TinySwitch4 Light Load Noise
Hi Everyone,
I have a problem with TinySwitch4 design. Basically, at light load (<0.5W) it produces audible noise (also visible at the output).
I checked all the information from here:
https://www.youtube.com/watch?v=92NjC0Noal0
However, it seems like I might have some other problem as switching pulses have low frequency (I assumed that even at light load they should not be audible) . As soon as I get 2W out of that power supply, they go above 20kHz.
Please see attached schematic and scope screenshot (measured between transformer secondary, before rectifier, to show the frequency).
Also, I would appreciate for any other comments on the design.
Thank you for any help.
Steve
댓글
Hi Kryten,
Thank you for quick response.
Please see attached design.
A couple of clarifications:
- C3 should be 100nF, not sure how to change it in PI Expert (do you know?)
- transformer in fact has slightly different amount of turns (please see notes on schematic from previous post). The purpose is to use the same transformer type for use in 9V and 12V power supplies. Also I'm not sure how to change number of turns in PI Expert, it only gives you the optimal design.
| 첨부 파일 | 파일 크기 |
|---|---|
| TinySwitch-4_9V.uds (517.5 KB) | 517.5 KB |
Hi,
Varnishing the transformer and applying glue on top of the cores will help reduce the vibration of the cores and thus reduce audible noise.
You can also try reducing the flux density of the design. This helps reduce audible noise.
Best Regards,
PI-Kryten
Hi Kryten,
Thanks for response.
I understand that reducing vibration etc. is a one method of dealing with problem. However, what I meant is - is there any way of optimising power supply so it works always >20kHz? In TinySwitch-4 datasheet, there is an information that it works at 128-136kHz. That is a true for a full load operation. So is there any way to make a power supply that could work with high and low load above 20kHz?
Regards,
Steve
Hi,
Thank you for considering Power Integrations for your solution.
Please also provide transformer documentation and spreadsheet such as the one from the PI-Expert tool.
Best Regards,
PI-Kryten