LM2596 高压输入 可否启动？

guozs1984

LM2596 输入电压有要求，最大 40V，
如果输入在40-60V之间，采用电阻分压形式，不知道启动瞬间如何？能否正常启动？
还有就是，这种电阻分压可靠不？
我见过有用LM317 前段 电阻分压，当时电路图是48V输入的。因为317是线性的，而2596是开关的，不知道是否有硬性？
自己感觉，开关的是一段时间开，一段时间关，那工作的瞬间，电压还应该是 输入电压 40-60V之间，如果输入电压56V，
那么，LM2596 工作时，输入电压也应该是56V，请牛人指点。
PS： 我说的不知道清楚没？呵呵。附图如下。

kevin_me

串降压管稳当些，启动瞬间也是从管子走过来的。但是大功率的稳压管占地方。

DOER

这样设计很不妥当，万不可用在产品上。有很多DC/DC输入可以超过60V

RUANJI

不是有个高压系列的，HV。

lw2012

LM2576/LM2576HV Series
SIMPLE SWITCHER®3A Step-Down Voltage Regulator
General Description
The LM2576 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving 3A load with
excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V, 15V, and an
adjustable output version.
Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency
compensation and a fixed-frequency oscillator.
The LM2576 series offers a high-efficiency replacement for
popular three-terminal linear regulators. It substantially reduces the size of the heat sink, and in some cases no heat
sink is required.
A standard series of inductors optimized for use with the
LM2576 are available from several different manufacturers.
This feature greatly simplifies the design of switch-mode
power supplies.
Other features include a guaranteed±4% tolerance on output voltage within specified input voltages and output load
conditions, and±10% on the oscillator frequency. External
shutdown is included, featuring 50 µA (typical) standby current. The output switch includes cycle-by-cycle current limiting, as well as thermal shutdown for full protection under
fault conditions.
Features
n 3.3V, 5V, 12V, 15V, and adjustable output versions
n Adjustable version output voltage range,
1.23V to 37V (57V for HV version)±4% max over
line and load conditions
n Guaranteed 3A output current
n Wide input voltage range, 40V up to 60V for
HV version
n Requires only 4 external components
n 52 kHz fixed frequency internal oscillator
n TTL shutdown capability, low power standby mode
n High efficiency
n Uses readily available standard inductors
n Thermal shutdown and current limit protection
n P+ Product Enhancement tested
Applications
n Simple high-efficiency step-down (buck) regulator
n Efficient pre-regulator for linear regulators
n On-card switching regulators
n Positive to negative converter (Buck-Boost)
Typical Application (Fixed Output Voltage
Versions)
SIMPLE SWITCHER®is a registered trademark of National Semiconductor Corporation.
01147601
FIGURE 1.
August 2004
LM2576/LM2576HV Series SIMPLE SWI

guozs1984

Wide input voltage range, 40V up to 60V for
HV version
57V for HV version

多谢大家，
我找找看看高压的，HV version 。

lw2012

guozs1984 发表于 2014-2-4 13:33
Wide input voltage range, 40V up to 60V for
HV version
57V for HV version

57v是输出电压，输入电压最大是60V

gyzzg2030