Blast from the Past...

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  • JonMarsh
    Mad Max Moderator
    • Aug 2000
    • 15315

    Blast from the Past...

    Revisiting this topic and paper came about because of some former colleagues asking questions about early work that was topic related to another former colleague, who joined us from a company very involved in Class D (Extron) and went back to them, and the curious tale of how I knew their research director long before this employee did, because of an AES presentation I gave and an invited paper that resulted from that presentation. Of course, it's about Class D design and development strategies.

    I shared that with Sven this weekend, as he needed reading material on his flight back from India (I don't think this is what he was expecting, though!) and he suggested I create a post for it in case anyone else might be curious...

    Keep in mind, this work was done WAY BACK before a lot of things we have and take for granted, including high speed computers and modern simulation tools and device models. All the simulation and development work was done on my personal home built 80386, which was blazingly fast and capable (32 bit!!) compared with what we had in the office for Application Engineers.

    And I'll admit that it may seem a bit cheesy that I cited myself (in published papers) as a reference 5 times out of 19 cited references. But hey, prior art and all!

    This presentation and publication got me a lot of interesting questions from the handful of other people active in class D development efforts. Sort of like making your own invitations...

    The most curious and intriguing thing about re-reading this was noting in the power supply section (SMPS, not big transformers and caps) I had been developing what I called a ZVS-QRC, or Zero Voltage Switching Quasi-Resonant Converter, and I'll be dipped if that wasn't pretty much an LLC converter, using a special IGBT with fast switching and very low tail current losses, made lower with a half sine current profile this converter used. I don't recall LLC being a "thing" back in those days, not until the late 90s, though. And LLC analysis and design synthesis is what I focused much of my work on the last 5 years. My last work was an APEC professional education seminar on that topic, about 130 foils... drop me a PM if you have Apple messaging and I can send you the 50MB file. ;^)

    OK, Peabody set the wayback machine to 1990!

    Page 1.

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    the AudioWorx
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    Resistance is not futile, it is Volts divided by Amperes...
    Just ask Mr. Ohm....
  • JonMarsh
    Mad Max Moderator
    • Aug 2000
    • 15315

    #2
    Page 2, Class D

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    the AudioWorx
    Natalie P
    M8ta
    Modula Neo DCC
    Modula MT XE
    Modula Xtreme
    Isiris
    Wavecor Ardent

    SMJ
    Minerva Monitor
    Calliope
    Ardent D

    In Development...
    Isiris Mk II updates- in final test stage!
    Obi-Wan
    Saint-Saëns Symphonique/AKA SMJ-40
    Modula PWB
    Calliope CC Supreme
    Natalie P Ultra
    Natalie P Supreme
    Janus BP1 Sub


    Resistance is not futile, it is Volts divided by Amperes...
    Just ask Mr. Ohm....

    Comment

    • JonMarsh
      Mad Max Moderator
      • Aug 2000
      • 15315

      #3
      Page 3, Class D


      Click image for larger version

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Size:	1.25 MB
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      the AudioWorx
      Natalie P
      M8ta
      Modula Neo DCC
      Modula MT XE
      Modula Xtreme
      Isiris
      Wavecor Ardent

      SMJ
      Minerva Monitor
      Calliope
      Ardent D

      In Development...
      Isiris Mk II updates- in final test stage!
      Obi-Wan
      Saint-Saëns Symphonique/AKA SMJ-40
      Modula PWB
      Calliope CC Supreme
      Natalie P Ultra
      Natalie P Supreme
      Janus BP1 Sub


      Resistance is not futile, it is Volts divided by Amperes...
      Just ask Mr. Ohm....

      Comment

      • JonMarsh
        Mad Max Moderator
        • Aug 2000
        • 15315

        #4
        Page 4, Class D.


        Click image for larger version

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        the AudioWorx
        Natalie P
        M8ta
        Modula Neo DCC
        Modula MT XE
        Modula Xtreme
        Isiris
        Wavecor Ardent

        SMJ
        Minerva Monitor
        Calliope
        Ardent D

        In Development...
        Isiris Mk II updates- in final test stage!
        Obi-Wan
        Saint-Saëns Symphonique/AKA SMJ-40
        Modula PWB
        Calliope CC Supreme
        Natalie P Ultra
        Natalie P Supreme
        Janus BP1 Sub


        Resistance is not futile, it is Volts divided by Amperes...
        Just ask Mr. Ohm....

