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???
11/29/11 19:04
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 		 #184942 - Disadvantage of switched-mode supplies...
Responding to: ???'s previous message
Oliver said:
All the 'wall-warts' and 'power bricks' I've bought in recent years (all the way down to my dinky phone charger) are switching supplies, driven by the consumers expectation of ever high power densities.

Saftey class II switched-mode power supplies suffer from high input to output capacitance due to the obligatory 4,7nF Y-cap, required to keep the self-produced output common mode noise within the allowed level. This directly transports all kinds of "dirt" from the mains voltage just into circuit's signal ground.

Tiny mains transformers, on the other hand, provide only one tenth of this coupling capacitance and are much quieter. So, in sensitive circuits I still use the good old mains transformer to provide proper isolation, put a high efficient switcher at the storage cap for pre-regulation and use a linear regulator for fine-regulation.

Kai Klaas

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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