how to calculate the duty ratio of L4981??? - 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 May 2005, 06:58 AM   #1
diyAudio Member
 
Join Date: May 2005
Location: wuhan city
Default how to calculate the duty ratio of L4981???

anyone know how to calculate the duty ratio of L4981???
i just want to use this IC for a battery charger, but don't know how to use it,
  Reply With Quote
Old 19th May 2005, 07:09 AM   #2
diyAudio Member
 
Ouroboros's Avatar
 
Join Date: Dec 2003
Location: Nottingham UK
How exactly do you want to connect the L4981 in a battery charger?

The chip is a boost power-factor-correction circuit, and is normally used to convert 120/230V input mains to 400V dc, while keeping the input current from the mains at close to a power factor of one.

I use the L4981B as the PFC stage in a 300W off-line SMPSU that I have designed here at work. It seems a strange chip to use as part of a battery charger.
  Reply With Quote
Old 19th May 2005, 08:33 AM   #3
diyAudio Member
 
Join Date: May 2005
Location: wuhan city
Default L4981b for battery charger

i mean the circuit is one phase bridge with two switch, 220v AC input and 36VDC output ,i want to use L4981B to control the two switch in the bridge,

may be i should pose my circuit here
  Reply With Quote
Old 19th May 2005, 08:33 AM   #4
diyAudio Member
 
Join Date: May 2005
Location: wuhan city
Default any suggestions for my design

well, if i want to design the battery charger,with 220vac input and 36vdc 5a output ,could anyone give me any suggestion please?
  Reply With Quote
Old 19th May 2005, 08:33 AM   #5
steveu is offline steveu  United States
diyAudio Member
 
Join Date: May 2005
Location: Colorado Springs
The duty cycle output of a PFC chip varies; follows the 120Hz/100Hz full wave rectifier output, so that the input current flows for (most of) the whole AC power cycle, not just on peaks. For a 240VAC input, when the AC input voltage is at 45, the duty cycle will be about 30%, falling to near zero% at the 90 peak. With lower voltage input, the duty cycle is higher. The PFC circuit dumps a constant ~400VDC through a single diode to the main input storage capacitor. That is then the input for another switcher, the one that produces useable voltages like 12V, 5V etc.

If you haven't already, download the ST pdf data and study the specs and examples.
Steve
  Reply With Quote
Old 20th May 2005, 09:59 AM   #6
diyAudio Member
 
Join Date: May 2005
Location: wuhan city
ok, i get it now, many thanks to you
  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
SE transformer for PP duty? Ty_Bower Tubes / Valves 1 14th September 2008 06:51 PM
mid for 3 way duty pvl1 Multi-Way 6 22nd June 2008 12:12 AM
How to calculate S/N ratio synthius Chip Amps 3 28th April 2008 04:39 AM
heavy duty grille. matteroftaste Multi-Way 0 24th May 2007 01:32 PM
What of these for sub duty? leadbelly Subwoofers 25 22nd December 2004 07:31 PM


New To Site? Need Help?

All times are GMT. The time now is 09:03 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