The first channel is input ac voltage: Scale : 100V/divHi,
increase the value of C14.
Just as a guess, because I miss a circuit, and where you did the measurement. And what´s the input signal of channel 1 and channel 2.
And what is the scale of the two channels .... and so on.
Please understand that we first need useful informations ... then we can help you.
Klaus
Yes the Vcc is not stable. The simulation is working fine. I used LT1242 instead of UC3842 for simulation. Its attached for your reference.It sounds like you are saying that the Vin supply to the UC3842 is not stable?......where is it coming from?, a bias coil, a high voltage linear regulator, or somewhere else?
50k also sounds very high value for the timing resistor in uc3842.
Why not get an equivalent circuit going in LTspice then send it to us here....LT1243 and family are the saem pinout and function as uc 3842, so you can use that. Most probably, when you make out the simulation, you will realise what is the problem.
Hi KlausST, I have attached simulation file for your reference.Hi,
seems you don´t want to...
Klaus
This is a .rar file ... my old tablet can´t open it.Hi KlausST, I have attached simulation file for your reference.
Dear Klaus ,Hi,
This is a .rar file ... my old tablet can´t open it.
I asked for a schematic. It´shouldn´t be that difficult to post YOUR schematic as a picture.
I wrote "YOUR" in capitals, because I want to emphase that we need the information of the "not properly working" circuit.
As far as I understand the simulation is working properly ... while your REAL circuit does not.
Let´s say you have two (identical) cars. Let´s call them "S" and "R".
Car "R" does not work properly. Car "S" does work as expected.
Which car do you to give to the garage for inspection?
Klaus
The output and aux winding have same turns. The output is designed for 12V. Will increasing the resistor R2 (in path of diode in aux charging path) to say more than 25 ohm help. I have tried both 22 ohm and 4.7 ohm, but it has no effect.Looks to me like you are set up for, and maybe not escaping,
"hiccup mode". I see what looks like a boot winding diode-
OR'd to Vcc, and a skinnky 50K pullup. So every time you
cross UVLO rising, you get one "yip" out the back which (you
hope) will pump the bypass cap hard enough to not hit UVLO
again on the bleed-out.
But I don't know if you can k-couple three inductors at once
(see only one k factor, think got three windingss there ought
to be at least three coupling factors?). The boot winding has the
same L as the output winding and if that's for 5V, will not produce
enough to rectify and get >8V to keep out of UVLO.
Look to that (bootstrep charging) branch and see if it's pulling
its weight.
The issue was due to the gate resistor being damaged. it was measuring 56k instead of 10 ohm. However, now the regulation aspect needs to be check as output is around 20V.Hello - pretty simple - the C on the Vcc charges up - then the flyback starts - but there is insufficient time for the 1000uF output cap to charge ( hence not enough volts out of L3 ) before the cap on the control IC discharges to the point the IC latches out, then the cycle repeats - this is a classic newbie thing.
..Yes indeed, good point....i changed the 1mF to 47uF straight away to make it quicker to simulate...so didnt run into that problem...I suppose in this way i unintentionally cheated. Does OP wish to re-post latest issue in ltspice and we can assist?Hello - pretty simple - the C on the Vcc charges up - then the flyback starts - but there is insufficient time for the 1000uF output cap to charge ( hence not enough volts out of L3 ) before the cap on the control IC discharges to the point the IC latches out, then the cycle repeats - this is a classic newbie thing.
aah - damaged from the last blow up - it does seem more likely the new mosfet would have gone POOF ! too, with 56k drive and 15k pull down.The issue was due to the gate resistor being damaged. it was measuring 56k instead of 10 ohm. However, now the regulation aspect needs to be check as output is around 20V.
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