IR2110 gate driver issues.

[Joerg]

Hello Graham,

Oohh ! BAVs ! Just 1N914 / 4148 / 4448s here.

I like the BAV and BAT series because you can get two diodes in one
SOT23, any configuration. Contract assemblers can't mess up the
placement and it's cheaper, especially since they are now produced by
more companies than just Philips and Siemens/Infineon. Even before that
you didn't have to ask much if it was on their jelly bean list. In most
parts of the world they were as ubiquitous as rice cakes and apples at
the grocery.

I do like the BAV21 for higher voltages though.

Guess you meant the BAS21. Yes, a nice low cost diode for higher
voltages and pretty zippy, too.

Regards, Joerg

http://www.analogconsultants.com

 

[Pooh Bear]

Terry Given wrote:

< big snip about stuff I need to look into >

I'm not sure if you have a half- or full-bridge converter.

Half bridge.

Al = 4.2uH typ, 3.15uH min, 5.25uH max

Lp = 806uH ~ 1344uH use 800uH

Yes, my calculations and measurements correlate.

V = 320V
Ton = 4.5us
Aemin = 209mm^2

Bpp = 320V*4.5us = 430mT (full bridge)
-----------
16*209mm^2

so about +/-215mT. Note that the first time you turn it on, Ton better
be less than 4.5us or B will try to ramp up to +430mT and the core will
saturate.

That's why I'm using the UC3525 anyway. Pulse width ramps form zero to full. I
have some other questions I have in mind about Bmax - but I'll leave them to
later.

Peak Current-Mode Control will do this automatically, *but*
dI/dt can be pretty high, so loop delays (comparator, gatedrive, FET
etc) can really hurt. I would be tempted to have a few more turns, and
keep Bpp below 330mT so that saturation cannot occur (other than by
heating to Tcurie >= 220C).

if its a half bridge, then Bpp = 215mT and the turn-on problem isnt there.

Quite. I was targeting Bmax =250mT

Imagpp = 320V*4.5us = 1.8A max, 1.1A min
----------
800uH

thats pretty high for a full bridge. for a half bridge, its 0.9A and
0.6A respectively.

Yeah - I'm seeing about 400mA pk. IIRC. Nice triangle waveform at my current
monitor point ( apart from some shit when the devices switch ).

215mT peak at 100kHz gives 500kW/m^3 for 3C90, about 12W of core loss.
Its gotta be a half-bridge...

You're right. It is indeed. Runs cool for core loss.

108mT peak at 100kHz gives 70kW/m^3 for 3C90, about 1.7W of core loss.

Its a half-bridge, in which case the numbers work out pretty good.

what are the secondaries - 5T+5T centre-tapped?

8+8 actually for the main output(s). I.e. +/- 80V DC.

have you interleaved the windings?

Uhuh. That is when I actually get past driving the primary.

It'll be...

1 layer primary.

1 layer S1 + S2.

1 layer primary

1 layer S3 + S4.

With some lower voltage low power aux secs wound in there somewhere too.

Using litz wire for the main windings ( approx 1.6mm^2 - I think that's about 18
AWG ) - probably around 150 strands - type 1 construction. Plan to use 'safety
litz' - the triple insulated stuff to avoid margins. Pack in Germany and New
England Wire make it. Also made in their Chinese factories where the product will
be built.


Regds, Graham