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参数资料
| 型号： | FA5501AN |
| 厂商： | FUJI ELECTRIC CO LTD |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, PDSO8 |
| 封装： | SO-8 |
| 文件页数： | 7/26页 |
| 文件大小： | 228K |
| 代理商： | FA5501AN |
FA5500AP/AN, FA5501AP/AN
15
Quality is our message
10. Description of each circuit
(1)Error amplifier
The error amplifier controls the output voltage of PFC
converter
to
be
constant.
The
amplifier
is
a
transconductance
type,
which
has
controlled
voltage-to-current gain.
The non-inverting input is internally connected to the
reference voltage of 2.5 V (typ.) and the inverting input
is pinned out to FB pin. The output of PFC converter is
divided down by resistor and monitored by the FB pin.
In
addition, 2.5A
of constant-current source is
internally connected to the FB pin for “Open/short
protection at FB pin”.
The output of error amplifier is connected to the
multiplier. According to the dynamic range of multiplier,
the output voltage of error amplifier ranges from 2.04 V
to 3.54 V (typ.) in normal operation. The lower output
voltage of error amplifier is limited by a diode
connected between the input and the output of error
amplifier, in order to prevent over drop in a transient
condition such as rapid change of the load.
The output voltage of PFC converter contains low
frequency ripple voltage associated with 2X the line
frequency. If too much ripples appear at error amplifier.
output, the PFC converter does not operate stable.
Therefore, a capacitor is connected between COMP
pin (the error amplifier output) and GND so that the
cutoff frequency is set to about 20Hz in order to
suppress the ripple voltage.
2
1
7
COMP
C3
ERRAMP
VREF
=2.5V(typ.)
2.5A
FB
MUL
1.09VREF
OVP
SP
0.3V
OUT
R2
R1
Vo
Fig.5 Error amplifier circuit
(2)Overvoltage limiting circuit
This
circuit
prevents
the
PFC
output
voltage
exceeding the programmed voltage. The output voltage
may exceed the voltage programmed by error amplifier
when the converter starts up or the load changes
rappidly. This circuit limits rise of the output voltage in
such cases.
As shown in Fig. 5, the overvoltage limiting circuit
consists of a comparator (OVP) with threshold voltage,
which is set to 1.09 times of the reference voltage
(VREF).
In
normal
operation
the
FB
pin
voltage
is
approximately 2.5 V, roughly the same as the reference
voltage VREF. If the PFC output voltage rises more
than normal voltage and then the FB pin voltage
reaches the threshold of OVP comparator, the output of
the comparator (OVP) turns to low and stops output
pulses.
When the output voltage comes back to normal,
output pulses appear again.
(3)Open/short protection at FB pin circuit
In the circuit shown in Fig. 6, if FB pin cannot monitor
the PFC output voltage because of a short-circuit
failure in voltage dividing resistor R2 or an open failure
in R1, the PFC output voltage abnormally rises. The
overvoltage limiting circuit does not operate either in
this case, because the output voltage is not monitored.
To avoid these, this IC features a open/short
protection at FB pin circuit. This circuit consists of a
comparator (SP) with threshold voltage of 0.3V (typ.). If
the input voltage of FB pin drops below 0.3V due to a
short-circuit failure in R2 or an open failure in R1, the
output of comparator (SP) turns to low and stops the
output pulses.
In the PFC converter, because of a boost type
topology, the voltage rectified the AC line is supplied to
the PFC output even before the converter operates.
Therefore, if the PFC converter is normal, voltage is
always applied to FB pin and this protection circuit
does not operate.
If an open failure occurs between FB pin and the
voltage divider, the FB pin voltage is forced to lower by
the
2.5A
of
constant
current
source
internally
connected to FB pin. Then comparator (SP) stops the
output pulses in the same way.
If the FB pin voltage comes back to normal after this
protection circuit operates, output pulses appear again.
7
1
OUT
FB
2.5A
0.3V
SP
VFB=0V
R2
R1
Vo
open
short
detect
shutdown
Fig.6
Open/short protection at FB pin
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PDF描述 |
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| FA5500AN | 1 A SWITCHING CONTROLLER, PDSO8 |
| FA5500AP | 1 A SWITCHING CONTROLLER, PDIP8 |
| FA5516N | 1 A SWITCHING CONTROLLER, 143 kHz SWITCHING FREQ-MAX, PDSO8 |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| FA5501AP/AN | 制造商:未知厂家 制造商全称:未知厂家 功能描述: |
| FA5502 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:FA5502P/M is a control IC for a power factor correction system. |
| FA5502M-H1 | 制造商:Fuji Electric 功能描述: |
| FA5502M-TE1 | 制造商:Fuji Electric 功能描述:1.5 A POWER FACTOR CONTROLLER, 150 kHz SWITCHING FREQ-MAX, 16 Pin Plastic SOP 制造商:Fuji Semiconductors, Inc. 功能描述:1.5 A POWER FACTOR CONTROLLER, 150 kHz SWITCHING FREQ-MAX, 16 Pin Plastic SOP |
| FA5502P/M | 制造商:未知厂家 制造商全称:未知厂家 功能描述:FA5502P/M is a control IC for a power factor correction system. |
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