ER.AMP output
(VFB pin)
VDET
Vm
characteristics
• • • • • (8)
t
t
t
t
of