PWM to mosfet - using isolator or ? - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th December 2004, 05:11 PM   #1
Gerlu is offline Gerlu  Mexico
diyAudio Member
 
Join Date: Dec 2004
Location: M.H.
Question PWM to mosfet - using isolator or ?

I try to build a converter, but I am not sure how the connection is made from the output of PWM to mosfet. Would it require an isolator ? Can someone show me in diagram ?

The mosfet I used should be p-channel. And I need some suggestions on what mosfet I need, is RFP30P06 ok ? The incoming supply is 28V with switching frequency 100kHz.

The diagram is as below, any problem with that ?

I am new to this design and here too. Hopefully I am posting in the right place. Appreciate and expecting any suggestions. Thanks.
Attached Images
File Type: jpg converter.jpg (26.9 KB, 452 views)
  Reply With Quote
Old 22nd December 2004, 05:16 PM   #2
Gerlu is offline Gerlu  Mexico
diyAudio Member
 
Join Date: Dec 2004
Location: M.H.
AnyOne ? Plz ..
  Reply With Quote
Old 22nd December 2004, 06:33 PM   #3
diyAudio Member
 
Join Date: Jan 2001
Location: Scandinavia
Nobody is answering because your question is not answerable.

There simply isn't enough information to provide a meaningful answer.

May I suggest you use a reference design from one of the manufacturers instead?

Please note that there is limited competency in SMPS on this board - true some individuals are highly skilled but the traffic on SMPS is very limited.

Petter
  Reply With Quote
Old 23rd December 2004, 07:17 AM   #4
Gerlu is offline Gerlu  Mexico
diyAudio Member
 
Join Date: Dec 2004
Location: M.H.
I see .. thx ! Will try your suggestion
  Reply With Quote
Old 23rd December 2004, 10:02 AM   #5
diyAudio Member
 
Circlotron's Avatar
 
Join Date: Jun 2002
Location: Melbourne, Australia
Have a look at an IR2121 or an IR2125. Not sure which one but they are similar.
Seeing your converter will have a negative output voltage, will the error amplifier input on the controller chip work ok with this?
__________________
Best-ever T/S parameter spreadsheet.
http://www.diyaudio.com/forums/multi...tml#post353269
  Reply With Quote
Old 23rd December 2004, 12:29 PM   #6
Gerlu is offline Gerlu  Mexico
diyAudio Member
 
Join Date: Dec 2004
Location: M.H.
Quote:
Originally posted by Circlotron
Have a look at an IR2121 or an IR2125. Not sure which one but they are similar.
Ok, will check it out.

Quote:
Originally posted by Circlotron
Seeing your converter will have a negative output voltage, will the error amplifier input on the controller chip work ok with this?
Yup, by first inverting it with another error amplifier (inverting amplifier -- positive input to ground)
  Reply With Quote
Old 14th January 2005, 02:52 PM   #7
raypsi is offline raypsi  United States
diyAudio Member
 
Join Date: Jan 2005
Location: middle earth
Default pwm

Your schematic shows 2 grounds, ya? So either a toroid transformer or opto isolator are required. Usually the feedback reference is isolated too.
__________________
semper fi
  Reply With Quote
Old 14th January 2005, 03:38 PM   #8
diyAudio Member
 
sivan_and's Avatar
 
Join Date: Dec 2004
Location: B'lore/ Calicut India
Send a message via Yahoo to sivan_and
Somewhat confusing circuit.
If u are looking for a step down conv,,,Try a single chip solution like MAX 724.
www.MAXIM-IC.Com
For MAX 724. i/p can go upto 40 Volts and O/p Variable can sink upto 5 Amps.

Or SG3524 (both o/p added for max duty cycle.and IR2110 or any high side driver.
__________________
SivanandBalan
  Reply With Quote
Old 14th January 2005, 06:56 PM   #9
raypsi is offline raypsi  United States
diyAudio Member
 
Join Date: Jan 2005
Location: middle earth
Your circuit looks ok to me. look up an 4n36 here:

http://www.fairchildsemi.com/ds/4N/4N36.pdf



Page 25 has a schematic how to connect an opto coupler:
http://focus.ti.com/lit/ds/slus565f/slus565f.pdf
__________________
semper fi
  Reply With Quote
Old 15th January 2005, 01:48 AM   #10
diyAudio Member
 
sivan_and's Avatar
 
Join Date: Dec 2004
Location: B'lore/ Calicut India
Send a message via Yahoo to sivan_and
Even the outputs can be connected directly to MOSFEt w/o isolator,if u r using SG3524 or TL494.Since the IC output transistors collectors and emitters are easily accessible,can be configured freely...
__________________
SivanandBalan
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Orion MBR70 battery isolator oPossum Car Audio 1 21st June 2009 10:22 AM
Velcro as Vibration Isolator Buckapound Parts 5 9th May 2009 06:58 PM
question about isolator behind transistors Ground Zero Parts 3 28th January 2009 08:56 AM
DIY cable tv ground loop isolator. please help imperfectcircle Parts 0 31st January 2007 09:13 PM
Looking for optical isolator for audio FastEddy Solid State 0 27th September 2006 05:40 PM


New To Site? Need Help?

All times are GMT. The time now is 09:50 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2