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???
11/27/11 17:09
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 		 #184926 - Perhaps, but where else would ripple originate?
Responding to: ???'s previous message
In linear supply design, the filter cap design is classically based on "tolerable" ripple under full load. The old (Originated with NSC) formula for computing filter cap size (before the regulator) was
8000 uF / ampere at full load / volt of tolerable ripple, or something on that order. Now that "volt of tolerable ripple" figure was at the regulator circuit (not the regulator IC) input, and it had a small amount of additional capacitance, e.g. about 2.2 uF plus 100 nF at its input and a little more at its output.

Where, other than mains would any ripple originate?

The very first power supply I used in my lab, some 35 years ago, put out plenty of power at several voltages, yet maintained on the order of 5 mV of random noise even when powering a couple of pretty large stepping motors at about 600 Hz. There was a bit of discernible signal on the 48-volt output, but only about 6 mV. The 5-volt supply never saw it.

That supply had a constant-voltage transformer at its input, so managing the mains-originated ripple was pretty easy, I guess. That supply was a pretty old design even when I got it and yet was VERY quiet.

RE


List of 26 messages in thread
TopicAuthorDate
a myth debunked ?            01/01/70 00:00      
   Same old?            01/01/70 00:00      
   Hhm...            01/01/70 00:00      
      no, I did not            01/01/70 00:00      
         Babble of marketing people...            01/01/70 00:00      
            read it all            01/01/70 00:00      
               There's no need for HF-ripple rejection...            01/01/70 00:00      
               ... what's more important ...            01/01/70 00:00      
                  whatever            01/01/70 00:00      
                     But the article claims it...            01/01/70 00:00      
                        even the article states            01/01/70 00:00      
                           Switchers ARE beautiful...            01/01/70 00:00      
                        do linear regulators ever "produce" ripple?            01/01/70 00:00      
                           getting more and more irrevelant            01/01/70 00:00      
                              Perhaps, but where else would ripple originate?            01/01/70 00:00      
                                 still missing the point            01/01/70 00:00      
                                    Why do you see this as "becoming more mandatory"?            01/01/70 00:00      
                                       you can't do PFC without            01/01/70 00:00      
                                          Vice versa...            01/01/70 00:00      
                                             Not so fast            01/01/70 00:00      
                                          fortunately, PSU's are not on my deliverables list            01/01/70 00:00      
                                       I'm with Eric            01/01/70 00:00      
                                          Disadvantage of switched-mode supplies...            01/01/70 00:00      
                                             Huge crest factor            01/01/70 00:00      
                                                Numbers...            01/01/70 00:00      
                           It depends on load            01/01/70 00:00      

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