Hacking EKA K201 230VAC to 5V+/-0.5V USB small trafo based converter teardown - Page 1
Forum section: electronics / projects

author: eneuro
author_rank: Super Contributor
timestamp: November 19, 2015, 06:50:59 pm
content: Hello,I've on my desk this EKA K201 230VAC to 5V+/-0.5V USB charger which looks like thisUpdate: It outputs 5.44V open circuit from 230VAC mains, so within its "specs"While they claim things like this 1A output current It puzzled me what is inside, especially while they wrote in description:5V+/-0.5AIt has some kind of CE mark, but... it was made in China and bought in... shop in Europe owned by oryginal China man, so... the only rule apply:DO NOT TURN IT ON, TAKE It APPART !!!!Its oryginal top and bottom (flipped to easier reverse this quite simple circuit):More datailed views around top pcb there:I've removed this useless 230VAC mains plug (there is no fuse or current limiting resistor) and output USB connector and soldered wires to make some measurements.I'll add red diode indicator at output while there are already free pads/vias.It looks like it works in flyback configuration and output transformer wire througth diode charges 407uF 10V capacitor with feedback made of optoisolator (PS 817D, but similar to PC817).It is interesting, that probably this PC817b feedback looks like this, but unfortunatellyI can't find ANY datasheet of LM13003 (top TO-92), while bottom C945 is NPN (TO-92)Ground after 230VAC input diodes (1N4007) is connected with secondary ground via 1KV 222 capacitor...Tried connect this thing to 12V car starter battery, but nope output voltage doesn't go too much above 0V, while my plan is maybe try to hack this thing to output ~5V from 24VAC or so, or even 12VHowever, this misteriousLM13003 JVI PBused in this very cheap <1.5$ USB charger puzzles methis TO-92 IC is and where to find its datasheet?Probably, when PCB circuit will be drawn it will be more visible what this IC might do in this converter, but maybe someone knows IC similar to this LM13003 TO-92 ?Update: This YXC marked capacitor is of course 400V 2.2nF after rectified mains

author: eneuro
author_rank: Super Contributor
timestamp: November 19, 2015, 08:17:18 pm
content: Probably L M 13003 is something like those high volatge NPN transistor:ST13003 HIGH VOLTAGE FAST-SWITCHINGNPN POWER TRANSISTORorTS13003 - High Voltage NPN TransistorandKSE13003 - High Voltage Switch Mode Applications, so lets determine its CBE and reverse engineering this PCB

author: Gyro
author_rank: Super Contributor
timestamp: November 19, 2015, 11:03:05 pm
content: The clearances on that thing are awful! I also can't see ANY form of protective device (even a fusible resistor) between the mains and the rectifiers/cap.

author: eneuro
author_rank: Super Contributor
timestamp: November 20, 2015, 07:05:32 am
content: Quote from: Gyro on November 19, 2015, 11:03:05 pmIt is ONLY ~1mm between transformer primary and secondary on top PCB where they tried hard route thisSR160 - 1A 42V reverse RMSto 470uF 10V capacitorSo, they had more than 5mm between transformer primary secondary pins, but while tried to fit into this single layer PCB size they additionally put two tracks inside PC817 optocoupler and now it is 1mm-1.5mm onlyIt is also less than half milimeter between rectified mains diodes output and yep no fuse, no resistor to blow, but... probably the only hope is those crappy white thin wires which connect PCB 230VAC input to mains socket plug should fail first before PCB tracks.Anyway it is sold in EU, so who takes responsibility if this thingCE markedwill go into flames eg. when this 400V 2.2nF capacitor fails and short circuit mains without any fuse, but only those white thin wires goes into flames?

author: eneuro
author_rank: Super Contributor
timestamp: November 20, 2015, 08:20:14 am
content: While decoding values of four resistors there I've found something interestingThree are cleary visible and starting from top are:5.1M 5%470 5%6.8 5%BUT this 220 Ohm (multimeter confirms this) close to optocoupler looks like someone PAINTED its precision oryginal color gold with... green?This green painting is worse quality from PCB side, so gold oryginal color easier to notice thereWhen we try decode with green instead of gold, we have: green brown red red = 5.1k 2%, but it is 220 Ohm 5% on PCBhttp://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-resistor-color-code-4-bandNow, we are even more motivated to reverse engineering this circuit, while probably this IC marked "L M 13003", where "L M" are spaced (not "LM") looks like faked IC or remarked another from ???13003 NPN high voltage transistors family , similar to faked "PS 718D" instead of well known PC817Update: Yep, changed PC817 to.. PS817 leads after "smart" Google serach to thisParadox Switching Power Supply PS817BTW: Capacitor in the middle on primary is 472 if someone wanted to have some fun to reverse engineering this circuit, too

author: Srbel
author_rank: Frequent Contributor
timestamp: November 20, 2015, 08:28:04 am
content: Quote from: eneuro on November 20, 2015, 07:05:32 amHa ha ha. xD

author: Gyro
author_rank: Super Contributor
timestamp: November 20, 2015, 10:09:48 am
content: ... and that 2n2 1kV primary - secondary EMC cap next to the opto is Required to be Y1 rated (and isn't!). That might well be the first thing to kill the user holding the USB device... assuming that the house fire doesn't get them first!You don't say what country you're in (aside from Europe) but having seen and understood it, it's pretty much your duty to take it to your local Trading Standards authority so that they can be removed from sale, recalled, and the importers strung up from the nearest streetlamp!

