There is a problem trying to use the INN3166C.

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Hello.

I made a 27V 1.3A power using PI EXPERT.

The drain waveform was taken during the test with increasing load.

The switching frequency gradually increases and does not go up at 34 kHz. Increasing the load in that state will automatically restart.

According to the power meter, the frequency no longer increases.
BPP pin.
10 W at 0.47 uF, 14 W at 4.7 uF

trans EE28 core.

What should I see?

Thank you.

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Dear Heyon.

Would you mind provide the following waiveforms?
1) Output voltage
2) FWD pin voltage
3) Bias voltage value

Moreover, to se if the probelm lies in the liner regulator action on VOUT Pin you could modify your lower feedback resistor in order to have 20V output or lower, then short the linear regulator Q1 and see if the problem persists.

Looking forward to hearing back form you
Best regards.
PI-Star Lord