How to failure test --> Laptop 19v Power Supply and specs - Page 1
Forum section: electronics / projects

author: ez24
author_rank: Super Contributor
timestamp: May 01, 2015, 01:53:10 am
content: HiI am starting to work on a project (unknown power demand) and I am going to start with a laptop power supply (requirement) to build a power supply with different voltages and here is the first one I bought:[url=http://www.ebay.com/itm/291090803947?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT]http://www.ebay.com/itm/291090803947?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITIt has a DC plug that I can get to bare wires without any soldering using adapters (requirement). With my Dell PS I cannot get to bare wires without soldering. Also I made a mistake in getting this one with 3 prong AC.This ps is rated as:Output : DC 19V 4.74A 90WConnecter size : 5.5mm/2.5mmI read somewhere here to use 70% of the rating, which would be 4 ampsBut I want to test several units. To evaluate units should I test to spec (90w in this case) or go higher to failure.I would like to go to failure but I do not know what will happen. I would also like to short out the dc plug.If I will cause a fire, I would like to know so I can do the test outside. So I am asking for advice on how to test laptop power supplies that are from China.I have several 1 ohm 100 watt resistors to use on this project.Summary:1. I would like to short out the plug ie R = 02. Using Ohms Law (I hope) P = IE 90 = I * 19v I = 90w/19v = 4.7 ampsThis requires V = IR or 19v = 4.7amp * R R = 4 ohmsRun at 4.7 amps for at least x hours (any suggestions) using 4 ohms with power resistors.3. Reduce R until failure happens (any guesses on what will happen ?)4. Run the same test on different units to find the best one in regards to safety. Safety means highest I and /or lowest temp ??Also if anyone has done this and is willing to share the results - I would appreciate itHere is another ps and specs:[url=http://www.ebay.com/itm/20V-4-5A-90W-AC-Adapter-For-IBM-Lenovo-idealpad-Laptop-Charger-Power-Supply-Cord-/381226781926?pt=LH_DefaultDomain_0&hash=item58c2e30ce6]http://www.ebay.com/itm/20V-4-5A-90W-AC-Adapter-For-IBM-Lenovo-idealpad-Laptop-Charger-Power-Supply-Cord-/381226781926?pt=LH_DefaultDomain_0&hash=item58c2e30ce6Specs and questions for this one:1. 4Line regulation (full load): ??0.5%-- what is this ??2. Peak- to -peak ripple: < 100MV-- I suppose I can test this with a scope. Does it matter what amps I should do the test on?3. Working temperature: 0-35??@100%,50??@70% load-- does this mean it can run at 90 watts between 0-35 degree C ? and between 35 to 50 C 70%5. Setup rise hold up time: 100ms,50ms,20ms@240VAC input-- I do not know what this means5. Strong made totally compatible part-- ok5. Over voltage protection: 115%-135% rated output voltage-- how would you get this - does this mean the output voltage is guaranteed not to go over 25.65 volts (this sucks)5. Withstand voltage: I/P-O/P 3Kvac,1 minute-- I/P O/P what is this Does this mean I could input 3,000 AC volts for 1 minute5. Over load protection: 115%-135% fold back current limiting, Auto-recovery-- I have no idea what this meansthanksRoger

author: lukaq
author_rank: Regular Contributor
timestamp: May 01, 2015, 04:03:47 am
content: QuoteThis means, output voltage will stay in 0.5% of voltage at full load, when input voltage will change over converters input range, could be 90-260Vac, could be 230Vac +/-10%, depends on what is written on supply for its input voltage range.QuoteThis should be under max output current, since then you will have biggest output voltage ripple (And I think at highest input voltage at the same time)QuoteYes, that is was it looks like to me too, and it makes sense.QuoteIt means, that supply won't shutdown if input goes away for up to 100ms. Energy is used from all internal capacitors, while there is no energy coming from the wall.5. Strong made totally compatible part-- okQuoteYes, over voltage protection is set 15-35% higher then rated output voltage. But you would have to drive very inductive load and switch is on and off (off could be the problem with some big motor). I don't think you will ever have a problem with this.QuoteIt means it passed 3kVac test, if that voltage was present on input and looked at output and other way around (for at least 1min supply would not arc from input to output and other way around. Supply itself would die of course)QuoteThis means, you are protected against shorts and overloads. In overload situation, it could current limit to 15-35% above rated current. Fold back current limiting means, current would be at max (15-35% still over rated current), but voltage would drop, since bigger and bigger load would need higher and higher current at the same voltage.In other words, voltage is at rated output voltage up to 115-135% of output current, then voltage starts to drop and probably shuts down if it has some under voltage protection, say at 80% of rated output voltage

