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參數(shù)資料
| 型號： | AN8027 |
| 廠商： | PANASONIC CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | AC-DC switching power supply control IC with standby mode |
| 中文描述： | 1 A SWITCHING CONTROLLER, 80 kHz SWITCHING FREQ-MAX, PSIP9 |
| 封裝： | PLASTIC, SIP-9 |
| 文件頁數(shù)： | 13/28頁 |
| 文件大?。?/td> | 301K |
| 代理商： | AN8027 |
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13
Voltage Regulators
AN8027, AN8037
I
Application Notes (continued)
[1] Operation descriptions (continued)
4.
Power supply output control system (I
FB
: feedback)
Constant-voltage control of the power supply output is performed by changing the on- and off-period of the
power MOSFET. The on- and off-period are controlled with the photocoupler connected to the FB pin (Pin 9). The
photocoupler adjusts the current at the FB pin according to the signal that is output from the output voltage detection
circuit on the secondary side and changes the V
FB
voltage. Refer to figure 4.
The higher the AC input voltage is and the lower the load current is, the higher the current flow from FB pin,
the higher the V
FB
voltage, and the shorter the on-period (or longer the off-period in standby mode) will be.
Note that a current cancellation capacity of about 200
μ
A is provided to compensate for the dark current of the
photocoupler. Refer to figure 5.
Figure 4. Power output control
Figure 5. Feedback current vs. V
FB
characteristics
5
4
3
2
1
00
0.2
0.4
0.6
0.8
1.0
V
FB
(V)
I
FB
(mA)
Dark current
Primary side
Secondary side
Power output on
secondary side
AN8027, AN8037
7.1 V
200
μ
A typ.
V
FB
20 k
PC
9
FB
1 : 5
PC
AN1431T/M
Soft start current
is discharged
when the IC is
not in operation.
A minimum of 1 mA
is required for biasing
the AN1431T/M.
5.
Soft start
When a power supply is started, it starts up in an overload state due to the capacitor connected to the power
supply output. At that moment, the output voltage is low. Therefore, the IC in usual voltage regulation tries to start
up the power output circuit at a maximum duty cycle. Although the IC tries to limit the current by the pulse-by-
pulse overcurrent protection at the CLM pin, the pulses cannot be suppressed to zero due to delays caused by the
filter. As a result, high current flows to the main switch (i.e., power MOSFET) and to the diode on the secondary
side. Therefore, in the worst case, these components are totally broken. To prevent this, soft start is used to
suppress inrush currents at power supply startup.
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相關(guān)代理商/技術(shù)參數(shù) |
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| AN-8027 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:PFC+PWM Combination Controller |
| AN8027/AN8037 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:AN8027. AN8037 - AC-DC switching power supply control IC with standby mode |
| AN8028 | 制造商:PANASONIC 制造商全稱:Panasonic Semiconductor 功能描述:Self-excited RCC pseudo-resonance type AC-DC switching power supply control IC |
| AN8029 | 制造商:Panasonic Industrial Company 功能描述:IC PANASONIC |
| AN8031 | 制造商:PANASONIC 制造商全稱:Panasonic Semiconductor 功能描述:Active filter control IC |
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