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參數(shù)資料
| 型號： | FA3647 |
| 廠商： | FUJI ELECTRIC HOLDINGS CO., LTD. |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | PWM control IC with light load power saving function For Switching Power Supply Control |
| 中文描述： | 輕負載的PWM與節(jié)水開關電源控制功能電源控制IC |
| 文件頁數(shù)： | 14/21頁 |
| 文件大?。?/td> | 406K |
| 代理商： | FA3647 |
FA3641P(N), FA3647P(N)
71
Fig. 21 Vcc voltage at startup with an adequate capacitor
Fig. 22 Vcc voltage at startup with an inadequate capacitor
Fig. 23 Startup circuit (3)
(b) To supply IC consumption current 100
μ
A (max.) (Vcc =10V)
in latch mode:
...................................(12)
(c) To supply IC consumption current 200
μ
A (max.) (Vcc = 17V)
in the off state under the on/off function:
...................................(13)
R1:
Vac: Effective value of AC input voltage [V]
Startup resistance [k
]
If neither the latch nor the on/off functions are used, only the
expression in (11) needs to be satisfied.
In this method, after latch mode operation, smoothing capacitor
C1 in the main circuit supplies current to the IC via the startup
resistor even if the AC input is shut down. Therefore, some time
must elapse before the latch mode is reset.
3. Determining the Vcc capacitor value
To properly start the power supply, a certain value is required
for the capacitor connected to the VCC pin.
Figure 21 shows the Vcc voltage at start-up when a proper
value is given to the capacitor.
When the input power is turned on, the capacitor connected to
the VCC pin is charged via the startup resistor and the voltage
increases. The IC is then in standby state and almost no
current is consumed. (Icc < 2
μ
A)
Thereafter, Vcc reaches the ON threshold voltage of UVLO and
the IC begins operation.
When the IC begins operation to make output, the IC operates
based on the voltage from the auxiliary winding. When the IC is
just starting up, however, it takes time for the voltage from the
auxiliary winding to rise enough, and Vcc drops during this
period.
Determine the Vcc capacitor value so that Vcc will not drop
down to the OFF threshold voltage of UVLO during this period.
If the Vcc capacitor value is too small, Vcc will drop to the OFF
threshold voltage of UVLO before the auxiliary winding voltage
rises enugh. If so, Vcc repeatedly goes up and down between
the UVLO threshold voltages, and the power supply cannot
start up. (Figure 22)
4. Shortening the startup period
Increasing the resistance of the startup resistor to reduce loss
prolongs the startup period. Figure 23 shows a circuit for
shortening the startup period. The C2 capacitance is
decreased to shorten the startup period and, after the IC starts
up, power is supplied from C3.
5. Setting soft start period and OFF latch delay independently
Figure 24 shows a circuit for setting the soft start period and
OFF latch delay independently. In this circuit, capacitance CS
determines the soft start period, and capacitance CL
determines the OFF latch delay.
If the overload shutdown or overvoltage shutdown functions
raise the CS pin voltage to around 5V, zener diode Zn becomes
conductive to charge capacitor CL. The OFF latch delay can be
thus prolonged by capacitance CL.
Fig. 24 Independent setting of soft start period and
OFF latch delay
When the capacitor value is adequate
When the capacitor value is inadequate
R1 [k
] <
2
Vac
–
10
0.1
R1 [k
] <
2
Vac
–
17
0.2
相關PDF資料 |
PDF描述 |
|---|---|
| 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 |
| FA3675F | For Switching Power Supply Control |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| 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: |
| FA3647P | 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 |
| FA3647P-D1 | 制造商:Fuji Electric 功能描述: |
| FA365 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:THIN SMD HIGH-FREQUENCY CRYSTAL UNIT |
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