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參數(shù)資料
| 型號： | LM5115MM |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Secondary Side Post Regulator Controller |
| 中文描述： | 次級端后穩(wěn)壓控制器 |
| 文件頁數(shù)： | 11/17頁 |
| 文件大小： | 725K |
| 代理商： | LM5115MM |
Error Amplifier and Soft-Start (FB,
CO, & COMP, SS)
(Continued)
fier is configured as an open drain output it can be disabled
by connecting FB to ground. The current sense amplifier and
current limiting function will be described in a later section.
Leading Edge Pulse Width
Modulation
Unlike conventional voltage mode controllers, the LM5115
implements leading edge pulse width modulation. A current
source equal to 3 times the I
SYNC
current is used to charge
the capacitor connected to the RAMP pin as shown in
Figure
4
. The ramp signal and the output of the error amplifier
(COMP) are combined through a resistor network to produce
a voltage ramp with variable dc offset (CRMIX in
Figure 4
).
The high side MOSFET which drives the HS pin is held in the
off state at the beginning of the phase signal. When the
voltage of CRMIX exceeds the internal threshold voltage CV,
the PWM comparator turns on the high side MOSFET. The
HS pin rises and the MOSFET delivers current from the main
converter phase signal to the output of the auxiliary regula-
tor. The PWM cycle ends when the phase signal falls and
power is no longer supplied to the drain of the high side
MOSFET.
Leading edge modulation of the auxiliary PWM controller is
required if the main converter is implemented with peak
current mode control. If trailing edge modulation were used,
the additional load on the transformer secondary from the
auxiliary channel would be drawn only during the first portion
of the phase signal pulse. Referring to
Figure 5
, the turn off
the high side MOSFET of the auxiliary regulator would cre-
ate a non-monotonic negative step in the transformer cur-
rent. This negative current step would produce instability in a
peak current mode controller. With leading edge modulation,
the additional load presented by the auxiliary regulator on
the transformer secondary will be present during the latter
portion of the phase signal. This positive step in the phase
signal current can be accommodated by a peak current
mode controller without instability.
20134914
FIGURE 4. Synchronization and Leading Edge Modulation
20134920
FIGURE 5. Leading versus Trailing Edge Modulation
L
www.national.com
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相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM5115MMX | Secondary Side Post Regulator Controller |
| LM5152 | CABLE |
| LM5152BCN | Dual and Quad High Speed/Low Power 75 MHz GBW Rail-to-Rail I/O Operational Amplifiers |
| LM520A | WARM WHITE LAMP LED |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM5115MMX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Secondary Side Post Regulator Controller |
| LM5115MTC | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5115MTC/MEY8 | 制造商:Texas Instruments 功能描述: |
| LM5115MTC/NOPB | 功能描述:DC/DC 開關(guān)控制器 Secondary Side Switching Reg RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| LM5115MTCX | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
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