Saturday, December 27, 2025

Projects: My Nixie Clock

Preface

The much I love tubes the more I prefer my amplifiers to be linear. So for over a decade I felt the urge to build a nixie clock - but I needed a little trigger to get the ball rolling.
Some years ago a friend of mine told me that he saw a video online and fell in love with nixies. He asked me whether I know about them - at a time when I was pregnant with the idea of building a nixie clock for quite a while. We talked to another friend of us who also loves the idea of some 'vintage, early cold war days'-energy wafting through his living room. As he is experienced in working with sheet metal we made a deal that he is going to design and build a nice stainless steel enclosure.

Yes, this is the n-th nixie-clock project on the internet. However, it might be somehow interesting because it does not use parts made from unobtainium and uses a little trick in the HV-supply you might not have seen before.

Design Targets

  • The clock should be supplied with 5V via a mini-USB jack (MOLEX) so it is possible to use one of these ubiquitous USB chargers.
  • Each nixie 'lives' on a separate daughter-board. This makes it easy to replace a nixie or to build a clock with some other tube than the IN-14 we used.
  • Four IN-14 nixies (hour, minute) only. But it shold be easy to derive a 6-nixie motherboard from the original design.
  • No LEDs (we think that the nixies stand for themselves and must not be accompanied by some fancy semiconductor illumination).
  • No Arduino (it's pretty easy to get a running AVR µC on a cusom PCB)
  • No DCF77 - for the sake of simplicity

Electronics

Driving the nixies

It seems to be a common technique to drive the nixies using the 74141 chip or its soviet counterpart. And somehow it seems to be harder to get one of these chips than some nixies. I guess that this is why some people try to build a clock using this chip only once - which leads to anode multiplexing:

My quesions is: if you are already fiddling around with some HV-BJTs why would you opt for wasting brightness by turning on each tube for only a fraction of a given time interval (in order to get the count of obsolete chips down) and not for avoiding obsolete parts in general and designing a proper nixie-driver using some more (cheap) BJTs?

The solution presented here uses one HV-BJT (e.g. BF820) in SOT23 per cathode. These transistors and a couple of resistors are directly placed on the nixie-daughterboard. 



In addition there is a 10-bit latch per tube and all latches are driven from a single BCD-to-DEC (HEF4028) converter. So we need just 8 µC pins (4x latch enable and 4 BCD-lines) to drive four tubes. Everything is orchestrated by my favourite 8-bit µC: ATmega8 which is further equipped with a 32.768kHz XTAL and two microswitches to independently adjust hours and minutes.



About power

The HV supply runs directly from the 5V input whereas all the logic stuff runs from a regulated (MC...) 3V3 rail. Therefore every logic chip (ATMEGA8L, HEF4028, SN74LVC841) is specified for 3.3V operation.

HV Section

There are several options of how to convert a given DC voltage (5V) into a higher voltage (170V). The most well-known might be the boost converter and flyback converter. Both have some drawbacks:
  • The biggest drawback of the boost converter is that it's duty-cycle is directly linked to the ration of input to output voltage. In this application we would end up well above 90%. Event if in the end it is no real deal-breaker it is definitely not convenient.
  • While the flyback converter does not suffer from the duty-cycle issue (as the winding ratio can be adjusted to the voltage ratio) voltage stress in the components is higher as when either the transistor or diode blocks it 'sees' the reflected voltage from 'the other side' on top of the voltage from the 'own side'. Also the current stress for the components gets higher.
So I wanted to try something else. There is a less-known hybrid form of both converters, where the inductor is uses as a 'tapped' inductor - just as in an autotransformer. Only a part of the windings are used to store energy but the full amount of windings is used to discharge the inductor.


Here you can find a little (LTSpice) simulation showing the three topologies exemplarily doing the same job: stepping 10V / 2A up to 20V / 1A. Switching frequency is identical for all converters but component values are adjusted to achieve CrCM (transistor turns on again in the very moment the core is completely demagnetized) in each case.

