Resonant Converter Control - UC2875

S

Scott Hill

Guest
Hi!
I am building a resonant power converter for my degree project using a bunch
of IGBT's in an H-bridge and require them to be phase controlled.
This chip does the job, but i need a had wiring the thing together!
any help would be greatly appreciated

many thanks
scott :)

hawk-eye@ntlworld.com
 
Scott Hill wrote:
Hi!
I am building a resonant power converter for my degree project using a bunch
of IGBT's in an H-bridge and require them to be phase controlled.
This chip does the job, but i need a hand wiring the thing together!
any help would be greatly appreciated

many thanks
scott :)

hawk-eye@ntlworld.com
Click to expand...
Hmmmmmmmm.... I'll bite. You want us to refine your thesis project
for you?

Are you serious?

-M
 
"Scott Hill" <hawk-eye@ntlworld.com> wrote in message
news:fQkrd.1082$HZ.873@newsfe5-win.ntli.net...
Hi!
I am building a resonant power converter for my degree project using a
bunch > of IGBT's in an H-bridge and require them to be phase controlled.
This chip does the job, but i need a had wiring the thing together!
any help would be greatly appreciated

many thanks
scott :)

hawk-eye@ntlworld.com
Click to expand...
No you're not.

Give me the name and address of the miscreant that gave this as a final year
project and me and my mates from 'Leather Dyke Riding Bears R Us' will come
round and transform his ass.

DNA
 
Scott Hill wrote...
I am building a resonant power converter for my degree project
using a bunch of IGBT's in an H-bridge and require them to be
phase controlled. This chip does the job, but i need a had
wiring the thing together!
Click to expand...
I prefer the more modern ucc3895 chip.


--
Thanks,
- Win
 
Genome wrote...
Scott Hill ...
Hi!
I am building a resonant power converter for my degree project using a
bunch of IGBT's in an H-bridge and require them to be phase controlled.

No you're not.

Give me the name and address of the miscreant that gave this as a final
year project and me and my mates from 'Leather Dyke Riding Bears R Us'
will come round and transform his ass.
Click to expand...
Scott means phase-shift PWM, not to be confused with phase-control
ac-line power control, as in the old triac days. In case that's
what you were thinking of, dna.


--
Thanks,
- Win
 
Genome wrote:
"Genome" <dna@nothere.net> wrote in message
news:x_prd.736$pO.411@newsfe5-gui.ntli.net...

"Winfield Hill" <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote in
message news:col4a601bas@drn.newsguy.com...

Genome wrote...

Scott Hill ...

Hi!
I am building a resonant power converter for my degree project using

a

bunch of IGBT's in an H-bridge and require them to be phase

controlled.

No you're not.

Give me the name and address of the miscreant that gave this as a

final

year project and me and my mates from 'Leather Dyke Riding Bears R Us'
will come round and transform his ass.

Scott means phase-shift PWM, not to be confused with phase-control
ac-line power control, as in the old triac days. In case that's
what you were thinking of, dna.


--
Thanks,
- Win

Oh shit, I have to admit that black women have tempting buttocks. It's not

a

substitute for love and that sort of stuff but they are immensely warm and
cuddly.

I'm just guessing.

DNA





Whoops, Semi-Sober mode on. Yup, since UC2875 is in the subject line then
Scott does mean phase-shift PWM. I realised that.

I just thought that such a converter for a final year degree project would
be a major challenge and would question the sensibility of the person
setting the project. The mention of IGBT's makes me worry a bit more.

Now, you've built these things so if you asked one of your students to take
one on as a final year project it wouldn't be so worrysome. You know how to
do it and you know what's needed to get the job done.

Your student wouldn't be asking questions in a newsgroup.

However, Scott has asked the question in a newsgroup. OK, 'good' use of
available resources but, if he needs advice, his first port of call should
be the person who set the task.

Unless that person, for whatever reason, isn't up to the job.

DNA
Click to expand...
I did a 3-month stint at a major university in NZs largest city, it was
edifying. The EE dept had a set of design rules for PCB layout, that
stressed using single-sided artwork (so they could make it themselves)
and widely spaced components. My job was to troubleshoot a 3-phase
phase-shifted IGBT dc-dc converter, that had an MTBF of about 3 minutes.

The problems were caused mostly by poor construction (wrt layout) but
the PCBs were atrocious. I especially liked the 12V:24V single ended
100kHz dc-dc converters that used a 1kV FET. The original design came
from the company I used to work for (45V FET) and used Cds to resonantly
reset the xfmr. Turns out that 1kV FETs behave differently. And the
output electrolytics had about 30 ohms ESR. not good. So I re-did the
PCB layouts as DSPTH, spec'd appropriate components and removed huge
amounts of wiring inductance, and the design worked first time. still does.

I was aghast that NOBODY seemed to know ANYTHING about real component
behaviour.

