Questions about symmetric dc/dc converter

[auto_mitch]

Is it possible to built a symmetric dc to dc converter (e.g. +/12Vdc) using only one mc34063. If it's not possible how can i get the middle point of the measurement (+12V com -12V) by using two of them. Any ideas?

 

[FvM]

Re: symmetric dc/dc converter

Can work as flyback converter with transformer. But for non-isolated supply, I would prefer separate converters due to better regulation.

 

[tpetar]

Re: symmetric dc/dc converter

Do you want to do strictly with MC34063 or can be any other ?

 

[auto_mitch]

Re: symmetric dc/dc converter

No i dont want to design it strictly with MC34063 it was an ic that i have already in stock i am open in any design with any converter

 

[tpetar]

Re: symmetric dc/dc converter

Input voltage can vary, or you want to make the same level ?

 

[D.A.(Tony)Stewart]

Re: symmetric dc/dc converter

That IC has an App Note for its Buck-Boost configuration adapted to dual output with a transformer with twice the inductance per leg. Since it is switched high side, you can connect the floating secondary to Gnd. The current load ought to be similar since you can only regulate one output with one regulator. https://www.st.com/internet/com/TEC...AL_LITERATURE/APPLICATION_NOTE/CD00043744.pdf p28

The secondary output may be ~10% lower depending on mutual inductance or coupling. I suggest you wind your own torroid with bi-filar windings and experiment with secondary going into a diode cap of similar size as primary side.

 

[FvM]

Re: symmetric dc/dc converter

To get symmetrical (tracking) dual voltage output, the primary output must be connected as "inverting boost" (flyback) converter. The second winding will generate the positive output voltage.