Theoretically it would make sense to use thicker wire for the 'primary' or 'charging' winding - but that would have been a custom choke. Without that a fancy Coilcraft LPH8045 is going to do the job. The cool thing about the 1:1:1 winding scheme is that is allows for an effective 1:3 catio in the HV supply which brings the duty-cycle well below 50% which again allows to use a cheap and simple UCC3805 without the need for slope compensation or other nasty tricks. Almost. Because this chip needs 1V on the CS-pin which is a lot of voltage drop over a shunt resistor in the transistor's source path when you only have 5V available. So I decided to throw in an INA10A1 to compensate for that. 

Finally you will find a simulation of the entire HV section here.


Schematics






Manufacturing Data

Here are links to everything necessary for creating a copy of the project:

Issues

There are two known issues with the design that were not fixed in the manufacturing data:
  • issue: unfortunately I messed up the pin mapping of the Coilcraft LPD inductor
    • fix: if you do not assemble it as shown in the 3D screenshot above (the silk layer does not contain any mounting info anyway) but as in the photo shown below everything is correct
  • issue: C15 needs way more capacitance than shown in the SCM / BOM (this is why the respective line of the BOM is highlighted)
    • fix: as replacement it is possible (also see photo below) to solder 2x 47µF 16V X5R caps in parallel (e.g.: 1210YD476MAT2A)

Software

The software of the project is super simple. Yes, I'm aware that an ESP32 board is dirt cheap and might get the time via NTP an what not. But this really is not my piece of cake. So everything can be found in one file. Sorry, but the variable names are crap - "uos" means "units of seconds" and so on. 

I used ATMEL-Studio 6 (or 7 I don't remember exactly) and compiled it into a little binary that I flashed onto the controller using this adapter.

I'm still in love with this mesmerizing effect:



Housing

Well, I guess that is a real shortcoming of the project. As I'm not a mechanical guy at all I cannot provide you with any details about the housing at all. It exists and it somehow fits. This is all I know. However, as I had not foreseen any means for fixation on the PCB itself I simply glued everything into the housing which doesn't have a bottom cover.
While the electronics can be built 'as is' and the software can be used 'as is' this topic certainly needs some skills and creativity...




Cheers,
P.
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Tuesday, December 9, 2025

Class-D Tales: 4041411 The Number Of The Beast - Or: How To Improve The UcD?

Foreword

Let's start this thing with a look into linear amps. In order to increase the efficiency of Class-AB amps it's a common practice to modulate the  rail voltage of the output stage transistors so to minimize their Vce. As Bob pointed out in chapter 5.6 of his book [1] there is some conflicting terminology - because it's also the way I learned it I'll use Bob's way of naming things.

Class-H

In case these modulation happens step-wise the concept is called Class-H. Although there were many designs out there none of them did something spectacular. The only implementation that stood out a little was the 'VZ'-design by Crown which did not only change the voltage but also the impedance of the supply.


Class-G

In case the modulation is done in a continuous fashion the topology is called Class-G. For sure, the most straightforward way to do this is to put even more BJTs into the box (see below). But the smarter way of course is to use a buck regulator. And of that there were three implementations we're going to discuss briefly.


Lab.Gruppen

They used a plain and simple clocked (614kHz) buck converter with PI controller in their FP series amplifiers [2]. Nothing spectacular but apparently they were quite successful with that.


Yamaha

These guys had a quite innovative idea - they kept the Class-G BJT stage but sensed its collector current [green parts]. When a certain threshold is exceeded another transistor is switched on that then feeds via an inductor [orage parts] current into the common node between Class-G stage (emitter) and output stage (collector) [blue]. Once the sensed current fell below the threshold a gate discharge circuit caused the FET to turn off fast.

This is nothing more than a self-oscillating, hysteretic current-mode buck-converter with linear ripple eater. Isn't that beautiful compared to the Lab.Gruppen design? (Think about "technical minimal systems"... [3]).


Philips

Then again there were people at Philips [sic!] who did this [4]:


Wait a second isn't that a UcD? Yes, it is - two unipolar ones. In 1985! The patent spec. states:

" 

An oscillation is produced in the feedback loop formed by the components 16, 19, 20, 21, 22 and 23 when the gain in the loop is higher than unity for signals experiencing a 180° phase shift. The loop components are chosen so that this is indeed the case at a comparatively high frequency. [...]

The degree to which these components are suppressed will depend on the ratio between the oscillation frequency of the loop and the resonant frequency of filter 22. A high oscillation frequency therefore has an advantageous effect. In one embodiment the oscillation frequency was 400 kHz and the resonant frequency of filter 22 was 40 kHz. [...]

