Author Topic: Voltage regulator inrush current  (Read 864 times)

0 Members and 1 Guest are viewing this topic.

Offline LaserTazerPhaserTopic starter

  • Regular Contributor
  • *
  • Posts: 203
  • Country: us
Voltage regulator inrush current
« on: September 14, 2019, 08:48:27 pm »
Is there any method to implement soft start into this regulator?

With small filter cap & load current the overvotlage is large, however with larger caps and high load current there isn't any over voltage however over voltage can occur rapidly if load varies. The current surges during startup and will likely also surge during changes in load current.

* vreg.asc (2.89 kB - downloaded 61 times.)
« Last Edit: September 14, 2019, 09:32:07 pm by LaserTazerPhaser »
 

Online ledtester

  • Super Contributor
  • ***
  • Posts: 3283
  • Country: us
Re: Voltage regulator inrush current
« Reply #1 on: September 14, 2019, 09:04:01 pm »
Posting an image would help out everyone.

835440-0
« Last Edit: September 14, 2019, 09:14:46 pm by ledtester »
 
The following users thanked this post: LaserTazerPhaser

Offline MagicSmoker

  • Super Contributor
  • ***
  • Posts: 1408
  • Country: us
Re: Voltage regulator inrush current
« Reply #2 on: September 14, 2019, 09:42:11 pm »
Is there any method to implement soft start into this regulator?
...

Yeah, by not using a freaking 555 timer as your controller; you might as well use a potato.

 
The following users thanked this post: LaserTazerPhaser

Online ledtester

  • Super Contributor
  • ***
  • Posts: 3283
  • Country: us
Re: Voltage regulator inrush current
« Reply #3 on: September 15, 2019, 05:31:24 am »
It's only going to last for 40us... is that going to be a problem?

835656-0
 
The following users thanked this post: LaserTazerPhaser

Offline MagicSmoker

  • Super Contributor
  • ***
  • Posts: 1408
  • Country: us
Re: Voltage regulator inrush current
« Reply #4 on: September 15, 2019, 09:56:16 am »
It's only going to last for 40us... is that going to be a problem?

Inrush in the boost can be a problem if it causes the inductor to saturate and the switch starts switching at that time.

And note (to the OP) that inrush is unavoidable in the boost converter because of the direct connection between the input and output, but in low power converters like this it is frequently ignored or only addressed by slowly ramping up duty cycle (because a saturated boost inductor will allow peak current to go too high). In commercial boost PFC stages some of the inrush current is routed around the inductor via another diode in parallel to it, and at higher power levels a conventional precharge resistor with relay/switch bypass is typically used.

 
The following users thanked this post: ledtester, LaserTazerPhaser


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf