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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: power supply idea
Date: Tue, 23 Apr 2024 01:09:10 +1000
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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.

-- 
Bill Sloman, Sydney