FA5502PM Fuji Electric holdings CO.,Ltd, FA5502PM Datasheet - Page 20

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

(4) Output overvoltage at light load
(5) Notes for setting the output voltage and
FA5502P/M
R12
R11
for preventing an overvoltage when light or no load.
Though, according to the condition, this circuit may not
compensate enough and overvoltage may occur. To
prevent overvoltage, the following condition must be
satisfied.
depending on the line voltage or load current.
Therefore, the output voltage may be lower than the
voltage calculated by expression (1) in "8-(2)". When
setting the output voltage, sufficiently evaluate it on an
actual circuit.
overvoltage setting is fixed at 1.058 times the output
voltage setting.
output
additionally to OVP pin as shown in Fig.23.
for setting the output voltage has troubled, the
overvoltage limiting circuit operates properly, thereby
preventing the output voltage from rising excessively.
A compensation circuit for light load is incorporated
- Noise filter resistor Rn connected to IDET pin (pin
- As shown in Fig.22, DC gain limiting resistor R10
In the actual circuit, the output voltage drops
On the circuit shown in Fig.6 in "8-(2)", the
For setting the overvoltage independently of the
On the circuit in Fig.23, even if the voltage divider
overvoltage limit
Fig.22 Prevention of overvoltage at light load
16) must be below 27 .
for current error amplifier must not be connected
between IFB pin (pin 1) and IIN- pin (pin 2).
Fig.23 Independent setting of OVP limit
R2
R1
R10
voltage
Vo
R3
R4
setting,
C3
R5
C1
C2
connect
5
6
4
VFB
VIN-
OVP
2
1
IIN-
IFB
FA5502
ER.AMP
OVP.COMP
Vr
=1.55V(typ.)
Vp
=1.058Vr(typ.)
voltage
divider
MUL
F.F.
(6) Improvement of output voltage regulation
20
Fig.24 ER.AMP circuit for improvement of regulation
with input voltage or load current on the circuit in Fig.6
in "8-(2)", thereby causing a problem in some case. In
such a case, the circuit in Fig.24 may improve the
regulation.
Voltage gainAv2 of this circuit is expressed by:
Referring the following relations or the example
applied to “10 Example of application circuit”, adjust
the values on actual circuit.
characteristics at a steady status but also transient
response to line voltage and load current may change.
Before
sufficiently.
R2
R1
As stated in “9-(5)”, the output voltage may change
Optimum values depend on an each circuit.
- Set the voltage gain Av2 at 100 or 120 Hz almost
- Determine C8, C9 and R13 so as to satisfy the
In
Vo
the same as before changing the compensation
circuit.
following relations.
• Set fz determined by the following expression to
• Set fp determined by the following expression so
*Example of values applied to “10 Example of
(These values are given as references and not
intended for guaranteeing the operation in any
circuit.)
A
V
this
several Hz to several ten Hz.
that the fp/fz ratio is about 10.
application circuit”
f
fp
2
Z
R3
determining
C8=0.033µF, C9=0.15µF,
R13=330kΩ, R3=100kΩ
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2
j
2
circuit,
C8
((
C
C
C
1
9
8
1
R
13
R
C
13
1
R13
C9
) 9
not
the
j
• • • • • (19)
j
C
C
only
5
6
9
C
VFB
VIN-
circuit
8
C
R
C
13
8
C
8
9
the
C
C
Vr
=1.55V(typ.)
R
9
9
values,
13
• • • • • (20)
output
R )
3
• • • (18)
evaluate
MUL
voltage