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An investigation about ripple current of Kunkin KP184

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Everbrave:

--- Quote from: torch on August 23, 2023, 03:50:37 pm ---
--- Quote from: Everbrave on August 17, 2023, 09:58:53 pm --- I looked-up the prices: IRFP250N is around 1.5USD, IRFP264 is around 5.3USD

--- End quote ---

And there we go...  :-DD

Hey, at least they seem to have sprung for the genuine article.

--- End quote ---

I got in touch with the one of the developer and talked to him on several topics:
MOSFET type: they use IRFP250 for production and the IRFP264 when they are temporarily out of stock
Ripple: the modification made in board V7 to minimize ripple was to move the display 5V ground, since the display draws a significant amount of current. The ripple is at 100Hz
Firmware: FW2303 on V7 is not applicable to V6 (seemingly, different Beeper driver)

Hence, I repeated my ripple measurements using a low ripple power supply, Rigol 832, and optimizing the wiring in the set-up and obtained for my V6 Board a 100Hz (distorted) ripple value of around 2.8mV rms (see pic.). The high frequency noise is around 800uV.
I can live with this amount!

torch:

--- Quote from: Everbrave on August 28, 2023, 10:54:10 am ---Firmware: FW2303 on V7 is not applicable to V6 (seemingly, different Beeper driver)

--- End quote ---

I don't know what the earlier beeper sounds like, but the V7 emits charming musical chimes instead of an annoying beep. Quite a nice touch actually, and different chimes for different functions.

Everbrave:

--- Quote from: torch on August 28, 2023, 11:17:31 am ---
--- Quote from: Everbrave on August 28, 2023, 10:54:10 am ---Firmware: FW2303 on V7 is not applicable to V6 (seemingly, different Beeper driver)

--- End quote ---

I don't know what the earlier beeper sounds like, but the V7 emits charming musical chimes instead of an annoying beep. Quite a nice touch actually, and different chimes for different functions.

--- End quote ---

I forgot to mention that the ripple value is almost independent of the load current and voltage, which supports the hypnosis that it is actually due to the display current. The picture I made is at 30v,2A load. Once the developer approves, I can post his exact reply.
I don’t know what the pictures you posted show, since it is not periodic! May be you can extend the time base until you capture the periodic 100Hz ripple?;)

torch:
I'm not at home right now, but I'll try to remember to do that when I get back there.

torch:

--- Quote from: Everbrave on August 28, 2023, 11:37:44 am ---I don’t know what the pictures you posted show, since it is not periodic! May be you can extend the time base until you capture the periodic 100Hz ripple?;)

--- End quote ---

I got nothing. On the Siglent or on my old school analog Tek 475.

If I extend the time base to 2mS to match your capture, that brief pulse I showed just gets lost in the noise. The only way I can track it all the way to 2mS is to set the triggering to trigger on that specific pulse AND to use averaging to minimize noise. It seems to have a weird period of 68.5 Hz. It is definitely caused by the Kunkin; it disappears when the unit is powered off, appears at about the same point the boot reaches the model/version/ID splash screen and is there independent of whether the load is on or off.

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