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參數(shù)資料
| 型號： | FA3641P |
| 廠商： | FUJI ELECTRIC CO LTD |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | PWM control IC with light load power saving function For Switching Power Supply Control |
| 中文描述： | 1 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | DIP-8 |
| 文件頁數(shù)： | 15/21頁 |
| 文件大?。?/td> | 406K |
| 代理商： | FA3641P |
FA3641P(N), FA3647P(N)
72
6. Overvoltage protection using the VCC pin
These ICs contain an overvoltage protection function detecting
the Vcc voltage using internal ZD (See item 6 in
“
Description of
each circuit
”
). If Vcc voltage exceed about 32V, the current of
13mA flows through the internal ZD and the overvoltage
protection function operates.
After this protection function operates, the IC continues to
consume the large current if high voltage continues to be
applied to the Vcc pin. Mind that total IC loss does not exceed
the rating.
If the voltage source applied to Vcc pin has relatively high
impedance and cannot supply the current of 13mA, overvoltage
protection function does not operate. But the internal ZD
maintains the Vcc voltage 32V or less and protects the IC.
7. Overvoltage protection using CS pin
These ICs contain the overvoltage protection function detecting
Vcc voltage. However, the threshold voltage is fixed. Adding a
circuit to CS pin enables the overvoltage protection detecting
desired voltage.
7.1 Detecting on secondary side
Figure 25 shows the overvoltage shutdown circuit based on the
signal from the secondary side. The optocoupler output
transistor is connected between the CS and Vcc pins. When
the output voltage is put in the overvoltage state, the
optocoupler output transistor goes on to raise the CS pin
voltage via resistor R2. When the CS pin voltage exceeds the
reference voltage (8.5V) of comparator C2, the output of the
comparator C2 goes high to turn off the 5V REF circuit.
Accordingly, the IC enters the OFF latch mode and shuts the
output down. The IC consumes current 45
μ
A (typ) (Vcc = 10V)
in latch mode. This current must be supplied via startup
resistor R1.
The overvoltage protection circuit can be reset by lowering the
supply voltage Vcc to below 9.0V or forcing the CS pin voltage
below 7.9V.
In normal operation, the CS pin voltage is clamped by the 4V
zener diode with maximum sink current 50
μ
A . Therefore, to
raise the CS pin voltage to 8.5V or more, 50
μ
A or a higher
current needs to be supplied from the optocoupler. Set the
current input to the CS pin to 1mA or less.
7.2 Detecting on primary side (detecting Vcc voltage)
To attain overvoltage protection, the CS pin voltage is forcibly
raised from outside the IC until it exceeds the reference voltage
(8.5V) of the internal comparator C2. When the reference
voltage is exceeded, the IC enters latch mode and shuts the
output down. Connect a zener diode (ZD) and resistor between
the Vcc and CS pins as shown in Figure 26. When the Vcc
voltage exceeds about ZD voltage + 8.5V, the ICs enter the
OFF latch mode and shut the output down. If Vcc remains high
even after shutdown and current is input to the CS pin, set the
current to 1mA or lower.
Set the zener voltage of the ZD connected to the CS pin higher
than the UVLO ON threshold voltage. Startup is disabled below
this voltage.
Figure 27 shows another circuit for enabling latch mode
shutdown by detecting a desired Vcc voltage using the CS pin.
In this circuit, overvoltage shutdown works when the Vcc
voltage is about the same as the ZD voltage.
For this circuit also, use a ZD voltage higher than the UVLO ON
threshold voltage. Set the current flowing into the CS pin to
1mA or lower.
Fig. 25 Overvoltage shutdown circuit (1)
Fig. 26 Overvoltage shutdown circuit (2)
Fig. 27 Overvoltage shutdown circuit (3)
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| FA3647 | PWM control IC with light load power saving function For Switching Power Supply Control |
| FA3647N | PWM control IC with light load power saving function For Switching Power Supply Control |
| FA3647P | PWM control IC with light load power saving function For Switching Power Supply Control |
| FA365 | THIN SMD HIGH-FREQUENCY CRYSTAL UNIT |
| FA-365 | THIN SMD HIGH-FREQUENCY CRYSTAL UNIT |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| FA3641P_00 | 制造商:FUJI 制造商全稱:Fuji Electric 功能描述:PUJI Power Supply Controllc |
| FA3641P-D1 | 制造商:Fuji Electric 功能描述: |
| FA3647 | 制造商:FUJI 制造商全稱:Fuji Electric 功能描述:PWM control IC with light load power saving function For Switching Power Supply Control |
| FA3647N | 制造商:FUJI 制造商全稱:Fuji Electric 功能描述:PWM control IC with light load power saving function For Switching Power Supply Control |
| FA3647N-H1 | 制造商:Fuji Electric 功能描述: |
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