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參數(shù)資料
| 型號： | NCP1239 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | Low−Standby High Performance PWM Controller |
| 文件頁數(shù)： | 30/38頁 |
| 文件大?。?/td> | 1145K |
| 代理商： | NCP1239 |
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NCP1239
http://onsemi.com
30
Figure 50. NCP1239F
An (averaged) portion of the input voltage is applied to the brownout pin. A current source proportional to this voltage, flows through an
external resistor Rcomp to form an offset proportional to the (average) input voltage. Rcomp should be selected so that the offset compen-
sates the overcurrent sensed by the current sensing resistor Rsense.
+
CLK
to
Current Sense
Comparator
Rcomp
+
5
9
10
Current Sense
to BrownOut
Comparator
BrownOut
Over Power
Limit
Rramp
Rsense
V
comp
0.5V
Vdd
V
pin5
Vin
Rbo1
Rbo2
Cbo
V
comp
= k*R
comp
*V
pin5
80 A/V*V
pin5
S
R
Q
Q
LEB
P
Maximum Duty Cycle Limitation (NCP1239V)
Pin 9 sources a 55 A current. By placing a resistor
between this pin and ground, one builds a voltage that forces
the maximum ontime. Practically the Pin 9 voltage is
compared to the positive ramp of the internal oscillator and
the power switch is allowed to be on, only when the ramp is
below V
pin9
.
Then the maximum ontime is given by:
Cosc
(ton)max
Vpin9
Iosc
where Cosc and Iosc are respectively the capacitor and the
charging current of the oscillator.
V
pin9
being the product of the Pin 9 current by the Pin 9
resistance (R
pin9
– external resistor connected to Pin 9),
results in:
Cosc
IDmax
Iosc
Pin 9 current source.
One can deduct the maximum duty cycle (Dmax) by
dividing by the period T:
Cosc
IDmax
Iosc
T
(ton)max
Rpin9
, where I
Dmax
is the
Dmax
Rpin9
KDmax
Rpin9
where
KDmax
K
Dmax
is specified within the parameters’ table. Please
note that Cosc and Iosc are the internal capacitor and current
(respectively), that set the switching period (T). Hence,
Cosc
Iosc
T
switching frequency.
In the NCP1239F, the maximum dutycycle is fixed (80%
typically).
Cosc
IDmax
T
Iosc
.
is a constant and K
Dmax
is independent of the
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| NCP1239FDR2 | Low−Standby High Performance PWM Controller |
| NCP1239FDR2G | Low−Standby High Performance PWM Controller |
| NCP1239VDR2 | Low−Standby High Performance PWM Controller |
| NCP1239VDR2G | Low−Standby High Performance PWM Controller |
| NCP1271 | Soft−Skip Mode Standby PWM Controller with Adjustable Skip Level and External Latch |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NCP1239D | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Low-Standby High Performance PWM Controller |
| NCP1239F | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:AC-DC Offline Switching Controllers/Regulators |
| NCP1239FDR2 | 功能描述:電流型 PWM 控制器 Low Standby Power RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1239FDR2G | 功能描述:電流型 PWM 控制器 Low Standby Power High Performance PWM RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1239V | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:AC-DC Offline Switching Controllers/Regulators |
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