To start with, I'll say that I'm NOT an electrician/circuit designer - if my idea isn't feasable or just plain impractical, shoot it down.
What we all want is basically a PSU that works both in the car and in the house. Simple solutions are having 2 PSUs for the computer (AC->DC and DC->DC). I've been thinking of a different solution - one that takes AC or DC input and provides the outputs for an AT or ATX motherboard. Overall, here's what it would look like as a block diagram:
The two key things are:
1. when the power exits the AC->DC inverter is that it's regulated 12V at 11 amps.
2. when power exits the tank circuit on the diagram, it is also regulated 12V at 11amps.
The shutdown controller is fairly simple - when the accessory line goes hot, it lets voltage go through it. When accessory is turned off, the controller uses the battery line for a user-defined set of time (say 2-15 minutes) before not outputting power, thus turning the computer off regardless of the motherboard being AT or ATX.
At the point they come together, there is either a switch, some diodes, or some relays to control which input (AC or DC) is in use and keep them isolated from each other. Once it exits this part of the circuit, it goes to a voltage splitter which outputs the different voltage levels (+12, -12, +5, -5, +3.3) for the motherboard, hd, cd, etc.
The reason for the high output (12V at 11amps = 132watt) is to allow for some of todays processors to run. Outputs would be like zootjeff's new mbps :
+5 @ 10 amps
+12 @ 4 amps
+3.3 @ 5 amps
+5 STDBY @1.5 amps
-12 @ 100 mA
The key point is that the voltage splitter receives regulated voltage instead of unregulated. Does this idea look reasonable, or is it foolish?
Problems I see:
1) How do you propose to regulate the car battery voltage down to 12v on the output of the tank circuit? You'll need a pretty special regulator there to cope with the high currents you propose. (not to mention that you'll be regulating from input voltages ranging from around 12v up to 14.5v).
2) Voltage splitter??? This is effectively a dc to dc power supply. I think the term "voltage splitter" trivialises the problem somewhat.
I have a system which works both in the house and in the car by just feeding my regular dc 2 dc supply with unregulated 13v from a car battery charger transformer and a bunch of smoothing capacitors. Works fine for me.
Hmm... interesting idea.... but........ I was trying to come up with a AC-DC-DC powersupply myself... but I took I totally (well, as totally as you can get) approach to the idea. The problem with your idea is that I wanted a powersupply that would power ANY system in teh house or car. This included my home PC (AMD Thunderbird 1ghz, 512megs ram, 80gig HD, DVD drive, AGP graphics card, ect.) and your idea just wouldn't cut it... Even if you could come up with a DC-DC supply with enough OOMF I doubt that you could make an AC-DC 12volt PS that could supply enough current to output the DC-DCs full potential.... My approach was to use a standard 300watt AC-DC supply, with a different transformer and primary circuit for teh DC-DC section, and use teh original secondary, low voltage, side of the Original PS for teh DC-DC as well as the AC-DC..... any problems with this idea???? perhaps someone could desig a PCB for teh foward converter??? this would make my progress alot quicker.. :D
This is like what I was going for in my Modify Sproggy for 12V 5A out? thread. A lot of the new Mini-ITX cases have an internal DC-DC supply, and a laptop-like external AC-DC converter. My idea was to make something simple to provide the regulated input to the DC-DC supply from the car's power and just use that in place of the supplied adapter. Then you could just leave the original AC-DC in the house... It's not as hefty as what you want, but it seems like a relatively easy way to go. Make one power supply, with external AC and DC parts for supplying input to the actual power supply...
How about follow the presslab tutorial by arby - you get a high wattage dc-dc power supply cheap! I'm gonna try soon and will report back! I wanna run a duron 900 ish (I just have one doing nothing so thought I might as well use it). However first of all I need to get a new mobo!
I agree with Andrew, Using presslabs converter this would be pretty easy. What you would do is simply use the complete original PSU plus an additional transformer + presslabs circuit and attach the outputs off both transformers to eachother, zo that the transformers are "in paralell"
You do need some bad-*** diodes to make sure that when you use either the presslab or original circuit the other ciruit won't be blown op by the outop currents of the first.