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  1. #1
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    Gate driver for non inverting buck+boost converter

    Hi!
    I am wondering what kind of gate driver is used for a non inverting buck+boost converter. (Not the normal buck-boost).
    I am referring to the circuit attached in the image here.

    My concern is when the diodes are replaced by MOSFETs for synchronous rectification...
    The high side buck MOSFET will have to remain ON through if the circuit is operating under boost mode. And in the buck mode it will be desirable to have the boost diode (MOSFET) ON continuously. This continuous ON period is will not allow the conventional bootstrap method for high side MOSFETS.
    One way could be to use isolated supplies. Is there some other gate driver circuit/IC that is "commonly" used for this type of converter?

    I am of the opinion that a dedicated buck + boost converter will have better noise performance and power handling capability than a typical buck-boost converter. Am I correct?

    Thank you

    •   Alt14th September 2017, 17:16

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    Re: Gate driver for non inverting buck+boost converter

    Have a look here.

    - - - Updated - - -

    Quote Originally Posted by mrinalmani View Post
    I am of the opinion that a dedicated buck + boost converter will have better noise performance and power handling capability than a typical buck-boost converter. Am I correct?
    In my opinion not.
    Your buck+boost converter has 4 switches against 2 switches of the buck-boost => higher noise
    Your buck+boost converter has more components than the buck-boost => less efficiency and more expensive

    Only advantage I see in this converter is the non-inverting feature.



    •   Alt14th September 2017, 19:53

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  3. #3
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    Re: Gate driver for non inverting buck+boost converter

    Thanks for the reply.
    By better performance I meant less noisy.
    Consider a buck-boost converter operating in buck mode. In every cycle, all the energy needed by the load is first stored in the inductor and then dumped into the load.
    However in a dedicated buck converter, energy need not be stored in the inductor. There is direct transfer of energy from the source to the load. This perhaps insinuates larger power handling capacity and also less noise. (Not sure, but it "feels" so)
    Same is the case in boost mode. In a dedicated boost converter only some energy is stored in the inductor (during ON period) and during OFF period there is direct transfer from source to load. But in buck-boost "ALL" the energy must first be stored and then later be released.



    •   Alt14th September 2017, 20:29

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    Re: Gate driver for non inverting buck+boost converter

    But in buck-boost "ALL" the energy must first be stored and then later be released.
    Not clear which buck-boost topology you are referring to. Complete energy storage necessarily happens in inverting buck-boost or transformer buck-boost.

    Non-inverting buck-boost regularly uses a topology similarly to the post #1 schematic, either asynchronous transistor-diode switchers, or 4 transistor synchronous buck-boost. Integrated controllers are e.g. made by Linear Technology, performance is quite good.


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    Re: Gate driver for non inverting buck+boost converter

    I was saying that "ALL" the energy is stored in inverting bubk-boost converter. And in non-inverting buck-boost all the energy need not be stored. So I was wondering whether a non-inverting buck boost converter will provide better performance than the inverting version? (For power levels around 100W and current of 5A)



    •   Alt15th September 2017, 05:57

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    Re: Gate driver for non inverting buck+boost converter

    Here's an efficiency graph of a synchronous buck-boost driven by Linear LTC3780

    Click image for larger version. 

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