TOP 243Y Explosion failure

Hi:

I did take a look of your schematic, before going into detail analysis, would you please let me know whether you use a zener or TVS in your claping circuit?The schematic is not clearly showed, I can not tell the reference of this part, but I mean it is the 200V zener (or TVS) for 503?

Thanks

Hi Terry,

It is a 200V TVS for 503 claping circuit.

Thank You,

Del                      Hope to here from you.

Hi, thanks for the information.

I just notice the 22kohm resistor in the clamping circuit is a little lower than normal, with clamping voltasge equal to 200V, will get the power dissipation of this resistor to be 1. 82W which is close to the rating 2W. Did you see this resistor getting black in the field?

Did you also notice some abnormal components on the failed board? Did you test the drain votlage during the startup at highest input voltage and maximum load, what is the margin do you get?

Thanks

Hi Terry,

Your right the Axial leaded 22K Resistor body temperature max. input voltage--max. load no air 103c@27c ambieant.

The unit does have air flow. Never saw the resistor changing colors. No other components failed on  board except

top switch. Attachments are turn on picture and continuous on. Drain,source voltage. Conditions 264vac ,Max. load.

Note: I am using a boost front end pfc circuit 390vdc +/-5V. Top switch input voltage same. Another attachment is

the transformer design if you could please take a look . Pins 1-2 and 9-10 not used.

Thank You,

Del

Hi,

Thanks for the file.

The power supply only failed after 3-5 months' operation. That is a indicator that some components may be damaged firstly that causes the TOP switch eventurally failed. The failure may relate to the application condition (temperature, humility, ect.) in the field too, this may cause the insulation failure or transformer satuation which may cause the failure of the topswitch too. Do you have any clue that this power supply only fail at some specific applition?

The other thing I can think is the PFC circuit, are you sure the output voltage of the PFC is guaranteed to be inside of 390Vdc?

What is the peak flux density of the transformer you designed?

Hi Terry,

When the units are sent back from the field for repair 4 out of 10 are the top switch only. Replaced  top

switch and recycled through test, burn-in and final test unit ok. In some locations the temp. of top switch my run  

case 100c continuous.  The same top switch is used on other projects. I will check on the return rate failure of the top switch only. The pfc is guaranteed  to be within limits of  390vdc+/5V. Designed Peak flux density  (<2000).

Thank You, Del

Hi Terry,

Waiting for reply. Sent oct.18-2013.

Hi,

Unfortunately I do not think we can come to a clear conclusion of the failure reason at this point with the limited information. I will suggest you to contact with PI quality department through PI FAEs to help you to do more close analysis. You may need to send the failure parts and board for analysis.

Thanks