KiCad universal DC-DC module design

New component layout, roughly. All connections are moved to the left for that single (and optionally splittable) ground point. The single header pin on the right is just an optional mechanical support. PCB size still 26x10mm.

Why are you considering an isolated convertor here? You would have to completely change the electronic design for a transformer coupled one.

Will it be stable in case of capacitive load? R5 and Cload form the pole. Have You made loop stability analysis?

He’s not considering an isolated version with this design. As he mentions in his first post his idea is to have multiple versions of DC-DC converters with the same form factor and connector pinout etc. One such design could include an isolated converter only if he provides for separate ground pins on the connector.

My experience of isolating convertors is that they require far more filtering to avoid generating common mode noise, unlikely to fit in the same form factor

Your schematic doesn’t indicate which version of the AD5241 you are planning to use but in any case I would rethink the value of R1.

This design is not of much use for a primary power supply as it requires being enabled via I2C. The wiper of the digital pot will be at midpoint on power up also likely to require programming via I2C before enabling.

Stability shouldn’t be an issue for any reasonable capacitive loads (less than a few thousand uF). Yes, R5 and Cload will form a pole and the ESR of any bulk capacitor will form a zero improving stability.

Switchers using the isolated flyback topology don’t generally require any more filtering than the typical buck/boost topology. The only added complexity would be the opto-coupled feedback.

It may or may not fit in the same form factor but that’s not particularly relevant to the current discussion.

Yes, you are correct that the value wasn’t right (it was on the todo list). My first iteration was based on a 1M digital potentiometer, the current one is 100k (the datasheet recommends avoiding >400k) with a series resistance of 6.8k to shift the working range down a bit (from just over 12V down to just under 1.5V):

I’ve made some other small adjustments: The horizontal grouping of pins will allow use of a 1x4 header as well, or even a left and right non-controllable module on each side.

Thanks again for all the great feedback!

I’m much more at ease with this version. :slight_smile:

Some layout pics:

Edit: And for the interested a zip of the KiCad project:

uPSU100.zip (2.8 MB)

1 Like

I think, it will be better to have feedforward capacitor. It could be populated after stabibilty/transient response measuremnent.

There is a small bit of internal feedforward capacitance, 15 pF:
http://www.ti.com/lit/ds/symlink/tps62135.pdf#page=16

I’ve tried to follow the datasheet pretty closely (TI’s examples generally performed really well for me in the past), but I can look at adding a footprint for it in some future version.

Everybody seems to have a different form factor for their universal power supply :slight_smile:
I made it easy for myself and bought a bunch of LM2596 boards from China.
But whenever I design a PCB I tend to put the power supply on it, so no messing around with extra pcb’s. My default is probably going to be MP1584. PCB’s with this chip starting from about USD0.60 from china…

About your design:
I do not agree with your decision for 2mm connectors.
I use power adapter boards such as these mainly for experimenting on breadboards, veroboard etc and anything which does not have a 2.54mm spacing is a nuisance.
If you are afraid of sticking components in the wrong socket then mark it on the pcb with a sharpie or similar or make labels in a spreadsheet. ( line spacing of 2.54mm, Adjust text size so it fits, print it, add transparant adhesive tape before cutting it out with a scissors). Glue them to your vero board, or make holes with a needle and then stick a connector right through the label.

Apart from my critique, I like your design. PCB layout looks good, connector with all signals on one side of the pcb, Extra hole for stability / support on the other side. And the connector can be placed on either side. I would place the connector on the other side though by default. After initial testing/debugging access to the components on the pcb is not so important, and if you’re being mooned you have lots of space for silk screen text etc. I would probably also put the I2C address tabs on the bottom side (with addressing comment).
I would also put the silk screen text for Input / output voltages / current next to the respective pads of the connector.

Last remark: Adding thermal reliefs to the connector pads will make hand soldering a bit easier / faster / more reliable.

Hi,
sorry to chime in so late…

but I too am working on a F7 pcb
and I also have included a power supply…

do you think your power supply has too many parts ?

check this one…
only half way through…

Hey there,
i know, that this Topic is about 2 years old.
Can anyone explain me this Circuit? I need a DC-DC converter that can handle up to 3-3.5 Amps. do i need a MCU connected all the time to control this converter? Or can i “programm” it to an Output Voltage and disconnect my MCU?

Greetings from Germany,
Sascha

In this case the programmable resistor in the middle of the (last) schematic starts in mid-position. The MCU is required. There are other similar ICs that are able to store the selected value. If it’s just a fixed voltage DC-DC you want there are simpler implementations (follow the datasheet for the TI TPS62135 for example).

1 Like

Do you need a boost or a buck converter?

Chips like XL4015 and XL6006 are often used in those cheap modules from Ebay / Ali / China / etc.

Sir this Zip file is not open it give me an error . can you please share me a kicad project file. i am very thankful to you

I want to design a high voltage step down convertor which convert 1400-2200vDC input into 48V DC Output .Anyone Available to help me?

I hope you get an answer from StefanHamminga (you can try sending them a message), but it’s possible they don’t monitor this topic anymore after 4 years.

As for your second request, this is an electronic design question and outside of the topics of this forum which is for the KiCad ECAD software. Also I’d be very very very cautious around the high voltages you cite if you don’t know what you are doing.