LMR14020: Positive buck-boost

Umberto Frangi

Part Number: LMR14020

Hi,

I would like to know if we can do an application similar to the below with one of our LMR or Simple Switchers in general.

Thanks

Umberto

over 7 years ago

0 JohnTucker over 7 years ago

TI__Guru**** 191445 points

Moving to Simple Switcher Forum...

0 Umberto Frangi over 7 years ago in reply to JohnTucker

TI__Expert 4045 points

Ok, I am not sure if the picture is attached, pls look at:
www.st.com/.../en.CD00217462.pdf

0 YangZhang over 7 years ago in reply to Umberto Frangi

TI__Genius 11085 points

There are a few concerns with this topology.

The circuit shown in the attached PDF (page 34) states the input range is 4.5V to 28V, but the FET Q1 gate drive voltage is rated up to 16V. If Vin is above 16V, Q1 will be damaged. Be careful with the Vin range in your application.

The buck-boost topology has different loop response than a buck topology. This application idea did not provide how to properly calculate the type III compensation network so that it is stable with the buck-boost topology. The LMR14020 has internal compensation network for ease of use. The compensation network is not tested in the buck-boost configuration.

The inductor in the buck boost topology conducts much more current than it is in a buck converter. Be careful with the current rating of the inductor if you decide to proceed with this topology.

Hope this helps.

Yang

0 Luke Pan over 7 years ago in reply to Umberto Frangi

TI__Intellectual 2790 points

Hi,

Yes, we did similar reference design before. Here is the PPT.Positive Buck-boost Converter .pptx

Power management

Power management forum

LMR14020: Positive buck-boost