參數(shù)資料
型號： LM2577SX-15/NOPB
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 穩(wěn)壓器
英文描述： 6 A SWITCHING REGULATOR, 62 kHz SWITCHING FREQ-MAX, PSSO5
封裝： TO-263, 5 PIN
文件頁數(shù)： 11/34頁
文件大?。?/td> 1008K
代理商： LM2577SX-15/NOPB
Application Hints (Continued)
FLYBACK REGULATOR
A Flyback regulator can produce single or multiple output
voltages that are lower or greater than the input supply volt-
age.
Figure 18 shows the LM1577/LM2577 used as a fly-
back regulator with positive and negative regulated outputs.
Its operation is similar to a step-up regulator, except the out-
put switch contols the primary current of a flyback trans-
former. Note that the primary and secondary windings are
out of phase, so no current flows through secondary when
current flows through the primary. This allows the primary to
charge up the transformer core when the switch is on. When
the switch turns off, the core discharges by sending current
through the secondary, and this produces voltage at the out-
puts. The output voltages are controlled by adjusting the
peak primary current, as described in the step-up regulator
section.
Voltage and current waveforms for this circuit are shown in
Figure 17, and formulas for calculating them are given in Fig-
ure 19.
FLYBACK REGULATOR DESIGN PROCEDURE
1. Transformer Selection
A family of standardized flyback transformers is available for
creating flyback regulators that produce dual output volt-
ages, from ±10V to ±15V, as shown in
Figure 18. Figure
20lists these transformers with the input voltage, output volt-
ages and maximum load current they are designed for.
2. Compensation Network (C
C,RC) and
Output Capacitor (C
OUT) Selection
As explained in the Step-Up Regulator Design Procedure,
C
C,RC and COUT must be selected as a group. The following
procedure is for a dual output flyback regulator with equal
turns ratios for each secondary (i.e., both output voltages
have the same magnitude). The equations can be used for a
single output regulator by changing
∑I
LOAD(max) to ILOAD(max)
in the following equations.
A. First, calculate the maximum value for R
C.
Where
∑I
LOAD(max) is the sum of the load current (magni-
tude) required from both outputs. Select a resistor less than
or equal to this value, and no greater than 3 k
.
B. Calculate the minimum value for
∑C
OUT (sum of COUT
at both outputs) using the following two equations.
The larger of these two values must be used to ensure regu-
lator stability.
DS011468-17
FIGURE 17. Flyback Regulator Waveforms
DS011468-18
T1 = Pulse Engineering, PE-65300
D1, D2 = 1N5821
FIGURE 18. LM1577-ADJ/LM2577-ADJ Flyback Regulator with ± Outputs
www.national.com
19
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM2577SX-ADJ 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT
LM2577SX-ADJ/NOPB 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT
LM2577T-12 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT
LM2577T12 制造商:Texas Instruments 功能描述:SWITCHING REG 3A 12V 2577 TO2205
LM2577T-12/LB03 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT
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