author: eneuro
author_rank: Super Contributor
timestamp: November 20, 2015, 11:22:49 am
content: Quote from: Gyro on November 20, 2015, 10:09:48 amIt was bought to plug LEDs lamp powered oryginally by 3x AAA 1.5V batteries, so with one 1N4007 and voltage drop ~0.7V it works fine.Hopefully, there is no metal parts in this lamp-output from this "USB charger" using standard USB wire male connector is connected to lamp from its back and lamp has only one plastic button, which preses switch inside lamp to turn it On/OFF, so very little chance to touch any mains under normal conditions and this is not for resale.Battery pack at the bottom is disconnected from oryginal circuit.Just needed 230VAC to 5V wall socket converter, so I fought it might be interesting what they put into this cheapy crappy looking oneI thought, that it is filled inside and completly filled with electric insulator, but PCB looked at shown in first photos-didn't touch it-just removed plastic case.Now, it is clear it can be dangereus for people charging their phones/tablets while playing live with those things during charging (many people do this) especially, while they are priced at very low cost <$1.5 in China local small shop market, so there is huge probability a lot of people can buy thisUSB charger and have no idea what is inside-they even do not care about CE mark, when see better price...

author: nukie
author_rank: Frequent Contributor
timestamp: November 20, 2015, 11:45:01 am
content: 13003 is widely used in many 5V chargers, power supplies, compact fluorescent drivers, LED drivers and etc. Commonly found in very cheap electronics gear but also found in Philips cfl bulbs.Next step up is 13005 it will handle higher power.

author: eneuro
author_rank: Super Contributor
timestamp: November 20, 2015, 04:58:18 pm
content: Quote from: nukie on November 20, 2015, 11:45:01 amYep, I've found teardown of similar (fake)Tiny, cheap, and dangerous: Inside a (fake) iPhone USB chargeralso with dangerous very small creepage between mains and output secondary with similar 13003 and 817 optoisolator as feedback from reference voltage, but they used 431 2.49V voltage reference and it is made in SMD version, but similar SMPS design, so I wonder how many cheapy USB chargers uses this dangerous low creepage between mains and secondary on PCB topologyI've noticed the same in this my (fake) China charger that those USB D+/D- lines were simply connected on this PCB shown in posts above while, they wrote in link above something like this and it makes sense:QuoteJust thinking-maybe we could try distinguish better USB charger from crap just by connecting own USB cable with those D+/D- lines available, so we could use in shop multimeter to make measurements between D+ and D- lines and ground, to easy catch such crappy (fake) USb chargers like those cheapy China, while probably market is floode by thi sort of crap?Yep, never go for shopping without... multimeter in your handsI think I will make such male USB connected wires and tomorow will go to this China shop for hunting for another similar"safe USB chargers" crap-probably by testing those D+/D- lines resistance we should be able catch those cheapy crappy USb chargers without need to make any teardown and loose $1.5

author: mich41
author_rank: Regular Contributor
timestamp: November 20, 2015, 06:11:35 pm
content: Looks like one ofthese.Transistors top to bottom: NPN, NPN; BCE, BCE.To run it from lower voltage, you would probably need to tweak the middle resistor.Not that it's worth it, there are better DC step-down converter modules for similar money.BTW, "cigarette lighter socket"?

author: eneuro
author_rank: Super Contributor
timestamp: November 20, 2015, 08:17:22 pm
content: Quote from: mich41 on November 20, 2015, 06:11:35 pmThanks for this link-it should help a lotThis is what I'm interested now, since successfully was able easy change output voltage by desoldering this crappy Zenner diode and by replacing with TL431I with two additional resistors I was ablethis xx817 optoisolated feedback easyI might prefere close to 8V instead of 5V to be able run MPU with LM7805 or other 5V LDO

author: eneuro
author_rank: Super Contributor
timestamp: November 20, 2015, 09:15:03 pm
content: Quote from: mich41 on November 20, 2015, 06:11:35 pmAdded TL431I with two extra resistors and now we have 8.9V ~9V, so this thing could be usable at lower input voltage, if I was able tweak this PCB transformer primary circuit for 24VAC or even 13.5VDCUpdate: Probably changing transformer primary might be needed, since this thing was designed for 230VAC, not 24VAC-order of magnitude higher voltages, but we'll try understand better its primary circuit, since transformer secondary is already hacked successfully to desired output voltage -close to 9V batteryNote: There is some hope, they wrote 100V-240V input, but still 4-8 times higher voltage than I'd like to run this thing from 12V-35V (24VAC)We should be able adjust with TL431I output voltage starting from ~3.6V by adjusting only two resistors, so quite interesting SMPS development kit for $1.5

