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參數(shù)資料
| 型號(hào)： | NCP1239 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | Low−Standby High Performance PWM Controller |
| 文件頁(yè)數(shù)： | 29/38頁(yè) |
| 文件大?。?/td> | 1145K |
| 代理商： | NCP1239 |
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NCP1239
http://onsemi.com
29
t
Actual Peak Current
High Input
Voltage
Low Input
Voltage
Vopl/Rsense
Wished Maximum
Peak Current
I
HL
I
LL
Figure 49.
The propagation delay ( t) produces overcurrents ( I
LL
at low line, I
HL
at high line in the figure) that are proportional to the input
voltage. As a consequence, the actual maximum current and then the power limit gets higher when the AC line increases.
t
Imax
Vocp
Rsense
Vin
t
Lp
, where Vin is the converter
input voltage and t is the total delay in turning off the
power switch.
The NCP1239 enables the compensation of the second
term in the Imax equation for a precise limitation of the peak
current. A current source (I
pin9
) proportional to the Pin 5
voltage flows out of Pin 9. Since Pin 5 receives a voltage
proportional to the input voltage for brownout detection,
I
pin9
is proportional to the input voltage too. An external
resistor Rcomp can be connected between Pin 9 and the
positive terminal of Rsense, so that Pin 9 monitors the
following voltage:
Vpin9
[Rsense
(Ip
Ipin9)]
(Rcomp
Ipin9)
I
pin9
being small compared to the inductor current, the Pin 9
voltage simplifies as follows:
Vpin9
(Rsense
Ip)
(Rcomp
Ipin9)
I
pin9
is proportional to the Pin 5 voltage (80 A/V*V
pin5
–
see parameters specification table) and V
pin5
is a portion of
the input voltage (V
pin5
= k
BO
*Vin). Finally,
Ipin9
80 A V
kBO
Vin
The voltage V
pin9
is compared to the internal reference
Vocp. When V
pin9
reaches Vocp, the corresponding
threshold current (Ipth) is deducted from:
Vopl
(Rsense
Ipth)
(Rcomp
80 A V
kBO
Vin)
Then,
Ipth
Vopl
(Rcomp
80 A V
Rsense
kBO
Vin)
Taking into account the overcurrent resulting from the
propagation delays, the maximum current is finally:
Imax
Vocp
Rsense
Rcomp
80 A V
Rsense
kBO
Vin
Vin
t
Lp
Choosing Rcomp so that
Rcomp
80 A V
Rsense
kBO
t
Lp
,
the current limit is made constant in the whole input voltage
range (
Imax = Vocp/Rsense
).
As an example, let’s assume that:
the minimum input voltage for operation is 100 V =>
k
BO
=0.5/100=0.005,
Rsense is 0.25 ,
Lp=500 H,
The total propagation delays are t = 350 ns,
Then, the Rcomp resistor should be:
t
Rsense
80
kBO
Lp
80
Rcomp
350 n
0.005
0.25
500 m
438
.
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相關(guān)代理商/技術(shù)參數(shù) |
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| 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(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)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(kāi)關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)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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