Powering a computer without inverting.

[Darfk]

I know this is possible I just need some help/advice with it.

I want to power my computer from my 12 volt car battery. I do not want to use an inverter. I do not need to use a monitor just a motherboard (w/CPU,RAM,GFX card), hard drive, and a sound card. The CPU is an old AMD Socket7 1.63GHz. Hard drive is a 80GB Seagate.
Anyway I want to know if I can regulate voltages accurately and efficiently enough to keep my system stable with several LM337s and LM317s (negative and positive voltage regulators)? At first I only want it running off a battery ie. no car attached.

Can anyone suggest a better regulator for my application?
Is there an existing project that solves my problem?
Or is it more affordable/easy to invert?

Help would be very appreciated.

 

[kchriste]

Or is it more affordable/easy to invert?

You don't have your location filled in, but where I live you can buy a 800 watt inverter for under $100 CDN. This is the method I would use myself. Linear regulators, such as the LM317 etc, would generate too much heat and you would still have to "invert" for the -12V line though your motherboard may not use it for anything other than serial IO.

 

[Darfk]

I have been looking around for power inverters and they are fair expensive about $180AUD for a modified sine wave @ 600W. I can't afford this at them moment as I am a student
I am aware that I will have to use several regulators to spread the load across.
And I am under impression that the LM337 outputs a negative voltage using a positive input. <<-- correct me if I am wrong.

 

[mvs sarma]

If you try to generate +5V from 12V battery with HiGH current demand, you will be wasting lot of power as heat.

once the battery -ve has been used as common for the PC, you will not be able to to use LM337 etc for generating -ve voltages (-5 and -12V) unless the switch mode techniques are used.

I presume thatyou only wanted to to avoid going to 12V DC to 230V AC conversion!! Perhaps you areaiming for a DC-DC converter with input 12V battery (13.8 to 10.8 on the lower side) and with normal outputs that are required for a PC mother board and HDD etc. It is possible and there are some manufacturers supplying such DC-DC converters.

One such psu is M2-ATX manufactured by www.mini-box.com

By such a method you may reduce losses that arise due to double conversion.

 

[pasanlaksiri]

R u trying to make a CAR PC. Awesome

 

[Ambient]

Great website man! They have some really nice stuff.

 

[mvs sarma]

I know this is possible I just need some help/advice with it.

I want to power my computer from my 12 volt car battery. I do not want to use an inverter. .............................
Can anyone suggest a better regulator for my application?
Is there an existing project that solves my problem?
Or is it more affordable/easy to invert?

Help would be very appreciated.

Try LM25 series switching regulators . you may google for details or datasheets at www.alldatasheet.com

 

[Gordz]

You need -12v and -5v for most PC's so you will have to invert somewhere along the line and the current required for the +5 will be pretty high. The Simple Switcher series from National Semiconductor will be good for this project as they will allow 'simple' inversion as some can be configured as buck/boost/invert.

 

[Nigel Goodwin]

I have been looking around for power inverters and they are fair expensive about $180AUD for a modified sine wave @ 600W. I can't afford this at them moment as I am a student

Remarkably good value, if you can't afford it you probably can't afford to build anything either!.

I am aware that I will have to use several regulators to spread the load across.
And I am under impression that the LM337 outputs a negative voltage using a positive input. <<-- correct me if I am wrong.

Sorry, but you are completely wrong, it's a negative regulator for a negative supply.

 

[Super_voip]

https://www.mini-box.com/s.nl/sc.8/category.13/.f is the first site on a google search

 

[ericgibbs]

R u trying to make a CAR PC. Awesome

Hi Pasan,
Its already been done,, it called a 'Laptop'!

 

[ericgibbs]

I know this is possible I just need some help/advice with it.

I want to power my computer from my 12 volt car battery. I do not want to use an inverter. I do not need to use a monitor just a motherboard At first I only want it running off a battery ie. no car attached.

If you used a 2nd 12V battery, you could get the +12v/5V and -12v/-5v supplies required.
The negative supply requires less current than the positive supplies to your motherboard etc..

Without using SMP'S, a linear +5V would not be efficient.
Also the +12v psu for the PC, from a 12v battery would not be regulated.

How much current on each power rail, is the PC going to require?

IMO, a SMPS would be the best way to go.

 

[mvs sarma]

Simple concept Eric, now he should have two chargers for the battery maintenance, I fear.

 

[ericgibbs]

Simple concept Eric, now he should have two chargers for the battery maintenance, I fear.

Hi Sarma,
As they say 'there's no such thing as a free lunch'

Thats why man invented the SMPS and mains invertor!

 

[pasanlaksiri]

Hi Pasan,
Its already been done,, it called a 'Laptop'!

. But where is da fun

 

[Oznog]

You're totally barking up the wrong tree.

PCs are sensitive to power supply problems. It would be risky as hell to build your own off of a car's noisy 12V off homemade regs at these current levels.

Additionally linear regs are gonna be not only inefficient but hot and require huge heatsinks. And LM317 in a TO220 pkg won't even have the current OR heat dissipation rating your need, and no you can't put several in parallel to improve the ratings. You could use a bipolar power transistor as a follower but there are are more issues that come with that and it does nothing to improve the efficiency anyways.

You need a 110V inverter- end of story.

 

[Nigel Goodwin]

You need a 110V inverter- end of story.

Actually not, what you want is a PC power supply that's switchmode, accepts 12V DC from a car battery, and generates the require motherboard voltages directly. Generating 110V from 12V first is inefficient, and 12V PC power supplies are available - but probably MORE expensive than a mains inverter.

 

[Glyph]

Getting around the problem

PC power supplies can actually run off DC if the voltage is equal to the peak voltage of the AC they are supposed to run on. This is because most PC power supplies rectify the mains voltage into DC before they do their SMPS magic on it.

So all you really need is a high current DC-DC boost converter circuit that will boost your 12v up to say 180v. Regulation doesn't need to be perfect as long as you make sure there are no damaging spikes.

You're still messing with SMPS circuits but technically you are "inverting" nothing.

And since its DC and its only one voltage the complexity is greatly reduced. the PC PSU does most of the work for you.

 

[mvs sarma]

As Darfk has mentioned in his first post, there is no car involved- only a 12V battery.
I feel, converting 12V to 120V or 230V depending on the country concerned, the efficiency works out around 80%. then the PC psu( again SMPS) has its own efficicency. thus overall losses are more.

If a single DC -DC converter is designed with charging facility for the battery( which itself can float across with charge controll element, it will work ot almost at the same price or a 10% extra.
Now the overall efficiency will be better. It is imperative that +12 and +5 also need to be produced from the same Converter as the battery voltage may varry between 10 to 13.8V.

Finally Darfk will have to use a converter- call it inverter or any other name..

Telecom installations follow this method of course at 50V DC.
The computer terminals of electronic exchanges used to be supplied with 50V DC workability.

 

[Darfk]

PC power supplies can actually run off DC if the voltage is equal to the peak voltage of the AC they are supposed to run on.

This is very interesting Glyph, I will have to look into it!

By the way, thanks everyone.
I have considered almost every reply.