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Inn2003 making reset after some time off operation

Posted by: M.Harms on 05/20/2022

Hi there,

i had made a design with the Inno2003. It works well und was also tested.

Now the first 1k of electronics are build and during a long therm test some electronics gets problems. I checked the electronics and findout the power supply is not ok. The Inn2003 works only for around 300ms. In the moment the SR PWM is send out, the output voltage goes down and the device make an reset. 

Can I get this problem by a broken transistor at the SR pin?

Any other ideas why the chips makes resets?

Comments

Submitted by PI-Wrench on 05/20/2022

It would be a good idea to monitor the drain current on the primary side using a current probe to see if the drain current is rising to the overcurrent protection threshold. A broken SR fet or mis-timed SR fet drive would make that happen. It would also be a good idea to monitor the SR fet drive on the secondary side to make sure that the SR fet stays off while the primary switch is on.

Submitted by M.Harms on 05/23/2022

During the measurement of the SR fet the electronic get damage.

A high current goes through the primary side and destroy the IC. A new placed IC doens´t work on the electronic. I will wait for the next damage electronic, to take some measurements. 

Submitted by M.Harms on 05/24/2022

I get a other electronic with the same behave.

This time i could take some measurements. I don´t have a current probe to measure the drain current of the primary MOSFET.

Attachment Size
Vout 39.21 KB
SR Fet Gate 43.45 KB
SR Fet Source 55.98 KB
SR Fet Drain 67.38 KB
Submitted by PI-Wrench on 05/26/2022

An output sync fet cross-conduction event can break either the primary switch fet or the output sync fet, or both.  Please share you design files, including layout (if possible). An image file is preferable for the layout rather than a Gerber file, due to layout program compatibility issues.

Submitted by M.Harms on 06/08/2022

Here the schematic of the power supply.

If the primary switch is broken, there should be no switching on the primary side either the secoundary side right?

Attachment Size
Zwischenablage01.png 50.02 KB
Submitted by PI-Wrench on 06/13/2022

True - if the primary switch is shorted, there will be no primary or secondary switching, likely no input fuse as well.

 

It would be a good idea to monitor the voltage on the secondary synchronous rectifier, the drive signal to the sync fet, and the primary switching waveform to make sure that there are no cross-conduction events, and that the drain voltage rating of the output synchronous rectifier is not being exceeded. Non-optimal PCB layout may make cross-conduction events more likely.