Hi, Can we use SMPS Bench Power Supply for Laptop troubleshooting?

[shamsudeen]

Hi all, I just need to know that, can i use SMPS type power supply to test and short circuit detection on a laptop motherboard?
I saw 95% of repair guys are using only Linear bench power supply. linear bench power supply is pricy, thats why i planned to get one SMPS supply.

i know that in linear power supply the noise will be very low comparing to SMPS supply.

[stj]

i dont see an issue,
laptop chargers are shit SMPS units anyway.

[sam_sam_sam]

I have one question about doing this what about laptop computers that have a special center pin in the power jack that is required or you will get an power supply error how are you going to do deal with this I am very interested in this answer

[m1ch43lzm]

I have one question about doing this what about laptop computers that have a special center pin in the power jack that is required or you will get an power supply error how are you going to do deal with this I am very interested in this answer

Search for "universal laptop charger tips", you'll find a set for several brands, they accept a standard 5.5x2.1mm barrel plug at the input
Those work for the "regular" laptops as the ID pin is set for 65W or 90W, at least on the ones I got for HP, Dell, Lenovo square plug
For gaming laptops that's another story, you can probably take the cable from a dead charger and mimic the resistor inside the charger for HP/Lenovo, or program an 1-wire EEPROM for Dell with the correct ID for a 230W charger or something like that

EDIT: Found a project on github for the Dell charger emulator with an ATTINY85
https://github.com/KivApple/dell-charger-emulator

EDIT2: I use a linear 30V 5A PSU, for injecting voltage into a shorted rail
Haven't tested how a bench SMPS reacts to that, if it has short circuit protection it won't work for that purpose, unless the SCP can disabled by a switch (the PSU works in constant current mode, as set by the current limit, dropping the voltage while pushing current through the short circuit)

[sam_sam_sam]

I think ideally you would want a switching power supply that voltage and current that are control able not just voltage as far as simulation the control pin was my thought as well the ones that have the erom pin is hole another story I not sure the best way to work around that one

The only issue that you need to be aware of is that switching power supplies that have voltage and current controls the current usually does not have very good current control below 200 milliamperes it drops rapidly not smoothly just be aware of this issue some switching power supplies that have both voltage and current controls are better than others

[m1ch43lzm]

as well the ones that have the erom pin is hole another story I not sure the best way to work around that one

There's also the "Dell/Alienware power meter box" from here https://www.thingiverse.com/thing:7031863
The middle ID pin just passes through from the original AC adapter to the output cable, the volt-amp meter is wired to the input DC jack, and the output is a cable cut from a dead charger
Lets you use regular Dell AC adapters, of course only for Dell laptops
It relies mostly on the short circuit protection on the original Dell AC adapter, it's useful to measure power draw, not so when injecting voltage into a short circuit
Instead of powering the laptop from the bench/lab SMPS, you power it from the original charger with that meter box inline, as gaming laptops can exceed 5A when booting in some cases

For the USB-C powered laptops, get a 100W USB-C PD charger from a reputable brand and use an inline USB-C volt/amp meter, you have to check if the laptop negotiates 20V from the charger, or gets stuck at 5V/looping 5v-0v
Ideally you don't want to push 20V through the USB-C connector, the laptop has to negotiate first