power supply questions

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sparky!(Sean)

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I am looking to build a 10 a power supply with a current limiter and am wondering which ic to use because previously I have used a lm317t and the max current is 1.5a the lm350's max current output is 3a I am trying to find a voltage regulator that has a max current output of 10a any help is greatly appreciated
 
I am fine with not being able to go down to zero, but I can't see that pic very well do you think you can find a bigger one I already got a big enough transformer it was from a furnace I might need a bigger bridge rectifier though
 
Believe me or not: buy one. They are so cheap now, it makes no sense to build one. A linear 10A power supply is the size and weight of a boat anchor, you can't build one for less than the cost to buy.
 
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The problem OP is going to find is HEAT. A linear regulator for that sort of current 10A needs a voltage overhead - and- it's difficult to arrange this what with the transformer regulation and the need to use something that is just "handy" ( Make that "free").

I have found heatsinks with fans available ex-PC at computer fairs - these cost less than a new fan as they are designed for a specific old-processor - but a plain heatsink is still a heatsink and the fan is well connected to the metal . . . in effect you are getting a large heatsink in a small space, provided you don't mind the fan-noise. For greater reliability fit a second fan, or replace with new.

Has OP smoothed the supply? - because that 723 will need a decent supply to maintain its operation and 10A will need Big C's to keep ripple current low, so the caps don't overheat. I'd suggest as a mimimum the supply is smoothed with caps making at least double the ripple-rating . . . . but others with a mathematical mind may be able to put figures to it . . . . can OP suggest the rating of the Caps he's proposing?
 
A 1,000 u per amp seems to be a rule of thumb, so long as your cans can take the ripple current sounds like they'll be fine, if you dont know the ripple current you'll soon find out when you use the supply, too low a ripple current and they'll get mad hot.

I checked the link it seems fine to me, are you still having trouble with it?
 
The datasheet for the LM317 shows how to add power transistors so that the output voltage is still regulated perfectly by the LM317 but the output current can be much more.
 
With a load of 10A and 10,000uF filter capacitor then the ripple at the input of the regulator will be about 10V so the regulator will not regulate. Use 4 or 5 10,000uF capacitors in parallel.
 
In honesty, I don't recommend a novice trying to build a 10A power supply. It won't end well. And FYI: using an LM317 with external transistors means that it has no current limiting or thermal protection, the supply will blow up the first time someone accidentally overloads it.

If you would specify what you need: input voltage range, input current range, any special features I will try to find one for you
 
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Hello,

The LM317 based design with added pass transistor does not blow up with overload if it is done right. The trick is to always have the LM317 handle some of the current so that when the current does go too high the LM317 start to limit it's own current and by design that limits the drive to the added transistors. I cant say a linear alone is a great idea, but hey it is possible.

Did anyone mention the required output voltage and the transformer that is to be used?
 
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