Not getting fix frequency and Pulse width from TOP246GN

Posted by: sandeep.yadav on 07/14/2015

Hi,

We are using TOP246GN with our design but not getting fix pulse width & switching frequency from the TOP switch and also geting high ringing on Drain pin.

Please find attached Drain waveform (Red color) and suggest about the behaviour of TOP switch.

Why frequency is not establizing?

Sandeep

Files

Capture.JPG (98.18 KB)

Comments

Hi,

Do you see this operation only at light load or no load? If yes, this is expected. If on the other hand this is also seen at moderate to high loads, this is an indication of instability. Instability can result from poor layout or incorrect selection of components.

Please review the datasheet of the part for guidelines for board layout to follow.

The ringing that you are showing in the waveform is the ringing between the magnetizing inductance of the primary winding and the MOSFET drain source capacitance. This is typical of flyback converters and as such is not related to TinySwitch specifically. Generally this ringing is harmless unless it shows up in the EMI signature in which case it can be damped using snubbers.

Thanks and Regards

PI-Sarek

Hi,

I have had a similar problem. Have you had any occurance of the TOP246 blowing up when applying power?

Hi Motech,

Can you raise a new question in the forum so that it can be addressed as a seperate design?

Regards,

PI-NANO