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參數(shù)資料
| 型號： | NCP1207A |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | PWM Current Mode Controller for Free Running Quasi Resonant Operation(電流模式控制的PWM控制器，用于自由振蕩的“準(zhǔn)諧振”操作) |
| 中文描述： | PWM電流模式控制器運(yùn)行準(zhǔn)諧振操作（電流模式控制的脈寬調(diào)制控制器，用于自由振蕩的“準(zhǔn)諧振”操作免費(fèi)） |
| 文件頁數(shù)： | 13/16頁 |
| 文件大?。?/td> | 239K |
| 代理商： | NCP1207A |
NCP1207A
http://onsemi.com
13
Calculating the Vcc Capacitor
As the above section describes, the fall down sequence
depends upon the V
CC
level: how long does it take for the
V
CC
line to go from 12 V to 10 V The required time depends
on the startup sequence of your system, i.e. when you first
apply the power to the IC. The corresponding transient fault
duration due to the output capacitor charging must be less
than the time needed to discharge from 12 V to 10 V,
otherwise the supply will not properly start. The test consists
in either simulating or measuring in the lab how much time
the system takes to reach the regulation at full load. Let’s
suppose that this time corresponds to 6.0 ms. Therefore a
V
CC
fall time of 10 ms could be well appropriated in order
to not trigger the overload detection circuitry. If the
corresponding IC consumption, including the MOSFET
drive, establishes at 1.8 mA (e.g. with an 11 nC MOSFET),
we can calculate the required capacitor using the following
formula:
t
i
t of 10 ms, C equals 9.0 F or 22 F for a standard value.
When an overload condition occurs, the IC blocks its
internal circuitry and its consumption drops to 330 A
typical. This happens at V
CC
= 10 V and it remains stuck
until V
CC
reaches 5.3 V: we are in latchoff phase. Again,
using the calculated 22 F and 330 A current consumption,
this latchoff phase lasts: 313 ms.
V
C
, with V = 2.0 V. Then for a wanted
HV Pin Recommended Protection
When the user unplugs a power supply built with a QR
controller such as the NCP1207A, one instance can occur:
A negative ringing can take place on pin8 due to a
resonance between the primary inductance and the bulk
capacitor. As any CMOS device, the NCP1207A is sensitive
to negative voltages that could appear on it’s pins and could
create an internal latchup condition.
For this reason, we recommend adding a resistor between
the bulk capacitor and the V
CC
pin.
Operation Shots
Below are some oscilloscope shots captured at
V
in
= 120 VDC with a transformer featuring a 800 H
primary inductance.
Figure 25.
This plot gathers waveforms captured at three different
operating points:
1
st
upper plot: free run, valley switching operation,
P
out
= 26 W
2
nd
middle plot: min T
off
clamps the switching frequency
and selects the second valley
3
rd
lowest plot: the skip slices the second valley pattern
and will further expand the burst as P
out
goes low
Figure 26.
V
GATE
(5 V/div)
V
Rsense
(200 mV/div)
200 A X R
SKIP
Current Sense Pin (200 mV/div)
This picture explains how the 200 A internal offset
current creates the skip cycle level.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NCP1207A_06 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:PWM Current−Mode Controller for Free Running Quasi−Resonant Operation |
| NCP1207A_07 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:PWM Current-Mode Controller for Free Running Quasi-Resonant Operation |
| NCP1207A_10 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:PWM Current--Mode Controller for Free Running Quasi--Resonant Operation |
| NCP1207AADAPGEVB | 功能描述:電源管理IC開發(fā)工具 NCP1207A 24 W RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| NCP1207ADR2 | 功能描述:電流型 PWM 控制器 Quasi Resonant 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 |
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