        Comment

        • JonMarsh
          Mad Max Moderator
          • Aug 2000
          • 15315

          #5
          Page 5 Class D


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          the AudioWorx
          Natalie P
          M8ta
          Modula Neo DCC
          Modula MT XE
          Modula Xtreme
          Isiris
          Wavecor Ardent

          SMJ
          Minerva Monitor
          Calliope
          Ardent D

          In Development...
          Isiris Mk II updates- in final test stage!
          Obi-Wan
          Saint-Saëns Symphonique/AKA SMJ-40
          Modula PWB
          Calliope CC Supreme
          Natalie P Ultra
          Natalie P Supreme
          Janus BP1 Sub


          Resistance is not futile, it is Volts divided by Amperes...
          Just ask Mr. Ohm....

          Comment

          • JonMarsh
            Mad Max Moderator
            • Aug 2000
            • 15315

            #6
            Page 6 Class D



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            the AudioWorx
            Natalie P
            M8ta
            Modula Neo DCC
            Modula MT XE
            Modula Xtreme
            Isiris
            Wavecor Ardent

            SMJ
            Minerva Monitor
            Calliope
            Ardent D

            In Development...
            Isiris Mk II updates- in final test stage!
            Obi-Wan
            Saint-Saëns Symphonique/AKA SMJ-40
            Modula PWB
            Calliope CC Supreme
            Natalie P Ultra
            Natalie P Supreme
            Janus BP1 Sub


            Resistance is not futile, it is Volts divided by Amperes...
            Just ask Mr. Ohm....

            Comment

            • JonMarsh
              Mad Max Moderator
              • Aug 2000
              • 15315

              #7
              Page 7 Class D paper.



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              the AudioWorx
              Natalie P
              M8ta
              Modula Neo DCC
              Modula MT XE
              Modula Xtreme
              Isiris
              Wavecor Ardent

              SMJ
              Minerva Monitor
              Calliope
              Ardent D

              In Development...
              Isiris Mk II updates- in final test stage!
              Obi-Wan
              Saint-Saëns Symphonique/AKA SMJ-40
              Modula PWB
              Calliope CC Supreme
              Natalie P Ultra
              Natalie P Supreme
              Janus BP1 Sub


              Resistance is not futile, it is Volts divided by Amperes...
              Just ask Mr. Ohm....

              Comment

              • JonMarsh
                Mad Max Moderator
                • Aug 2000
                • 15315

                #8
                Class D Paper Page 8



                Click image for larger version

Name:	P8 Class D.png
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ID:	951456
                the AudioWorx
                Natalie P
                M8ta
                Modula Neo DCC
                Modula MT XE
                Modula Xtreme
                Isiris
                Wavecor Ardent

                SMJ
                Minerva Monitor
                Calliope
                Ardent D

                In Development...
                Isiris Mk II updates- in final test stage!
                Obi-Wan
                Saint-Saëns Symphonique/AKA SMJ-40
                Modula PWB
                Calliope CC Supreme
                Natalie P Ultra
                Natalie P Supreme
                Janus BP1 Sub


                Resistance is not futile, it is Volts divided by Amperes...
                Just ask Mr. Ohm....

                Comment

                • JonMarsh
                  Mad Max Moderator
                  • Aug 2000
                  • 15315

                  #9
                  Class D Paper Page 9



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                  the AudioWorx
                  Natalie P
                  M8ta
                  Modula Neo DCC
                  Modula MT XE
                  Modula Xtreme
                  Isiris
                  Wavecor Ardent

                  SMJ
                  Minerva Monitor
                  Calliope
                  Ardent D

                  In Development...
                  Isiris Mk II updates- in final test stage!
                  Obi-Wan
                  Saint-Saëns Symphonique/AKA SMJ-40
                  Modula PWB
                  Calliope CC Supreme
                  Natalie P Ultra
                  Natalie P Supreme
                  Janus BP1 Sub


                  Resistance is not futile, it is Volts divided by Amperes...
                  Just ask Mr. Ohm....

                  Comment

                  • JonMarsh
                    Mad Max Moderator
                    • Aug 2000
                    • 15315

                    #10
                    Class D Paper page 10



                    Click image for larger version

Name:	P10 Class D.png
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ID:	951460
                    the AudioWorx
                    Natalie P
                    M8ta
                    Modula Neo DCC
                    Modula MT XE
                    Modula Xtreme
                    Isiris
                    Wavecor Ardent

                    SMJ
                    Minerva Monitor
                    Calliope
                    Ardent D

                    In Development...
                    Isiris Mk II updates- in final test stage!
                    Obi-Wan
                    Saint-Saëns Symphonique/AKA SMJ-40
                    Modula PWB
                    Calliope CC Supreme
                    Natalie P Ultra
                    Natalie P Supreme
                    Janus BP1 Sub


                    Resistance is not futile, it is Volts divided by Amperes...
                    Just ask Mr. Ohm....

