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UCC28019 based PFC blows up the mosfet

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Ashwin619:
Hi,
I am trying to design a PFC circuit (370V, 1kW) using the UCC28019. A prototype single-layer board has been made for this purpose and calculations were done as per design note SLUC069. Initially, a couple of 60W bulbs (parallel) were placed in series with the input of the board, and the Output was observed. The mains is a 240V source. The NTC thermistor was heating to quite an extent along with input bulbs glowing brightly (slow flickering).

I then tried to provide it with a variable input through an autotransformer without the series bulb and that ended up blowing the thermistor and the MOSFET (all leads were short). This process was repeated again but now monitoring the gate waveform and found out that the gate PWM becomes almost close to 100% once the input crosses the VIN enable threshold level which in our case was around 85V. Before reaching this level, the gate was low.

I also tried removing the MOSFET and replace the IC and then operate it with varying input and found out that the same thing happens as above with some of the pin voltages being

VCOMP = 7.55V, VSEN = 1.57V, VINS = 2.08V, ISEN = 0, VCC = 11.85V and ICOMP = 1V.

The Inductor waveform (wire through toroid core) shows that the PWM (65kHz) to be in kind of a burst mode followed by a slow switching waveform (~12Hz) which is visible through the flickering of the input bulb. There are also some spikes on the waveform when the PWM is active which makes me believe that perhaps the overcurrent (PCL) might be triggering. The images are of PWM and slow flickering respectively,
[attachimg=6]

The gate waveform is as follows,
[attachimg=7]

The PWM triggers after every 20m sec (T = 80m sec, 12.5Hz) as seen above.

Note: A 60W Incandescent bulb has been used as a load. The component values in light blue are the ones that are used in the circuit.

Here's the schematic of the PFC board
[attachimg=8]

inductor waveform with visible bursts of PWM
[attachimg=9]

Any kind of help or suggestion is highly welcomed and appreciated,

Regards,
Ashwin619.





Faringdon:
Your C7 looks a bit too big in value.
Also, whats your switchign frequency?
Dont make it too high.
You coudl be better off using eg a very soft diode, (powerintegrations make some)  or SiC

Your MOSFET is here (so we can see it when we come back to help you more later)
https://www.onsemi.com/pdf/datasheet/fcp190n65s3r0-d.pdf

The attached is your PFC in a "quick" sim, with the control "hacked" to constant DC at the level which gives 1kW of power.
Its at 100khz, but you can change this down as you please....it gives you an idea of what goes on without taking ages to simulate like most pfc stages.
this one is in LTspice

Ashwin619:
Hi Faringdon,
Thanks for your reply,

The UCC28019 CCM PFC ic works at a constant PWM frequency of 65kHz and it's visible in the in-between bursts of the inductor waveform. The period between two PWM bursts is around 80msec (~12.5 Hz).
As far as the C7 value is concerned it was obtained through the design note SLU069 from TI.
Do you think that the cap might be getting fully charged (kind of like filtering) the pulsating DC which thus might not be able to provide the required input voltage reference?

I have done the simulation of the above circuit in TINA TI software and it seems to work there.

Note:- Initially I had connected the Vbridge_gnd net as the GND reference for the IC and its passive components, however someone from the TI forum suggested providing the MOSFET source referenced gnd to the IC and other components. I have made the changes however it hasn't resolved the issue.

I'll surely try your LTspice simulation. I wish TI could have provided with an unencrypted spice model of UCC28019  :(

Please let me know if there's any other possible correction in the circuit.

Regards,
Ashwin619.

Faringdon:
What about PCB layout, did you follow the attached

Ashwin619:
Thanks for providing the PCB layout guidelines, Here's my design,
[attachimg=1]
[attachimg=2]
I am aware that I may have skipped quite some PCB layout guidelines (especially the length of the MOSFET gates track length), however, I don't think that it should be a reason for the circuit to not work at all. Let me know if you feel otherwise.

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