Ferrite Inductor help

[abicash]

Hello

I am trying to build an Inductor based on an App note from ST for L6562A .

The inductor specified is
Primary: 105 turns (20x0.1mm)
– Secondary: 11 turns (0.1mm)

What does this mean?

Please provide an insight

 

[dougy83]

The primary is 105 turns and secondary is 11 turns. When you wind the primary, use 20 strands of 0.1mm enamelled copper wire, wound dodecfilar (multifilar - see litz wire if it helps; the idea is the same https://en.wikipedia.org/wiki/Litz_wire). When you wind the secondary, use a single strand of 0.1mm enamelled copper wire.

 

[abicash]

Hello Doug

Thanks.
Was doing the same thing but found that the primary doesn't fit into the bobbin.
So thought, maybe, it says something else.

 

[dougy83]

If you're using the specified core and bobbin, I assume it should be possible. What's the App Note?

 

[abicash]

Here's the link

EVAL6562-80W

 

[dougy83]

The E25x13x7 E-core has an area of 43.5mm^2 for all 105 turns to pass through -- this is with a single E core (E-I final), if you use two E cores, as seen in the app note, you'll get twice the area. The single E core allows 217 turns if each strand was laid out in a 0.1x0.1mm box (so more turns are possible), and twice that for the appropriate two E cores. So there's enough space in the core; I guess your bobbin is too fat or ill-fitted, or your winding technique could be made tighter.

 

[abicash]

Okay
will follow your instructions.
Thanks

 

[dr pepper]

Non perfect wire lay will also reduce coupling bewteen the 2 inductances.
Is this an smps?

 

[abicash]

Hello

(A problem relating to the Inductor designed above)

Built EVAL6562-80W
But instead of the L6562 , used direct replacement UCC38050
I put a 60W Lamp load to the output (400VDC).
At close to I/P =85Vac , O/P is boosted to 250Vdc , and close to I/P=110Vac , O/P reaches 400Vdc as designed.

I get a clean sine-wave input current waveform from mains.
The problem starts at I/P 150VAC . The current waveform becomes jittery and the Inductor starts making noise.
O/P voltage remains close to 400VDC (390VDC).
I tried fine tuning the capacitor across pins 1-2 of the controller (UCC38050) which improves the response to an extent but nothing more than that.

I have captured a VIDEO which shows the current waveform on channel-1 of an oscilliscope , and Waveform observed at the Drain of the MOSFET, observed on Channel-2.

Please provide an insight...
If the post is misplaced, please guide me to the correct location.

 

[dr pepper]

It doesnt look like your 'scope is triggering well, maybe its a random switching waveform.
I dont really get how your circuit is operating, do you have a schematic?

 

[rumpfy]

Abi,
i've been sort of half watching your progress.
The thing you are building is a Power FActor correction controller.
At 230 Volt mains supply, these things generally produce around 400 Volt DC.
I guess at a 110 Volt supply, these things will produce about 210 Volt DC.
its not clear to me what mains voltage you are designing for.
I note you say you get a good sine wave input current at 85 volt.
What is the intended input voltage range.

 

[abicash]

Hello

Thanks for the interest guys.Much appreciated.

It doesnt look like your 'scope is triggering well, maybe its a random switching waveform.
I dont really get how your circuit is operating, do you have a schematic?

Heres which its based on EVAL6562-80W , it carries the schematic.
Regarding the triggering, i have captured this with a phone camera and the scope is a CRO, maybe due to that you see flickering.

What is the intended input voltage range.

If you check the App note, you will see that it is intended for a wide supply voltage (85V - 265V)
I start getting a good sine current at input voltages below 150Vac, but after that there is random switching on the current waveform which i am unable to rectify, by playing around with minor changes in the part values.

 

[rumpfy]

I've sort of read the datasheet at some time previously, but can I suggest that maybe you need to load the output with a load of some kind to keep the input switch working. I think these things operate intermittently at light loads and this may be what you are seeing.

 

[abicash]

Hi rumpfy

It is loaded with a 60w load

 

[rumpfy]

OK.
I have some stuff on the 6561 and this is a 80 W PFC converter.
I cant help much more except to say that some of these switched mode devices do operate in an intermittent fashion and this is by design. I think your problem was an 'erratic operation' as shown by the cro trace. I can say from experience that when these things operate in their 'intermittent mode' it is almost impossible to get sensible cro traces. If your converter is giving the correct 400 volt output, then I can only say that the thing is working properly and that more load should sort it out. Go up to the full 80 watt (and beyond) and see what happens.