SSLC084V42 Switch Mode Power-supply / Li-ion Battery Charger - Page 1
Forum section: electronics / repair

author: Mad Professor
author_rank: Regular Contributor
timestamp: July 24, 2015, 02:44:46 pm
content: Hi All.I am looking for some help and advice with regarding to fault finding and repairing a SSLC084V42 Switch Mode Power-supply / Li-ion Battery Charger.This is the 2nd unit that has failed, the 1st failed unit was just scraped, this unit is just over a year old and has also now failed in the same way.QuoteI have done very little work with SMPS, I have always mainly used linear power supplies.The fault / problem is that there is no output from the unit.So far I have checked the fuse and the bridge rectifier on the mains side.There is rectified mains voltage all the way though the circuit up to the switching FET but nothing out of the FET.Near to the switching FET is a small SMD IC, I am guessing that this is the driver for the switching FET, but once again I can't seem to see any output from this to the FET.The MOSFET is aSMK1060IC1:OB2202CPCan anyone here please advice where I should start looking to try and find the fault with this unit.Thanks for your time.Best Regards.

author: tautech
author_rank: Super Contributor
timestamp: July 25, 2015, 02:56:22 am
content: Quote from: Mad Professor on July 24, 2015, 02:44:46 pmMost likely so. This you need to identify it and get the datasheet.You can then check if it has power to its supply pin, normally there will be a resistor from HV (rectified mains) and some bulk capacitance ~20-50uF.I've seen faulty caps and/or open resistors prevent these IC's from starting up.Operation of the IC can be confirmed with a scope on the gate of the MOSFET while the IC is powered ONLY with DC from a PSU.

author: Rasz
author_rank: Super Contributor
timestamp: July 25, 2015, 04:08:32 am
content: Quote from: Mad Professor on July 24, 2015, 02:44:46 pmread the markingson the pic it looks like R1 and R2 make a divider powering this chip? check voltage

author: Mad Professor
author_rank: Regular Contributor
timestamp: July 25, 2015, 10:11:47 am
content: Thank you for your replies.I have been able to read the markings on the ICIC1:OB2202CPTesting the Pin8 (BO), and Pin6 (VCC) came back with zero volts. with the unit disconnected from the mains I did a continuity test, and found a dead short from GND and VCC. Looking over the PCB some more I found a solder bridge across C2 (10uf 50v) this is across the power rails for the IC, after removing the solder bridge I now have some voltage readings at the IC.Pin4 (GND) and Pin6 (VCC) = 1.91vdcPin4 (GND) and Pin8 (BO) = 1.40vdcPin4 (GND) and the output between RX1 and RX2 = 24.5vdcLooking at the datasheet the min VCC voltage for this IC is 11vdcI have been trying to draw a Schematic but I can't get my copy of DaveCAD working and I keep on making errorsLooking at the PCB and tracing back from Pin6 (VCC) it seems to be getting power from the output between RX1 and RX2, via R5 a 100k resistor. one side of the resistor is reading 24.5vdc the other side is reading 1.91vdc

author: tautech
author_rank: Super Contributor
timestamp: July 25, 2015, 10:44:48 am
content: Quote from: Mad Professor on July 25, 2015, 10:11:47 amUVLO = 14V min. You must have this voltage for it to start.To check the IC is working power it with a PSU and scope pin 5 Gate.Check current draw also, datasheet says ~5mA, if it's drawing lots more than that I'd be concerned.

author: Rasz
author_rank: Super Contributor
timestamp: July 25, 2015, 03:27:18 pm
content: Quote from: Mad Professor on July 25, 2015, 10:11:47 amthat is a little disconcerting. How could that happen? some lose solder rattling lose inside? shorting and immediately melting? this is weird, where did it come from? something else must be burnedyour pic is too weak for inspection, cant see any burn marks/components

author: qu1j0t3
author_rank: Regular Contributor
timestamp: March 18, 2018, 07:16:20 pm
content: I have the same unit, with same fault. Green LED lights, but 0V on output.I did replace the two 470µF capacitors and that didn't change a thing.So I wonder if it is the same root cause as OP's. I'm prepared to dig further. I have good DVM, scope, but not a lot of experience debugging SMPS.

author: keymaster
author_rank: Regular Contributor
timestamp: March 18, 2018, 07:34:40 pm
content: Be aware that most of the chargers for lithium won't output voltage ,if they don't see a battery plugged in .

author: qu1j0t3
author_rank: Regular Contributor
timestamp: March 18, 2018, 08:53:05 pm
content: Ah, I was wondering about that. So I could set up a dummy load of sorts. Any suggestions of current?