DPS5020 dual power supply build

[Dannyx]

Re: DPS5020 dual power supply build

Speaking of fuses and stuff "blowing". I once had a freak mishap with my existing supply made from the same UPS transformer: it tripped the main breaker when I plugged it into the wall outlet. To this day I have no idea why it happened, but it hasn't happened since...I thought inrush current caused it, but that means it should've tripped again after that as well, which it hasn't done so far, so I have no idea what that was all about I saw a little spark flying out of the wall socket as well, so maybe it was a faulty outlet, though I remember wiring that outlet myself and plugging in lots of stuff in it before without a care....strange :|

[redwire]

Re: DPS5020 dual power supply build

If the primary fuse is slow-blow and it can handle it, then I would keep it simple.
Above around 20,000uF is when I add a soft-start to a mains transformer, or just listen to the mains wiring rattle in the walls when I turn on power.

[stj]

Re: DPS5020 dual power supply build

i wouldnt bother, the Q of the transformer will limit the inrush.

[Dannyx]

Re: DPS5020 dual power supply build

Back on this project, I was thinking of adding an NTC thermistor in series with the secondary of the transformer to limit inrush on those large caps after the bridge rectifier.

[Dannyx]

Re: DPS5020 dual power supply build

they arent cheap to begin with.

Correct - they were not exactly cheap, so here's hoping they don't bulge after a few hours

[stj]

Re: DPS5020 dual power supply build

i'v not seen fakes with snap-in style base.

i suppose a company could re-sleeve another brand, but it's unlikely - they arent cheap to begin with.

[Dannyx]

Re: DPS5020 dual power supply build

What makes you think that they are not real

Ok, maybe I was a bit harsh on Ali with that statement. Funny thing is that I once saw a video of Dave from EEV Blog where the took apart a cheap subwoofer and projector and he found some Elna and NCC caps inside and he was having a very hard time believing they were real. The people in the comments however disagreed with him and pointed out that it's unlikely they'd counterfeit the logos on the caps as well, so it could be the same in my case

[sam_sam_sam]

Re: DPS5020 dual power supply build

What makes you think that they are not real

[Dannyx]

Re: DPS5020 dual power supply build

Got the caps today. As you can see, they claim to be Nippon Chemi Cons

[Dannyx]

Re: DPS5020 dual power supply build

You short each winding and measure capacitance from pri-sec, pri-core, sec-core.
It's good to know how much the leakage currents might be. Some 600VA big toroids are 100's nF pri-sec.

Does "core" in this case refer to the metal chassis of the transformer where earth would go ?

[redwire]

Re: DPS5020 dual power supply build

You short each winding and measure capacitance from pri-sec, pri-core, sec-core.
It's good to know how much the leakage currents might be. Some 600VA big toroids are 100's nF pri-sec.

[Dannyx]

Re: DPS5020 dual power supply build

The small capacitors I'm suggesting are not for EMI or compliance, but are to swamp the power transformer's winding capacitance.
You can measure it, pri-sec, sec-core (with windings shorted) and see how much it is.

How do you do this ? Haven't done it before. A capacitance meter with one probe on the shorted windings of the primary and the other probe on the shorted secondary windings ? Worth a try I guess...

[Dannyx]

Re: DPS5020 dual power supply build

what are the transformers, cubes or toroids??

See post no. 8: they're laminated ("E-I") UPS transformers, not toroids.

[stj]

Re: DPS5020 dual power supply build

what are the transformers, cubes or toroids??

[redwire]

Re: DPS5020 dual power supply build

maybe update your schematic and see if everyone likes.
The small capacitors I'm suggesting are not for EMI or compliance, but are to swamp the power transformer's winding capacitance.
You can measure it, pri-sec, sec-core (with windings shorted) and see how much it is.

[Dannyx]

Re: DPS5020 dual power supply build

Btw, imo your're overdoing the filter stage.

Yeah you are probably right.

[megaraider]

Re: DPS5020 dual power supply build

Btw, imo your're overdoing the filter stage leading me to believe you might have forgot the overall picture.
Voltage ripple before the DPS5020 stage is not a concern, but the inrush current value is!

Why isn't ripple a concern at that stage? Because that job is up to the next stage: the DPS5020 module.

The only thing you must ensure is that the input voltage never falls below the minimum threshold at maximum output power set (highest voltage and current values).
Within the expected ripple frequencies 100Hz (120Hz USA) it can be feed even with a saw tooth wave for that matter, because the DPS5020 module has a feedback sample frequency in the tens of KHz at least.

[megaraider]

Re: DPS5020 dual power supply build

I believe he's referring to the primary of the transformer (hot) and the secondary of the transformer ("analog") respectively, though I would like a confirmation indeed.

Yes.

Sure sounds industry-standard to have a y-cap between your regulated ("cold") output and chassis (earth) GND....true, SMPSs are not designed with series-connection in mind, so I'm not sure how well the concept would transfer to our build here.

Being a consumer and industry standard it's also applied in electronic lab equipment (mainly due to EMI test compliant), but with a big twist:
With the electronic lab equipment design engineer wariness of demand for flexibility in lab environment the connection from PE to ground is done only to bypass the compliant tests.
Therefore if any qualified experienced user needs to break it it's easily spotted and undoable, i.e. PE to analog connection only (PE to chassis and to cold ground remains connected).
See schematic for the KSGER 96W 24V 5A Electric Power Supply Unit in this post
Note the remark: “Skinny trace for PE GND”
Why skinny? Good example for the above mentioned isn't it?

[Dannyx]

Re: DPS5020 dual power supply build

Does this bother anyone? Imagine looking at it every day.... every day...

Other than the DPS being ever so slightly crooked, it's decent

[redwire]

Re: DPS5020 dual power supply build

Does this bother anyone? Imagine looking at it every day.... every day...