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I have recently leared about bidirectional buck/boost converters. They can be used in hybrid vehicles for optionally charging a 12v battery from a higher voltage battery or vice versa. How would one of these perform differently than separate buck and boost circuits with switches to determine which one is active at any given time?

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Well you could make a bi-directional buck/boost controller from seperate buck and boost circuits: -

enter image description here

Or you could just omit the components marked in red boxes and get an improvement in efficiency: -

enter image description here

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  • \$\begingroup\$ I don't think this answers what I was asking about, but maybe I wasn't clear. By bidirectional, I mean both ends can be both input or output. I need one side to be high voltage and the other low. There are bidirectional DC/DC converters that do this, but I'm wondering about how that is different from using two separate regulators: one buck and one boost. \$\endgroup\$ – Westin Jul 5 '18 at 21:00
  • \$\begingroup\$ @Westin the circuits in my answer are bi-directional - you can freely interchange input and output - just look at how the MOSFETs are arranged - do you see anything fundamentally different between one side and the other? \$\endgroup\$ – Andy aka Jul 5 '18 at 21:04
  • \$\begingroup\$ Other than the lack of the output capacitor, there isn't a difference. I'm trying to figure out how much of a difference there is between a circuit like this and a buck and boost circuit next to each other with switches to determine which is currently on. I am wanting to move a lot of power and am concerned efficiency. \$\endgroup\$ – Westin Jul 5 '18 at 21:53
  • \$\begingroup\$ Well, I’ve shown two pictures and one is a buck converter followed by a boost and the second picture is a combined buck boost and of course it doesn’t have the inductor and capacitor shown in the red boxes. I’m not sure what else you are expecting for an answer given what you have asked. \$\endgroup\$ – Andy aka Jul 5 '18 at 22:20
  • \$\begingroup\$ In the text above the second picture, you mentioned removing the components in the red boxes will boost efficiency. In practice, how significant of a difference do we see in efficiency between the first and second images? \$\endgroup\$ – Westin Jul 6 '18 at 14:13

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