author: ez24
author_rank: Super Contributor
timestamp: May 01, 2015, 08:14:53 pm
content: thanks lukaq

author: Christopher
author_rank: Frequent Contributor
timestamp: May 01, 2015, 08:20:10 pm
content: Start with a high resistance (low current, 0.5A?) measured input power, output voltage & current (for efficency), temperaturesleave here for an hour and measure again.Increase current and try again!Rinse and repeat.Leave on a maximum load (i.e 4A) overnight.Don't forget to put an effing great heatsink on those resistors. Remember voltage drop of cable can be significant so use a high gauge of cable

author: ez24
author_rank: Super Contributor
timestamp: May 02, 2015, 12:07:29 am
content: Thanks ChristopherI had not thought about the cables so I am going to start making them.And for the procedure

author: radioFlash
author_rank: Regular Contributor
timestamp: May 02, 2015, 01:39:00 am
content: A properly designed power supply should have short-circuit protection, over-current protection, and thermal shutdown so it doesn't burst into flames under these faults. The power supply you linked to looks like a generic power supply built for the lowest possible cost, so it's probably not particularly reliable and may or may not properly implement these features. You may want to look for one of the "genuine" power adapters for a Lenovo or other well known brand. The link below looks like it might be a genuine power supply, although of course it could be a knockoff.http://www.ebay.com/itm/Genuine-90W-Power-Adapter-Charger-Lenovo-ThinkPad-Edge-E430-E435-E520-E530-E535-/271117698059?pt=LH_DefaultDomain_0&hash=item3f1fdfc40b

author: DanielS
author_rank: Frequent Contributor
timestamp: May 02, 2015, 02:20:18 am
content: Quote from: radioFlash on May 02, 2015, 01:39:00 amThe cheapest PSUs you can build would use an all-integrated switching controller in TO220 or similar package like a TOP250 that has nearly everything except the rectifier bridge, input filter cap and output transformer built-in for the primary side. That makes it difficult to omit over-temperature and over-power/current protection even if you wanted to.

author: ez24
author_rank: Super Contributor
timestamp: May 02, 2015, 07:00:48 pm
content: QuoteI was shocked on how bad my power supply was. Someday I will destructive test it. Also I realize for any units I sell I will have to include a UL listed ps.The one you linked to has UL on it. The plug size is different that the one I have and the adapters I have. So if I can find some adapters like this one:[url=http://www.ebay.com/itm/DC-Power-Female-Jack-Connector-Plugs-5-5x2-1mm-For-LED-Single-Color-Strip-5PCS-/351387615989?pt=LH_DefaultDomain_0&hash=item51d05582f5]http://www.ebay.com/itm/DC-Power-Female-Jack-Connector-Plugs-5-5x2-1mm-For-LED-Single-Color-Strip-5PCS-/351387615989?pt=LH_DefaultDomain_0&hash=item51d05582f5I will get some of these power supplies. They are $10 cheaper than any UL that I have found.thanks

author: ez24
author_rank: Super Contributor
timestamp: May 02, 2015, 07:19:46 pm
content: Found one (with standard 2.5x5.5 plug): ($23.00)[url=http://www.ebay.com/itm/Original-Toshiba-pa3516u-1aca-Global-90W-AC-Adapter-OEM-/280683893374?pt=LH_DefaultDomain_0&hash=item415a10527e]http://www.ebay.com/itm/Original-Toshiba-pa3516u-1aca-Global-90W-AC-Adapter-OEM-/280683893374?pt=LH_DefaultDomain_0&hash=item415a10527ehave to be very careful with this seller look at this one ($220.00 + 10.00):[url=http://www.ebay.com/itm/Genuine-Toshiba-pa3290u-1aca-p10-s429-p15-Adapter-OEM-/290569390949?pt=LH_DefaultDomain_0&hash=item43a7490b65]http://www.ebay.com/itm/Genuine-Toshiba-pa3290u-1aca-p10-s429-p15-Adapter-OEM-/290569390949?pt=LH_DefaultDomain_0&hash=item43a7490b65whew and he sold 11 of these (different size plug). Seems it would be cheaper to buy a new computer.I will check my purchase very carefully and make sure I get the $23 one. So I will order a couple of the $23 ones with standard 2.1x5.5 plugsthanks