Innoswitch3-CE max switching frequency

Hi Barfly,

Thank you for considering Power Integrations products.
You may use PI Expert software to set the worst case switching frequency of your InnoSwitch3-CE design.
https://piexpertonline.power.com/site/login
More details on how to design with InnoSwitch3 family IC can be found in the application note below
https://ac-dc.power.com/design-support/product-documents/application-notes/an-72-innoswitch3-family-design-guide/

Regards,
PI-Spark

I have an existing design in production with the Innoswitch3-CE.

I reviewed AN-72 and still can't find any reference to how you set the switching frequency limit. This application note also contains the statement:
"It is unique feature in InnoSwitch3 that a designer can set the operating switching frequency between 25 kHz to 95 kHz depending on the transformer design."

Obviously entering the switching frequency into PI Expert software does not actually alter the behavior of the part...

Thanks,
Josh

Hi Barfly,
The PI Expert software will re-compute the primary inductance of your transformer when you change the user input maximum switching frequency.
Before setting the maximum switching frequency, make sure that Step 1 (Application Variables) and Step 2 (Primary Controller Selection) are already filled up as shown in the application note.
Also take note that the resulting primary inductance depends on the user input maximum switching frequency and VOR (reflected output voltage), among other, in the spreadsheet.
VOR selection is also discussed in the application note.
To summarize, you may achieve a target max frequency by following the computed primary inductance in the PI Expert software.
Hope this helps.
Regards,
PI-Spark

So the max switching frequency is set only by the primary inductance?

Hi Barfly,
You can control the maximum switching frequency of the design by adjusting the primary inductance.
But I recommend that you think of it with this perspective:
"With the given input/output specifications of the power supply and the chosen primary controller device, the worst case frequency of the design can be limited to this user-input value if the computed inductance and number of turns (primary and secondary) in the PI Expert software are followed".

Just to clarify, since InnoSwitch3 is a variable frequency controller, this worst case switching frequency will only occur when operating at full load with minimum VAC input, minimum primary inductance (considering tolerance), and an InnoSwitch3 device with current limit at lower end of datasheet tolerance.
When operating at light load or at higher input VAC, the power supply will operate with a different (lower) switching frequency to regulate the output.

Regards,
PI-Spark