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Disable or trick pulse-skipping/skip-cycle/eco-mode

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b_force:
I have here a power supply with a NCP1239.

I am pretty happy with the overall design around this chip, except for the fact that it goes into some kind of "eco-mode" with light loads.
Unfortunately this is causing all kinds of noise issues in my design (which has a dynamic load).
Before I go for a different power supply, I was wondering if this mode can be tricked somehow?
I am fine trading in some efficiency for this obviously.

I have been searching and looking around for a bit, but can't really find any satisfying solution so far.
(for the record, I am skilled in working with main voltages and designing similar designs myself, so I am only just asking for a solution to disable this mode)

Wimberleytech:

--- Quote from: b_force on May 22, 2019, 02:47:11 pm ---I have here a power supply with a NCP1239.

I am pretty happy with the overall design around this chip, except for the fact that it goes into some kind of "eco-mode" with light loads.
Unfortunately this is causing all kinds of noise issues in my design (which has a dynamic load).
Before I go for a different power supply, I was wondering if this mode can be tricked somehow?
I am fine trading in some efficiency for this obviously.

I have been searching and looking around for a bit, but can't really find any satisfying solution so far.
(for the record, I am skilled in working with main voltages and designing similar designs myself, so I am only just asking for a solution to disable this mode)
If you are willing to sacrifice some efficiency, just add a fixed load.  Not so pretty, but it will address the problem.  Most likely you have thought of this and have reason not to do it.

--- End quote ---

b_force:

--- Quote from: Wimberleytech on May 22, 2019, 03:15:30 pm ---
--- Quote from: b_force on May 22, 2019, 02:47:11 pm ---I have here a power supply with a NCP1239.

I am pretty happy with the overall design around this chip, except for the fact that it goes into some kind of "eco-mode" with light loads.
Unfortunately this is causing all kinds of noise issues in my design (which has a dynamic load).
Before I go for a different power supply, I was wondering if this mode can be tricked somehow?
I am fine trading in some efficiency for this obviously.

I have been searching and looking around for a bit, but can't really find any satisfying solution so far.
(for the record, I am skilled in working with main voltages and designing similar designs myself, so I am only just asking for a solution to disable this mode)

--- End quote ---
If you are willing to sacrifice some efficiency, just add a fixed load.  Not so pretty, but it will address the problem.  Most likely you have thought of this and have reason not to do it.

--- End quote ---
Obviously I have, the problem is that this fixed load has to be pretty big to get out of this eco mode.
Wasting around 1A around 24V.
A little bit to big to my liking, so I was wondering if there other ways to do this?

Wimberleytech:
Going into skip mode below 1A doesn't feel right.  1A is not "light load"

b_force:

--- Quote from: Wimberleytech on May 22, 2019, 03:33:01 pm ---Going into skip mode below 1A doesn't feel right.  1A is not "light load"

--- End quote ---
Well, around 1A it goes into a lower frequency, around 20kHz which is causing a lot of noise issues.
Going down to around 500mA and this frequency is even lower.
With no load it's completely unusable, go to around 4-5kHz or thereabouts.

This power supply can deliver around 150W, so I guess 24W is considered a light load?

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