                    Comment

                    • JonMarsh
                      Mad Max Moderator
                      • Aug 2000
                      • 15315

                      #11
                      Class D paper page 11



                      Click image for larger version

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                      the AudioWorx
                      Natalie P
                      M8ta
                      Modula Neo DCC
                      Modula MT XE
                      Modula Xtreme
                      Isiris
                      Wavecor Ardent

                      SMJ
                      Minerva Monitor
                      Calliope
                      Ardent D

                      In Development...
                      Isiris Mk II updates- in final test stage!
                      Obi-Wan
                      Saint-Saëns Symphonique/AKA SMJ-40
                      Modula PWB
                      Calliope CC Supreme
                      Natalie P Ultra
                      Natalie P Supreme
                      Janus BP1 Sub


                      Resistance is not futile, it is Volts divided by Amperes...
                      Just ask Mr. Ohm....

                      Comment

                      • JonMarsh
                        Mad Max Moderator
                        • Aug 2000
                        • 15315

                        #12
                        Class D Paper page 12


                        Click image for larger version

Name:	P12 Class D.png
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ID:	951464
                        the AudioWorx
                        Natalie P
                        M8ta
                        Modula Neo DCC
                        Modula MT XE
                        Modula Xtreme
                        Isiris
                        Wavecor Ardent

                        SMJ
                        Minerva Monitor
                        Calliope
                        Ardent D

                        In Development...
                        Isiris Mk II updates- in final test stage!
                        Obi-Wan
                        Saint-Saëns Symphonique/AKA SMJ-40
                        Modula PWB
                        Calliope CC Supreme
                        Natalie P Ultra
                        Natalie P Supreme
                        Janus BP1 Sub


                        Resistance is not futile, it is Volts divided by Amperes...
                        Just ask Mr. Ohm....

                        Comment

                        • theSven
                          Master of None
                          • Jan 2014
                          • 1422

                          #13
                          Awesome share! Thanks for posting this JonMarsh!
                          Painter in training

                          Comment

                          • letiennam
                            Junior Member
                            • Mar 2016
                            • 14

                            #14
                            Awesome share! Thanks for posting this

                            Comment

                            • JonMarsh
                              Mad Max Moderator
                              • Aug 2000
                              • 15315

                              #15
                              You're quite welcome- it's interesting to see how much has changed, and how similar some things still are, from over 30 years ago...
                              the AudioWorx
                              Natalie P
                              M8ta
                              Modula Neo DCC
                              Modula MT XE
                              Modula Xtreme
                              Isiris
                              Wavecor Ardent

                              SMJ
                              Minerva Monitor
                              Calliope
                              Ardent D

                              In Development...
                              Isiris Mk II updates- in final test stage!
                              Obi-Wan
                              Saint-Saëns Symphonique/AKA SMJ-40
                              Modula PWB
                              Calliope CC Supreme
                              Natalie P Ultra
                              Natalie P Supreme
                              Janus BP1 Sub


                              Resistance is not futile, it is Volts divided by Amperes...
                              Just ask Mr. Ohm....

                              Comment

                              • dar47
                                Senior Member
                                • Nov 2008
                                • 876

                                #16
                                Just saw this interesting read and I wonder if there is some more work to do on the power supply side for class D.

                                I had no issue with switch mode power supplies on the pro-audio side of amps for subwoofers but starting with Ncore and a nameless power supply used for these and the new Purify amps seams to not last very long under light conditions. In my very little circle of 3 people we have had 3 flaky power supplies. After my NC500 build flaked I wanted to try Purify so I went with an affordable NAD C298 with Purify and NAD's power supply and liked the sound upgrade from Ncore but worried the long term reliability of the power supply might not be there. Now I think class A/B manufacturers have had to adjust pricing from the introduction of these new wonderful affordable Class D's to the market but do they have issues with longevity of the power supplies? The power supply is complicated, is this the issue?
                                I started thinking just go with the newer Bryston 3B3 or 4B3, 20 Year warranty and sounds wonderful! This amp is close to $8,000 cad. but is on the lower end of really good A/b's or get the Masters NAD M23 with a little different design and hope my light use will last me.



