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參數資料
| 型號： | NCP1381 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | Low−Standby High Performance PWM Controller |
| 文件頁數： | 12/26頁 |
| 文件大?。?/td> | 559K |
| 代理商： | NCP1381 |
NCP1381
http://onsemi.com
12
Figure 12 depicts the internal comparator arrangement.
The FB pin level is permanently compared to a fixed level,
V
skip
, also available on Pin 5 for adjustment. As a result, the
user can wire a resistor to ground and alter the skip level in
case of noise problems. When the FB pin is above V
skip
, the
comparator is transparent to the operation. When the load
becomes lighter, the FB level goes down too. When it
reaches V
skip
, the comparator goes high and resets the
internal flipflop: the driving pulses are stopped. As a result,
V
out
starts to also decrease since no energy transfer is
ensured. Detecting a decay in the output voltage, the FB loop
will react by increasing its level. When the level crosses
V
skip
plus a slight hysteresis, pulses restart again: a ripple
occurs on the FB pin. Please note that the softstart will be
activated every time the skip comparator asks to restart.
Therefore, instead of having sharp skip transitions, a smooth
current rampup can be observed on the current envelope.
This option significantly decreases the acoustical noise.
Figure 13 shows a typical shot and Figure 15 portrays
several skip cycles.
Figure 11. The Skip Cycle Takes Place at Low Peak
Currents Which Guaranties Noise Free Operation
0
100
200
Width
C
Recurrence
Skip Cycle
Current Limit
Maximum
Peak Current
Figure 12. A Resistor to GND can Adjust the Skip
Level
+
V
skip
V
DD
V
DD
5
8
6
30 A
R
25 k
Reset
SoftStart
Activation
Hysteresis = 50 mV
As soon as the feedback voltage goes up again, there can
be two situations as we have seen before: in normal
operating conditions, e.g. when the drain oscillations are
generous, the demagnetization comparator can detect the
45 mV crossing and gives the “green light”, alone, to
reactive the power switch. However, when skip cycle takes
place (e.g. at low output power demands), the restart event
slides along the drain ringing waveforms (actually the valley
locations) which decays more or less quickly, depending on
the L
primary
C
parasitic
network damping factor. The situation
can thus quickly occur where the ringing becomes too weak
to be detected by the demagnetization comparator: it then
permanently stays locked in a given position and can no
longer deliver the “green light” to the controller. To help in
this situation, the NCP1381 implements a 8 s timeout
generator: each time the 45 mV crossing occurs, the timeout
is reset. So, as long as the ringing becomes too low, the
timeout generator starts to count and after 8 s, it delivers its
“green light”. If the skip signal is already present then the
controller restarts; otherwise the logic waits for it to release
the reset input and set the drive output high. Figure 14
depicts these two different situations:
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| NCP1381DR2G | Low−Standby High Performance PWM Controller |
| NCP1395APG | High Performance Resonant Mode Controller |
| NCP1395ADR2G | High Performance Resonant Mode Controller |
| NCP1395BDR2G | High Performance Resonant Mode Controller |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| NCP1381 AM90 WAF | 制造商:ON Semiconductor 功能描述: |
| NCP1381ADAPEVB | 功能描述:BOARD EVAL NCP1381 RoHS:是 類別:編程器，開發系統 >> 評估演示板和套件 系列:* 標準包裝:1 系列:PCI Express® (PCIe) 主要目的:接口，收發器，PCI Express 嵌入式:- 已用 IC / 零件:DS80PCI800 主要屬性:- 次要屬性:- 已供物品:板 |
| NCP1381DR2G | 功能描述:電流型 PWM 控制器 ANA PWM CONTROLLER RoHS:否 制造商:Texas Instruments 開關頻率: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 輸出端數量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1382DR2G | 功能描述:電流型 PWM 控制器 L-STNDBY PWM CNTRLR RoHS:否 制造商:Texas Instruments 開關頻率: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 輸出端數量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1392B | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:High-Voltage Half-Bridge Driver with Inbuilt Oscillator |
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