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Laptop charger as input for Ryden power supply DPH3205 - Good Option ?
jayfree:
Hello All,
I would like to use a laptop charger(Lenovo 170W laptop charger) to power up the Ryden DPH3205. I can see used laptop chargers for cheap price.
laptop charger (link updated)- https://www.amazon.com/Lenovo-170W-Replacement-Slim-Adapter/dp/B078XJPY49
RD DPH 3205 - https://www.aliexpress.com/item/32762131242.html?spm=a2g0o.detail.1000023.30.6d7469f3zUltEO
Does anyone has built such a power supply using laptop charger ? My concern is that will this laptop charger burn after sometime? Their cases are completely closed without any air circulation.
My main need it to power small circuits (like arduino). Maximum I will run 12V DC motors. For sure, I wont be loading them for continuous 1 hour at its max power.
Please share your feedback.
tunk:
I guess it will work fine, but remember that the specs of many Chinese
products are a bit optimistic, so I wouldn't run it at e.g. more than 3A.
Do you have that Lenovo charger or will you buy it for that price?
If the latter, for 150$ you can get reasonable bench PSU.
Ian.M:
Its very unlikely to be satisfactory, as the laptop PSU you linked to has a two pin mains input, but as it isn't a medical grade PSU, will have a significant Y capacitor leakage current. In most countries, regulations limit the leakage current to 0.75mA, and the typical leakage current is usually over 1/3 of that. The result will be a line frequency common mode voltage on your PSU output of approximately half your mains supply voltage, with approximately half a mA 'drive' behind it, which is more than enough to almost instantly destroy MOSFETs and other highly ESD sensitive devices, simply by touching their gate terminal with a grounded soldering iron bit without either fully disconnecting the PSU from your circuit, or the PSU from the wall socket.
A three pin input grounded output laptop charger wouldn't have the Y capacitor leakage current problem, but a bench PSU with a grounded output is a PITA, and if interconnected with high current loads and an Arduino with USB connection to a PC, you can easily end up with significant ground loop currents, risking a blown PC motherboard.
Its possible to mod a floating output open frame PSU, replacing the Y capacitor with two in series with the intermediate node grounded via a choke, to virtually eliminate line frequency leakage current without significantly degrading its EMI performance, but obviously that's not an option for a sealed laptop charger with a two pin input.
Other options are a floating output medical grade (low leakage current) PSU, which will usually use a grounded inter-winding screen to eliminate leakage current without the need for a Y capacitor, or an 'old-skool' line frequency transformer + bridge rectifier + resevoir capacitor PSU. You'll need a 22V 300VA transformer with 10% or better regulation to get full output from the DPH3205, which wont be particularly cheap. A lower voltage or lower VA transformer either wont be able to deliver full output or will overheat on sustained full output. A higher voltage or worse regulation transformer will over-voltage (and possibly destroy) the DPH3205 during low load operation if the mains supply rises towards the upper end of its tolerance range.
NiHaoMike:
Easiest way to shunt out the leakage without directly connecting the output to ground is to connect the ground via a series RC network, something like 1uF (nonpolar) and 100 ohms would be a good start. Then a 1M across the capacitor can discharge any charge that does build up.
Then there's hacking the power supply to connect the Y capacitors to neutral, so there would only be the tiny leakage from stray capacitance. It's also possible to power the supply from a half wave rectifier so that the power supply doesn't see AC at all.
jayfree:
I have updated the charger link. Actually I wanted to use 3 pin plug(I mean with ground).
What I mainly wanted to know is that if the charger will catch fire after continuous usage as it doesn't have any air circulation an d laptops might not consume 170w all the time(it stops after the battery is charged)
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