FA5502PM Fuji Electric holdings CO.,Ltd, FA5502PM Datasheet - Page 14

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

(2) Voltage error amplifier and overvoltage
Fig.6 Voltage error amplifier and overvoltage limiting
FA5502P/M
R2
R1
voltage feedback loop for keeping the output voltage
constant.
connected to reference voltage Vr of 1.55V (typ.).
Fig.6 shows the connection. The output voltage is
determined by:
(pin 5). Between VFB pin and VIN- pin, RC network
are connected for loop compensation. The voltage
gain Av is expressed by
Cutoff frequency fc is expressed by:
amplifier output, the PFC converter will not operate
stably. Therefore, determine C1 and R4 so that voltage
gain Av at 100 Hz or 120 Hz will be small enough. Also
set fc to approximately 1Hz to ensure a stable
operation. Practically, the optimum value should be
determined by evaluation in the actual circuit.
the normal voltage, overvoltage limiting comparator
OVP.COMP is incorporated. Its threshold voltage Vp is
as follows:
output overvoltage is limited to 1.058 times (typ.) the
normal output voltage.
V
P
Vo
ER.AMP is an error amplifier which constitutes a
The error amplifier output is pinned out at VFB pin
If 100Hz or 120Hz ripples appear at the error
To limit the output voltage when it has risen above
According to the connection in Fig.6, therefore, the
limiting circuit
circuit
V
A
f
C
O
V
Vr
2
R3
R
R
1
The
C
3
R4
R
(α=1.058(typ)) • • • • • (4)
1
1
1
1
R
R
2
j
R
4
non-inverting
4
C
Vr
C1
1
• • • • • (3)
• • • • • (1)
R
4
5
6
4
VFB
VIN-
OVP
• • • • • (2)
input
ER.AMP
OVP.COMP
Vr
=1.55V(typ.)
Vp
=1.058Vr(typ.)
is
internally
MUL
F.F.
(3) Current error amplifier and overcurrent
Fig.7 Current error amplifier and overcurrent limiting
14
C3
Rn
currnet
detection
current loop to control the line current to a sinusoidal
waveform. As shown in Fig.7, to IIN- pin (pin 2), a
multiplier output is connected via resistor RA as a
current reference signal. Inductor current is monitored
by IDET pin (pin 16). The IDET pin should be used
within the voltage range from 0V to –1.0V in normal
operation. RC network for loop compensation is
connected between IFB pin and IIN- pin. According to
the circuit in Fig.7, the characteristics of voltage gain
AV are as shown in Fig.8. Where,
IDET pin and IFB pin) in Fig.8 is:
adequate phase margin. The output of current error
amplifier is input to PWM comparator.
The optimum value of loop compensation should be
determined by evaluation in actual circuit referring to
application circuit, etc.
comparator OCP.COMP is provided. The threshold
voltage at IDET pin is -1.10V (typ.). If a noise is picked
up at IDET pin, suppress it by connecting Rn and Cn.
Rn must be lower than 27
CUR.AMP is an error amplifier which constitutes a
Voltage gain (G1) between Z and P (gain between
Select C2 and C3 so that P/Z will be about 10 for
To
limiter circuit
R5
circuit
P
G
Z
C2
1
limit
Cn
2
2
20
Quality is our message
Quality is our message
Quality is our message
Quality is our message
R
R
log
1
16
5
5
1
2
1
the
IFB
IIN-
IDET
C
C
. 0
3
75
overcurrent,
4.85k
• • • • • (5)
C
11k
RC
RA
RA
R
5
MUL
C
C
2
2
1
Vm
OCP.COMP
CUR.AMP
.
RB
15k
0.39V
C
C
3
3
• • • • • (7)
overcurrent
• • • • • (6)
REF
5V
F.F.
PWM
comparator
limiting