innoswitch flyback with low frequency and high peak sec current
Posted by: treez
on
Hi,
I just did a PI Expert design with innoswitch EP for a 100-265vac flyback of 24vout and 1A out.
The PI Expert came up with this...
https://piexpertonline.power.com/piexpert/design/index?tab=tab2
..At full load /min vin, it has a dead time of about 7us. The sec peak curren is over 10 Amps.
Why did innoswitch insist on using the current limit of 1.595A?....why did it not reduce the current limit and increase the switching frequency, so as to get a lower peak secondary current?
Hi treez,
the link you provided doesn't go to a design, so I can't comment directly on it, but I created a similar design:
https://piexpertonline.power.com/piexpert/design/select?share=e181e45945e52b898078e86f156cca84f2a4adf6be8971b247a889714ea3a186
As you see it has a similar problem, with very high KP and a lot of dead time.
The reason is that within the InnoSwitch EP family there are multiple sets of devices, grouped by MOSFET breakdown voltage. Each of those MOSFET types is designed for a particular power range: https://www.power.com/sites/default/files/documents/innoswitch3-ep_family_datasheet.pdf
There are some specifics to each MOSFET type that prevent PI Expert from switching it after design creation. During design creation on the first page of the Design Wizard you can choose the type from a drop down menu. The default value is 750 (PowiGaN), which are designed for power ranges of 75+ Watts and have the appropriate current limits. In your case you should pick the 725V, which is designed for 12W - 45V.