                                New M23
                                Click image for larger version

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                                On another note maybe I am just a worry wort but I also change the power supply in my Eversolo DMP-6 streamer to a leaner one and maybe I here a difference LOL.
                                Last edited by theSven; 14 April 2024, 01:26 Sunday. Reason: add photo inline

                                Comment

                                • dar47
                                  Senior Member
                                  • Nov 2008
                                  • 876

                                  #17
                                  With the new M23

                                  Click image for larger version

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                                  Comment

                                  • JonMarsh
                                    Mad Max Moderator
                                    • Aug 2000
                                    • 15315

                                    #18
                                    Well, you know, that's the funny thing... a standard linear power supply is pretty much rock solid, lasts dang near forever, but as is hinted in the post above, a switch mode power supply can be a bit of a tricky beast. I was a "Distinguished Engineer" the last 8 years in my career of 35 years with a German semiconductor company, and that was due to contributions in understanding how best to use different types of switching power transistors, and a much more thorough examination of some key topologies like LLC push-pull resonant converters. The popular method of modeling the latter is called FHA, for First Harmonic Approximation, which is basically treating the power topology as if it was a linear network like a loudspeaker crossover network. That works OK EXACTLY at the resonant frequency, but is various forms of screwed up anywhere else. What I showed in this paper above and described as a ZVS-QRC converter (with our special IGBTs) is basically a subset of the LLC converter. In their 2001 paper, Lazar and Martinelli proposed a discrete time based analysis mode, which I guess folks weren't keen on because the math was hard!

                                    🤣

                                    But that is what works... it took a training campaign internally with webinars back in 2016 to start convincing at least a few folks at my former employer about that, but it grew in scope to where the last project I did was a 120 page APEC PES (Professional Education Seminar) for 2021, which my partner in crime on this topic would have to present with out me, as I retired the end of 2020...

                                    Now, I am still thinking about an SMPS solution for Class D amps, I'm even attending a 9 hour development forum from Europe from my former employer on Widebandgap power transistors on April 16, from 12 AM to 9AM. But I've already done some homework for that, and fired in some relevant questions and suggestions ahead of time, so it will be interesting to see how it goes. I know about half the guys presenting personally, and all on the SiC transistor side, and didn't ask easy or comfortable questions.

                                    OTOH, Infineon has just introduced their 2nd generation 650V SiC MOSFETs, and they're doozies- and priced very competitively also. I did a comparison of a number of current MOSFETs in a simple chart, not focused on ID or Ron rating, but selecting parts with a common Qoss range and Coss at 400V characteristics- this is a key spec for resonance and high frequency switching, correlates with the net drain active area, and it's interesting to see how the other stuff falls in place from various competitors.

                                    Look at the bottom selection area for Qoss, Coss, and Co(tr) (Time related) and Co(er) (Energy related)- commonality was the point, as these would all be usable in the same resonant switching circuit. But the conduction characteristics- the other side of the figure of merit expression, you could make it Ron X Qoss, or 1/ID X Qoss, the smaller the number, the better. Hints about dynamic switching characteristics can be seen comparing gate charge, and especially focusing on gate to drain switching charge, as this is the gate energy and correponsing time necessary for a turn-on drain voltage transition.

                                    This is from a more recent "educational" presentation I put together for a former colleague to bring him up to speed in a new role he has... at another company.


                                    Click image for larger version

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                                    This is all from public data sheets- no proprietary information involved. I do have knowledge of a lot of the changes in device structure and manufacturing techniques that resulted in the improvements in the just released early this year IMBG65R040M2 (M2 = 2nd generation) and some bits you can find in published paper, like the use of an asymmetric trench gate technology to both reduce voltage stress on the gate oxide and support a trench gate design achieving higher mobility and lower net source Ron (just compare the Id-Pulse ratings to see the impact from this as well as the Ron of this part versus the IMBG65R072M1H).

                                    Fun stuff!



                                    the AudioWorx
                                    Natalie P
                                    M8ta
                                    Modula Neo DCC
                                    Modula MT XE
                                    Modula Xtreme
                                    Isiris
                                    Wavecor Ardent

                                    SMJ
                                    Minerva Monitor
                                    Calliope
                                    Ardent D

                                    In Development...
                                    Isiris Mk II updates- in final test stage!
                                    Obi-Wan
                                    Saint-Saëns Symphonique/AKA SMJ-40
                                    Modula PWB
                                    Calliope CC Supreme
                                    Natalie P Ultra
                                    Natalie P Supreme
                                    Janus BP1 Sub


                                    Resistance is not futile, it is Volts divided by Amperes...
                                    Just ask Mr. Ohm....

                                    Comment

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