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From: John Larkin <jjSNIPlarkin@highNONOlandtechnology.com>
Newsgroups: sci.electronics.design
Subject: Re: power supply idea
Date: Mon, 22 Apr 2024 09:04:21 -0700
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On Mon, 22 Apr 2024 16:32:00 +0100, John R Walliker
<jrwalliker@gmail.com> wrote:

>On 22/04/2024 16:09, Bill Sloman wrote:
>> On 22/04/2024 10:57 pm, Don wrote:
>>> John Larkin wrote:
>>>>
>>>> If one had, say, a 48 volt power bus, you could hang a half-bridge
>>>> switcher to ground, and a lowpass filter out. If the drive has duty
>>>> cycle n, the output voltage is 48*n. So we have a programmable power
>>>> supply with no feedback, which will be stable into any load.
>>>>
>>>> The load regulation will be mediocre, but we could almost sell it
>>>> as-is.
>>>>
>>>> So now, sense the output voltage and compute the error against the
>>>> target, run through a slowish integrator, and tweak the PWM to get
>>>> zero output voltage error. Gross transient response is basically the
>>>> response of the output filter, with some modest drool from the
>>>> integrator.
>>>>
>>>> We can constrain the influence range of the integrator, just enough to
>>>> give the regulation that we need. That limits output swing in case the
>>>> feedback is wrong, as one could get from a botched remote sense
>>>> connection.
>>>>
>>>> https://www.dropbox.com/scl/fi/2fysyvkl4eim7vujhaobh/FFINT_PS_1.jpg?rlkey=rug6yi3cgemi9vvbz8apgboqi&raw=1
>>>
>>> Is your "spread spectrum" dodad supposed to mitigate EMI?
>> 
>> It smears it out over a range of frequencies, and makes it look better 
>> on the screen - no big frequency spikes, but many more smaller ones.
>> 
>> "Mitigate" depends on how the hash messes up your particular system.
>> 
>
>Yes, but the only one that most designers care about is the EMC
>receiver at the compliance test lab.
>
>John

It won't reduce ripple or fast switching spikes, which is what my
users might care about. It would improve the peaks on a spectum
analyzer, which is what regulators (government regulators, not voltage
regulators) care about.

Actually, the DC power that one sees on an airplane or in a car is
nastier than anything I can reasonably make, even on purpose. So my
concern is stability and not blowing anything up.