Recommendation for Lab PSU (SMPS) - Page 1
Forum section: electronics / beginners

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 08, 2018, 08:18:11 am
content: i dont have time to build another one, or to repair my damaged recently built one SMPS. the earlier one with CC feature havent been completed, so i got fed up... enough rant... now i need a lab PSU quick, please recommend me to buy one thats is bang for buck, search in eevblog doesnt give specific what i need, mostly linear, or low power version. here is what i need...i dont need super low noise output, but the lowest noise figure will help. i need high power because i'm thinking to power motors and power resistors with it etc, along with supplying low power digital circuit such as mcu etc which i can provide local low noise linear regulator to them such as 78L05, LM317 etc if i need low noise. so this calls for SMPS version PSU, lightness of it will give merit. spec is somewhere like 1V - 60V give or take, it can be 3-40V etc if 1-60V is not available in the market. the lowest the low volt range is better, the biggest volt for high range is better. amperage is preferably up to tens of ampere, maybe 30-60A? but if price too much, i can tolerate lower 10-20A. budget is somewhere from $0 - $500 (i dont mind 2nd hand as long as its working), constant current limit is much much much preferable. i dont need fancy constant power or constant resistance etc, only current limit and constant voltage (normal mode) will do. so basically the spec is like below (not very strict, i can tolerate a little bit of lower spec)1-60Vlow - 30V range30A max (preferably throughout voltage range)CL, CV mode only.larger spec at the budget will be golden. Thank you...edit: more than one floated output in one unit is preferable so i can save lab space.

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2018, 08:29:13 am
content: Got some small SMPS from these guys before and they've been good.This might be what you're after:http://www.china-mch.com/index.php/en/info/252.htmlHere's their Aliexpress shop:https://www.aliexpress.com/store/group/MCH/1910099_512554430.html

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 08, 2018, 09:05:09 am
content: thanks tautech. looking at the price, i may want to lower the spec to 30V max as i'm thinking about it i will seldomly use up to 60V. i can see there are cheaper china version for 30V/30A such as this...https://www.ebay.com.my/itm/0-30V-0-30A-DC-Switching-Power-Supply-Precision-Variable-Adjustable-KXN-3030D/112662732582?hash=item1a3b38df26:g:9zcAAOSwa0VaBB1nbut that is big footprint (i'm going to need 2 unit for symetrical dual ±V PSU). smaller footprint can go to 10A like these...https://www.ebay.com.my/itm/10A-30V-DC-Power-Supply-Adjustable-Dual-Digital-Variable-Precision-Lab-Grade/251705177148?hash=item3a9acc343c:g:G-8AAOSwEOpaBI12https://www.ebay.com.my/itm/DC-Power-Supply-30V-10A-Precision-Variable-Digital-Lab-Adjustable-with-Cable/122836309781?hash=item1c999d5715:m:ml4uqgy02swOWcc3iqR6k5Ahttps://www.ebay.com.my/itm/30V-10A-220V-Digital-Switching-DC-Power-Supply-Adjustable-Variable-Precision-Lab/132613751949?hash=item1ee065448d:g:K9cAAOSwAINa7~ffi may have to admit the 10A limitation (big motor use another PSU) but i'm not sure these china brand is trustworthy or durable. i'm not sure if they have been reviewed in this forum... i'll check again.

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2018, 09:34:52 am
content: They can be patchy !A customer got another model 10A MCH single SMPS and they are garbage. Please be warned.This one I think !https://www.ebay.com.my/itm/30V-10A-220V-Digital-Switching-DC-Power-Supply-Adjustable-Variable-Precision-Lab/132613751949?hash=item1ee065448d:g:K9cAAOSwAINa7~ffTheir linear should be OK.I've got a good few of their little K305D (30V 5A) SMPS and we can't break them !!These:https://www.eevblog.com/forum/testgear/cheap-variable-switching-power-supply/

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 08, 2018, 09:36:22 am
content: someone was doing stress test on it, price is cheap i can buy 2 and glue together to get dual output footprint should be not too bad...

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 30, 2018, 06:24:09 am
content: now that they arrived in cold blood...

author: tautech
author_rank: Super Contributor
timestamp: July 30, 2018, 07:33:11 am
content: Quote from: Mechatrommer on July 30, 2018, 06:24:09 amFirst job: beat them up heaps !See how they each handle a series pair of forward biased stud diodes to give ~1.3V conduction then wind the voltage around a bit between CV and CC modes. Take note of what the fan and your nose tells you.That's what we did to K305D's and they handled it with ease.Good luck.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 04, 2018, 12:13:37 pm
content: i have a chance (mood) to do quick performance test on the PSU (using my diy adjustable load)... test voltage = 15.4VCH1 (yellow): output voltage at load end. DC coupledCH2 (cyan): output voltage at load end. AC coupledCH3 (purple): shunt resistors voltage. DC coupled (to check current flow)1st pic: voltage ramp, no load (quite noisy 10 - 20+ Vpp spikes, 160 - 200ms to stabilize)2nd pic: voltage steady state, no load (2.5Vpp noise)3rd pic: ~0.5A load (CV mode, 0.2+ Vpp noise)4th pic: ~1A load (CL mode)5th pic: ~2.5A load (CV mode, higher load = higher ripple (no pictures))6th pic: ~2.5A pulsed 50% 15Hz PWM load (sometime it catches into CL, sometime it misses the 15Hz load (stayed in CV mode) ie slow acting)