The feedback networks 23 and 23' are in the form of networks which are commonly referred to as phase lead networks. These networks shift the frequency at which 180° phase shift occurs in the feedback loops to a higher value so that these loops will oscillate at a high to very high frequency. 

"

So Bruno Putzeys did not invent the UcD [5]? Well, I guess he did - but at the time he was struck by enlightenment the novelty was already gone.

Nowadays he is fully aware of that - maybe because a swede came across his way...


Once upon a time

I searched the internet. I don't exactly remember what I entered into the google search bar but this URL was part of page three (back in the day when there was no AI one sign of true desperation was feeling the urge to open page 2 ff. of google results):

Sounds like a thriller, right? So I had a look at the URL and asked myself what would happen if I changed the parameter ordnr=xx. Well, it appears that there are even more exciting documents! Here are the most relevant ones:
At the time I initially stumbled over this I downloaded all the files manually. Nowadays things are easier so I vibe-coded a little python script that does the job for you (if you want) and also gives the files some meaningful names. download


Lingua franca

Unfortunately, I do not understand Swedish. But apparently the link to German is so short that it was no big deal for me to grasp at least some parts of the last document. Apparently section 1.4.1 tells us, that the UcD was invented in the '70s by Clayton S. Sturgeon [6].

A vibe-translation looks as follows:

"
Patrik realized early on that the technology commonly referred to as UcD is very powerful, as it can achieve good performance with low complexity. Bruno Putzeys (“Bruno”) had filed a patent application for this technology in 2001 when he was working at Philips. Bruno was now working at Hypex in the Netherlands, which had purchased a license for UcD from Philips. For this reason, Patrik and Jan-Peter van Amerongen from Hypex began discussing possible forms of collaboration in 2005. Shortly thereafter, Patrik found a patent application from the mid-1970s (US4041411) by Clayton S. Sturgeon, which described UcD, meaning that UcD is open technology. This was communicated to Hypex, with Bruno noting that he had not been the first to invent the technology referred to as UcD. Also note that the definition of UcD in the Agreement refers only to Hypex’s own implementation of UcD.
" 

Now the very interesting part is, that in one of his most recent interviews [7] Bruno actually refers to that - maybe with a grain of salt - by stating:

" 
So, to help liberate the IP, a gallant competitor generously spent time on Google Patents and ferreted out a lapsed patent from 1977 by one Clayton Sturgeon (US4041411), which describes a similar arrangement! 
" 

But I guess at least it's some sort of achievement to be seen as a competitor by Bruno :-P

 

4041411 - the number of the beast

The basis for the UcD comes on two pillars:
  • in order to obtain a load independent frequency response and minimal output impedance the feedback of an amplifier circuit must be taken from the output (also knows as 'global feedback'). However, in case of an SMPA the LC filter is inbetween...
  • This filter comes with two state variables (inductor current and capacitor voltage) and in order to get a stable system both must be fed back (at least partially over frequency)
    • Inductor current
      • In SMPS design it's common practice to nest a current control loop inside a voltage loop in order to 'solve' the 'feedback from behind the filter'-problem.
      • In 1999 Dave Edwards (analogspiceman) adapted this method for SMPA which is also known as "Leapfrog" method [8].
      • Another well-known implementation is the BPCM from Høyerby [HOY05].
      • However, the big problem here in general is that the inductor current also carries the output current of the amplifier - something that doesn't need to be fed back - just 'the ripple' is of interest. Also Edwards (at least kind of) figured out that the capacitor current could be the perfect 'replacement' as it covers the ripple but not the load current.
    • Capacitor current
      • To my knowledge there is only one implementation that really sensed the capacitor current - which is the mueta-amp [HUL02]. All other implementations also use the capacitor current - but in a smarter way.
    • Capacitor current estimation
      • Have a look at the unipolar UcD again. The capacitor in the lead-lag network does nothing less than 'estimating' the current in the LC-filter capacitor where R17/R18 act as the 'shunt' resistance for converting the current into a voltage. The resistor in series with the capacitor helps in minimizing the frequency range of the estimation.
      • Without that resistor we end up at the GLIM amplifier [POU04a].


