TNY280 Burning

Hi claudiosantiago,

Thank you for using Power Integrations' part.  

Regarding your issue, is the failure happens upon full load start-up or when your burn-in the unit running at full load? What is the failure input voltage? Is your application an open frame or adaptor/with enclosure?  Can you elaborate more on the failure test condition?

I observed that you have your design at maximum power limit for open frame design.  Another observation is you have ckt for bias circuitry on your layout but you don't have on your schematic.  Do you have bias winding for BP supply?  If you don't have bias circuit for BP supply, your power supply is less efficient with more dissipation on the internal controller regulator which degrade the maximum power capability of the controller. Thanks.

Hi PI-Mallora

The power suply is 25W opem frame, into normal operation consume less than 3W, however at switch the printer have short peaks of up to 22W. The failure occurs both at start up, as in burn-in, often at 220V, but also in 110V and always printer is off.

I do not have the ckt the bias winding on the power supply.

Our second objective is to improve the lay out, and perhaps develop a new power supply for this application, the TNY280 is the best choice?

Hi PI-Mallora

The power suply is 25W opem frame, into normal operation consume less than 3W, however at switch the printer have short peaks of up to 22W. The failure occurs both at start up, as in burn-in, often at 220V, but also in 110V and always printer is off. I do not have the ckt the bias winding on the power supply.

Our second objective is to improve the lay out, and perhaps develop a new power supply for this application, the TNY280 is the best choice?

Thanks

Hi Claudiosantiago,

Since it is an open frame you can still use the TNY280 but add the bias winding ckt to improve thermal performance and efficiency.  Is it driving the printer motor or just the printer control?  If it is driving the motor, I suggest to upgrade your controller to TNY290K so you'll have better thermal package and peak power margin.  See below link of the controller.  Thanks.

https://ac-dc.power.com/sites/default/files/product-docs/tinyswitch-4_family_datasheet.pdf

Hi PI- Mallora

My printer is thermal, and as informed, the failure ocurrs both at start up, as in burn-in, and always printer is off.

The project has more than three years, however it began to burn in the last 3 months, so I understand that add the bias winding ckt is an improvement, but not the source of my problem.

Have any suggestions to modify the project, to the power suply that are already produced?

Any reason for the waveform of Vds be different from the datasheet?

In the datasheet, the Vds is about 15us is high (400V) before the oscilation and shutdow, in my waveform, I do not have more than 2us.

I've attached the image zoom.

What can I do to diagnose the source of failures?

Please, I need help, because the power supply continue to burn on the field, and so far do not have a suspect.

I'm sorry for bad english.

Thanks

Hi Claudiosantiago,

I don't see any difference with your waveform that may cause the failure.  You have different spike at turn-off due to different snubber used.  Is the TNY280 is the only component getting damaged?  Thanks.