Emitter switching: Damn! Who said that bipolars were slow and hard to drive? - 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 2nd April 2006, 11:50 AM   #1
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Talking Emitter switching: Damn! Who said that bipolars were slow and hard to drive?

Check this out. I'm very sorry to not have tried that before!!

This is the collector voltage waveform at turn-off for a $1 MJE13009 bipolar transistor after having charged the load inductor to 12A during the on-time. Voltage scale is 50V/div (from 100:1 HV probe). Vce for Ic=12A is just 0.8V for a 5:1 forced gain.

Now try to get that 50ns rise time with the bulky bank of 500V MOSFETs required to get 0.8/12=0.066 ohms rds-on without special gate buffers!!

Click the image to open in full size.


And this is the test circuit that made the miracle possible (in breadboard!):
Click the image to open in full size.


BTW: Turn on is also damn fast and free of storage/saturation losses because the energy stored in the 1uF capacitor during turn-off is used back to boost the base drive during the first microsecond of the conduction period. Actually, what the circuit does is to transfer back and forth all the base charge between the transistor and the capaciror
  Reply With Quote
Old 2nd April 2006, 02:43 PM   #2
subwo1 is offline subwo1  United States
diyAudio Member
 
subwo1's Avatar
 
Join Date: Jan 2002
Location: North American Continent
Excellent!
__________________
USMPS
http://groups.yahoo.com/group/switchmode/
  Reply With Quote
Old 2nd April 2006, 06:18 PM   #3
Onra is offline Onra  Germany
diyAudio Member
 
Join Date: Jul 2005
Location: near Frankfurt/M
Hi Eva,
This principle was afaik described in the 80s / early 90s in the German "elektronik" magazine. I must have a copy anywhere.
Nowadays you may use one device as seen at:
http://www.st.com/stonline/prodpres/...ebipo/esbt.htm
There may be other manufacturers too.

Regards
Onra
  Reply With Quote
Old 2nd April 2006, 06:39 PM   #4
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
I know ST "ESBT" modules, but they are both expensive and very hard to find while their specs are not quite suitable for what I want. Also they are more aimed at operating from 380V, 415V and 450V AC rectified industrial mains voltages (650V DC) instead of 230V conventional mains (350V DC). On the other hand, the two devices that I employed are industry standard, very easy to find and very cheap, yet they yield excellent performance.

These are the datasheets for the four ESBT models that ST appears to manufacture:

HYBRID EMITTER SWITCHED BIPOLAR TRANSISTOR - ESBT" 1500 V - 3 A - 0.55 Ohm


HYBRID EMITTER SWITCHED BIPOLAR TRANSISTOR - ESBT" 1700 V - 3 A - 0.55 Ohm


HYBRID EMITTER SWITCHED BIPOLAR TRANSISTOR ESBT 1500 V 8 A 0.075 Ohm


HYBRID EMITTER SWITCHED BIPOLAR TRANSISTOR ESBT" 1000 V - 50 A - 0.026 Ohm POWER MODULE


Note how all except the bulky latter one are not suitable for a 230V AC SMPS due to the low current rating. In contrast, my device combination is rated at 700V 12A 0.012ohms, is truly useable at Ic=12A without reliability issues and costs $2. I'm not aware of any other manufacturer producing ESBT, as everybody seems to be very focused either in IGBT or MOSFET stuff now.

And yes, I'm also aware that emitter switching was introduced in 1980s, and indeed I think that it has not received all the attention that it deserved.
  Reply With Quote
Old 2nd April 2006, 06:53 PM   #5
Onra is offline Onra  Germany
diyAudio Member
 
Join Date: Jul 2005
Location: near Frankfurt/M
Hi,
Pardon, but your headline sounded like "Heureka"
My intention was to point out, that this circuit is well known.
It is basically a cascode of a FET and a grounded Base bipolar Transistor.
Major advantages are faster switching than a grounded Emitter and higher Breakdown Voltage.
Worse is the need of a separate power supply for Base current.
Onra
  Reply With Quote
Old 2nd April 2006, 07:13 PM   #6
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi Onra,
can you explain this
Quote:
Worse is the need of a separate power supply for Base current
?

The posted schematic shows just one 20V supply.
__________________
regards Andrew T.
  Reply With Quote
Old 2nd April 2006, 07:40 PM   #7
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
AndrewT:

The need for an additional power supply depends on how your drive the base. In ST application notes you may probably see constant base current drive through an additional supply. In contrast, in my circuit the base current is obtained through a current transformer, thus no additional supplies are required, except for the 15K biasing resistor that is required to put some charge into the 1uF capacitor to allow the circuit to turn-on the first time.


Onra:

I said "I'm very sorry to not have tried that before!!". Indeed, I could have tried that a lot of years ago, but I was stupidly regarding it as impractical Also, don't get me wrong, my headline should sound like "how really old stuff can outperform brand new stuff".
  Reply With Quote
Old 2nd April 2006, 08:00 PM   #8
Onra is offline Onra  Germany
diyAudio Member
 
Join Date: Jul 2005
Location: near Frankfurt/M
Hi,
Eva wrote, she built her circuit on a breadboard.
Therefore i think she did a simple and quick work to demonstrate the function.
The separate power supply may be part of the main PSU, but a saturated BJT needs an IC/IB ratio of 10, some of down to 5 (like Eva did). Working with Collector currents of 20A and more requires a base current of at least 2 to 4A during switch on. Switch off is done by a required negative Base current of about 6 Amperes and more, depending on switching speed.
I looked up the App-Notes at ST and found the AN9464, which contains some scope screen shots (currents and voltages)
http://www.st.com/stonline/products/...re/an/9464.pdf
Hope, this will help.

@Eva: Did you perform a research "Back to the roots"?
In my opinion the amount of necessary devices may have prevented this circuit from common use.

Regards
Onra
  Reply With Quote
Old 2nd April 2006, 08:04 PM   #9
diyAudio Member
 
Join Date: Dec 2002
Location: Slovenia
Hi,

IR app note AN-946B (1982)

I am slowly feeling I am getting old.

Best regards,

Jaka Racman
  Reply With Quote
Old 2nd April 2006, 08:30 PM   #10
diyAudio Member
 
Join Date: Dec 2004
Location: Berlin
Jaka:
"IR app note AN-946B (1982)

I am slowly feeling I am getting old."

Thank You, now I can stop searching exact this,
and yes I am 55!

Regards
Heinz
  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
Do we always need an emitter follower to drive a LATFET output stage??? Leolabs Solid State 37 9th January 2011 04:16 PM
SSD vs Hard Drive smithy666 Digital Source 36 22nd August 2008 05:28 PM
Hard Drive problem lawbadman Everything Else 20 24th July 2007 01:42 AM
mp3 or wma hard drive mp3 player martin88 Digital Source 2 6th August 2004 09:50 AM
Hard drive vs. CD playback Bill F. Digital Source 5 14th February 2003 12:42 PM


New To Site? Need Help?

All times are GMT. The time now is 03:36 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