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參數(shù)資料
| 型號： | LM3524 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Regulating Pulse Width Modulator |
| 中文描述： | 調節(jié)脈沖寬度調制器 |
| 文件頁數(shù)： | 13/22頁 |
| 文件大?。?/td> | 1172K |
| 代理商： | LM3524 |
Typical Applications
(Continued)
BASIC SWITCHING REGULATOR THEORY
AND APPLICATIONS
The basic circuit of a step-down switching regulator circuit is
shown in
Figure 12
, along with a practical circuit design
using the LM3524D in
Figure 15
.
The circuit works as follows: Q1 is used as a switch, which
has ON and OFF times controlled by the pulse width modu-
lator. When Q1 is ON, power is drawn from V
IN
and supplied
to the load through L1; V
A
is at approximately V
IN
, D1 is
reverse biased, and C
o
is charging. When Q1 turns OFF the
inductor L1 will force V
A
negative to keep the current flowing
in it, D1 will start conducting and the load current will flow
through D1 and L1. The voltage at V
A
is smoothed by the L1,
C
o
filter giving a clean DC output. The current flowing
through L1 is equal to the nominal DC load current plus
some
I
which is due to the changing voltage across it.
A
good rule of thumb is to set
I
LP-P
.
40% x I
o
.
Neglecting V
SAT
, V
D
, and settling
I
L+
=
I
L
;
where T = Total Period
The above shows the relation between V
IN
, V
o
and duty
cycle.
as Q1 only conducts during t
ON
.
The efficiency,
η
, of the circuit is:
η
MAX will be further decreased due to switching losses in
Q1. For this reason Q1 should be selected to have the
maximum possible f
T
, which implies very fast rise and fall
times.
CALCULATING INDUCTOR L1
Since
I
L
+ =
I
L
= 0.4I
o
Solving the above for L1
00865016
FIGURE 12. Basic Step-Down Switching Regulator
00865017
FIGURE 13. Relation of Switch Timing to Inductor Current in Step-Down Regulator
L
www.national.com
13
相關PDF資料 |
PDF描述 |
|---|---|
| LM3524D | Regulating Pulse Width Modulator |
| LM3524DN | Regulating Pulse Width Modulator |
| LM2524 | Regulating Pulse Width Modulator |
| LM2524D | Regulating Pulse Width Modulator |
| LM2524DN | Regulating Pulse Width Modulator |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM3524D | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Regulating Pulse Width Modulator |
| LM3524DM | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM3524DM/NOPB | 功能描述:電壓模式 PWM 控制器 REGULATING PULSE WIDTH MODULATOR RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM3524DM/NOPB | 制造商:Texas Instruments 功能描述:Pulse Width Modulation (PWM) Controller |
| LM3524DMX | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
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