TIDM-02010: PFC Issue

Thanks for reaching out. I'll assign the thread to our experts in digital power to answer PFC related issue.

Best Regards,

Masoud

Hi Akbar,

To better understand the situation can you answer the following.

Do you mean to say three components, PFC IGBT, PFC Diode and 15A Fuse are blowing at maximum load?
Does it happen due to thermal failure or over voltage failure?
What is the load at which the fuse is blowing? Can you specify the power, voltage and current.
Do you have any protection strategy in your hardware?
What is the control strategy that you adopt? Did you follow any reference design to make your solutions/

Regards,
Harisyam

Hi Harisyam,

Yes, primarily PFC IGBT is blowing and causing high current to introduce in the circuit causing the blowing of the fuse.

Over voltage failure is not possible because we are continuously observing the voltage it is stable. About thermal failure, ca you explain me in depth.

During failure i have observed that

Vac:234

Iac: 6.8A

PF: 0.98

Vdc:368(After enabling PFC)

You can refer to the attached schematic to see the protection strategy in the design

We have referred to the TIDM 02010 Hardware and Software for the design. 

Help me to understand and solve the problem

Hi Akbar,

Since the PFC is operating at lower power and is failing at higher power, I wanted to know if it is thermal failure. If the temperature is rising above what the device can handle and failing. If so, you need to recheck the thermal design. Can you also share the waveform at lower power to see if there is any problem with the control. 

I could not figure out the protection strategy from the schematic. What is your protection scheme, is there any software protection?

The schematic also does not show the MCU connections.

Regards,
Harisyam

Hi Harisyam,

I have attached the PFC current sensing circuitry and the corresponding MCU section for your reference.

Yes, we are using the TIDM-02010 PFC software libraries, and all the relevant PFC current protection parameters are enabled in our implementation.

Could you please explain how to evaluate or verify the thermal design of this circuitry? Specifically, what components or measurements should we focus on to identify any thermal-related issues?

I look forward to your valuable response.

Thank you.

Hi Akbar,

Can you also share the PFC waveforms (grid voltage, current and DC bus voltage) to check see if the PFC operates as expected at lower power.

Can you also list down the protection features that you have configured for this design.

To verify the thermal design, firs the converter loss needs to be estimated to check if this can be dissipated from your system. You can also monitor the temperature of the device and heat sink while you run the converter to verify the thermal design. If this is not in safe limits, this has to be redesigned. 

Regards,
Harisyam

pfc Pwm.zip

Hi Harisyam,

I have attached a ZIP file containing a video in which I am probing the PFC switching waveform at the IGBT collector.

Regarding the protection features you mentioned, could you please clarify whether you are referring to the software protections or the hardware protections implemented in the design?

Also, could you please share any reference documents, application notes, or other resources that explain how to measure or calculate the PFC/IGBT losses? These references would help us validate our design and perform the loss analysis correctly.

Looking forward to your valuable response.

Thank you.

Hi Akbar,

Can you share the grid voltage, grid current and DC bus voltage waveform to verify the operation of PFC. 

Regarding the protection, I was referring to software protections like CMPSS being used to trip the PWM for over current. It can also include other software protection for over current and over voltage.

In order to estimate the losses and temperature rise, it is recommended to follow the application note from the IBGT manufacturer.

Regards,
Harisyam