Hi,
I have a Meanwell LRS-200 48V power supply that I bought by mistake. I've no way to send it back for a refund or replace it with another.
Just don't want it to toss it in the bin, so I need to buy a buck converter to use it with a CLASS D amp I own, the WONDOW JAB5. This amp works with 24V-36V, so I need a good buck converter.
I've seen ton of them in Aliexpress, but IDK if they are reliable or not. So, my question is:
-. Would you recommend any seller in Aliexpress that provides a good buck converter?
-. If not in Aliexpress, maybe in another marketplace?
-. Any spec I should keep an eye on, for a good performance?
Thanks in advance.
Cheers.
I have a Meanwell LRS-200 48V power supply that I bought by mistake. I've no way to send it back for a refund or replace it with another.
Just don't want it to toss it in the bin, so I need to buy a buck converter to use it with a CLASS D amp I own, the WONDOW JAB5. This amp works with 24V-36V, so I need a good buck converter.
I've seen ton of them in Aliexpress, but IDK if they are reliable or not. So, my question is:
-. Would you recommend any seller in Aliexpress that provides a good buck converter?
-. If not in Aliexpress, maybe in another marketplace?
-. Any spec I should keep an eye on, for a good performance?
Thanks in advance.
Cheers.
Aliexpress power supplies and DC converters are hit and miss. Many of the designs are based on known circuits and aren't anything special. But manufacturing is less than ideal with cheapest possible components. A couple of DC buck converters that I bought for some experimenting all had the input and output capacitors swapped. So the input capacitors had too low voltage rating and were smaller capacitance, and vice versa. Also the buck converter had a maximum input of 40V, but they used a 78L05 regulator (for the constant current circuitry) that is certainly not specified for such a high voltage (they are usually max 30-35V). The only real advice I have is to oversize it a lot power wise and for input voltage. Otherwise buy from some more reliable supplier.
Recommending a particular seller is hard, because they all seem to sell the same stuff.
Recommending a particular seller is hard, because they all seem to sell the same stuff.
Hi , try to find schematic of your 48v psu , maybe its possible to reduce output voltage by changing feedback resistors , while still keeping psu operating. Also some have potentiometer for voltage adjustment in some range , like +-5 percent ,but can be extended. Worth try i think .
Thanks for your replies.
The PSU has a knob to ajust voltage, but the lower I can go is 40v. The schematics is availably, but it's beyond my knowledge to change the resistors...
I bought this: https://www.aliexpress.com/item/1005001636280545.html?spm=a2g0o.order_list.0.0.21ef1802sHXVD8
But for the price I am considering it's too cheap to work properly.
Do you know any other reliable supplier?
The PSU has a knob to ajust voltage, but the lower I can go is 40v. The schematics is availably, but it's beyond my knowledge to change the resistors...
I bought this: https://www.aliexpress.com/item/1005001636280545.html?spm=a2g0o.order_list.0.0.21ef1802sHXVD8
But for the price I am considering it's too cheap to work properly.
Do you know any other reliable supplier?
Can you post schematic here? Usually if you reduce resistor in series with adjustment knob , output voltage will reduce.
https://www.meanwell.com/Upload/PDF/LRS-200/LRS-200-SPEC.PDF
Nope. I think I was wrong... the schematics is not available by Meanwell.
I'll keep searching
The link leads to a boost converter. You will get higher voltage output than input, that's not what you want. I wouldn't trust the power rating of these cheap converters, you should at least double or triple them. Many of them require a fan to be able to operate at rated power.
It helps to lower the output of your PSU as much as possible, then a DC buck converter has less work to do. 40V to 36V for a "cheap" buck converter might do, but don't buy those that are rated for max 40V input. They should tolerate at least 50V for a safe margin.
You can find DC converters on Mouser, but they are usually very expensive. It will be cheaper to buy another PSU.
But yes, if you can modify your own PSU, that would be best.
Disclaimer. Note that modifying a mains connected SMPS could be dangerous work and shouldn't be attempted if you don't know the risks/don't have experience.
It helps to lower the output of your PSU as much as possible, then a DC buck converter has less work to do. 40V to 36V for a "cheap" buck converter might do, but don't buy those that are rated for max 40V input. They should tolerate at least 50V for a safe margin.
You can find DC converters on Mouser, but they are usually very expensive. It will be cheaper to buy another PSU.
But yes, if you can modify your own PSU, that would be best.
Disclaimer. Note that modifying a mains connected SMPS could be dangerous work and shouldn't be attempted if you don't know the risks/don't have experience.
This might do the trick: https://www.ebay.ca/itm/275074499659
Another option would be to use a string of 5W zeners to pisse away the extra voltage as heat. Not elegant but cheap.
Another option would be to use a string of 5W zeners to pisse away the extra voltage as heat. Not elegant but cheap.
On the web page for the Wondow JAB5 it says that power supply is 10-39V DC. Then you could use your own PSU. Turn it down to 40V and put two rectifier diodes in series in between.
Be careful with converters ! From photo is clear ,that it has no big output capacitors ,so it must have higher ripple at output ,than psu itself .D class will supply all noise from power supply lines to speaker , that will degrade audio quality .Adding big capacitor may disturb some converters operation .
