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Hi Mick,
"Ok now I understand what is happening with your power supply asymmetry, but pumping in one direction is very interesting. Maybe this is common to class D half bridge topology... "
The problem shows up when getting too close to 90 degrees phase shift (reactive or reflected power) between the voltage and current. When crossing the line the setup becomes very unstable by pumping power either to one side or the other until the safety circuit of the amp shuts it down. When the power has dissipated the amp wakes up again to just shut down in repeating sequences.
"What is the Russian schematic you are citing?"
Sorry that was in another group. It's this one: https://groups.yahoo.com/neo/groups/ferd/attachments/120187998 https://groups.yahoo.com/neo/groups/ferd/attachments/120187998
No need to log in to be able to see it. The transformer is driven by two thyristors in push-pull mode. The thyristors are controlled by an astable multivibrator. This is even simpler than the class D amplifier. The load is impedance matched by using a double variable autotransformer. As the input voltage is a square wave the current then becomes a triangular wave.
Figure 1 of the document linked to above:
Regards
Ole
---In [email protected], <mkjekyll@...> wrote :
Ole,
Ok now I understand what is happening with your power supply asymmetry, but pumping in one direction is very interesting. Maybe this is common to class D half bridge topology...
Reminds me of guitar amp designs where in a push pull class A output stage they create a voltage offset asymmetry on purpose in order to generate even harmonics.
I looked at the class E amp and it looks more like a power oscillator designed around a tank circuit. Seems as if one would be tied to the frequency for the design which looks like a class C amp driving a tank circuit and designed as a ZCS or ZVS or combo. Maybe I am overlooking something here and not grocking it all, but it does not look wideband like a class D. Notwithstanding the schematic I was looking at seemed as if it would allow for ringing and harmonic 3rds and all of the things we might desire to drive another reactive load if not simply using the tank part for our energy harvesting.
Other than that it does seem like an excellent source for power, once one has the frequency and load figured out. I think you're right in your desire for a proper load. All of these tuned resonant designs the curse and the challenge is finding a very static stable load.
What is the Russian schematic you are citing?
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