Cheers
Terry
 
On Fri, 03 Dec 2004 13:44:48 +1300, Terry Given wrote:

Bob Stephens wrote:
On Fri, 03 Dec 2004 10:58:30 +1300, Terry Given wrote:


Genome wrote:

"Genome" <dna@nothere.net> wrote in message
news:x_prd.736$pO.411@newsfe5-gui.ntli.net...


"Winfield Hill" <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote in
message news:col4a601bas@drn.newsguy.com...


Genome wrote...


Scott Hill ...


Hi!
I am building a resonant power converter for my degree project using

a


bunch of IGBT's in an H-bridge and require them to be phase

controlled.


No you're not.

Give me the name and address of the miscreant that gave this as a

final


year project and me and my mates from 'Leather Dyke Riding Bears R Us'
will come round and transform his ass.

Scott means phase-shift PWM, not to be confused with phase-control
ac-line power control, as in the old triac days. In case that's
what you were thinking of, dna.


--
Thanks,
- Win

Oh shit, I have to admit that black women have tempting buttocks. It's not

a


substitute for love and that sort of stuff but they are immensely warm and
cuddly.

I'm just guessing.

DNA





Whoops, Semi-Sober mode on. Yup, since UC2875 is in the subject line then
Scott does mean phase-shift PWM. I realised that.

I just thought that such a converter for a final year degree project would
be a major challenge and would question the sensibility of the person
setting the project. The mention of IGBT's makes me worry a bit more.

Now, you've built these things so if you asked one of your students to take
one on as a final year project it wouldn't be so worrysome. You know how to
do it and you know what's needed to get the job done.

Your student wouldn't be asking questions in a newsgroup.

However, Scott has asked the question in a newsgroup. OK, 'good' use of
available resources but, if he needs advice, his first port of call should
be the person who set the task.

Unless that person, for whatever reason, isn't up to the job.

DNA

I did a 3-month stint at a major university in NZs largest city, it was
edifying. The EE dept had a set of design rules for PCB layout, that
stressed using single-sided artwork (so they could make it themselves)
and widely spaced components. My job was to troubleshoot a 3-phase
phase-shifted IGBT dc-dc converter, that had an MTBF of about 3 minutes.

The problems were caused mostly by poor construction (wrt layout) but
the PCBs were atrocious. I especially liked the 12V:24V single ended
100kHz dc-dc converters that used a 1kV FET. The original design came
from the company I used to work for (45V FET) and used Cds to resonantly
reset the xfmr. Turns out that 1kV FETs behave differently. And the
output electrolytics had about 30 ohms ESR. not good. So I re-did the
PCB layouts as DSPTH, spec'd appropriate components and removed huge
amounts of wiring inductance, and the design worked first time. still does.

I was aghast that NOBODY seemed to know ANYTHING about real component
behaviour.

Cheers
Terry


It probably looked great on the simulator ;)


Sorry - couldn't resist.


Bob

Hi Bob,

thats a very good point - it certainly did. It also looked good on the
schematic - I did not make any changes to that, other than part numbers
(OSCON caps are great BTW). All the real work went into the
layout/construction.

Cheers
Terry
Click to expand...
Hmmm... I hadn't heard of OSCON Caps so I looked here:
http://www.diyparadise.com/oscon.html

We have been using Taiyo-Yuden MLCC's for our low ESR requirements.


Bob
 
Scott Hill wrote:

Hi!
I am building a resonant power converter for my degree project using a bunch
of IGBT's in an H-bridge and require them to be phase controlled.
This chip does the job, but i need a had wiring the thing together!
any help would be greatly appreciated

many thanks
scott :)
Click to expand...
Reference me in you thesis then:

Firstly, ensure that the DC bus inductance is nice and low. IGBTs DO NOT
LIKE VOLTAGE OVERSHOOT and will die. To whit, L*dI/dt is the killer. If
your big DC bus cap is 6" away from the H-bridge and connected with a
pair of untwisted wires, expect many dramatic failures. Current flows in
loops, keep them small (inductance is proportional to loop area). You
cant do anything about the internal packaging inductance (other than buy
a package with lower L) and that sets a limit on Vdc wrt Iout.

Then watch what happens under fault conditions - IGBTs limit fault
current (like FETs) due to Vg, but often its 10x rated current. So dI
gets a whole lot bigger when the IGBT turns off under fault conditions
(say by a desat detector), and LdI/dt then blows the IGBT up. So L must
be minimised, and using a large Rgoff for faults is helpful - dt gets
larger.

The gate wiring itself needs very low inductance - Mr Miller tries to
turn IGBTs off when you turn them on, and on when you turn them off
(look at slope of Vce). If you are stupid enough to use a very large Rg,
you will discover this in the first dozen or so switching cycles.
Normally its Lg that causes problems here. Over-current fault turn-off
can actually yank gates high enough to break them.

Its not so much what you do, as how you do it :)

Cheers
Terry
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top