Use of zener or diode in series is partial option , all those devices deviate their voltage drop depending on load current . Diode drop may vary from 0,4V with let's say 30ma and 1,3V a 3Amperes, so you will get unregulated output in such case .
If you would like to modify psu , i can try to help .Looks like you have a DMM , so you can measure voltage adjustment potentiometers surrounding components . If more clearly , you need to locate one resistor , which is connected in series with adjustment potentiometer . Need to connect many times higher resistor ohms resistor in parallel with that resistor (solder on top ,don't touch existing one) ,and measure output voltage then .Lets say you find resistor 33k , so solder on top 330k for testing .If you located proper resistor on board , voltage would reduce .If wrong resistor, voltage will increase .Keep adjustment potentiometer at minimum voltage position .If voltage will be lower ,but still too high , use slightly less ohms additional resistor .If psu will begin to click ,turn off ,then restart , don't continue ,leave it as is ,it's output is allready at minimum ,or it needs additional load to operate at that reduced voltage .Internal circuits in psu needs some voltage to operate too , and that voltage mostly is associated with output voltage .In example old hp laptop psu from 19v can be tweaked to 12v , but less than ~10V it won't output with low power load .So analyse carefully what you have ,post photos of both sides of pcb if you can't figure out itself .
Offcourse , wait several hours before opening disconnected psu ,until all capacitors discharge .
Use of zener or diode in series is partial option , all those devices deviate their voltage drop depending on load current . Diode drop may vary from 0,4V with let's say 30ma and 1,3V a 3Amperes, so you will get unregulated output in such case .
If you would like to modify psu , i can try to help .Looks like you have a DMM , so you can measure voltage adjustment potentiometers surrounding components . If more clearly , you need to locate one resistor , which is connected in series with adjustment potentiometer . Need to connect many times higher resistor ohms resistor in parallel with that resistor (solder on top ,don't touch existing one) ,and measure output voltage then .Lets say you find resistor 33k , so solder on top 330k for testing .If you located proper resistor on board , voltage would reduce .If wrong resistor, voltage will increase .Keep adjustment potentiometer at minimum voltage position .If voltage will be lower ,but still too high , use slightly less ohms additional resistor .If psu will begin to click ,turn off ,then restart , don't continue ,leave it as is ,it's output is allready at minimum ,or it needs additional load to operate at that reduced voltage .Internal circuits in psu needs some voltage to operate too , and that voltage mostly is associated with output voltage .In example old hp laptop psu from 19v can be tweaked to 12v , but less than ~10V it won't output with low power load .So analyse carefully what you have ,post photos of both sides of pcb if you can't figure out itself .
Offcourse , wait several hours before opening disconnected psu ,until all capacitors discharge .
No ,this is kinda of generic datasheet about possible topologies, tests , typical solutions ,used in power supplies. To op - need to measure adjustment potentiometer at minimum voltage position, when psu is off , resistance is minimal or maximal . Typical schematic showing a adjustment potentiometer connected to ground part of voltage divider , it means i was wrong with which resistor to choose for reducing output voltage.
I found another cheap DC buck converter on Aliexpress that at least looks to have much better specifications than the usual cheapest of cheap that are sold all over the place (with components wrongly assembled on PCBs etc). It's this one:
https://www.aliexpress.com/item/1005004192411912.html
It seems that it has a better regulator than the usual XL4015/XL4016 and actually takes input voltage up to 60V. Output goes also lower than the cheap regulators, down to 400 mV (according to a youtube video). I'm going to get this one for some experiments.
Still, I would recommend to check at least polarity and placement of electrolytic caps, if used for anything serious. If anything else is wrongly assembled, it will probably misbehave or let out the magic smoke.
https://www.aliexpress.com/item/1005004192411912.html
It seems that it has a better regulator than the usual XL4015/XL4016 and actually takes input voltage up to 60V. Output goes also lower than the cheap regulators, down to 400 mV (according to a youtube video). I'm going to get this one for some experiments.
Still, I would recommend to check at least polarity and placement of electrolytic caps, if used for anything serious. If anything else is wrongly assembled, it will probably misbehave or let out the magic smoke.
i have tried to solve a similar problem.
i have a 40 v smps for a class a amp; but also need 12v for the filament of tubes @ 400ma. a drop down resistor is a waste of energy. so in comes the buck down converter. a "good"one, based on LM2569 chip.
but it generates a lot of noise i saw on the scope. that is seen on the earth everywhere. so i had to lift it fom earth. i made a gyrator for the plus and minus. now the noise is about 0,5 milivolts rms.
so be aware that this could happen.
i add the simulation.
though i doubt it is of any help to you.
i have a 40 v smps for a class a amp; but also need 12v for the filament of tubes @ 400ma. a drop down resistor is a waste of energy. so in comes the buck down converter. a "good"one, based on LM2569 chip.
but it generates a lot of noise i saw on the scope. that is seen on the earth everywhere. so i had to lift it fom earth. i made a gyrator for the plus and minus. now the noise is about 0,5 milivolts rms.
so be aware that this could happen.
i add the simulation.
though i doubt it is of any help to you.
Hi, I have a Power-One ABC400-1024G, 24V 17A, brand new sealed. Care to do a straight swap for the Meanwell?