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MOSFET (Si/SiC) Forum Discussions

ashwani
Level 2
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Level 2

Hello 

Recently we have purchased the infineon Technologies 3300W 54V bi-directional phase-shift full-bridge (PSFB) evaluation board EVAL_3K3W_BIDI_PSFB.

EVAL_3K3W_BIDI_PSFB - Infineon Technologies

Initially it was working fine but yesterday when I connected the input supply to the converter the primary side mosfet of the converter blows off and it stopped working, I am not getting the reason of this failure and how to fix it. Nothing has been changed in the evaluation board, no primary side wrong connection, no over voltage is applied then why this fault occur.

The evaluation board is very costly, I can not purchase the new one. 

Does the fault occur because of the quality of the mosfet ?

I am attaching the picture of the board for reference.

So please connect me to the designer of the board and help me to solve this problem and if something needs to be changed in the board then please give me support to do it.

Waiting for your response

Thanks and regards 

Ashwani Gautam

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1 Solution
Meghana
Moderator
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Moderator

Hello Ashwani,

Like mentioned in my previous reply, this inductor placed on the DC+ line, will cause higher Vds spike. Our suspection is that the primary MOSFETs must have experienced multiple avalanches which has eventually led to damage of the MOSFETs. To confirm this we need the measurements of Vds while the board was working. Can you please let us know if you have these Vds measurements, taken while board was ok.

Regards

Meghana R

 

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Meghana
Moderator
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Moderator

Hello Ashwani,

Can you please share the complete test set up details  and the test conditions under which you observed this failure. Also please let us know which MOSFET among the four primary MOSFETs was damaged.

Regards

Meghana R

 

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Meghana
Moderator
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Moderator

Hello Ashwani,

Also please measure impedance between drain to source and gate to source of the damaged MOSFETs and share us your observation.

 

Regards

Meghana R

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ashwani
Level 2
25 sign-ins 5 questions asked 10 replies posted
Level 2

Hello Meghana 

In the test setup I was using Mean well SMPS CSP-3000-400 as the input supply for the evaluation board since the SMPS is giving output as 400 volt DC which is the input to the evaluation board and the output voltage of the EVAL_3K3W_BIDI_PSFB  was set at 48 volt DC and the load was the resistive load i.e. the load bank.

But the mosfet blows off when the output load was not switched on.

I have highlighted the mosfet which got damaged.

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Meghana
Moderator
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Moderator

Hello Ashwani,

The MOSFETs in the positive path has been damaged. There could be several reasons for this to happen. 

1. Input reverse polarity : Based on your information, we can rule out this cause.

2. Input overvoltage: Please confirm if the voltage was well within limits

3. Output Short circuit : This will result in saturation of the transformer primary resulting in very high current flow through the primary MOSFETs causing its damage

4. Vgs under voltage : This would cause MOSFETs to work in linear mode which might result in overheating and eventually leading to a damage

5. Incorrect feedback: If the Current feedback path has some fault and the information given to the control loop is incorrect, if might have resulted in improper current reference value which in turn may allow high primary current resulting in damage of the switches. 

So can you please run below tests on your board and share us the feedback, so that we can evaluate more. 

1. Check the Drain to source and gate to source impedance of the damaged MOSFETs

2. Check the state of the gate drivers of the damaged MOSFETs. Check if the output stage is damaged or healthy. 

3. If the gate drivers are ok, then depopulate the primary MOSFETs of the main converter. Turn on the input supply and measure the gate supply voltage . 12Vpri

3. Measure the impedance at the output terminals of the main converter keeping the load bank connected but in turned off condition.

4. Validate the current feedback path of the main converter. Check whether the circuit connectivity and the components in the feedback circuit are in good health. 

5. How is the input connection between the power supply and the evaluation board. Please let us know the approx length and gauge of the wires used for the input connection between the supply and the evaluation board.

Please share us your observation. We will try to evaluate and suggest you the changes. 

 

Regards

Meghana R

 

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ashwani
Level 2
25 sign-ins 5 questions asked 10 replies posted
Level 2

Hello Meghana

The Input voltage was within the safe operating limit.

There was no output short circuit connection.

The gate to source voltage is supplied through a inbuilt flyback converter so the Vgs is at sufficient limit. 

The input of the Evaluation board was connected to the SMPS with a wire and one MCB was connected between SMPS and Evaluation board also one inductor was connected to limit the inrush current in the input side of the Evaluation board.

Nothing has been changed in the Evaluation board then how could this happen.

I am not getting any answer of this.

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Meghana
Moderator
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Hello Ashwani,

Can you please let us know the value of inductance that was use on the input line? 

Regards

Meghana 

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ashwani
Level 2
25 sign-ins 5 questions asked 10 replies posted
Level 2

Hello Meghana 

The value of inductance was 4.7 milli henry.

Regards 

Ashwani

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ashwani
Level 2
25 sign-ins 5 questions asked 10 replies posted
Level 2

Hello Meghana 

Any suggestions ?

would someone reply on the problem if possible ?

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Meghana
Moderator
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Moderator

Hello Ashwani,

The inductor placed on the DC input line will result in VDS spikes. Adding to this inductance, the length of the wire you might have used to connect from power supply to the eval board, will also have some parasitic inductance which will contribute to this spike. I'm suspecting, that the MOSFETs would have undergone multiple avalanches when the board was working and eventually led to the damage. Do you have measurements of Vds of the MOSFET taken while the board was working? 

Transformer primary inductance itself would cause slow rise of current. Can you please tell me based on what recommendations, this additional inductance was placed? 

Regards

Meghana

ashwani
Level 2
25 sign-ins 5 questions asked 10 replies posted
Level 2

Hello Meghana

There was a MCB connected between Power supply and evaluation board and it was working as hot plugging between capacitors so to reduce the inrush current in the beginning the inductor was placed so it will prevent the change of current in the beginning.

So according to you what could be the possible reason to damage the primary side mosfet.

Regards 

Ashwani

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ashwani
Level 2
25 sign-ins 5 questions asked 10 replies posted
Level 2

Hello Meghana 

Any suggestions ?

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Meghana
Moderator
Moderator 50 solutions authored 5 likes given 100 replies posted
Moderator

Hello Ashwani,

Like mentioned in my previous reply, this inductor placed on the DC+ line, will cause higher Vds spike. Our suspection is that the primary MOSFETs must have experienced multiple avalanches which has eventually led to damage of the MOSFETs. To confirm this we need the measurements of Vds while the board was working. Can you please let us know if you have these Vds measurements, taken while board was ok.

Regards

Meghana R

 

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Meghana
Moderator
Moderator 50 solutions authored 5 likes given 100 replies posted
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Hello Ashwani,

Can you please also measure the impedance of Drain - source and Gate-source of damaged MOSFETs. And confirm if the gate drivers of the damaged MOSFETs are functionally ok or damaged? 

And could you measure gate driver supply voltage ?

Regards

Meghana R

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ashwani
Level 2
25 sign-ins 5 questions asked 10 replies posted
Level 2

Hello Meghana 

Gate driver supply voltage is ok and it is under the limit.

 

Gate - source impedance of damaged MOSFETs - 0

Drain - source impedance of damaged MOSFETs - 4.82nF

Regards 

Ashwani

 

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Meghana
Moderator
Moderator 50 solutions authored 5 likes given 100 replies posted
Moderator

Hello Ashwani,

Could you please measure the impedance in ohms? Also, is it possible for you to replace the damaged MOSFETs and re-test the board? 

Regards

Meghana

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