How much ripple and noise damages a cellphone battery or charging circuit parts - Page 1
Forum section: electronics / projects

author: sx57
author_rank: Contributor
timestamp: October 21, 2024, 05:18:05 am
content: Hello dear members of eevblog great community.for some time, I have been testing some phone USB chargers, for example Samsung 25W original and fake ones or apple 20w and many other brands.First there was the dilemma of adding a 10uf and 0.1uf capacitor to oscilloscope probes, at the output of the charger ,point of measuring, in order to measure the noise and ripple.After some experiments and reading a lot of methods recommended to measure PSU ripple, like Intel ATX ,and some other PSU manufactures plus YouTube videos, I came to conclusion that adding caps is probably the right way. because, although not using the caps makes the test show the real output of the charger specially switching noise, but adding them actually helps me distinguish between fake and original ones .it seems that original chargers engineers take into account the filtering caps in the charging circuits of the phones. I don’t know If I am right or wrong though.For example: Samsung 25w EP-T2510 chargers, has a noise output of 640 mv peak to peak, while a fake 25w charger has 477mv, so the fake one is better in output quality! then i added the caps, original 25w chargers noise output became about 148mv while the fake one became 252 mv. As you can see now there is a huge difference between the two in favor of the original. I saw a similar pattern between some fake and original apple 20w chargers. The original performs way better with added caps.Most of the fake ones normally show worse performance of course, whether I use the caps or not but in some cases as the example just wrote, adding the caps changes the better charger. I mean some chargers specially originals, perform better when I add the capacitors to measurement point.My oscilloscope is Owon 1022(not isolated version) and though it is humble and on a budget, it is really good enough.When I have the money I will better ones.I use the small ground spring on the prob.It is on 10X to have maximum bandwidth.I use peak detect mode because it shows peak noise and ripple way better than sampling.I uploaded the pics of 25w Samsung chargers’ measurement on 1ms time base because it shows more ripple and noise than shorter time bases.The oscilloscope is connected to a laptop using only the BATTERY when measuring ripple and noise.I use multilayer caps because they are better than ceramic and electrolytic.My goal is to sell chargers and review them based on their performance. Ripple and noise are measured for this. To see what is better and what may DAMAGE the battery or the components of the phoneI now have these questions please help me understand:1-at what ripple output, RMS and PEAK TO PEAK, the charger actually starts damaging cellphone battery, components or charging circuit in the phone, if I measure with the caps added to measuring point and the probes?2- What about if I measure without any caps? What is the damaging ripple and noise voltage output with no caps at the probes?3-does the shape and frequency of the ripple or noise matter? I mean can there be for example one shape and frequency of ripple with 200mv P to P amplitude that is healthy for the phone, while another shape and frequency with the same 200mv P to P amplitude but dangerous and damaging to the phone or battery?4-in all ripple and noise measuring guides, P to P is important, does it mean RMS doesn’t really matter?5-Which method is better any way, adding caps or not?7-does adding caps simulate charging circuit filtering in the phone or it actually does something else?8-am I wrongly measuring noise and ripple? Should I change the way I do it?Sorry for so many questions.It will be very kind of you to even partially answer some of them so I know how to better evaluate the charger’s quality according to their ripple output.I uploaded 25w Samsung fake and original ripple and noise tests and pics of measuring point and probe so you may see how I performed the tests.Thanks a lot, to all of you.

