Voltage regulation

[sushmithks]

As per my knowledge LDO, zener diode, DC/DC converters can be used as voltage regulators to get desired voltage. But i would like to know how do we select which one to use? what are the major difference?

 

[donkey]

ok so LDO is LOW dropout, if you need lets say 12 volts regulated from 12.1volts this is the item to use
Zener diode is used to give you a rough voltage when used right they will never go over the voltage needed but will alow the lesser voltages through... may not be good for what you need
a DC?DC regulator is used on batteries to get different voltages...
the question I have for you is what do you have in mind?
personally I would not use anything unregulated so I know the exact voltage coming out.
also DC/DC converters and LDO use MOSFET's or transistors, so there are current limits and heat sinks needed.

tell us what you plan to do and someone may know a very good idea on how to do it... there are 1 or 2 smart people in here.... not me but there are some

 

[sushmithks]

Thank you.. If you are designing a circuit board and you need to derive 12V from 28V which one do you use? LDO or DC/DC converter and why?

My doubt is regulators like LM2805 is available for 5V and PCB mount DC/DC converters also available for 5V. In such cases which one do you prefer?

 

[donkey]

ok to better understand this I will need detail about your project.

to get 12volt from 28v you need a dc-dc converter, nothing else... but how much current you looking at?

for 5volts output, what input do you use and what current do you need?

 

[(*steve*)]

Is this homework or an actual problem?

 

[sushmithks]

It is just to understand. Say I have 12v source in my board. I need to derive 5v/200mA from that which one should I use? Regulator or dc/dc converters?

 

[(*steve*)]

Is this homework or an actual problem? (or was this the "just to understand")

In any case, the answer depends on what else is on the board and whether you want efficient or electrically quiet.

 

[BobK]

And whether you want things getting hot or not. Dropping 7V at 200mA is 1.4W of power, enough to need a heat sink if a linear regulator is used.

Bob