want to convert -48vdc to +12vdc

[ud23]

hi all i want to convert negative (-48v)dc source in to continuous +12v dc supply. i found lm2678 but that required only positive input voltage can any one suggest me solution????

 

[Arch Zone]

can't you just reverse the polarities? Use -48V as 0V and 0V as +48V.

 

[ud23]

ya i can but max input voltage for lm2678 ic is +40v so how can i do with reverse polarity with some lower voltage in range of 8v to 40v dc how can i do that?

can i use high value capacitor in reverse arch?

 

[Arch Zone]

You need such as transformerless power supply or try PT4485.

 

[kak111]

Goto
**broken link removed**

I tried with input 45...50Vdc / output 12Vdc - 2A
gives 10 diffferent solutions and schematics

 

[ud23]

thnx arch and kak for reply. arch in pt4485 can i use it with -48v as gnd and 0v as +48v mean as single supply.and i try find its prize its not available in ti website.

 

[kak111]

What is output current you need......
Here is schematic for 2A , output ripple 30mVpp , effiency 88.6%

 

[ud23]

output current requirement is 5A.

 

[kak111]

Webench design parameters
Vin = 45...50Vdc
Vout = 12Vdc
Iout = 5A
gives IC`s

LM5088
LM5116
LM5117
LM5119

 

[Arch Zone]

Goto
**broken link removed**

Great link. Very useful :idea:

 

[ud23]

thnx kak and arch great solution

 

[billnaylor]

A simple flyback should be able to do this:
Flyback Converter Design

You can simulate it in LTSpice:
LTSpice Tutorial | The Complete Course