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I am making a PFC circuit for AC-DC converter. I am facing a weird issue. As per my design the output of the circuit should be 390VDC, but I am getting 311VDCrms with ringing (overshoot 360V, undershoot 270V).

Here is my circuit (the red marks are the only differences between TI's circuit and my circuit, like, in TI circuit inductor is 2mH and in mine it is 0.56mH). enter image description here

And this is the output waveform.

Output waveform when Vcc is present to IC

Here it is zoomed

Here it is zoomed

When I turned off Vcc to the controller IC, the output voltage of the circuit is also 311VDC !!!!!

Output waveform when Vcc is turned Off to IC

Here is the input of pin 4 in oscilloscope

enter image description here

Here is output of pin 5 in oscilloscope

enter image description here

Here is input of pin 3 in oscilloscope

enter image description here

I am fully confused on what is happening. Please help me !!!!

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    \$\begingroup\$ What do the waveforms look like at the FET Gate and Drain, and pin 5 of U1? What are the voltages on pins 3,4,6 and 7 of U1? \$\endgroup\$ – Bruce Abbott Aug 13 at 7:15
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    \$\begingroup\$ On top of what Bruce is asking for, I'd like to see the current through your boost inductor. (Does TI even make this anymore? I can't find a datasheet) What is your switching frequency and your output power? \$\endgroup\$ – Stiddily Aug 13 at 11:55
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    \$\begingroup\$ "pin 5... is mostly looking like a straight line is having a voltage dip and again turning on instantly" - A picture is worth 1000 words. Show us the waveforms on pins 3, 4, and 5. Why did you reduce the inductor value to 560uH, and why did you not change the sense resistor to suit? \$\endgroup\$ – Bruce Abbott Aug 14 at 19:25
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    \$\begingroup\$ Pin 5 is the output of your compensation network, it should not have any sudden changes like that. A picture would definitely help. 350W @ 390V is less than 1 amp. The 560uH inductor is probably way too small. If you're in CrCM, your ripple current is going to be .9A (full output current). Putting your numbers into the Lbstmin equation from your datasheet gives a minimum inductance of closer to 1.5mH. This doesn't account for DC bias, so the actual inductance would be even higher than that. \$\endgroup\$ – Stiddily Aug 15 at 17:14
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    \$\begingroup\$ Which other components did you have to change? The inductor value is based off of your maximum allowable ripple current, the voltage difference between input and output, and your switching frequency. That .56mH also becomes much lower once you apply DC bias. The DC bias loss is probably listed in the datasheet. \$\endgroup\$ – Stiddily Aug 16 at 11:57

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