Hi,

I have been working on a PFC circuit and ran into a problem with my MOSFET. It is making a vibrating sound and gets hot. I get a decent output in my load though. I have no idea what is going on with the MOSFET and how to fix it.



Specification:

I design the circuit by following the guideline here :
http://www.onsemi.com/pub_link/Collateral/AND8184-D.PDF

And this is the schematic of the circuit

 

Hi,
can you give your mosfet type details you used.

 

I used MTP3055

 

try R3 10k to slowly increase the value and see result.

 

Can you explain the reason?

Thank you for you suggestion.

 

What is the peak saturated current rating of the inductor?
According to my functional simulation, the peak inductor current will be close to 3 amperes.
If the inductor saturates at or below that current (at which point its inductance will go essentially to zero) then there will be high peak inductor and MOSFET currents, limited only by the circuit and MOSFET resistance, which can cause the noise (at twice the line frequency or 120Hz) and overheating you are experiencing.

 

increasing the r3 values regulate the gate voltage by increasing the impedance that will cause the rapidly turning on of gate that cause the heating of the mosfet.

 

the rapidly turning on of gate that cause the heating of the mosfet.

That does not cause heating of the MOSFET.
A slow turn on or turn off however, can cause heating.

 

What is the peak saturated current rating of the inductor?
According to my functional simulation, the peak inductor current will be close to 3 amperes.
If the inductor saturates at or below that current (at which point its inductance will go essentially to zero) then there will be high peak inductor and MOSFET currents, limited only by the circuit and MOSFET resistance, which can cause the noise (at twice the line frequency or 120Hz) and overheating you are experiencing.

Thank you for your response
I have no idea what saturated current rating response is. If this is the case , how can I tackle it?

The only calculation I did for the coil was the pk-pk ripple of the coil current , which is around 0.45current.

 

I have no idea what saturated current rating response is.

The only calculation I did for the coil was the pk-pk ripple of the coil current , which is around 0.45current.

The inductor has no marking?
Where did you get it from?

You can determine the saturation current of an inductor if you have a 5A DC power supply, a fast transistor switch, and an oscilloscope. Do you have those?

It's the total current, not the ripple current that's critical.

 

The inductor has no marking?
Where did you get it from?

You can determine the saturation current of an inductor if you have a 5A DC power supply, a fast transistor switch, and an oscilloscope. Do you have those?

It's the total current, not the ripple current that's critical.

The inductor is made by a ferrite core with wire wrapping around it. My instructor requires me to made the inductor by myself.

 

The inductor is made by a ferrite core with wire wrapping around it. My instructor requires me to made the inductor by myself.

Then you need to either measure it's saturation current, or calculate it from the core magnetic characteristics and the number of turns on the core.
That's an unavoidable process you need to do when designing an inductor that carries DC current.
You can't use a random core, add some wire turns, and expect it to work.
Bad things can happen if an inductor saturates in a switching regulator.

 

Hi,

I have been working on a PFC circuit and ran into a problem with my MOSFET. It is making a vibrating sound and gets hot. I get a decent output in my load though. I have no idea what is going on with the MOSFET and how to fix it.



Specification:
View attachment 116743
I design the circuit by following the guideline here :
http://www.onsemi.com/pub_link/Collateral/AND8184-D.PDF

And this is the schematic of the circuit
View attachment 116742

Is that 1milli-Farad after the PFC? - that might be a bit big!

Any regular switcher after the PFC will try to make the best of whatever the PFC puts out - maybe a resistive dummy load on the PFC will allow you to see what's really going on.

 

The inductor is made by a ferrite core with wire wrapping around it. My instructor requires me to made the inductor by myself.

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