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if i have a 12v battery and require +5 and +12volts input, how would i go about doing this?
thanks for the help
thanks for the help
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How much current are you driving? What is the max ripple that you can tolerate? What temperature range will this circuit be exposed to? Is space, cost, components, etc. a consideration? Try to explain EXACTLY what you are trying to do, and we will be able to help you figure out the best possible solution for your problem.
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- #3
Guest
i am trying to build a portable power supply for a pc/104 board. i can operate it of the floppy drive connector of an atx power supply.
this is the data sheet for the module im trying to run
this is the data sheet for the module im trying to run
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- #4
But aren't linears MUCH more robust than switchers? What happens if you have large current spikes on a switcher? I assume that you can't hang large caps off of the switcher because it will screw up the efficiency. Also, don't switchers perform poorly over temp due the the sensitivity of the circuitry?
Linears burn off the excess as heat. Wastes power, and gets hot 
Consider a two-stage supply. Use a switcher to knock the +12V down to something close to +5V, the follow that with a LowDropOut linear. That is, if you have the board space. This is how I'm doing it in the Datalogger project.
This will get you the cleanest and most efficient +5V. If you don't mind the heat and current draw, just do the linear - 3 parts : regulator and two caps. But it can get bloody hot dropping 12 down to 5 with any kind of real current.
A switcher is a few more parts. Regulator, 3 caps, an inductor and a diode. Then again, these can all be SMD devices ...
National has a great power supply generator on their site. Feed it all the parameters, and it spits out a circuit that it can simulate. They'll even build a sample and send it to you All SMD and tiny.
Dean.
Consider a two-stage supply. Use a switcher to knock the +12V down to something close to +5V, the follow that with a LowDropOut linear. That is, if you have the board space. This is how I'm doing it in the Datalogger project.
This will get you the cleanest and most efficient +5V. If you don't mind the heat and current draw, just do the linear - 3 parts : regulator and two caps. But it can get bloody hot dropping 12 down to 5 with any kind of real current.
A switcher is a few more parts. Regulator, 3 caps, an inductor and a diode. Then again, these can all be SMD devices ...
National has a great power supply generator on their site. Feed it all the parameters, and it spits out a circuit that it can simulate. They'll even build a sample and send it to you
All SMD and tiny.Dean.
msprayberry
Electrical
Try a PT6302 this will take a 12v input and produces a fairly stable 5V output ripple is only like 20mV(p-p) if I remember correctly. It has a 3A output max. It is made by Power Trends I use them alot. I get everything from 5V-9V out of these chips with a few mods. It comes with its' own heatsink so have the battle is complete
Some other things to considder!
The document talk about a +/- 5 V and 12 V connector, but do you need all foúr voltages ?
-5 V and/or -12 V are usually used for RS-232 only, but ... ?
You will need a switcher or an additional battery in order to get the negative voltages.
These seldomly pull more than 150 mA, however.
What kind of requirement do you have for the +12 V ?
If your battery is of the lead-acid type the voltage from it will drop from about
13.8 V to well below 11 V during its discharge from full to nearly flat.
The discharge curve is thus quite steep as compared to Ni-Cd and Ni-MH batteries.
The document talk about a +/- 5 V and 12 V connector, but do you need all foúr voltages ?
-5 V and/or -12 V are usually used for RS-232 only, but ... ?
You will need a switcher or an additional battery in order to get the negative voltages.
These seldomly pull more than 150 mA, however.
What kind of requirement do you have for the +12 V ?
If your battery is of the lead-acid type the voltage from it will drop from about
13.8 V to well below 11 V during its discharge from full to nearly flat.
The discharge curve is thus quite steep as compared to Ni-Cd and Ni-MH batteries.
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- #12
you should be ok with a switcher for the +5V.
But aren't linears MUCH more robust than switchers?
not switchers built for power.
use caps with a low virtual series resistance and you can add capacitance, but check the datasheets and be carefull.
for the +12 just use a linear it is much simpler.
But aren't linears MUCH more robust than switchers?
not switchers built for power.
use caps with a low virtual series resistance and you can add capacitance, but check the datasheets and be carefull.
for the +12 just use a linear it is much simpler.
Switchers cannot supply the large instaneous current like switchers. Grab 2 power supplies, 1 linear & 1 switcer, that are rated for same power (Volts and current), and you can easily trip out the switcher if there are large current spikes. True, the switching supply will be signifigantly smaller, and more portable, but if you need lots of current for a short period of time, good luck getting a switcher too work. I have spent too many hours troubleshooting problems back down to switching power supplies to ever recommend one over a linear. If you have the space, and can afford the heat, don't mess around.
you are just no fun melone, but I know what you mean
by the way la_mer, floppies and hard drives create pretty substantual current spikes, keep this in mind in your power supply design.
48 volts to 12,5,-5,-12 a switcher was the only option once the stupid sales engeneer said the existing product we made could be retrofitted into there old systems. The heat would have been to much especialy in that sardine can.
by the way la_mer, floppies and hard drives create pretty substantual current spikes, keep this in mind in your power supply design.
48 volts to 12,5,-5,-12 a switcher was the only option once the stupid sales engeneer said the existing product we made could be retrofitted into there old systems. The heat would have been to much especialy in that sardine can.
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