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2022-01-24, 16:41:56
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Author Topic: Itsu's workbench / placeholder.  (Read 48385 times)

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Yes, without increased output voltage to push the current into the inductor very quickly you are limited to low frequencies for the BH curve.
Because you took the hard way.

The easy way is to buy several pre-made isolated ±15V DC-DC converters to power the gates and use two isolated gate drivers (or digital isolators) for the high side MOSFETs. 
They are available now from Mouser, Digikey, RSonline, etc... but were not 8 years ago.

 O0  I have some RK-0515S DC2DC converters and some IL610 isolators, but i see that those are old and there are new ones integrated together like the ADUM5241ARZ

Itsu


   

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... and some IL610 isolators, but i see that those are old and there are new ones integrated together like the ADUM5241ARZ
These ADUM... digital isolators have 70ns propagation delay time.  Depending what your target frequency is, these might not be fast enough.
There are faster ones like the ADN4654BRWZ with 4ns propagation delay ...or even 2ns from Skyworks Solutions, Inc.

There are also gate drivers already integrated with isolators like the UCC21540DWK.
   

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YT has set your video referred there to "private"

Hmmm,  thanks, i notice YT has made some changes lately which i was not aware of (small print?) like ads on some of them and the change to private.

I have put that video on hidden again.

Itsu
   

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These ADUM... digital isolators have 70ns propagation delay time.  Depending what your target frequency is, these might not be fast enough.
There are faster ones like the ADN4654BRWZ with 4ns propagation delay ...or even 2ns from Skyworks Solutions, Inc.

There are also gate drivers already integrated with isolators like the UCC21540DWK.

Thanks for the info, i see many of those chips are not available due to the chip shortage.

Perhaps its faster to look for a completed product on Ebay or Ali.

Itsu
   

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Thanks for the info, i see many of those chips are not available due to the chip shortage.
Some are on Mouser some are on www.rs-online.com and some on Digikey and some on Farnell.com ...and if you don't mind CN then on lcsc.com

Perhaps its faster to look for a completed product on Ebay or Ali.
Let me know if you find something.
I don't think there is much consumer demand for MHz digital amplifiers with isolated inputs (so the FG is safe). 
Only EEs and scientists want them, because they do not contain an integrated power supply and music would sound horrible* if amplified by these amps.

* Unless PWM was added at their input and LC filter was attached to their output.
   

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I saw this experiment (see diagram) from member Jagau on aboveunity.com here:  https://www.aboveunity.com/thread/capacitor-recharging/

It shows what happens at the instance a charged capacitor (disconnected from its source (SW1 open)) is connected (SW2 closed) to an inductor.

Somehow i would have expected that the cap would not be negatively charged due to the diode, but it does.

Below screenshot shows:

blue:  the voltage across the cap (10uF)
yellow: the voltage across the coil (8.4mH)
green: current between C1 and SW2 (closed)

Traces have a small offset from zero for better visibility.

   
Itsu
   

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It is important to remember that a diode blocks reverse current - not reverse voltage.
   

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Actually a beautiful experiment.

It demonstrates nicely Capacitive Discharge and Inductive Charge and Discharge leading to Capacitive Re-Charge with Polarity Change.

A form of Resonant Charging but it would be better if the Capacitor was Non-Polarized.

This behavior is the "secret" to the Switching Converter which Changes Polarity of the Input Current when the Output is directed to an external Load.


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For there is nothing hidden that will not be disclosed, and nothing concealed that will not be known or brought out into the open.
   

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It is important to remember that a diode blocks reverse current - not reverse voltage.

Indeed, and this is a nice example of that IMO.

Itsu
   
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I saw this experiment (see diagram) from member Jagau on aboveunity.com here:  https://www.aboveunity.com/thread/capacitor-recharging/

It shows what happens at the instance a charged capacitor (disconnected from its source (SW1 open)) is connected (SW2 closed) to an inductor.

Somehow i would have expected that the cap would not be negatively charged due to the diode, but it does.
...

Yes, it is surprising. So I did the ltspice simulation, and it is confirmed.


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Thanks F6FLT,   i was thinking about doing a simulation, but as the circuit was so simple i went for the real one.

Glad you did the simulation and that it confirmed it  O0

Itsu
   

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For Jagau on his remark to me in the above mentioned thread (https://www.aboveunity.com/thread/capacitor-recharging/):

Quote
P.S to Itsu, If you do not want to see the parasitic resonance at the end of the waveform, place your scope probe on
the anode of the diode, you will have a cleaner waveform.

Thanks Jagau, but i do want to see/show this "parasitic resonance" on the inductor (yellow trace).
And, i did have the (blue) probe on the "anode of the diode" (SW2 closed) which indeed shows a cleaner waveform (and thus the lack of "parasitic resonance")  O0


Itsu
   
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you seem to me a good experimenter.
Tell me what type of current probe do you use?
thank you
   

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Hi Spark2,

i use a A6302 / AM 503B current probe / controller combo (Tektronix).

Itsu
   

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Without the diode the Jagau circuit and signals show as below.

Massive ringing on the resonance frequency of the cap (10uF) and inductor (8.4mH) on 549Hz.
   
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