How to improve the UcD?

The plain UCD comes with two 'issues' that will be individually covered in the following sections.

Closed loop frequency response

It's fairly easy to see that the closed loop response of the UcD is that of a first order low-pass. It would be desirable to keep amplitude and phase more stable across the (upper) audio band by turning it into a second order function.
One way to achieve this is to split up the feedback resistor and insert a capacitor to ground (or to the 'mirror node' in a balanced design).


For the design of the 'Eigentakt'-loop Bruno came up with another concept (using some more parts but giving a better controllable result) I'll cover in another post.

Increased loopgain

Please note: this post does not deal with clamping techniques as I'm convinced that this is the rather trivial part.

The UcD already gives a decent amount of loopgain (especially at the upper end of the audio range). However, it always makes sense to ask for more. How is it done? By nesting the UcD inside another feedback loop.


However, this again creates two dynamic nightmares:
  • Fist, the control loop does not 'know' about the first order behavior of the UcD so it will try to flatten it out - which doesn't make too much sense
  • Second, as the UcD is a quite linear device in itself the output of R(s) must not only carry the error correction signal but also the input signal
Both issues can be solved in several different ways:

Textbook method #1 (Hypex Ncore)

It's quite easy to see that the loop filter can be relieved of the task of providing the foll input signal at its output simply by additively feeding in (feed-forward) said input signal behind the filter. In a further step the input signal might be split into two paths
  • one still being the feed-forward path
  • the other being pre-filtered with a filter mimicking the closed-loop transfer function of the UcD
In general this scheme is well known in standard control theory "conditional feedback" / "Führungsgrößenfilter mit Vorsteuerung" [9], [10 : chapter 5.3.1] but most likely Bruno was the first one who adopted this scheme for SMPAs [PUZ09].


The cool thing is that this can be done easily in a fully differential manner [11 : page 16] (which is definitely what you want when designing a high-power SMPA [PUZ13]) without any additional OpAmps (except the one for the loop filter).

Textbook method #2

Let's think about error correction [V&L79] for a moment.

Obviously the red node carries the error signal. Which is not exactly true in our case as it also contains the inevitable upper&above audio-band roll-off of the actual amp. Pre-filtering the input signal again helps here (green).


This structure is a special case of the "Internal Model Control" (IMC) shown in [10 : chapter 5.3.2] - and the open question is how to shape the error term over frequency such that a desired loopgain function exists. I'll cover that in another post.

Patrik's method #1 ("Adaptive Modulation Servo" [AMS])

The idea is to take the error signal from the inverting comparator input, inversely amplify it and feed the result into the non-inverting comparator input [12]. This comes with a good and a very bad aspect:
  • Good: while in the aforementioned approaches the complexity of K'(s) goes up when designing K(s) with a non-1st-order closed loop response here this doesn't happen - simply because there is no (explicit) K'(s)-function involved. Still, the control loop doesn't 'try' to flatten change the frequency response of the actual SMPA.
  • Bad: this method only works with a single-ended circuit (which definitely is not what you want when designing a high power SMPA).

I guess this is why he wrote [13]:
"
There is one more input on the comparator.
"

Patrik's method #2 ("OP1 loop")

Here the first stage of the self osc. loop is an OPAMP which senses the input and output of the SMPA differentially. Form an IMD-perspective this is clearly not the best solution so carefully selecting OP1 is a must. Possible part choices are:
After OP1 the signal is split into (at least) to paths:
  • a lo-gain path that directly arrives at the comparator input
  • a hi-gain path that further amplifies the error signal and comes with additional clamping
Overall this kind of works like the AMS but the design can be made differential in all places where it really matters [14]. And yes, it is possible to build quite decent SMPAs with that (in this case also including a medium-gain path):


Cheers,
P.

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Sunday, November 30, 2025

Projects: My SFF Build

 A little bit of history...

As my parents were not very computerphile we had an own PC quite late. It was an 700Mhz AMD K7 with (I guess) 128MB RAM and some sort of Nvidia graphics card. At some point I was (together with friends from school) quite heavily into PC gaming so I had to replace this thing. I bought my first own hardware which was an AMD Athlon 64 3200+ on an ASUS board with an Nvidia GeForce 5200 which I later upgraded to a 6800GT. Woha.

