DPA423 soft start issue

Posted by: vojkob on 06/14/2013

Hello,

in our solar microinverter we use DPA 423 as flyback controller. We are very happy with it except one problem:

we need to increase soft start to apprx 1 second, in order to decrease needed power to charg secondarye capacitors.

5msec built into the cheap is too short and peak power at start is to high, causing panel voltage to drop at extremly low radiation levels.

Do YOu have any suggestion, how to increase soft start time to approx 1 second. I tought to use L pin and limit duty at start up. I can even add one digital output from our DSP in order to provide this function, but Im not sure if this is teh right solution.

Thank You for the answer,

Vojko

Comments

Hi, Thanks for contacting PI.

You could add external soft start circuits to reach your requirement.

Please refer to our design example from Top Switch.

http://www.powerint.com/design-support/reference-designs/reference-design-kits

The C20, D9 and R16 formed a external soft start circuits, this will be good for DPA switch too. Please try to see if this works for you.

Thanks

Hi,

on design, I dont use optocoupler feedback. I use aux winding on DPA. In link that was indicated in first reply, I couldn`t find the right schematics. Can You please explain what You mean with that link?

Regards,
Vojko

Hi,

Sorry, there is a issue on the link, please use the following one instead:

http://www.powerint.com/sites/default/files/PDFFiles/rdr142.pdf