Burning of resist. R154 of PM8834 auxiliary power to MOSFET driver of PFC of STDES-3KWTLCP ref dsgn

[DSHAR.31]

I have assembled PFC and LLC circuit of STDES-3KWTLCP reference design. I followed the procedure as described in the document to assemble whole circuit. When we gave AC voltage to PFC, resistance R154 gets heat up and eventually burn out. I double checked all the components value and their placement but couldn't find the cause for this behavior.

Can anyone please assist us in finding which part of the circuit or component is creating this issue so that it would help us in rectifying the cause?

 

Thanks.

[Peter BENSCH]

Well, if R154 gets too hot, there will obviously be too much current flowing through it. Please check C161 and its insulation. Then also check the signals on PWM1, PWM2 and OUT1, OUT2 on U105.

Regards
/Peter

[DSHAR.31]

I changed C161 and checked PWM1, PWM2,  OUT1 and OUT2 of U105 with No Load connected. All these 4 pins have PWMs on them. Still, R154 is heating too much.

[AScha.3]

Check generated voltages : VCC_+ 18A + 18B + 12 V  . ok?

[DSHAR.31]

Voltages are also OK.

[DSHAR.31]

Is there anything I can check to find the cause of this issue?

[AScha.3]

What i would do (at work) : look with a IR-camera , to see, whats getting suspicious "warm" ...

If you dont have this : the small transformer makes 3 outputs: VCC_+ 18A + 18B + 12 V ;

(minimum) one of them using too much power, so R154 gets hot.

Find out, where something gets hot, or where the power is going to.

[DSHAR.31]

We already checked with the IR-camera. Only  R154 gets suspiciously warm (temp. reaches to around 100 deg celsius). Rest all circuit remains cool. We also disconnected the MOSFET driver IC (U101 and U102) which runs by these 3 outputs. The purpose of removing the connection to U101 and U102 is to check whether R154 gets heated despite not being connected to any load. After doing this, only R154 gets too hot when looked by IR-camera.

[Peter BENSCH]

If you get a voltage of 50V at VCC_+18VA after removing D112, the maximum reverse voltage of one or all Schottky of the bridge rectifiers will be too low. Either replace the bridge rectifiers with 60V or 80V Schottky, as @AScha.3 suggested, or with ultrafast rectifiers with >80V.

[DSHAR.31]

Just to be sure that the issue is not with auxiliary supply, I removed the auxiliary circuit and gave all 3 VCCs externally using 3 different regulated power supply (2 X 18V and 1 X 12V).

What I observed is , both gate drivers STGAP2D  draws too much current that one of them burnt with flames, while other one also got damaged completely, with external VCCs dropping to 2V for 12V and 9V for 18V..

 

I still cannot understand which section is wrong.

 

[AScha.3]

Upps...now no need to understand which -- now repair ALL .

You have to replace all gate drivers, and when removed the old, check gates of mosfet/igbts for good or dead (most time short or low resistance, if damaged).

Was this 3kW inverter running ever ? What happened before ? 

[DSHAR.31]

Only once we got output as 400V from this PFC. But this output remained for only couple of seconds and R154 got burnt. 

After replacing R154, it got burnt several times but 400V output never came and MOSFET also got shorted couple of times.