CRC Power Supply Resistor Rating

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I'm playing about with a CRC power supply in SPICE. Looking at the power dissipation across the resistor, it shows a massive 38W peak while the capacitor charges. With a load drawing ~150mA, the resistor should only dissipate 150mW continuous. What sort of peaks could be expected in real life and what rating should be used to deal with them?
It will be powered from a 15Vac 15VA transformer.
 

Attachments

  • Screen Shot 2013-02-14 at 23.02.52.jpg
    Screen Shot 2013-02-14 at 23.02.52.jpg
    70.7 KB · Views: 282
  • Screen Shot 2013-02-14 at 23.04.49.jpg
    Screen Shot 2013-02-14 at 23.04.49.jpg
    79.8 KB · Views: 274
Just another Moderator
Joined 2003
Paid Member
Couple of things The first is that your transformer will have some resistance in the secondaries which will reduce the maximum current it can actually provide, though I'm not sure how to model this in spice, some series resistance in your voltage source is probably the best way to do it, but I'm not sure what is a reasonable value to use.

Second after you have a trace displaying in spice hold down <ctrl> and click on the series name at the top of the graph and it will bring up a dialog with the average and rms current over the time range you are displaying.

Tony.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.