Whats the difference between full bridge and half-bridge SMPS ? - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

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 5th March 2004, 06:53 AM   #1
skaara is offline skaara  Slovenia
diyAudio Member
 
Join Date: Jun 2002
Location: Europe, Slovenia
Default Whats the difference between full bridge and half-bridge SMPS ?

Whats the difference between full bridge and half-bridge SMPS ?


ty
  Reply With Quote
Old 5th March 2004, 08:31 AM   #2
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
http://www.irf.com/product-info/audi...sdtutorial.pdf

sreten.
  Reply With Quote
Old 5th March 2004, 11:05 AM   #3
skaara is offline skaara  Slovenia
diyAudio Member
 
Join Date: Jun 2002
Location: Europe, Slovenia
Very nice thanks i readt it all and learned smthin

But there isnt so detailed expl what the difference between half and full bridge is..
  Reply With Quote
Old 5th March 2004, 11:15 AM   #4
diyAudio Member
 
JensRasmussen's Avatar
 
Join Date: Jul 2002
Location: Denmark - Jutland
Send a message via ICQ to JensRasmussen Send a message via MSN to JensRasmussen
Default Bridge

Hi,

Here is what i could find:

\Jens
Attached Images
File Type: jpg bridge.jpg (7.3 KB, 605 views)
  Reply With Quote
Old 5th March 2004, 03:00 PM   #5
diyAudio Member
 
Join Date: Jan 2002
Location: Livermore, CA
Both driver the transformer flux in both directions, so the transformer utilization is higher.

The half bridge has only 1/2 the voltage swing of a full bridge, hence the transferred power relative to transistor VDS rating is not as good.

The half bridge is not suitable to current mode control, as it will walk the center point to one rail or the other.

Both the half bridge and full bridge, to take full advantage of the extended transformer range (using flux in both directions, must have some kind of flux balancing of the volt seconds in each direction. For the full bridge, this is provided automatically by current mode control. For the half bridge, the most common approach is capacitive coupling of the transformer, and derating the flux swing.

The full bridge can be adapted into a very efficient converter known as the Zero Voltage Switching Phase shift converter; each side of the bridge is driven by what is essentially a square wave, and the relative phase shift of the square waves is adjusted to control the transfered power. Typical controller is UCC3895., from TI.

The half bridge is typically in competition with the two transitor forward converter, which has similar transistor and driver count and voltage, but only drives the transformer flux in one direction, so it has a somewhat larger transformer, but can use current mode control with it's benefits. Two transistor forward converters have been used up to 1-2 KW, though usually in that range the Bridge supply in some variant is employed. Sometimes two two transistor forward converters are run together in an interleaved mode. Transformer is larger than for the bridge, but flux balancing isn't a concern, nor current mode slope compensation to prevent instability when net PWM duty cycle is over 50%.

Different tradeoffs for different applications.

~Jon
  Reply With Quote
Old 6th March 2004, 09:19 PM   #6
mwh-eng is offline mwh-eng  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Livingston, Montana
Quote:
Originally posted by JonMarsh
Both driver the transformer flux in both directions, so the transformer utilization is higher.

The half bridge has only 1/2 the voltage swing of a full bridge, hence the transferred power relative to transistor VDS rating is not as good.

The half bridge is not suitable to current mode control, as it will walk the center point to one rail or the other.

Both the half bridge and full bridge, to take full advantage of the extended transformer range (using flux in both directions, must have some kind of flux balancing of the volt seconds in each direction. For the full bridge, this is provided automatically by current mode control. For the half bridge, the most common approach is capacitive coupling of the transformer, and derating the flux swing.

The full bridge can be adapted into a very efficient converter known as the Zero Voltage Switching Phase shift converter; each side of the bridge is driven by what is essentially a square wave, and the relative phase shift of the square waves is adjusted to control the transfered power. Typical controller is UCC3895., from TI.

The half bridge is typically in competition with the two transitor forward converter, which has similar transistor and driver count and voltage, but only drives the transformer flux in one direction, so it has a somewhat larger transformer, but can use current mode control with it's benefits. Two transistor forward converters have been used up to 1-2 KW, though usually in that range the Bridge supply in some variant is employed. Sometimes two two transistor forward converters are run together in an interleaved mode. Transformer is larger than for the bridge, but flux balancing isn't a concern, nor current mode slope compensation to prevent instability when net PWM duty cycle is over 50%.

Different tradeoffs for different applications.

~Jon

My past SMPS work experience must be similar to yours. I've seen a method for using current mode with the half-bridge topology, to keep the balance. Seemed overly complicated for what you get. I like peak and average current mode, so I tend to stay with the forward, full-bridge, and push-pull. The Zero Voltage Switching Phase Shift Converter is a great way to go for medium-high and high power.

Slope compensation works, but puts the roll-off between 1 and 2 poles, partially negating the benefits of current mode. Even with this, I still prefer current mode in most cases.

I'm not a big fan of the 2 transistor forward converter. For low power, I like the one transistor forward converter without the reset winding. I prefer an RC snubber and zero voltage switching-off. This has pretty decent efficiency, but I agree with you about it not having great transformer utilization.

I agree - lots of trade-offs.
  Reply With Quote
Old 3rd February 2005, 07:23 PM   #7
edogd is offline edogd  United States
diyAudio Member
 
Join Date: Feb 2005
Location: CA
I have a question about power supply pumping in a full bridge.

I have only seen it mentioned in a presentation by IRC. at
http://www.irf.com/product-info/audi...sdtutorial.pdf on page 13.


My question is this:

On the first have cycle the current flow from the supply through the load (and its respective LC filters) and then to ground. On the next half cycle the current direction in the load can not change instantaneously because of the L's in the LC filters. So the current now flow from ground up through the load (and it respective LC filters) and up to the battery.

Isn't sending current back to the batter a BAD thing, especially if your battery is not rechargeable?

Can you also point me to references about power supply bus pumping.
  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
Full Bridge X Half Bridge: What's The Best? CHACALPOWERS Power Supplies 8 18th July 2008 04:45 PM
help me with a half bridge smps(sg3525) red_zone003 Power Supplies 10 22nd November 2007 11:27 PM
half-bridge VS. full-bridge gearheadgene Class D 3 25th May 2007 08:49 PM
The difference of Push-pull,Half-bridge,Full-bridge digi01 Chip Amps 0 8th September 2006 02:10 AM
Half or full H bridge? Reaper Class D 0 21st July 2004 03:48 AM


New To Site? Need Help?

All times are GMT. The time now is 05:18 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