When my friends went from Counter Strike 1.6 to MMORPGs I lost interest in gaming and used my PC for other things - such as running gentoo Linux. Which was nice but a problem at the same time: this still was the only PC we had and my mother wanted to use it as well - and yeah she was not really compatible with Linux.

One thing that changed the timeline a lot was when I started my studies - at university I got my hands on all these nice student licenses for Microsoft products. So I made sure my parents got their own PC bought another refurbished PC and installed Windows Server 2008. There it was. My own small active directory network. Including fancy thing such as booting and Windows installation via LAN.

At that time I also got something new and I wanted it to be small. So I put an Intel E8400 into an Shuttle XPC SG33G5M barebone and was happy for a quite long time until I somewhat outgrew the need of having a desktop PC and so it ended up in the attic.

Fast forward.

The 'server' (which was in the meantime replaced by something serious) is long gone, the barebone PC still in the attic and I got used to use my quite decent DELL Precision 5570 laptop from work for private stuff as well. But there were two reasons why this was not longer perfect for me:

  • the IT department got a bit restrictive over time and I didn't want them to spy on me in private time
  • I had no usable monitor anymore and the laptop screen is way too small (but the 4k IPS panel is quite nice) to do cool things such as PCB layouts

So I decided to have an own desktop PC again. 

My parents had a DELL all-in-one PC for 12 years which I recently replaced (because of Windows 11) with the 27" version of a newer HP model. I took the old DELL with me and while playing around with it I discovered a little bit of love for all-in-one PCs at my end. So I almost bought the 32" version of the HP which cost ~2200€.

Almost. Because I did a little research about what else I could get for the money - which is:

  • Case:       Fractal Terra Jade                169,00€          
  • Mainboard:  Gigabyte Aorus Z890I              300,99€
  • CPU:        Intel Ultra 7 265KF               277,00€
  • Cooling:    be quiet! pure loop 2 120mm        87,88€
  • RAM:        Patriot 32GB DDR5-8200            188,90€
  • Graphics:   Zotac GeForce RTX5060 SOLO        294,90€
  • SSD:        Verbatim Vi5000 SSD 1TB M.2        59,00€
  • PSU:        Seasonic Focus SGX 650W           129,20€
  • Monitor:    Philips Evnia 32M2N6800M          665,98€
  • SUM:                                         2173,55€

Actually everything fit nicely - just with the cooler I had the 'issue' that i needed to put the fan 'behind' it in order not to collide with the front USB socket and to get the pump of the cooler more to the inside of the case. The spine is in the 2 position. And yes, I turned around the CPU cooler block during the assembly ;-) 










Lovely!

Cheers,
P.

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Monday, November 17, 2025

Class-D Tales: The D is For Denmark (a comprehensive overview)

Origins

The origins of switch mode power amplifiers (SMPA) date back well into the era of vacuum tubes [1]. Once there was a website listing some patents of the early days which was quite helpful in order to get an overview over SMPA history [2]. 

My personal impression is that there was not so much momentum in the early days. When switch mode power supplies (SMPS) started to become popular (late 70's to early-mid 80's - most likely fueled by the work of Middlebrook and Ćuk and by the advent of suitable semiconductors [3]) also Class-D technology saw a little boost (e.g. Brian Attwood at Peavey). The whole thing really took off in the late 90's to early 00's (not only but significantly) driven by a group of former PhD students of Michael A. E. Andersen at DTU.

Class-D is called Class-D simply because at the time it arrived the amplifier classes A, B and C were already known and D is the next letter in the alphabet. However, due to the fact that a power sage switching between (at least) two discrete states is at the core of the concept people tend to misinterpret (yes, it is still ongoing) the D as abbreviation for ‚digital‘. Which is horrifically stupid.

D is for Denmark - which is the Class-D hotspot.


Literature

For long years there has been no comprehensive treatise on Class-D technology. Some days ago I found the book of Robert N. Buono on the interweb [4]. 
My first thought was: "woohoo, finally...". Then I read the name of the author and realized two things:
  • I've never heard of that guy
  • Apparently he is not danish
So my second thought was: "please, please, please don't be bullshit". I downloaded the masterpiece on scribd.com. And it was utter crap. Honestly, don't waste your money on this! It is frightening to see that there are people spending years on the topic who afterwards still have no clue about it. Another good example is the dissertation of Verena Grifone Fuchs [5]. 

