Author Topic: Understanding primary side regulation in this Flyback converter  (Read 613 times)

0 Members and 1 Guest are viewing this topic.

Offline Red_MicroTopic starter

  • Regular Contributor
  • *
  • Posts: 122
  • Country: ca
I'm going through this Reference Design and there is something I don't get. The controller LM5020MM-2 was not designed for primary side regulation, how does this power supply regulate through the primary side? How precise it is? Does it require certain minimum load to regulate?
 

Offline ahbushnell

  • Frequent Contributor
  • **
  • Posts: 751
  • Country: us
Re: Understanding primary side regulation in this Flyback converter
« Reply #1 on: August 10, 2020, 03:21:12 am »
I'm going through this Reference Design and there is something I don't get. The controller LM5020MM-2 was not designed for primary side regulation, how does this power supply regulate through the primary side? How precise it is? Does it require certain minimum load to regulate?
It is regulating on the  5/6 secondary of the transformer.   This feeds the voltage divider made of R17 and R30. I'm sure it's not tight regulation.   It's simple and provides isolation. 
 

Offline eblc1388

  • Frequent Contributor
  • **
  • Posts: 400
  • Country: gb
Re: Understanding primary side regulation in this Flyback converter
« Reply #2 on: August 10, 2020, 05:54:30 am »
I also has trouble understand how two MOSFET Q1 & Q2 rated at only 800V can share the high voltage when the supply voltage is 1260V.

Would OP or others shed some lights on the mechanism of this voltage sharing?
 

Online magic

  • Super Contributor
  • ***
  • Posts: 7454
  • Country: pl
Re: Understanding primary side regulation in this Flyback converter
« Reply #3 on: August 10, 2020, 06:24:55 am »
Q2 on: Q1 source is at 0V and gate is at 15V, Q1 is on
Q2 off: Q1 gate is pulled to 600V and source rises up until it reaches 600V, Q1 turns off

I couldn't promise that everything here works out alright, but it's a TI reference design so they hopefully tested it.
« Last Edit: August 10, 2020, 06:27:40 am by magic »
 
The following users thanked this post: eblc1388


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf