stealth17 Posted October 2, 2005 Report Share Posted October 2, 2005 I need a linear 5amp design that has ULTRA clean and stable power that is highly adjustable from 1.25-2v. I need the least droopage possible.Ive got a design for 5v to 2.5-4.1v now. Its a switching design. I also need this 1.25-2v design though.If someone could help me that woudl be SUPERB!Ive attached a schematic of the switching design and the parts are quoted below. If you all see a mistake or see somewhere that needs improving, please tell me.Thanks!!!-JordanT = STP55NF03LIC = TL431C1, C3 = 3300uF/6.3V low-ESRC2 = 100-470uF/16V low-ESRR1 = 390ohmR2 = 1.5KohmP = 1Kohm multiturn Quote Link to comment Share on other sites More sharing options...
ante Posted October 2, 2005 Report Share Posted October 2, 2005 Hi Jordan,Why do you call the attached design “switching”? Quote Link to comment Share on other sites More sharing options...
stealth17 Posted October 2, 2005 Author Report Share Posted October 2, 2005 Hi Jordan,Why do you call the attached design “switching”?I thought it was becuase of the switching mosfet ???Told you Im a noob lol.Now that you mention that, your right, its definatly linear. The guy said the mosfet gets very hot, and there arent any op amps. Do you think thats a good circuit for like 15amps of clean, stable power? Or, should I add a couple more caps and an inductor? Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted October 2, 2005 Report Share Posted October 2, 2005 Just because it uses a MOSFET it doesn't make it a switching regulator, MOSFETs can be used in thier linear region too you know, in fact all transistors can, well apart from the unijunction but it's not a proper transistor anyway.The MOSFET needs to be a low threashold type otherwise it will never turn on enough to provide the current you require. Quote Link to comment Share on other sites More sharing options...
ante Posted October 2, 2005 Report Share Posted October 2, 2005 Hi Jordan,Anyway, you can change this circuit from the 2.5 – 4.1V range to 1.25 – 2V if you like but it will get even warmer than before! If you parallel some MOSFETs and put them on a big heatsink with a fan you just might get away with it! If the computer in question is equipped with water cooling you can use a smaller heatsink with a channel and run the water through it, this will save some space and secure the cooling of the MOSFETs. 8) Quote Link to comment Share on other sites More sharing options...
stealth17 Posted October 2, 2005 Author Report Share Posted October 2, 2005 lol there isnt an easy way to do it without needing big heatsinks and stuff? Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted October 2, 2005 Report Share Posted October 2, 2005 Yes there is a way to convert 5V to 1.25-2V without a fat heatsink, a switching regulator will do this but in your first post you stated that you need a stable and clean supply, however a switching regulator will not provide this as the output will be very noisy. Quote Link to comment Share on other sites More sharing options...
stealth17 Posted October 3, 2005 Author Report Share Posted October 3, 2005 what kind of circuit did this guy use?http://www.xtremesystems.org/forums/showthread.php?t=73043he had 2mv droop is all too Quote Link to comment Share on other sites More sharing options...
ante Posted October 3, 2005 Report Share Posted October 3, 2005 Hi Jordan,A clean supply is not the same as a stable supply! Remember; all PSUs for computers are switchers and there are no problems getting a stable voltage from a switcher! I don’t think your computer will be disturbed by noise from a switching supply since every computer runs from one. The efficiency for a switcher might be as good as 90% or more but a linear supply can be as low as 15 – 20% depending on the difference between the input and the output voltage and the current needed. The rest will be heat whether you like it or not! 8) Quote Link to comment Share on other sites More sharing options...
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