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Hi all,
I've designed a 12V/0.5A flyback using PMP4367 PCB board and made the transformer by myself.
I found the frequency jitters is quite large even at full load. I tested the PMP4367 board either and found the jitters were large, too.
I would like to know why?
Thank you so much.
Hi Bernard,
The input voltage is 130V AC-265V AC, output voltage is 12V 0.5A. The two plots are in the same condition with twice triggering.
I've followed the PMP4367 with several parameters changed.
The transformer: Nps=10 Npa=6 Lp=3.1mH Rcs=1.7k
Output capacitance is 470uF+220uF
Fsw is blink around 40kHz -60kHz
I've tested the PMP4367 board, there are frequncy jitters too.
Thank you so much.
Best Regards
Hi all,
I re-design the transformer with fswmax=90kHz, and I tested again with parameters using calculations in the datasheet.
The fsw jitter is 61kHz to 75kHz. Is it normal?
I have tested three boards with my own parameters using PMP4367 board. I found the frequnecy jitter were very similar.
So I doubt whether it is normal for this device to have jitter abround 15kHz totally.
Is there anyone can answer my questions?
Thank you so much.
Hi Bernard,
Thanks for your reply.
I want to confirm that the deviation is +/-7.5% or +/-7.5kHz.
It is shown that it is +/-7.5kHz on the datasheet.
Best Regards
Jack Chen
Hi Bernard,
Sorry to bother you again.
I've met an issue that when the load is increasing from 0.6W to 3.2W, the frequency jitter becomes severe and the Vdd and Vout are shaking heavily, too.
But once the load is beyond 3.2W, up to full load 6W, the frequnency jitter, Vdd and Vout are normal during 3.2W to 6W.
And the abnormal waveforms are as below. Dark blue is Vdd (ac couple), light blue is Vdrain, Purple is Vout. (Test condition Vin=130Vac, load is between 0.6W to 3.2W). The transformer have shield layer and the magnetic is connected to aux GND.
Thank you so much.