Electronic – Bi-Directional Buck Boost Converter


I'm trying to build a Bi-Directional buck-boost converter. The input should be between 9-12 and output should be 12. Can any one recommend a good topology to follow. I also have a few conceptual questions. If anyone can recommend good topologies to follow along with a good chip I would really appreciate that.

  1. Are all buckboost converters bi-directional?
  2. Do i still need transistors for the switches? Or will the chip do the switching for me.

Best Answer

Are all buckboost converters bi-directional?

A non-synchronous switching converter uses a diode for one of the switches. Such a converter typically transfers power in only one direction. (Is there a better term for this than "non-synchronous switching converter"?)

A synchronous switching converter replaces each of those diodes with an actively controlled FET. Such converters are inherently bi-directional and usually more efficient than non-synchronous converters.

Do i still need transistors for the switches? Or will the chip do the switching for me.

If you only need 1 amp or so of input or output current, there are several switching regulator ICs available that have internal transistors that do all the switching for you. For example, you might look at the LM2587T-12 datasheet figure 13, which shows how to use that chip to produce 12 V regulated output from input anywhere in the range 8 to 16 V. (Alas, it is non-synchronous, transferring energy only in one direction).

If you need higher currents, you're pretty much forced to use external discrete FET transistors for the switches. The typical circuit is shown on the first page of the ADP1873 datasheet, which shows a synchronous (and therefore bidirectional) 10 amp switching converter.

recommend good topologies

Some tips have been collected at http://opencircuits.com/Switching_regulator .

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