i been trying to find a lm 317 type chip that can handle above 3 amps handeling 5 to 6 would be nice and ajust it with a pot ? any takers on other options for an ajustable power supply build ?
Page 17 of the [u]LM317 datasheet[/u] shows a "high current regulator" using some additional transistors.
When you get up around 3 Amps I'd say it's time to start thinking about a switching regulator. A switching regulator is much-more efficient and can put-out high-power without dissipating lots of power/heat inside the regulator itself. (Efficiency is more important in a variable-voltage design where the voltage "dropped" across the regulator can be higher than a fixed-output design.)
Off-hand, I don't know of any variable-switching power supply chips, but I'm sure you can find something, or someone else can suggest something.
You can buy adjustable regulators with output current limits of 5 to 10 Amps at DigiKey.com. They have 9 pages of options. Use parametric search to find devices that meet your requirements.
When dealing with adjustable linear regulators, certainly at the 3 amp output and greater the limit is going to be how large a voltage range you wish, as the lower the output voltage selected with a fixed DC voltage input feeding the regulator the higher the heat dissapation will be for the chip and will most likely be hitting automatic temperature shutdown well before you hit the devices maximum output current rating. So after you design in the needed heat management cost, size, noise, etc, you will wish you had started with using a switching regulator to begin with.
So state your total voltage range desire, and maximum current output desired. The highest output voltage sets the required filted DC input value needed for the circuit and the minimum output voltage running a maxium output current rating will determine the heat load.
Bottom line, don't use a linear regulator, buy an Asian adjustable Switching regulator and build a power supply around it, they are cheap and work great.
Lefty
well i was thinking of useing one of my 2 options to get power from 1 a hp printer transformer with a 32v leg at 4 amps...and the second leg 15v with 8amps option 2 is a computer power supply with the standard 5 and 12 volt out puts its a smaller compact model but the amps are like around 18 6 and .4 and some of my stuff i would like to control these legs better then the giant steps. in current and volts
When dealing with adjustable linear regulators, certainly at the 3 amp output and greater the limit is going to be how large a voltage range you wish, as the lower the output voltage selected with a fixed DC voltage input feeding the regulator the higher the heat dissapation will be for the chip and will most likely be hitting automatic temperature shutdown well before you hit the devices maximum output current rating. So after you design in the needed heat management cost, size, noise, etc, you will wish you had started with using a switching regulator to begin with.
So state your total voltage range desire, and maximum current output desired. The highest output voltage sets the required filted DC input value needed for the circuit and the minimum output voltage running a maxium output current rating will determine the heat load.
Bottom line, don't use a linear regulator, buy an Asian adjustable Switching regulator and build a power supply around it, they are cheap and work great.
Lefty
@retrolefty thank you that is a better idea i guess so do you know if this creates any heat or just less loss ?
and @johnwasser and DVDdoug thanks for the info i may change my direction to this no linear regulator then i just have make it adjustable and building the supply around some already made circuits sounds fun enough to get the project going ...
@retrolefty thank you that is a better idea i guess so do you know if this creates any heat or just less loss ?
Of course, even a switching regulator generates some amount of heat, almost all electronic circuits dissipate some amount of heat, otherwise they couldn't perform any real work. But that aside, most switching regulators work in the 80% to 90% efficiency range. To compare that to a linear regulator, that lets say you designed a 1 vdc to 24 vdc adjustable linear regulator with a 3 amp max output current. The efficiency rating will be inversely proportional to the output voltage setting and worst case would be if you set it to 1vdc out with a load resistance drawing 3 amps. The regulator would have to dissipate 23V X 3A or 69 watts of power to supply the 3 watts output power to the load (1V x 3A), that's 4.3% efficiency and a ton of heat to remove from the chip.
