DP100 PD-Power Supply 100Watt [0-30.00V / 0-5.000A) [∼50$]

[Phil1977]

Wow, thanks for the 5A-type, I was not aware of this high-current-version.

By chance I have a few of the standard 2A-versions of the same form factor laying around, so as soon as I receive my DP100 I´ll check out if there is some available space for this.

And yeah, it definitely will be more of something improvised than some clean PCB construction. But at least in my habitat such devices often have the longest life 

[MegaVolt]

Perhaps it would be easier to switch the output with a solid-state opto-relay?

[Phil1977]

Perhaps it would be easier to switch the output with a solid-state opto-relay?

Inside these relais there is either a TRIAC (high Uf and unsuitable for DC) or MOSFET (usually unipolar, usually with a minimum switch voltage or additional supply voltage)

5A-versions are quite large and may require a heatsink.

From my point of view you can either
- directly use a high-side- FET with low RDSon, or
- use a compact mechanical relais, or
- use an additional isolated DC-DC module in the input.

I have some positive experiences with the following (extremely cheap) boards:

https://de.aliexpress.com/item/1005006462467909.html
(not assosiciated anyhow with the seller...)

[Phil1977]

Just received my own unit: It´s a really nice toy and tool for mobile setups! Build quality and first impressions on DC-noise are absolutely positive.

Regarding the Low-Side-Switch-problem: I´ve checked the available space and as already mentioned in this thread there would be some space for a miniature relais. I think the problem of disconnecting the output pole could also be solved by some kapton tape on the PCB, a nylon-screw for fixing of the +jack and soldering a wire directly to the gold plated backside of the jack.

But:
- The power supply uses this low side switch for quick load disconnection, but the buck converter is also disabled in the off-state. The only energy that could flow over a parasitic ground connection could be the charge of the caps and the noise mentioned in the beginning of the thread.
- The current-sensing is also in the low side of the buck converter. This means, a parasitic ground connection heavily distorts current measurement and regulation. Neither the relais nor the high-side FET could improve that behaviour.

Conclusively I will use this thing on a power bank or use an isolated DC-DC in its supply. Else it´s not well suited for any lab-setup with common-ground DC supply.

Last but not least, this behaviour is even quite directly mentioned in the manual - but who the f... ever reads the manual of a power supply except in case of extreme procrastination   

[Dexter2]

I have received the DP100 PFET update PCB i designed a few days back and as promised below short update instructions and Gerber files if someone else wants to update this power supply.

First the measurement. The output switches now ON-OFF in about the same time with no load attached now. There is no coupled noise on the output anymore. It now performs as it should...



Upgrade procedure:

• Disassemble the unit
• Remove N-ch MOSFET, TVS, Fuse, LED, LED resistor and clean all pads from exes solder to get a nice flat surface, also clean the solder from TH capacitor pins
• Apply some capton tape the the back of the PCB (solder stop is not a guarantied insulator)
• Place the PCB to DP100 PCB and position with output terminal screws, and after that solder the PCB to the TH capacitor pins
• On the top part of PCB mount the TVS and a 100nF capacitor
• Connect the 5V and Enable wire
• Put everything back together

I also tested the thermal performance with shorted output at 5A (worst case scenario for P-FET). And it works perfect and its also dead cool. You could use a 10 or even 20mohm lower performance part...




I have 3 spare unpopulated PCBs so if someone needs i can send them out for free.

[Phil1977]

Fantastic mod and great results!

It´d be great if the manufacturer would have spent these additional cents.

But anyhow, even with the mod the PS can't be flawlessly used in any common ground setup - now just due to the current sensing on the low side. It´s fantastic that you offer the mod boards, but I´ll stay with the additional galvanic isolator in the back of the bench.