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參數(shù)資料
| 型號： | LM5115MMX |
| 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)： | 12/17頁 |
| 文件大?。?/td> | 725K |
| 代理商： | LM5115MMX |
Voltage Mode Control with Current
Injection
The LM5115 controller uniquely combines elements and
benefits of current mode control in a voltage mode PWM
controller. The current sense amplifier shown in
Figure 6
monitors the inductor current as it flows through a sense
resistor connected between CS and VOUT. The voltage gain
of the sense amplifier is nominally equal to 16. The current
sense output signal is shifted by 1.27V to produce the inter-
nal CV reference signal. The CV signal is applied to the
negative input of the PWM comparator and compared to
CRMIX as illustrated in
Figure 4
. Thus the PWM threshold of
the voltage mode controller (CV) varies with the instanta-
neous inductor current.
Injecting a signal proportional to the instantaneous inductor
current into a voltage mode controller improves the control
loop stability and bandwidth. This current injection eliminates
the lead R-C lead network in the feedback path that is
normally required with voltage mode control (see
Figure 7
).
Eliminating the lead network not only simplifies the compen-
sation, but also reduces sensitivity to output noise that could
pass through the lead network to the error amplifier.
The design of the voltage feedback path through the error
amp begins with the selection of R1 and R2 in
Figure 7
to set
the regulated output voltage. The steady state output voltage
after soft-start is determined by the following equation:
VOUT(final) = 0.75V x (1+R1/R2)
The parallel impedance of the R1, R2 resistor divider should
be approximately 2k
(between 0.5k
and 5k
). Lower
resistance values may not be properly driven by the error
amplifier output and higher feedback resistances can intro-
duce noise sensitivity. The next step in the design process is
selection of R3, which sets the ac gain of the error amplifier.
The ac gain is given by the following equation and should be
set to a value less than 30.
GAIN(ac) = R3/(R1|| R2)
<
30
The capacitor C1 is connected in series with R3 to increase
the dc gain of the voltage regulation loop and improve output
voltage accuracy. The corner frequency set by R3 x C1
should be less than 1/10th of the cross-over frequency of the
overall converter such that capacitor C1 does not add phase
lag at the crossover frequency. Capacitor C2 is added to
reduce the noise in the voltage control loop. The value of C2
should be less than 500pF and C2 may not be necessary
with very careful PC board layout.
20134915
FIGURE 6. Current Sensing and Limiting
L
www.national.com
12
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 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(fēng)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(fēng)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(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5115MTCX/NOPB | 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(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
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