Problem in bringing up LLC440W

Posted by: mehdi22@gmail.com on 02/17/2015

Hi
I have builded a LLC buck regulator based on datasheet of LCS708 from pi.
and gave it 380 v directly but response that i get is 3v instead of 44v i attached my schematic and pcb
my ic draw 80 ma current.
please check sch and pcb
thanks for any guidance

Files

LLC440Wrev3.pdf (243.42 KB)

llc440wSh1.pdf (57.02 KB)

Comments

Pls. attach the design spreadsheet.
Also, pls. probe the HB pin and post the image.

Hi
we have 3v output with and without input voltage(380v)and my ic draws
80 ma then probably ic is blowed. i checked double circuit and soldering after i saw my drawing current and i have
not examine with new one.i made a serie 68kohm resistor with 22kohm res from vcc for ov/uv pin for lower voltage but my response didnt change.
i attached spreadsheet and images.
1 v grid for hb pin voltage
Thanks for reply.

Attachment	Size
HiperLCS Design1.pixls (43.37 KB)	43.37 KB
WP_20150219_003[1].jpg (2.15 MB)	2.15 MB
WP_20150219_002[1].jpg (2.22 MB)	2.22 MB

Hi
i changed ic and started to rise voltage with variac and no load.but in 30v (input) output starts to rise up slowly from 6v to 30 v that i turned it off but my hb voltage is rectangular yet.
Thanks

1) What is the switching frequency of the rectangular voltage ?
2) i can't download the pixls file. What is your target operating frequency?

Hi
Frequency is 170khz
Strange for me is secondary waveform that increases slowly and triple that I've compelled to turn it off.
Output cap is electrolytic that I will change it.
Thanks alot

Hi
this is my spreatsheet and several pics of waveforms
i increased voltage to 50v output rised and ic was turned off with no voltage in output.
my problem is why voltage in output become more than input when this voltage should be about Vin/2Vout=Neq
Thanks

Attachment	Size
HiperLCS Design1.pixls (43.37 KB)	43.37 KB
WP_20150219_006[1].jpg (2.33 MB)	2.33 MB
WP_20150219_005[1].jpg (56.48 KB)	56.48 KB

Hi
i reached to regulated voltage at 40 % of nominal input voltage.and output is very good.
with load of 10w after 30 min my ic shut down happened.and after turning off input i saw my core is very very hot.
pls see spreatsheet.
thanks for your time

i think i found problem of core overheating.maybe is because of my low secondary turns that is 2.5 and BAC is 525.but in new spreadsheet because of my new constant Lres that is 70uH and is about high.i cant satisfy other conditions.
thanks alot.

Hi
When i increase voltage more than 340v my device goes to off state and out put decreases to .4v[with 8w load].
my ov/uv pin is disabled.
Thanks

And this is my hb and primary current on scope

Attachment	Size
WP_20150226_001.jpg (2.1 MB)	2.1 MB

And this is my hb and primary current on scope

Attachment	Size
WP_20150226_001.jpg (2.1 MB)	2.1 MB

My boss has bring his shotgun near my head! Please help me? I'm joking... Please enlighten me,

Your spreadsheet shows the secondary should be 5T + 5T and primary is 25T. Why do you say you have 2.5 T?

Pls. scroll up and look at my reply from 3/2.

Hi
excuse me for 2.5T correct is just 5T as in spreadsheet.in components of spreadsheet when i increase voltage very soon my ic offs.but i increased cres my ic didnt off but my transe overheated when i checked again lpri i saw it has changed fro 129 to 200 uh.may this problem is caused to overheating.
i changed cres to double with a new transe of pq35/35 at 30v input my primary current has a peak of 1 A and sinusoid.
thanks for your time