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How to utilize the inverted (+/-) oput of buck-boost conv?

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powersys

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If I'm not mistaken, the polarity of the output of a buck-boost converter is inverted. Is there any trick to utilize it to power normal circuit?
 

VVV

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Re: How to utilize the inverted (+/-) oput of buck-boost con

The ground of your "normal" circuit should be connected to the output of the converter and the + to the ground of the converter.
I personally do not like this kind of arrangement, but you can use it.
 

powersys

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Is there any "buck-boost" topology that the output is non-inverted? Thanks.
 

v_c

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Re: How to utilize the inverted (+/-) oput of buck-boost con

Yes, you can do this and there are even ICs that will let you control the circuit.
The one that I know for sure is to use a buck followed by a boost in a configuration
sometimes known as a buck+boost (as opposed to buck-boost). The configuration
is simplified to the one shown in Figure 2 in the attached file.

This topology uses 2 diodes and 2 switches. But depending on if you are in buck mode or boost mode, only one of the switches is being pulse-width modulated. The other switch would be off or on depending on the mode.

I hope this helps you out.

Best regards,
v_c
 

powersys

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Re: How to utilize the inverted (+/-) oput of buck-boost con

v_c said:
Yes, you can do this and there are even ICs that will let you control the circuit...
Thanks for the info. Would u pls advise the part# of ICs your meant in your message?
 

v_c

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Re: How to utilize the inverted (+/-) oput of buck-boost con

If you look at page 2 of the document that I attached, there is an example given with a MC34063.

I think you should take a look at a selection guide to see what is available.
Here's the selection guide for On Semiconductor.

https://www.onsemi.com/pub/Collateral/SGD504-D.PDF

If you go to page 66 of the document (page 67 in Acrobat), you should see the
"DC/DC Non-isolated Switching Controllers". On the right side of the page you should see a rectangle with "Multi Topology" area. There you can see the list of IC depending on if you want the transistor external or internal to the IC. With external transistors you can get much more flexibility in the performance.

I hope this helps you out.

Best regards,
v_c
 

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