Lefty
ohh wow thats horrid lol.... yeah thats no good for what i want to do .. that would some what act like a heating element then ans just run the electric bill up with power your not using then right ?
yeah i know nothing about this switching supply thing do you have and urls that you think i should read i tried to find some info for basic pcb circuit use but have only found some silcon looking chips they say are switching with like 5 to 6 pins ... maybe like was suggested earlier in this topic i should find a cheap already made foreign switching regulator and build my supply around it and maybe i can hack it for adjusting i was hopeing that this would turn up a simple answer to the lm 317 design not haveing to learn something al over again ahhaha.... jokeing learning is half the fun !
ok so i found this would this be what you are refuring to and with with the better efficiency
this was on ebay i think this one says its still like effeciency is based of the current resistance so eaither its still linner or i have no idea what part number i should look for lol..
let me know if im still headed in the wrong direction
If your HP Printer power supply or your PC power supply is a switch-mode supply, you MAY be able to make the output adjustable if they have an adjustable switched-mode regulator. Open it up and look for numbers on the chip(s).
Good thinking..
oh that would be even better ? so what your suggusting is if the regulator in the suply its self is an ajustable one then ii could remove the the buffer part of the supply and replace it with a pot or some thing of my own to control the voltage .in theroy ?
this says its switching with 92% eff... are they lieing ? lol or is this what i would need ?
http://www.ebay.com/itm/LM2596S-DC-DC-35V-to-33V
ez8mm:
this says its switching with 92% eff... are they lieing ? lol or is this what i would need ?
http://www.ebay.com/itm/LM2596S-DC-DC-35V-to-33V
"This listing () has been removed, or this item is not available."
i been trying to find a lm 317 type chip that can handle above 3 amps handeling 5 to 6 would be nice and ajust it with a pot ? any takers on other options for an ajustable power supply build ?
My answer is, if you don't mind some heat, the LM338K.
And maybe you are interested in developing an Arduino controlled regulated power supply, with current limit and constat current features. I´m playing with this proyect for a while.
http://www.ebay.com/itm/Low-Ripple-LM2596-DC-DC-Converter-Step-Down-Power-Module-In-4-40V-Out-1-5-35V-/170799546371?pt=LH_DefaultDomain_0&hash=item27c4724003
this is the one that i posted earlier it has some good photos to read the chip and caps.. but this listing does not have much info... like the one that was removed
sorry hopefully this link will work
below i found this one but it dose not say what they use but i think the ratings are what i need again it says 94% efficiency but i dont know what regulator they used but its probably cheaper then buy this one with all the spare parts i have around sorry about all the mix up and thank you for looking in to this again ... let me know if this is the switching non liner one that would be good for useing as a adjustable regulator for a home made power supply
as long as you think this is going to work
It is a switching regulator. It actually says: Efficiency up to 94%, note the up to part. The actually efficiency of any switching regulator will be a function of the input voltage, output voltage adjusted to and the current draw from the load. So its efficiency number is variable within a range. Most switching regulator datasheet will have graphs showing the efficiency Vs various operation conditions. But in all cases they all run much for efficient then linear regulators.
As far as buying that unit. I would hold off till you know more about it. I would want to know what regulator chip is being used in it as a minimum so I could consult its' datasheet to see more about its' capabilities and limitations. Also sounds like the seller is warning that output voltage above 8vdc the thing will get loud due to inductor noise?
Lefty
agreed lefty i had the same thought that i want to know what chip is in it ? it almost looks like they are hideing it .. not that im vary good at reading a data sheet and understanding it but i can pick out the real bad points and have an idea of whats there..
It actually says: Efficiency up to 94%, note the up to part. The actually efficiency of any switching regulator will be a function of the input voltage, output voltage adjusted to and the current draw from the load. So its efficiency number is variable within a range. Most switching regulator datasheet will have graphs showing the efficiency Vs various operation conditions. But in all cases they all run much for efficient then linear regulators.
im just guessing from what you said there .. but say the lower the input voltage is for a switching regulator say its good for the 4 to 48v in put but it s out put is 3 to 20v ... it would be more effciant to keep the in put on the lower side close to what you out put is to keep the heat and waste down ? so i would be useing the full 3 to 14v often so my in put should be 16v and that would be better then puting a full 20 to 32 in amppers aside.. i know ohms law will afect this but just for example is that what your saying from you quote above ?