author: NightMoth
author_rank: Contributor
timestamp: October 21, 2024, 11:10:50 am
content: HelloIt is not direct reply to your questions, but I also was interested in measuring ripple with or without capacitors.It is wery interesting that when I have tested my no-name Chinese wallplug adapter, I got very similar values:- ~600-700mV ripple without filter caps- 262mV ripple with filter caps across PS outputFirst i red about measuring ripple with capacitors in this article "How do you reduce voltage ripple?" here:https://www.powerctc.com/en/node/4569Also I discussed it here:https://www.edaboard.com/threads/ripple-voltage-measuring-confusion-with-using-of-capacitor-along-with-oscilloscope-probe.409230/Following suggestions received in discussion above, I made custom oscilloscope probe to check ripple of my wallplug adapter.And I used 50Ohm termination at oscilloscope side to match 50Ohm BNC cable.Attaching some pictures of my attenpts:

author: nctnico
author_rank: Super Contributor
timestamp: October 21, 2024, 04:06:50 pm
content: I'd measure ripple under normal use condition and at rated load. That gives a good indication what kind of ripple to expect.However, anything which charges a battery from the power supply will have a regulator sitting in between so the amount of ripple coming from the charger doesn't really matter. If it is a USB charger, then I'd check whether the voltages are within limits at rated load. Keep in mind that some adapters will drop their output voltage when the load increase. This is a way to tell the device there is a current limit. Typically devices won't load a charger further when the voltage has dropped to 4.75V. Maybe there are limits to ripple over a frequency range in the USB specification somewhere but I can't find these quickly.Where it comes to adapters I'd be way more worried about efficiency, maximum temperature of the housing (at maximum load), if the charger's construction is that same as the sample charger tested by the certification lab, if the charger meets safety regulations and whether the charger meets the specification (=can deliver the maximum power). IOW: is it a good quality product which works as promised?

author: sx57
author_rank: Contributor
timestamp: October 21, 2024, 05:40:39 pm
content: hey man. i actually read your thread before.it came on google results when I searched for capacitors used for ripple measurement.unfortunately I can't make a custom prob or use 50 ohm terminal. i prefer to use current probing technic if possible.regarding fake Chinese PSUs, it's a gamble, some of them are very clean some of the are crap.

author: sx57
author_rank: Contributor
timestamp: October 21, 2024, 05:48:55 pm
content: Quote from: nctnico on October 21, 2024, 04:06:50 pmI measure the ripple under max load. i understand that there is a charging circuit that helps reduce ripple but isn't there any limits?i mean if ripple is not really important, then why is it an important factor in charging reviews done by the pros and why the original brands always try to reduce it? doesn't more ripple mean more pressure on charging circuit itself and reduced lifetime of it's components like capacitors?Quote from: nctnico on October 21, 2024, 04:06:50 pmi test efficiency, maximum temperature and max power/voltage drop.can you kindly give suggestions about testing safety?will testing it with a megger for insulation be a good enough

author: nctnico
author_rank: Super Contributor
timestamp: October 21, 2024, 06:22:06 pm
content: There is a big difference between an ATX-style PSU and a charger (either phone or laptop). The output of an ATX style PSU is used to power devices (as in chips)/circuits directly so ripple can affect the circuits connected. Although this has become less true for modern devices which use DC-DC converters to create local power supply voltages. A charger / laptop adapter OTOH never supplies circuits directly. There is always a regulator (switching or linear) in between which makes sure the output ripple is within specifications for the circuit. This regulator acts as a filter and works for as long as the input voltage stays between the minimum and maximum input voltage.You could test breakdown voltage but I don't know enough about that whether you'd need to test a larger number of units to gather statistic data on how good the insulation is. Test conditions like humidy & temperature also play a role.Another thing you can look for is component quality but with a lot of fakes around, having a brand on a part doesn't say a lot.

author: sx57
author_rank: Contributor
timestamp: October 22, 2024, 08:56:51 am
content: dear nctnico, thank you for helpin me.i understand about the differece between atx and usb psus.because there are a lot of reviews of phone chargers that measire and ripple, i thought it is really important.by component quality do you mean opening the psu and seeing the components inside?" There is always a regulator (switching or linear) in between which makes sure the output ripple is within specifications for the circuit. This regulator acts as a filter and works for as long as the input voltage stays between the minimum and maximum input voltage."does the ripple affect this (regulator (switching or linear) in between ) life time or it doesn't matter?