Electronics > Projects, Designs, and Technical Stuff
Cheap Chinese Boost Converters?
(1/2) > >>
sourcecharge:
So, I've got a home project for a tool that requires 60v to 90v at about 2 to 3 amps, but I want to use an old pc ps unit that has been modified to turn on with the back switch.  So, I need a boost converter, and I figured I would look for something cheap and pre-made before making my own.

I found some cheap boost converters, and I found one that is sold as a 1200w, 1500w, and a 1800w.

Here is an excellent review of the 1200w version:

https://robojax.com/learn/arduino/?vid=robojax_1200W_20A_boost_converter

The website includes all of the pdf datasheet files except the diodes and opamp which after doing a digikey search, I was able to find their datasheets and I've included them below.

I bought the 1500w version and now I'm having second thoughts as I'm still waiting for it to arive.

The question is, what do you think can be done (other than putting a bigger heatsink and higher cfm fan) on it to make it more relieable or should I just return it?
trobbins:
Why would you think you need to make it more reliable as you indicate your load is no more than about 270W?  Are you planning on using a low input voltage where the input current would get close to input current limits?  Is your tool a resistive load, or do you know for sure its input requirements (especially at turn on and during operation)?

It is just a dc/dc converter module, so you do need to know how it operates, especially if you are going to approach any limits, and then work through ways to manage the operation.

The sales blurb identifies a 20A input limit, so if you want to watch a video that operates the unit above 20A then you have to ask yourself whether the video person knew about the 20A limit (or didn't appreciate that there would be a limit capability especially given a 15A fuse rating), or whether the sales blurb spec has changed since then to highlight that aspect.  Operating a unit to failure due to operation above limit levels does not really provide a good view of 'reliability' imho.
wraper:
You could replace electrolytic capacitors with higher quality ones if you plan for long term frequent use (over 2-3 years). Otherwise I don't think you should do anything about it given your load.
wraper:

--- Quote from: trobbins on May 25, 2020, 01:09:17 am ---Why would you think you need to make it more reliable as you indicate your load is no more than about 270W?  Are you planning on using a low input voltage where the input current would get close to input current limits?  Is your tool a resistive load, or do you know for sure its input requirements (especially at turn on and during operation)?

--- End quote ---
According to review of 1200W unit, 270W is likely about the max power you would comfortably run 1500W model.
sourcecharge:


--- Quote from: trobbins on May 25, 2020, 01:09:17 am ---Why would you think you need to make it more reliable as you indicate your load is no more than about 270W? 

--- End quote ---
Forgive me for not adding that I have read many reviews on amazon about these boost converters and that the reviews say it's hit and miss on the quality, and that even if the converter comes working, it fails after 1 or 2 years.
Also, something about it failing if you have it connected to a load while it is powering up.

--- Quote from: trobbins on May 25, 2020, 01:09:17 am ---Are you planning on using a low input voltage where the input current would get close to input current limits? 

--- End quote ---
The PC PS is 11.6V+,  so with a 80% efficiency, it would be pulling about 29A, but remember I got the 1500w model which has a 90V output with a 30A input max.

--- Quote from: trobbins on May 25, 2020, 01:09:17 am ---Is your tool a resistive load, or do you know for sure its input requirements (especially at turn on and during operation)?

--- End quote ---
The load(s) are steppermotor controllers that ultimately drive steppermotors, so the load is inductive and I'm not sure if this boost converter will work with inductive loads with only a 11.6v input.

--- Quote from: trobbins on May 25, 2020, 01:09:17 am ---It is just a dc/dc converter module, so you do need to know how it operates, especially if you are going to approach any limits, and then work through ways to manage the operation.

--- End quote ---
I was going to try to spice operation but it seems B2 does not have the TL494, and I'm not sure how to make one without the logic.  It would be nice if I could figure out how to convert LT spice models into B2 spice models.

This would be great to see if I could use different part that I have like the irfp260n or some other high voltage, high current, low Rd(on).


--- Quote from: trobbins on May 25, 2020, 01:09:17 am ---The sales blurb identifies a 20A input limit, so if you want to watch a video that operates the unit above 20A then you have to ask yourself whether the video person knew about the 20A limit (or didn't appreciate that there would be a limit capability especially given a 15A fuse rating), or whether the sales blurb spec has changed since then to highlight that aspect.  Operating a unit to failure due to operation above limit levels does not really provide a good view of 'reliability' imho.

--- End quote ---
The 1500x unit has a 90v output max with a 30A input max, so it's a little different but relatively the same because if you do search for the 1500w 90v version, there is 2 15A fuses instead of 1.

I think what the reviewer was doing was trying to make the point that the circuits (fuse) that were ment to save the unit, didn't work, so it's up to the user to limit the input or output in order for the unit not to fail.

Maybe the fuse should be changed to a quick instead of slow blow?


--- Quote from: wraper on May 25, 2020, 01:17:05 am ---You could replace electrolytic capacitors with higher quality ones if you plan for long term frequent use (over 2-3 years). Otherwise I don't think you should do anything about it given your load.

--- End quote ---

What would be your manufacturer recommendation for electrolytic caps?


--- Quote from: wraper on May 25, 2020, 01:23:55 am ---
--- Quote from: trobbins on May 25, 2020, 01:09:17 am ---Why would you think you need to make it more reliable as you indicate your load is no more than about 270W?  Are you planning on using a low input voltage where the input current would get close to input current limits?  Is your tool a resistive load, or do you know for sure its input requirements (especially at turn on and during operation)?

--- End quote ---
According to review of 1200W unit, 270W is likely about the max power you would comfortably run 1500W model.

--- End quote ---
What I'm really worried about is ESD because if you look at the Vdsmax of the main regulator of the 80V 1200w version, it's 85v.

This seems like it maybe a reason for failure long term wise.  The 1500w version supposidly is 90v output max so I'm guessing the mosfet would be about 100v.

The question really is whether using a mosfet with a higher Vdsmax is going to help even if the Rdon is 10 higher.

The reason why I'm asking is that the irfp260n has 250V Vdsmax and has 45mohms, vs the one on there estimated to be between 95 and 100V Vds and 3-5 mohms.

I'm thinking that if I just use a bigger heat sink, with a 120cfm 12v fan that it would then become bullet proof?   :-//


Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod