170vdc quasi resonant supply

I have made a circuit using the design note- DN06014/D (https://www.onsemi.com/pub/Collateral/DN06014-D.PDF) but the circuit is not working no output at both 12v and 170v.i have traced the circuit three times and connection is all good i dont know where the problem is in the circuit.please help thanks

Hi,

most probably the design note is correct... thus I assume the error is on your circuit.
--> you need to give us all informations about your circuit.

Klaus

There are a lot of places where you could have made an error, well over a hundred in fact, you could have a part backward or one pin not quite soldered - it is up to you to look CLOSELY and find YOUR error(s) ....

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most likely your transformer phasing is wrong?

i have made the circuit from the bridge section thus skipped the EMI filtering part , so it is necessary to build that too?

i have checked my circuit many times it doesnot hold error in soldering or connection also i have made transformer from vendor so i dont know much about its phasing can you help?

After inspecting the circuit assembly you'll power it and check all DC voltage levels and AC waveforms against expected values. Nothing that we can do from a distance.

There's a certain chance that you made a design error that can be revealed by a schematic review.

It's unlikely that the removing the EMI filter would cause it to be completely nonfunctional.

You don't give nearly enough information to even suggest a solution.

i dont know much about its phasing can you help?

Click to expand...

Try swapping the pins that go to the fet drain and Vcc, this may help.

If you have a 2 channel scope and a sig gen, oscillator, or the 5V signal on the scope - you can use this to determine the phasing ( dot notation) on the Tx wdgs and make sure they are correct in the ckt ...

i checked the working of ic ncp1308 without transformer and connected a bulb at primary where transformer was connected just to check the working of ic the bulb turn on and off for nearly 1 sec repeatably.
after that i connected same transformer again and when i gave supply of 90 vac the resister R3( 0.22ohm) burnt meaning current flow might be more, leading to again connecting the bulb in series just to prevent damage of that resistor.
After that output of nearly 5volt at 170v output came neglible voltage at 12v output.

the fet could be dead already, and or the driver chip ...

few components were dead i checked and replaced tl431 and fet, driver chip is working properly

Take your transformer......draw a pin diagram of it.....number each pin, then measure inductance between the pins and draw in the relevant coils connected to the pins.
Then when you have done this, you arbitrarily put a dot (for phasing), on any pin that you like. I will then tell you how to find out where the other dots go on the other coils.

....but i give a clue....you connect two coils in series....the way of connection which gives the highest inductance is the way that means those coils are connected dot_to_no-dot.

You understand?.....its all about whether or not the fields from the coils in the core cancel or not.

Unless of course you have a datasheet which gives the dot locations for you?

That lightbulb test you do is bad, please do not do this.

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and no you dont need to connect the full input filter, but you do really need to have some decent amount of input capacitance very tight up to your power switch loop.
And of course, pcb layout issues.....you dont want switching power current running through lengths of control ground.
You can of course, sometimes get some mileage out of a bad layout by increasing the fet gate series resistor....but not so much that you overheat the fet due to switrching losses.
I must admit id prefer a rcd clamp than what you have for the primary, just an r and c .

i have magnetic design data sheet for transformer and it is built according to that specification only i have also tested transformer at 40khz with input as 100v ac i got 11volt ac at 12v output and i got 144v at 170v output , also i checked mathematically the ratios of primary winding divided by secondary winding and they are approx same value so i conclude transformer is working.
i also did dot_to_no-dot soldering at pin 16(no dot) to 2(dot) and got144v output