FA5590 FUJI [Fuji Electric], FA5590 Datasheet - Page 11

• Manufacturer Part Number: FA5590
• Description: FUJI Power Supply Control IC
• Manufacturer: FUJI [Fuji Electric]

AN-016E Rev.1.2
April-2011
9. Outline of circuit operation
This IC is a power-factor correction converter
utilizing a boosting chopper, operating in critical
mode. Hereinafter is outline of the operation
consisting of switching operation and power-factor
correction operation using the circuit diagram
shown in Fig. 1.
This IC performs the switching operation in the
critical mode applying self-oscillation without using
an oscillator. Fig. 2 shows the outline of waveforms
of the switching operation in steady state. The
operation is as follows.
t1.
t2.
t3.
(1) Switching operation
terminal, and when the current becomes zero,
the output of the current detection comparator
becomes High to turn on Q1 after delay given
by the delay circuit, thus moving to the next
switching cycle
Fuji Electric Co., Ltd.
Q1 turns on, the current through inductor (L1)
amplifier
comparator, and when Vramp>Vcomp, Q1
turns off and the output of the ramp generator
drops.
When Q1 turns off, the voltage across L1
inverts and the current through L1 decreases
while the current is supplied to the output side
through D1.
rises from zero. At the timing of Q1 on,
Vramp; output of ramp generator states to
rise.
The current through L1 is detected by Is
Vramp and Vcomp; output of the error
are
(t1).
compared
AC
RTZC
RT
4
3
-10mV
FA5590/91
by
ZCD.comp
Iin
the
Fig.1 Block diagram of operating circuit
FA5590N,FA5591N
Delay
PWM
C1
I
L1
IS
5
-0.6V
Restart
RAMP
OSC
PWM.comp
COMP
OCP.comp
ZCD.comp.
PWM.comp.
Rs
L1
By repeating the operations of t1 ~ t3, the switching
in critical mode is continued.
With the power-factor correction circuit in the
critical mode, the switching frequency is always
changing due to instantaneous values of the AC
input
changes when the input voltage or load changes.
output
11
(Q1 gate)
2
(reset)
Vcomp
output
Vramp
(set)
OUT
Vds
Q1
I
L1
Fig. 2 Switching Operation, Waveforms
voltage.
ERRAMP
Q1
R
S
TIMER
Q
t1
http://www.fujielectric.co.jp/products/semiconductor/
Vds
UVLO
The
D1
Restart
2.5V
7
OVP
OUT
SP
switching
1
FB
t2
Vo
frequency
t3
t1
also