FA5502PM Fuji Electric holdings CO.,Ltd, FA5502PM Datasheet - Page 21

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

(7) Prevention of intermittent switching of low
(7-1) Lowering the dc gain of voltage error amplifier
(7-2) Connection of Rofst
(7-3) Change of compensation network of voltage
(8) Improvement of operation around zero
(8-1) Connection of Rofst
(8-2) Increase of Dmax
FA5502P/M
some application. It may be avoided by the following
methods. They are given as typical preventions of
intermittent switching and may not be effective for
certain
characteristics of PFC converter. Sufficiently check the
operation on a actual circuit.
Concretely, reduce the resistance of R4 on the circuit
in Fig.6 in "8-(2)". Note that, in this case, the line and
load regulation will be lowerd.
Concretely, connect a resistor Rofst of 1M
between REF pin and IIN- pin as shown in Fig.25.
Note that, in this case, the input current will be
distorted and the power factor will be slightly lowered.
voltage error amplifier with the circuit in Fig.24 in
"9-(6)”. Note that, in this case, the transient response
may be different from that before the change.
the line current around zero crossing. This surge
current may cause harmonic current especially in high
order. In such a case, the following method may
suppress this surge current.
As shown in Fig.25, connect resistor Rofst between
REF pin and IIN- pin. Use a resistor of about 1M
higher.
such a network of R
that C
An intermittent switching below 10 Hz may occur in
Lower the dc gain of the voltage error amplifier.
Adjust the offset of the current error amplifier.
Replace the compensation network connected to the
In some application, surge current may appear on
Increase the maximum duty cycle. Concretely, select
(See (9) Oscillator setting and maximum duty cycle.)
frequency
crossing
error amplifier
T
is a smaller and R
circuits.
R5
C3
Fig.25 Connection of Rofst
Rofst
They
T
and C
C2
T
13
a larger.
2
1
may
T
IIN-
IFB
REF
for the same frequency
FA5502
also
affect
or higher
the
or
(9) Oscillator setting and maximum duty
(10) Npte in use of SYNC pin
(11) Prevention of malfunction by noise
(11-1) REF pin
(11-2) IDET pin
(11-3) OVP pin
(11-4) CT pin
21
the OUT pin to be Low during the oscillator discharge
period. The oscillator discharge period changes with
R
and R
discharge period shortens and the maximum duty
cycle increases by minimizing C
(See characteristics curve.) The maximum duty cycle
may affect the input current waveform, particularly at
zero crossing. Therefore, sufficiently test C
before determining them. Too small C
a stable oscillation on account of noise, etc. It should
be 330pF or more according to the recommended
condition.
waveform or if has a trapezoid shape, a differentiating
circuit of RC network may not satisfy the waveform
condition shown in Fig.3 in “8-(1)”. In such a case,
convert the external synchronizing signal into a square
waveform by means of comparator or the like before
inputting it to a differentiating circuit of RC network.
(See "8-(1) Oscillator section".)
IC. If noise causes malfunction, see the notes
summarized below and confirm in actual circuit to
prevent malfunction.
connected as close to IC as possible so as to
suppress noise effectively.
IC as voltage source and reference voltage. A noise
applied to this pin may cause a malfunction of IC. To
suppress a malfunction by noise, connect a capacitor
of 0.1 F or more between REF pin and GND.
induvtor current, the overcurrent limiting circuit may
suffer from a malfunction. In such a case, insert an RC
filter at IDET pin.
connect a noise suppressing capacitor between OVP
and GND pins.
output, may disturb the oscillation frequency or OUT
pulses. The wiring between oscillator timing capacitor
C
suppress the noise to CT pin. Pay utmost attention to
T
T
The maximum duty cycle is determined by forcing
If the external synchronizing signal is not a square
Noise applied to each pin may cause malfunction of
Capacitor
REF pin voltage is supplied to each components of
If a noise is applied to IDET pin which detects
If a noise applied to OVP pin causes a malfunction,
A noise applied to CT pin, which is an oscillator
cycle
and C
and IC must be as short as possible so as to
T
providing the same oscillation frequency, the
T
Quality is our message
Quality is our message
Quality is our message
Quality is our message
connected to CT pin. On a network of C
for
noise
suppressing
T
and maximizing R
T
could not give
should
T
and R
be
T
T
T
.