Burning TNY288KG

Posted by: pironex on 01/19/2016

Hello,

we have a problem with our TNY288KG Design. It works fine for weeks and then the TNY288KG burns and pulls the fusable resistor.

I checked the temperature of the TNY288KG which is fine around 60°C and also checked the drain voltage with a maximum of 665V.

Any Idea whats wrong with the design?

Please find the schematic attached.

Thanks in advance.

Files

Schematic of TNY288KG (1.41 MB)

Scope of Drain Source Voltage (4.75 MB)

Defect of TNY288KG (1.14 MB)

Comments

How many units were tested?

Hello,

we produced 100 units and until now 30% have the defect described above.

Any ideas?

Oh ok , Where exactly they are failing? At what input voltage ? Are they failing during Burn in test? How did you choose fusible resistor and the bridge diode? Did you do any energy (i2t) calculations?

I also see that you are using Sync Rectification in the secondary side , did you verified Cross conductions which you are doing design? How did you did design and test?

Hello,

the input voltage is 230V AC at 50Hz. The devices fail after a couple of weeks in the field.

We did the calculation for the resistor to fullfill the requirement of the bridge rectifier.

The test of the sync rectification was done by oscilloscope and adjusted according to the datasheet.

Are there any parameters of the TNY288 which we may have missed to consider?

ok, what kind of testing you did on power supplies before going into production? Did you perform any life burn in test ? What kind of calculation you did on Fusible resistor? We cannot understand if you don't clearly explain the calculation analysis behind the selection of fusible resistor? did you verify any cross conduction between primary and secondary?