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Terry Lingle
01/15/06 23:20
Read: 1067 times
Clearwater
Canada


 
#107454 - inrush current
Responding to: Suresh R's previous message
If this was an ac circuit your analysis would be correct. It is a dc circuit. Heavy current flows into the capacitor (limited only by the total circuit impedance and the available voltage) until the capacitor charges. Each cycle sees an exponentialy decreasing current bump until the final steady state current that is the load current is all that is flowing. That low reactance helps keep the ripple at the input to the regulator as low as possible. Normally the reactance of the supply transformer limits the inrush current but care must be taken not to damage the input rectfiers if the transformer has a higher than the rectifier needs kva rating to support other secondary loads.

SMP's use feedback current limiting and much lower load side capacitances due to the high operating frequencys. The input capacitors on line operated smp's are also lower value capacitors but are much higher voltage a rough equivalance is
v1 X c1 = v2 X c2 where
v1 = line voltage c1 = input storage cap v2 output voltage c2 capacitor that would be used if this was a transformer supply for the desired dc output. Terry

List of 56 messages in thread
TopicAuthorDate
Circuit Analysis      Suresh R      12/27/05 00:40      
   Analysis      Farshid Jafari Harandi      12/27/05 04:15      
   Dangerous!      Kai Klaas      12/27/05 07:09      
      bungling amateurs "bragging" on the web      Erik Malund      12/27/05 08:55      
         Not electronic, but an amusing example      Joseph Hebert      12/27/05 09:58      
            OLD idea ?      Steve M. Taylor      12/27/05 12:09      
               New and improved      Joseph Hebert      12/27/05 17:11      
                  Safety first      Steve M. Taylor      12/28/05 06:43      
         I think you meant...      Kalpak Dabir      12/27/05 10:01      
         deja vu all over again!      Andy Neil      12/27/05 18:23      
      resistor replaced by capacitor      Suresh R      12/28/05 01:11      
         Phase shift      Kai Klaas      12/28/05 06:30      
         dissapation      Terry Lingle      12/28/05 06:38      
            Dissipation      Steve M. Taylor      12/28/05 06:48      
               It's a real world after all      Terry Lingle      12/28/05 07:11      
                  What ? Make mistakes ?      Steve M. Taylor      12/28/05 07:33      
                     are you sure      Erik Malund      12/28/05 09:05      
                     or ..      Andy Curda      12/29/05 13:21      
            Non ideal cap performance      Kai Klaas      12/28/05 06:58      
   Diodes!      Andy Neil      12/27/05 07:14      
   Current Limiting Capacitor      Joseph Hebert      12/27/05 09:47      
      Capacitor Filters      Suresh R      01/12/06 01:15      
         Some basic theory needed      Kalpak Dabir      01/12/06 01:25      
         12 */~2 ~ 17 so I doubt you see 19V      Erik Malund      01/12/06 06:31      
         Output voltage      Kai Klaas      01/12/06 07:54      
            Regulation      Steve M. Taylor      01/12/06 11:20      
            current flow      Suresh R      01/13/06 00:43      
               What current?      Kai Klaas      01/13/06 06:10      
                  What iam trying to know is      Suresh R      01/15/06 21:29      
                     inrush current      Terry Lingle      01/15/06 23:20      
                     Naiive analysis      Steve M. Taylor      01/16/06 06:33      
                        Laplace Transformation      Kai Klaas      01/16/06 07:19      
                           Could be worse....      Steve M. Taylor      01/16/06 11:39      
                              Me too!      Kai Klaas      01/16/06 11:58      
                                 Minds are failing      Steve M. Taylor      01/16/06 12:28      
                     DC component      Kai Klaas      01/16/06 12:03      
                        Suresh, have as look      Erik Malund      01/16/06 12:18      
                           analog and digital ground      Suresh R      01/17/06 00:24      
                              discussed ad nauseam do a search      Erik Malund      01/17/06 06:56      
                              Use a splitted ground plane      Kai Klaas      01/17/06 07:32      
                                 did i got it right      Suresh R      01/18/06 00:49      
                                    Also datasheet of ADUC can help you      Kai Klaas      01/18/06 06:44      
                                       Placing Vias      Suresh R      01/24/06 00:18      
                                          Maybe..      Kai Klaas      01/24/06 06:08      
                                             Copper fills      Terry Lingle      01/24/06 08:25      
                                          I do not know about 2 layers      Erik Malund      01/24/06 09:09      
                                        Auto route      Suresh R      01/25/06 00:00      
                                          Solid ground plane has to be solid!      Kai Klaas      01/25/06 08:37      
                                             Thank you Kai      Suresh R      01/26/06 21:12      
                                                circuit for a despensing unit      Suresh R      01/28/06 02:58      
                                                   ICM7555 + 2M2 + 68      Kai Klaas      01/28/06 10:14      
                                                      why a totally unrelated post in the midd      Erik Malund      01/30/06 08:07      
                              Separate signal traces.      Joseph Hebert      01/17/06 10:01      
                                 What has God to do with this??      Kai Klaas      01/17/06 19:20      
               DC DC      Steve M. Taylor      01/13/06 06:19      
               DC DC      Steve M. Taylor      01/13/06 06:19      

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