author: eneuro
author_rank: Super Contributor
timestamp: November 21, 2015, 08:29:29 pm
content: Quote from: mich41 on November 20, 2015, 06:11:35 pmYep, thanks again it is RCC circuit linked by you and correctly figured out those NPN transistorsReverse engineering of transofmer primary side (I've used in this simply simulator transformer, but have to be like this shoved above in classic RCC circuit) shows similar design to RCC linked aboveResistor 470 Ohm and capacitor 4.7nF define its working frequency ~100kHz and, so changing this cap doesn't help run this thing at lower input voltageIt looks like resistor 6.8 Ohm with NPN close to it limit current to ~100mA and together with optoisolator output shorts top power NPN base to its emiter which turns this RCC off.5.1M resitor helps start oscilations, so probably I will change it to lower value linked with lower voltageMaybe it helps run this thing at 12V-36V.Maybe we have to also make lower this 470 resistor and increase capacitor in series to keep similar frequency?What do you think-how to keep this thing running at order of magnitude lower input voltage, but we can assume not 50Hz, but it can be DC and up to 1A output probably not possible since we do not like change this transformer, so 100mA could be fine...Note: I've changed output Zener to TL431I and now we have 8.9V open circuit voltage...

author: eneuro
author_rank: Super Contributor
timestamp: November 22, 2015, 03:22:19 pm
content: I've made also measurements of resistance of transformer coils and it looks like as expected there is a few times higher number of turns on power coil, so I was wondering if by simply adjusting resistors values I will be able make this transofrmer primary to oscilateI was supprised, that by adding only three (soldered on bottom side for testing to easy go back to oryginal 230VAC version) primary transformer circuit resistors I managed to get again 8.96V output with described TL431I zener, despite secondary transformer output have fixed numer of turns from much higher voltage, but it has 8.96V open circuit output voltage from 24VAC inputI've increased switching frequency and lowered down power transitor base resistor, but also slightly increased maximum primary current by adding 10 Ohm resistor in parallel with oryginal I've got 4.4 Ohm now, so something around 150mA max or soNext step will be see if it works from 12V car starter battery, but we can use two in series if it doesn't work) and how much current we can get at output short circuit to lower voltage, but not so bad-without changing transformer we were able run this thing from 24VAC right now

author: eneuro
author_rank: Super Contributor
timestamp: November 23, 2015, 08:19:11 am
content: I've played a little bit with output load.When 27 Ohm were used with 24VAC, volateg drops from 8.9V open circuit to 3.6V so not so bad 130mA current at lower voltage due to given secondary transformer ratio, but we'll try also change switching frequency to 2-3 times the oryginal 100kHz, while it was not designed forhundreds of kilohertsAnyway, even with this configuration we have 8.9V when connected to 12V car starter battery, but not too much current, however more than 10mA without significant voltage drop from 9V, so even now this thing could be usable to isolate automotive car battery from linear regulator, while we have 400V caps on its primaryI think, we'll try ... desolder oryginal secondary coil from pcb and... add a few more turns to get better transformer ratio from lower input voltage and we'll see if we can increase by order of magnitue output current at 9V, while it could be quite easy way to make galvanic insulation from automotive noisy ICE car battery to power up a few MPUs with additional linear voltage regulators

author: eneuro
author_rank: Super Contributor
timestamp: November 24, 2015, 09:15:56 pm
content: Bingo, it looks like there is plenty of space to add additional secondary turns, so lets have some fun and try increase output voltage and current while running from 12V car starter battery, so after diodes we have only ~10V input voltage, but we want 9V galvanic insulatedNote: TL431I Zenner hack to have ~9Vmax output, since we have oryginal 10V 470uF output capUpdate: Unfortunatelly, I havent got such thin wire and without desoldering this oryginal transformer it could be difficult add more turnsAnyway, from 24VAC we have 8.5V at 100 Ohm load, so close to 90mA-not so bad.We have schematic now, so we can create custom PCB or desolder oryginal transformer and install another one.That is fine-it was interesting experiment and this thing can be now usable after 24VAC insualting transformer from 230VAC mains -we have ~9V DC to test low power modulesQuite interesting RCC circuit, so it was fun try to get desired voltage and current from this thing at lower input voltage.

author: Jief
author_rank: Newbie
timestamp: July 26, 2017, 11:11:21 am
content: Hi,I have a charger very similar to the one posted here.I'm wondering : is the 5.1MegOhm resistor enough to startup the transistor ? 310V on 5.1M is about 0.06 mA, right ?I'm referring to the schematics posted earlier. This one :