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參數(shù)資料
| 型號： | LM2577S-ADJ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SIMPLE SWITCHER Step-Up Voltage Regulator |
| 中文描述： | 6 A SWITCHING REGULATOR, 62 kHz SWITCHING FREQ-MAX, PSSO5 |
| 封裝： | TO-263, 5 PIN |
| 文件頁數(shù)： | 19/27頁 |
| 文件大?。?/td> | 889K |
| 代理商： | LM2577S-ADJ |
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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
20ists these transformers with the input voltage, output volt-
ages and maximum load current they are designed for.
2. Compensation Network (C
, R
C
) and
Output Capacitor (C
OUT
) Selection
As explained in the Step-Up Regulator Design Procedure,
C
, R
and C
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 I
LOAD(max)
in the following equations.
A.
First, calculate the maximum value for R
C
.
Where
∑
I
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
(sum of C
OUT
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
相關PDF資料 |
PDF描述 |
|---|---|
| LM2577S-15 | SIMPLE SWITCHER Step-Up Voltage Regulator |
| LM2577M-15 | Pressure Transducer, Series 19 mm, Compensated, Pressure Range: 0 psi to 50 psi, Gage, 1/4-18 NPT, 10 Vdc excitation |
| LM2577M-12 | Pressure Transducer, Series 19 mm, Compensated, Pressure Range: 0 psi to 50 psi, Gage, 1/8-27 NPT, 10 Vdc excitation |
| LM2585SX-12 | SIMPLE SWITCHER 3A Flyback Regulator |
| LM2585SX-3.3 | SIMPLE SWITCHER 3A Flyback Regulator |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM2577S-ADJ/NOPB | 功能描述:直流/直流開關轉換器 STEP-UP VLTG REG RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 |
| LM2577S-ADJ/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter (DC-DC) / Switching Regu |
| LM2577SX-12 | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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-12/NOPB | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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-15 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Current-Mode SMPS Controller |
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