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An investigation about ripple current of Kunkin KP184

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burkm:
To check, if that chip is really responsible for the measured and detected visible noise floor, one should look, if the application notes (spec sheet) for that chip have been observed in detail by the chosen PCB design (layout) and its components.
This will determine, if it really "cripples input by design"

burkm:
But there is still another "problem": instability of the electronic load in combination with specific power supplies as determined by some fluctuating output.
Any idea, how to get around it and what has to be done because of this...

electr_peter:
Noise in DC load can be mitigated if the source is known (mentioned by posters above in KP184 case).

Instability with active DC load can be broadly spitted in few categories:
* DC supply just cannot handle the load or load changes and goes crazy. DC load is not at fault, any other DC load with same parameters would cause same issue OR
* DC load just cannot maintain the load and is unstable by design. DC supply is not at fault OR
* DC supply and DC load in combination become unstable. This is because control loops in DC supply and DC load fight against each other, creating feedback loop with wild oscillating results.Combination is the most likely cause, as others are easier to solve. Actual strategies to limit instability:

* from DC load side - do nothing and continue to "maintain" load (most DC loads, including KP184)
* from DC load side - admit failure, i.e., show that oscillation occurs via "Unregulated load" error message and/or
turn off DC load
* manually change DC load and/or DC supply parameters (loop speed) to reduce oscillation capability. Only some DC loads and DC supplies are capable of this
* modify external circuitry between DC load/DC supply if you have idea what is causing itIn general, Mr Murphy ensures that it is possible to create unfavorable conditions for any DC load. EEVblog has several videos with DC loads oscillating, especially in CR mode.

atarian:
>>To check, if that chip is really responsible for the measured and detected visible noise floor, one should look, if the application notes (spec sheet) for that chip have been observed in detail by the chosen PCB design (layout) and its components.
This will determine, if it really "cripples input by design"

I was referring to their own characteristics published in linked datasheet, namely IN voltage waveforms. And they of course represent best case scenario of flawless implementation "by a book".

burkm:

--- Quote from: electr_peter on February 21, 2022, 07:18:27 pm ---Noise in DC load can be mitigated if the source is known (mentioned by posters above in KP184 case).

Instability with active DC load can be broadly spitted in few categories:
* DC supply just cannot handle the load or load changes and goes crazy. DC load is not at fault, any other DC load with same parameters would cause same issue OR
* DC load just cannot maintain the load and is unstable by design. DC supply is not at fault OR
* DC supply and DC load in combination become unstable. This is because control loops in DC supply and DC load fight against each other, creating feedback loop with wild oscillating results.Combination is the most likely cause, as others are easier to solve. Actual strategies to limit instability:

* from DC load side - do nothing and continue to "maintain" load (most DC loads, including KP184)
* from DC load side - admit failure, i.e., show that oscillation occurs via "Unregulated load" error message and/or
turn off DC load
* manually change DC load and/or DC supply parameters (loop speed) to reduce oscillation capability. Only some DC loads and DC supplies are capable of this
* modify external circuitry between DC load/DC supply if you have idea what is causing itIn general, Mr Murphy ensures that it is possible to create unfavorable conditions for any DC load. EEVblog has several videos with DC loads oscillating, especially in CR mode.

--- End quote ---

Any idea, what can be done about this ???
I got this same problem in combination KP184 and BK 9174 power supply. The BK 9174 was quite expensive and it goes into overvoltage or overcurrent protection below the range extremes quite often, when this happens...

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