Buck boost design helps for the bidirectional battery charges

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deepakchikane

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Hi

can anyone help me build a Buck-Boost converter.

application: Bidirectional Battery charger.

any articles.. idea will be appreciated.

1)12v dc-72v dc (Boost mode)

2)72v dc to 12 v dc (Buck mode)

What can be the control logic..??
 

aflex said:
Try out IC LT®8705. It will be mapped for both of your needs - boost and buck converter. The best thing about LT®8705 is that it can generate output voltage above, equal to or below the input voltage depending on the need.
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will it be bidirectional...??
 

I think the question is misleading. You are not actually looking for a buck-boost converter. What you need is a simple synchronous switcher (two switches + one inductor) that is controlled for bidirectional operation. Buck in one direction, boost in the other.

Unfortunately I'm not aware of a switch controller IC supporting bidirectional operation (Some might exist though). You can design your own analog controller around existing PWM controller ICs or use a dsPIC or similar fast microcontroller to setup a digital controller.
 

FvM said:
What you need is a simple synchronous switcher (two switches + one inductor) that is controlled for bidirectional operation. Buck in one direction, boost in the other.
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yes fvm.. it is right.

can u help me to design such projects..??

one basic thing, i want to design for 100 w @100 khz...

pls,help me to calculation of inductor for that and also capacitor selection..
pls
 

Inductor can be choosen as for standard boost or buck converters, e.g. 20 or 40% ripple current results in 64 respectively 32 µH. So 39 or 47 µH would be a good choice.

Capacitors at least some 100 µF at each side. High voltage side has discontinuous current and higher ripple, about 3.5 A rms, capacitors must be prepared for it.
 

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