Open Source Power Converter For The Masses

GaN or Gallium Nitride Transistors have been in the news for their high-frequency and high-efficiency applications. Anyone interested in the Power Converter domain will love this open-source project by Siemens. The offering is called SDI TAPAS and it is a multipurpose GaN FET based board with a TMS320F28x controller onboard.

A quick look at the schematic reveals a lot of stuff going on like current and voltage sense chips along with a neatly designed GaN power stage with by-the-book drivers. There is a plethora of connectors on-board including one for the Raspberry Pi which is an added bonus. The git repository comes with sample code to get you off the ground, with examples running BLDC motors as well as connect it to Siemens MindSphere Cloud Platform.

This platform can be used in a number of functions in addition to motor control, such as battery charging, solar energy harvesting, and wireless charging. There is a presentation(PDF) that is available for download, and if you are looking for use cases there are a number of user build projects on their community site. The schematic and board designs can be used to make your own, or you could ask them for a sample board and they might give away more on their community site.

For those starting out, you might appreciate this tutorial on Buck Converter Efficiency to get a feel for the hardware that goes into such experiments.

32 thoughts on “Open Source Power Converter For The Masses

      1. I’m not sure I really want to invest time learning and using the board if its not possible to actually buy new one. What is the plan for this? if all I get is one single unit its not really that interesting.

  1. Can someone please explain to me why this is good? Will these open source devices be produced by the usual Chinese sources that produce everything electronic and open source? What is the benefit of this, other than a PR stunt and personal information hoovering by Siemens? Why would makers be interested in these if the only source is a gift from Siemens?

    1. I will try … the point of TAPAS is to show that it can be easy to create power electronics applications – much like the RaspberryPi has done for embedded system. In the best case is will just be writing a few lines of code – hence the term Software Defined Inverter. TAPAS implements this concept with the help of novel GaN power semiconductors which makes it as cutting edge in power electronics as it gets. And we open sourced it.

      What Siemens gets out of this is a) to demonstrate that these software defined concepts actually work in practice and b) that GaN is reliable enough to survive in a whole lot of applications. Nothing more.

      As cool as the ideas in the challenge are, they mostly cover areas where Siemens is not active at all (Drift-Bikes?, Musical fans?). Also, since they are required to be open source, they are available to everyone including the competition.

      In terms of rolling your own, this is rather straightforward. TAPAS only uses standard components and Eagle reference designs for the most critical ones are readily available from the manufacturers web-sites (Texas Instruments DSP, EPC GaN chips). Simply pull the TAPAS schematics from the github and go.

      1. I appreciate the effort, but I would suggest if you plan any future open projects like this that you provide the files in KiCAD. Since EAGLE was acquired by AutoDesk it has lost a lot of its credibility in the open source community. Serious professionals on the other hand with the budget to spend use Altium, Eagle is going out of fashion fast.

        1. I know this is a common argument, but I feel like ranting this morning so here it goes

          You see, people keep saying “Eagle is going out” and to use KiCAD or Altium but I’ve never seen any proof of this or sources to back it up.

          Honestly, I’m loving the latest Eagle additions as well as the AutoDesk acquisition. Recently they’ve added a ton of nice functionality such as improved routing tools, a GOOD integrated library management system, and crossover to Fusion 360.

          And if you have or can get a student email then entire suite is FREE! Honestly their pricing is not bad either if you are using it for business.

          I have tried to use Altium – within the first couple hours I wanted to burn my computer to the ground in frustration with the Library management. Maybe this is different if you have the ridiculously priced full version with the cloud library? With Eagle I have nearly EVERY PART and EVERY REFERENCE DESIGN EVER and can design something in minutes because of it. I don’t design PCBs to spend all my time making part libraries – I design PCBs to actually build something.

          So thank you Siemens for releasing this in Eagle format! At least I’m wayyy more interested in trying out your board because I feel I have the freedom to modify and use it in my own designs. Just hurry up and make this board available in the US already!

        2. :) You’re quite the complainer! This company gives away everything for free, it’s open source, you get the schematics, you get a great github page with colorful pinouts and other details, you even get the hardware for free if you ask (!), and yet still you find some reasons to complain. Why don’t you make these great KiCAD files yourself? Being such an open source fanboy, this should be right up your alley.

  2. These are very good news. I use 280x DSPs from TI all the time to control power electronic converters, very useful.

    I like how this article combines the announcement of an excellent piece of hardware with a link to a shit tutorial about the efficiency of the buck converter that is full of misconceptions (e.g. “removing the diode” !!).

    1. “shit tutorial about the efficiency of the buck converter that is full of misconceptions”; A perfect example of how some people use their knowledge as an opportunity to belittle others instead of just sharing.

  3. “TAPAS features a 48V, 3-phase GaN power stage”: is it possible to use each “phase” as independant DC and/or AC supplies? For example 3 DC outputs like -5/+5/+12V DC? Or a combination of AC/DC like 48VAC/+5VDC/+12VDC?

  4. Very interesting. This is an interesting project and I like the open source but it feels quite rough.
    I’m unfamiliar with Github and find it quite hard to navigate trough the website.

    The BOM count is around 250 components. Does someone know the total BOM value?

    In the documents it’s stated this is a board intended for lab use and you should not leave the board alone.
    What does it take to make this device safe to use in non lab applications? (I prefer to not use ‘can catch fire’ products.)

    I’m looking for the Gerber and preferably design files.
    Are these available? I’ve not found them.

    I want to know if it’s feasible to use the technology for applications or if it’s still a ‘lab’ gimmick.

  5. Are there also examples on how to programm them on Arduino? I have just founds examples for IOT2020 which is arduino based (?). Also the examples are with phyton and I would love to get started with arduino, because i think it should be enough to drive my inverter with a drive :).

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