TOP270EG OUTPUT

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HI,

ALLREADY BUIL A DRIVER WITH PI EXPERT, U1 IS TOP270EG, BUT I GOT THE FOLLOWING:

OUTPUT WITH LOAD I HAVE ONLY 20V THE LED LIGHT IS OK.

OUTPUT WITH NO LOAD  HAVE 40V ??

IS THERE A MALFUNCTION ON THE IC DRIVER?

I NEED A HELP WITH THIS.

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TOP270EG OUTPUT369.5 KB

hi,

TOP-JX should regulate VOUT at no-load. It is most likely coming from the feedback circuit. Please double-check the divider resistor values, the TL431 reference voltage and the opto. Application note AN47 provides additional resources in designing TOP-JX if you need it.

Hi

R10 = 15000 ohm :

It seems too high.

look more carefully about it.

Hi,

Ok, let´s check, this value was gived fo the PI Expert, I will adjust it, I ´ll tell you what happen, or can you advise for.

thks

Hi, everyone,

Well, allready make the change, R10= 12700 Ω now, the driver is working nice, what do we have?

output with load= 20V

at no load = 32V

now is better, I left it for 1 hour without load and no problem, but, I left for 1 hour working and the output goes down 1V right now output is 19V .

what I can do to get the 24V 4.2A?

Hi

No Load condition:

I think R10=12700 is still high. In my eyes  2200<R10<6800 ohm is fine.

Full load:

you said the output voltage under load is 20 V, but how about the current?

there are several things that can cause ouput voltage drop. it strongly dependence on transformer design + blocking diode voltage ( try 180 V or 200 V instead of 150V) + L2 series resistance (should be as low as possible) + PCB traces ...

No load condition:

R10=8.5 kΩ with this value the output = 24.2V .

Full load:

20V - 1.5A, with blocking diode of 200V, the L2 = .240Ω

what do I have to do to get this results?

I use a variable resistor to found the R10=8.5kΩ, after change the GAP on the transformes(216uH in primary now) and put a BD to 200V, with the first GAP the current was .920A - 20V.

But, the start up now is in two steps 1 turn on =18V, and step 2 after 3 seconds =20V

I think I have to work with the transformer.

thanks.

Hi

ok - L2 resistance and blocking diode voltage are ok now. but I think LP=216 uH is still high - because your design syas it should be arround 160 uH. look! it is important. the air gap is also important. they need more carefull design.

Hi,

Allahyar, thanks for the advise,

Well, now I worked in the transformer, I build other T being carefull, with the following results:

LP=172 uH now this is ok, new PCB, the oldone was checked and found some lines damage or thin, but, I am very happy!

I come in doing with care, I connect a 50W load first and then the 75W and follow with 100W, results:

100W light up very nice, the readings now is output 21.3V  - 3.05A with temperature estabilaized.

What I did :

1 new transformer with flux band added.

2 I change the L1 6mH E core by the Toroid 6mH ( a little bigger but ok)

3 To make it reach the readings, I take out the R3,R4 and C3 of the clamping( I think this is Ok, the clamping still there)

4 better heat sinks.

What do you think? now is ON for 6 hr, temperature ok, and the readings follow the same.   

And at no load great 24.1v without switching noise ( I check allready) finally R10=8.1 kΩ

Hi

It seems everything is going well. congratulation :)

Just remember we can't ignore little things in a big design.

best wishes.