3 Output Battery Based Power Supply

Could use a potential divider circuit. Use a 3K and a 7K ohm resistor, and tap power off before them, in-between them and after the resistors, and if a quick bit of maths is right, you should have your desired voltages

It depends on how well you want the outputs regulated, how much current you intend to draw from each output and how efficient you want it to be.

Generally speaking, these factors are interrelated, and the cost and/or complexity will increase as each increases.

Can you put some figures to these factors?

the power supply has 24v, 7 ah battery at input, from which i want 3 outputs 5v/1 amp,12v/2 amp and 24v/3 amp.

What about regulation? How much deviation from the nominal output voltages is acceptable?

You realize that the 24V battery will not provide exactly 24V; the actual value will depend on the state of charge and the total current drawn.

hello sir i need constant output of the earlier mentioned value(5v/1a,12v/2a and 24v/3a=77watt) .I am assuming 75% efficiency of the batteries, battery will be able to give constant output for at least1 hour (77 watt/24X0.75=4a, 7ah/4a=1.7 hour). I want to use this power supply for only i hour without discharged.

sorry for the confusion, actually i need 24v/2amp that make 77 watts. i dont know much about batteries, bt i am assuming that batteries should not be fully discharged,and to be used only to their 75%. i am using smf lead acid battery.

Note on post 7... 7905 is a MINUS 5 volt regulator. I assume the - fell off the paper somewhere.

These are all linear regulators and very low efficiency. I would check with National Semiconductor. They have several switching regulators which are much more efficient, but they require more parts.

Bill

I have no idea what "smf" batteries are. If you can get them, I would use (what we call in the US) DEEP CYCLE batteries. Common automotive batteries are designed to do one thing only... provide one heck of alot of current (hundreds of amps) for a short period of time to start the car. Deep cycle batteries are designed to provide less current over a long period of time. Of course two 12 volt batteries in series = 24 volts, and might be cheaper than one 24 volt battery.

I would take a serious look at the load on the 24 volt output. If the load can handle say 22 through 28 volts, I would run it directly off the battery without regulation. Hey I am cheap. Otherwise, JohnDGs idea of a Low Drop Out regulator is good IF you have a full charge on the battery to begin with. I don't know how it would work after an hour of use. If the LDO regulator wouldn't handle it, I would look at a BOOST/BUCK switching regulator to get regulated 24 volts.

Next question is Where are You located? All our ideas are worthless if you cannot get the parts. If you are located in India (for example) we have several Indian engineers who would drop in to help. John is in UK... I am in US. Where are you?

Bill

Coming to the same conclusion.

I'd suggest (rather than getting bogged down at component level) this for the 24V output:

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6783571

... and the converters I mentioned in #6 for the 12V and 5V lines.

All are available from RS Components, in most regions of the globe.

(PS - think "smf" ≡ "sealed maintenance free").

can you please help me in getting circuit for three output power supply as mentioned in my previous posts?or rough outline of what you were telling me in the previous post