Clarification on Switching Frequency Selection for Reliable Transformer Design with InnoSwitch3-EP
Posted by: Manjesh
on
Hi Team,
I am currently designing a flyback converter using the InnoSwitch3-EP. According to the design guide, the recommended switching frequency range for Transformer design is between 25 kHz and 95 kHz. I have a question regarding how to correctly enter this parameter in the PI Expert tool.
Since the switching frequency varies dynamically depending on load conditions, how can I ensure that the transformer I design will remain thermally safe and reliable across this full range?
For example, if I choose 70 kHz as the design frequency in PI Expert, does this mean:
- 70 kHz is the minimum frequency at full load and low input voltage (i.e., worst-case condition), and the converter will operate between 70 kHz and 95 kHz?
- Or is 70 kHz the maximum frequency, meaning it will operate from 25 kHz up to 70 kHz?
- Or is it the typical frequency under nominal operating conditions?
I would appreciate some clarification on how this input should be interpreted for accurate transformer design.
Regards,
Hi Manjesh,
Good day! Thank you for using Power Integrations solutions.
The parameter we can set in PI Expert is FSWITCHING_MAX, which represents the maximum switching frequency at full load and at the valley of the rectified minimum AC input voltage. The second bullet point is correct—the operating frequency range should therefore be from 25 kHz up to the set FSWITCHING_MAX.