You could simply read the respective chapters in Bob Cordell's (otherwise very precious) book about linear amplifiers [6] and reach the same level of enlightenment easily - and Bob is clearly no Class-D guy.

After all this page is meant to contain a list of all literature that is relevant according to my impression:
  • Some of the links get you to archive.org - this is the case for everything that I could find somewhere on the internet.
  • The other links get you to a google drive - the files you get from there are password protected. Send me a message and I'll help you.
 After all, there is nothing like a step-by-step guide around a 'blameless' solution.

People


This is me in 2018 taking a little walk through the evening hours of Copenhagen after a fruitful day at the ICEpower office - a time I remember with great joy and pleasure (read [7] !)

Dichotomy and Archetypes

There is this ubiquitous myth that within self-oscillating topologies there is a dichotomy between phase shift controlled (PSC) circuits and hysteresis controlled (HC) circuits. However, Bruno showed that these can be analyzed using one unified framework [PUZ09]. Yes, there are differences when it comes to details but essentially PSC and HC are the same.

The only true dichotomy in Class-D is clocked vs. self-osc. Period.

Still, this circuit below is praised as the archetype of all Class-D amps basically everywhere. 


However, practical implementations of this tend to get quite complex due to several reasons:
  • When you go full digital (which indeed has some powerpoint appeal) you need ADCs, DSPs and what not to in the end still have an analogue amplifier [PUZ06a]
  • When you go analog you need a precision triwave generator.
    • One very well known solution to this problem is a circuit which is known as "Rechteck-Dreieck-Generator" in German. It comes with a nice feature that might be worth to chew on for a while:
      • By adding just one resistor to the circuit which forms an input node this thing starts acting as a full-blown HC-type Class-D modulator in itself. 
      • A fact Stefan Wehmeier thought he figured out himself [ELB98] but I guess the patent office had a different opinion so the application got stuck in A1-phase. 
      • Question: does it really make sense to hide an SMPA inside an SMPA? 
  • In both cases the fed back signal parts will cause the beautiful triangle to be disfigured and so the PWM process itself is not linear anymore (-> distortion). Ripple compensation [PUZ06b] is a way around it (doesn't matter whether analog or digital) but this again adds complexity. 
    • So while it is inevitably true that this circuit is the archetype of clocked SMPAs practical design  it is absolutely no technical minimal system.

What is a 'technical minimal system'? 

I first heard this term during a lecture held by this guy. Actually the concept is fairly easy to understand. Think about an AC supply circuit. All it needs to supply a load is two wires (often referred to as 'live' and 'neutral'). The big benefit over DC (which also required 'just' two wires) it that with AC the voltage can be stepped up/down using transformers so to overcome large distances. But there is one remarkable drawback: as power is the product of voltage and current and both have periodic zero crossings also the transmitted power oscillates between zero and twice the average value (assuming a pure ohmic load). A more steady power at the load can be achieved by adding a rectifier and a smoothing capacitor. But this comes at the cost of high peak currents in the AC line (deformed power / Verzerrungsblindleistung).

Now comes the magic: by adding just one wire it is possible to go from single-phase AC to a three-phase system (a neutral wire is not really needed if the load is well-balanced). Transformation is still possible and the transmitted power is steady again. For sure it is possible to add more wires anb phases - but nothing gets better by doing so.

For my LinkedIn profile I once described it like this: "What drives me is the eagerness to find „minimal systems“ which is the state of a device, circuit or system where removing or altering a single component severely worsens the overall performance but adding components does not lead to significant improvements."


Final words

Finally one might ask: "what is the archetype of self-osc. SMPAs"?. Well (cliffhanger incoming), we'll clarify this in an upcoming post. However, I'm, 100% convinced that the following circuit shows (following the argumentation in [1]) the technical minimal system of an SMPA in general:


Yes, there is a first-order closed loop response - but there is no circuit with less components that yields (at the same time):
  • the same order of robustness
  • the same order of load-invariance
  • the same order of loopgain at higher frequencies (check [PUZ11b] and [7])

Cheers,
P.

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Wednesday, November 12, 2025

Misc: Hello World!

Hi!

