FA5550 Fuji Electric holdings CO.,Ltd, FA5550 Datasheet - Page 10

• Manufacturer Part Number: FA5550
• Description: Power Factor Correction Converter
• Manufacturer: Fuji Electric holdings CO.,Ltd

(1) No.1 pin （ FB pin ）
Function:
(a) Input of feedback signal for setting output voltage
(b) Detection of FB pin short circuit
(c) Detection of output over-voltage condition
How to use:
(a) Input of feedback signal
・ How to connect:
・ Operation
(b) Detection of FB pin short circuit:
・ How to connect:
The same method as the input of the feedback signal
・ Operation
When the input voltage of the FB pin comes down under 0.3V
because of such as a short circuit fault in R2, etc. in the
voltage-dividing resistance circuit, the comparator (SP) turns
over its output to make stop the output of the IC.
(c) Detection of an output over-voltage:
・ How to connect:
・ Operation
Function:
(a) Phase compensation of the built-in ERRAMP output
(b) ON/OFF operation with external signals
How to use:
(a) Phase compensation of the built-in ERRAMP output
・ How to connect:
・ Operation
(b) ON/OFF with external signals
・ How to connect:
・ Operation
Rev.1 Feb-2008
(2) No.2 pin (COMP pin)
10. Descriptions for use of each pin
Connection of voltage-divided part into voltage-dividing
resistance circuit for setting output voltage
Vout, an output voltage of PFC, is controlled so that the
voltage input to the FB pin divided by using resistance
corresponds to the internal reference voltage (2.5V).
The same method as the input of the feedback signal
The usual voltage of FB pin operates with 2.5V almost the
same to the reference voltage of the error amplifier. When the
voltage of FB pin rises due to some sort of causes and
outreached the reference voltage (1.09*VREF) of the
comparator, the comparator (OVP) turns over its output in the
meantime to stop OUT pulse. When the output voltage comes
back to the normal value, OUT pulse is outputted again.
Connect C and R between COMP and GND as shown in Fig. 6.
Connect C and R to COMP pin so that FB output does not
have the ripple element which is the second harmonic of AC
line.
Pull down COMP pin with an external signal.
By pulling down COMP pin lower than VthCOMP, the output
pulse from the IC is interrupted.
FA5550 / 51
10
R1
R2
Vout
ERRAMP
Fig.7 COMP pin ON/OFF circuit
ERRAMP
FB
Fuji Electric Device Technology
Fig.6 COMP pin circuit
MUL
Fig.5 FB pin circuit
1
MUL
2
C1
COMP
ERRAMP
2
R3
VREF(2.5V)
VOVP(1.09*VREF)
COMP
C2
C1
ON/OFF
VSP(0.3V)
Signal
COMP
OVP
Q1
SP
C2
R3
R5
R4