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參數(shù)資料
| 型號： | NCP1200D |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | PWM Current-Mode Controller for Universal Off-Line Supplies Featuring Low Standby Power |
| 中文描述： | PWM電流模式控制器的通用離線用品，具有低待機(jī)功耗 |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 136K |
| 代理商： | NCP1200D |
NCP1200A
http://onsemi.com
12
Protecting the Controller Against Negative Spikes
As with any controller built upon a CMOS technology, it
is the designer’s duty to avoid the presence of negative
spikes on sensitive pins. Negative signals have the bad habit
to forward bias the controller substrate and induce erratic
behaviors. Sometimes, the injection can be so strong that
internal parasitic SCRs are triggered, engendering
irremediable damages to the IC if they are a low impedance
path is offered between V
CC
and GND. If the current sense
pin is often the seat of such spurious signals, the
highvoltage pin can also be the source of problems in
certain circumstances. During the turnoff sequence, e.g.
when the user unplugs the power supply, the controller is still
fed by its V
CC
capacitor and keeps activating the MOSFET
ON and OFF with a peak current limited by Rsense.
Unfortunately, if the quality coefficient Q of the resonating
network formed by Lp and Cbulk is low (e.g. the MOSFET
Rdson + Rsense are small), conditions are met to make the
circuit resonate and thus negatively bias the controller. Since
we are talking about ms pulses, the amount of injected
charge (Q = I x t) immediately latches the controller which
brutally discharges its V
CC
capacitor. If this V
CC
capacitor
is of sufficient value, its stored energy damages the
controller. Figure 22 depicts a typical negative shot
occurring on the HV pin where the brutal V
CC
discharge
testifies for latchup.
Figure 22. A negative spike takes place on the Bulk capacitor at the switchoff sequence
Simple and inexpensive cures exist to prevent from
internal parasitic SCR activation. One of them consists in
inserting a resistor in series with the highvoltage pin to
keep the negative current to the lowest when the bulk
becomes negative (Figure 23). Please note that the negative
spike is clamped to –2 x Vf due to the diode bridge. Please
refer to AND8069/D for power dissipation calculations.
Another option (Figure 24) consists in wiring a diode from
V
CC
to the bulk capacitor to force V
CC
to reach UVLOlow
sooner and thus stops the switching activity before the bulk
capacitor gets deeply discharged. For security reasons, two
diodes can be connected in series.
Figure 23. A simple resistor in series avoids any
latchup in the controller
CV
CC
D3
1N4007
8
7
6
5
1
2
3
4
+
Cbulk
+
1
3
CV
CC
Rbulk
> 4.7 k
8
7
6
5
1
2
3
4
+
Cbulk
+
1
2
3
Figure 24. or a diode forces V
CC
to reach
UVLOlow sooner
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| NCP1200AD100R2 | PWM Current-Mode Controller for Universal Off-Line Supplies Featuring Low Standby Power |
| NCP1200AD100R2G | PWM Current-Mode Controller for Universal Off-Line Supplies Featuring Low Standby Power |
| NCP1200AD40R2 | PWM Current-Mode Controller for Universal Off-Line Supplies Featuring Low Standby Power |
| NCP1200 | PWM Current-Mode Controller for Low-Power Universal Off-Line Supplies |
| NCP1200D100R2 | PWM Current-Mode Controller for Low-Power Universal Off-Line Supplies |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NCP1200D100R | 制造商:Rochester Electronics LLC 功能描述: 制造商:ON Semiconductor 功能描述: |
| NCP1200D100R2 | 功能描述:電流型 PWM 控制器 100KHz Current Mode 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 |
| NCP1200D100R2G | 功能描述:電流型 PWM 控制器 100KHz Current Mode SMPS 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 |
| NCP1200D100R2G | 制造商:ON Semiconductor 功能描述:Pulse Width Modulation (PWM) Controller |
| NCP1200D40R2 | 功能描述:電流型 PWM 控制器 40KHz Current Mode 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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