In case you're curious who is writing here let me put together some facts about myself.

I was born in 1990, my parents and me were living in a small town in southern Germany. In the neighbouring town (also small) the was a library and they had a book called "Elektronik gar nicht schwer, Bd.2, Experimente mit Wechselstrom". And this (while still being in school) was my first contact with electronics.

Most likely the first thing I ever built was an multivibrator with LEDs and a little battery holder that I glued to an old tie pin and gave it to my father (who wore ties at that time quite often). I should ask him whether he still has that thing...  

However, I spent a lot of my time at the computer back then and so I did more SW stuff (especially php) than HW but there were two topics that was always present: 

  • audio technology - I was obsessed with amplifiers and speakers and built some of these myself
  • high voltage stuff - at some point I tired to build a DRSSTC but it failed horribly (today I know exactly why)

At the end of my time in school the "what to do for a living" question boiled down to two options:

  • becoming a teacher
  • becoming an electrical engineer
A little bit of reflection led to the idea that not all pupils might have a good time with me (as I imagined myself clearly being more focussed towards the smarter ones while ignoring the needs of the others) so I opted for the latter.

The university I studied at (KIT) had a department of electrical engineering and information technology with (as far as I remember) 17 separate institutes specialized in different topics. After passing the first three semesters (unfortunately during my time at school I never learned how to learn - so I had to figure this out the hard way...) it became evident that my topic is power electronics & control theory (which essentially is quite equal to developing audio amplifiers - at least in my little world).

So for my bachelor's thesis I developed a (surprise) linear amplifier meant to power an Epstein frame. during that time I basically had a workplace in a lab with some other (already more experienced students) which was a great time of learning for me. After everything was finished my supervisor offered me to be hired as a student assistant so to keep my workplace and  to continue the project. 
I started my day at 8:30 in the lab, went to some lectures during the day and ended at 16:30. And despite the fact that I was just payed for 40h per month I did that every day as this was a very insightful time for me - especially because of the discussions with other students being on a similar path than I was. One guy I'll definitely never forget: Benjamin Weschenfelder

During my master studies it was obligatory to do an internship for some weeks - but for me it was clear that:
  • I wanted half a year
  • I wanted to do it in my second last semester (the last being blocked for my master's thesis) because I hoped to end up at a company that wanted to hire me afterwards
  • I wanted still be close to my small town (which I never really left - and will never leave)
  • I wanted to do audio stuff
Yeah and this is how it happened 🙈. 
I spent 6 months at d&b working on a new power supply concept and they wanted to have me back as soon as possible. After doing some 100kW inverter things for my master's thesis (and yes, Bernd, I'll also never forget you) which even culminated in a nice paper I was prepared for audio stuff again.

Shortly after I joined in Nov. 2015 the colleague who was responsible for developing the actual amplifier (we called it "Switch Mode Power Amplifier" - SMPA) inside the 19" amplifier device (which comprised also a SMPS, DSP and other things and was called "amp") left the company and I took over his topics. 
A while later Christoph joined and we were some sort of dream team. While I was juggling fancy ideas all the time he was deep in the details making sure that each part of a circuit was really doing what it is supposed to do. And yes, we both looooove transistor level circuitry. In the five years I spent with d&b I learned so many things. It was mindblowing, fulfilling and entertaining. I truly miss that time.



This was me in 2017 (top) and 2020 (bottom).
And this was our masterpiece: click me.

At d&b we had a little wiki space developers used to document their work and this was something which I loved from the beginning: structuring things and putting them together in a litte page that could be interesting for other as well - maybe written with a little sense of humor.

When COVID struck the company went into emergency mode including shutting down engineering. Something I really was not happy with so I quit - and ended up at instagrid in August 2020. As of now I'm in a kind of double role ("Head of Power & Controls Engineering"):
  • half of the time I'm doing something that could be called system engineering - which means that I create concepts of how to split devices into functions and assign them to assemblies including topics such as safety and EMC
  • the other half I'm leading a team of SW and HW people who develop the core pieces of the instagrid devices (such as charging/discharging functionality)
At instagrid there is no wiki. But it gives me the same feeling and I still love it. As you might have guessed this is also the reason for this blog. I want to write a bit about the things I'm doing :-)


Cheers,
P.

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