Solution Finder

12V / 6A Power supply. Help with Buck and Boost converters + OR'ing circuit

Posted by: esm on Thu, 06/07/2012

Hello all.
I would like to receive some suggestions of ICs / considerations about this design.
The attached picture states how this power supply should work.


1) IC 1 probably will be a LT3650-8.4 from Linear Technology. It supports up to 32V of input voltage (40V peak).

2) The power supply INPUT has only two states: (A) Floating (cut-off) and (B) 17 to 30VDC present at the input.

3) The OR'ing circuit at the OUTPUT, as the picture shows, doesn't mean it will be done with diodes. It can be done with MOSFETs, relays, or any kind of logic control like, for example: When the INPUT is connected to a 17 to 30VDC PSU, a logic LOW is present in an ENABLE pin of the BOOST converter, so that this remains in idle state (Output in high impedance). When there is no power supply connected at the INPUT, the same ENABLE pin goes logic HIGH, so the BOOST converter goes to active mode and presents 12V at its output.

4) The intention of using batteries is, case the INPUT be floating, maintain the circuit connected to the 12V OUTPUT working for at least 10 minutes (If more, better), through the BOOST converter

5) Which BUCK and BOOST controllers from Power Integrations could I use for this design (IC 2 and IC 3)?

6) How can I do the Or'ing circuit between Buck and Boost controllers? Some suggestions of PI ICs?

7) There are no restrictions if heatsinks are required. No restrictions with the final physical dimensions of the PCB. Just need to work.

8) No problem if external MOSFETs are required, both on Buck and Boost converters

9) Final cost of this PSU is not so important.

10) Preference to SMD packages in all the circuit, if possible.

11) The 12V OUTPUT can be designed to deliver more than 6A. No problem about that.

12) No need of insulation (Flyback / forward topology, for example). The topology can be modified to Flyback / Forward also

For the time, all I found is a Buck converter from Linear Technology, based on a LTC1624. Example of a 12V x 10A output with Vin range of 13 to 28V using this converter (attached)

Thanks in advance.


Attachment Size
PSU.png 35.79 KB
LTC1624.png 66.36 KB


Submitted by PI-NANO on Mon, 06/11/2012


Thank you for your interest in Power Integration's products.

We have DPA Switch which you can use it for buck stage (But it can be used for forward or flyback converter topologies).

But unfortunately any IC's for boost converter with such a low voltage input.

we don't have any Oring controllers at this point of time.


Submitted by esm on Thu, 06/14/2012

I was rethinking about this design.
The output current will be reduced to 4,5A at the maximum load, not 6A as the initial idea
I think now I can have a single solution based on a buck-boost topology, right?
My only experience with a buck boost IC was the TPS63000 from Texas, but it doesnt fit the requirements of this design.
Some other recomendations of buck boost ICs from PI now?

Best regards

Submitted by esm on Sun, 06/17/2012

Can you tell me the part numbers of these ICs that you are talking about?
I will check the datasheets.

Submitted by PI-NANO on Mon, 06/18/2012


For Buck, Boost and Buck-Boost configuration we do not have any IC's with such a low voltage input.

We have a DPA Switch which you can be used for forward or flyback topology with a minimum input voltage of 16V DC.

You can find the data sheet for DPA switch at following location