- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄384589 > LB03 (National Semiconductor Corporation) SIMPLE SWITCHER 3A Step-Down Voltage Regulator PDF資料下載
參數(shù)資料
| 型號： | LB03 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | SIMPLE SWITCHER 3A Step-Down Voltage Regulator |
| 中文描述： | 第3A的SIMPLE SWITCHER降壓穩(wěn)壓器 |
| 文件頁數(shù)： | 18/24頁 |
| 文件大?。?/td> | 750K |
| 代理商： | LB03 |
Additional Applications
(Continued)
The switch currents in this buck-boost configuration are
higher than in the standard buck-mode design, thus lowering
the available output current. Also, the start-up input current
of the buck-boost converter is higher than the standard
buck-mode regulator, and this may overload an input power
source with a current limit less than 5A. Using a delayed
turn-on or an undervoltage lockout circuit (described in the
next section) would allow the input voltage to rise to a high
enough level before the switcher would be allowed to turn
on.
Because of the structural differences between the buck and
the buck-boost regulator topologies, the buck regulator de-
sign procedure section can not be used to to select the
inductor or the output capacitor. The recommended range of
inductor values for the buck-boost design is between 68 μH
and 220 μH, and the output capacitor values must be larger
than what is normally required for buck designs. Low input
voltages or high output currents require a large value output
capacitor (in the thousands of micro Farads).
The peak inductor current, which is the same as the peak
switch current, can be calculated from the following formula:
Where f
= 52 kHz. Under normal continuous inductor
current operating conditions, the minimum V
represents
the worst case. Select an inductor that is rated for the peak
current anticipated.
Also, the maximum voltage appearing across the regulator is
the absolute sum of the input and output voltage. For a 12V
output, the maximum input voltage for the LM2576 is +28V,
or +48V for the LM2576HV.
The
Switchers Made Simple
(version 3.0) design software
can be used to determine the feasibility of regulator designs
using different topologies, different input-output parameters,
different components, etc.
NEGATIVE BOOST REGULATOR
Another variation on the buck-boost topology is the negative
boost configuration. The circuit in
Figure 11
accepts an input
voltage ranging from 5V to 12V and provides a regulated
12V output. Input voltages greater than 12V will cause the
output to rise above 12V, but will not damage the regulator.
Because of the boosting function of this type of regulator, the
switch current is relatively high, especially at low input volt-
ages. Output load current limitations are a result of the
maximum current rating of the switch. Also, boost regulators
can not provide current limiting load protection in the event of
a shorted load, so some other means (such as a fuse) may
be necessary.
UNDERVOLTAGE LOCKOUT
In some applications it is desirable to keep the regulator off
until the input voltage reaches a certain threshold. An und-
ervoltage lockout circuit which accomplishes this task is
shown in
Figure 12
, while
Figure 13
shows the same circuit
applied to a buck-boost configuration. These circuits keep
the regulator off until the input voltage reaches a predeter-
mined level.
V
TH
≈
V
Z1
+ 2V
BE
(Q1)
01147614
FIGURE 10. Inverting Buck-Boost Develops 12V
01147615
Typical Load Current
400 mA for V
IN
= 5.2V
750 mA for V
IN
= 7V
Note:
Heat sink may be required.
FIGURE 11. Negative Boost
01147616
Note:
Complete circuit not shown.
FIGURE 12. Undervoltage Lockout for Buck Circuit
L
www.national.com
18
相關PDF資料 |
PDF描述 |
|---|---|
| LB1962 | LINEAR INTEGRATED CIRCUIT |
| LBPC | Precision, 100uA Gain Selectable Amplifier |
| LCE13A | Silicon Avalanche Diodes - 1500W Axial Leaded Transient Voltage Supressors |
| LCE6.5A | Silicon Avalanche Diodes - 1500W Axial Leaded Transient Voltage Supressors |
| LCE8.0A | Silicon Avalanche Diodes - 1500W Axial Leaded Transient Voltage Supressors |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LB-030-09-3A20-01-N | 功能描述:LED電源 LED BALLAST 30W 3-9V 3.2A RoHS:否 制造商:Cree, Inc. 工作模式:Constant Voltage (CV) 輸出功率額定值: 輸入電壓:220 V to 240 V 輸出端數(shù)量:1 輸出電壓（通道 1）:40 V 輸出電流（通道 1）:900 mA 安裝風格:Screw 尺寸:90 mm L x 90 mm W x 37.5 mm H 商用/醫(yī)用:Commercial |
| LB-030-15-1A75-01-N | 功能描述:LED電源 LED BALLAST 30W 3-15V 1.75A RoHS:否 制造商:Cree, Inc. 工作模式:Constant Voltage (CV) 輸出功率額定值: 輸入電壓:220 V to 240 V 輸出端數(shù)量:1 輸出電壓（通道 1）:40 V 輸出電流（通道 1）:900 mA 安裝風格:Screw 尺寸:90 mm L x 90 mm W x 37.5 mm H 商用/醫(yī)用:Commercial |
| LB03-10B03 | 制造商:MORNSUN 制造商全稱:MORNSUN 功能描述:AC-DC CONVERTER |
| LB03-10B05 | 制造商:MORNSUN 制造商全稱:MORNSUN 功能描述:AC-DC CONVERTER |
| LB03-10B09 | 制造商:MORNSUN 制造商全稱:MORNSUN 功能描述:LB series ---- is a compact size power converter offered by Mornsun. |
發(fā)布緊急采購，3分鐘左右您將得到回復。