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    High Efficiency buck topologies

    Hi all,

    I am trying to design an isolated buck topology converter. The input is 100-120 volts and output is 60+-12 V with 600W power. I have seen many application notes for 600W converter using PSFB (400V to 12 V) having efficiency over 95%. I want to know whether using PSFB with or without syncrhonous rectification is suitable for my design with efficiency over 95%. Are there any alternate high efficiency isolated topologies for stepping down voltage from (120 to 60V typically) at 600W power.

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    Re: High Efficiency buck topologies

    Hi all,

    Any suggestions regarding the high efficiency buck topology. Also I want to know if PSFB will be more efficient than FB when steping down from 120 V to 60V at 600W. Please let me know any suggestion/reference regarding this. Thanks.



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    Re: High Efficiency buck topologies

    - Isolated means transformer converter, no matter if buck or boost.
    - optimal topology depends on additional parameters, e.g. required regulation respectively variation of voltage ratio
    - in terms of efficiency, a soft switching topology is preferred



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    Re: High Efficiency buck topologies

    A general strategy to improve efficiency is to locate and eliminate all the things that waste power and generate unwanted heat.
    Parasitic resistance in transistors, diodes, coil windings, capacitors, etc.

    The inductor is the heart of a switched-coil converter so it needs to be constructed so it can handle desired Ampere rating.

    isolated buck topology converter
    Isolation implies you expect to use a transformer, and that suggests a flyback converter.


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    Re: High Efficiency buck topologies

    Thanks BradtheRad for the reply.

    However, in literature flyback is said to be recommended for below 500 W application right.

    - - - Updated - - -

    Quote Originally Posted by FvM View Post
    - Isolated means transformer converter, no matter if buck or boost.
    - optimal topology depends on additional parameters, e.g. required regulation respectively variation of voltage ratio
    - in terms of efficiency, a soft switching topology is preferred
    Thanks FVM for the reply,

    As I mentioned regarding voltage converter requirement that it needs to step down from 120 V to 60 V and o/p power is 600 W. What isolated converters are used at this power level and voltage level having high efficiency



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    Re: High Efficiency buck topologies

    One of the most efficient tricks to improve efficiency is to reduce the switching frequency.......up to a point.

    Otherwise your magnetic components (transformer, inductor) become quite large and copper and core losses increase significantly.
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    Re: High Efficiency buck topologies

    LLC converter driven by half or full bridge, synchronous rectifier.


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    Re: High Efficiency buck topologies

    PSFB can easily regulate over a wide input/output range.

    LLC is probably superior if input/output voltages are relatively fixed.

    Though it depends mostly on your particular implementation. A bad implementation of either will be inefficient. A good implementation of either will be 95% plus. PSFB is may be easier to implement in my opinion but may or may not be easier to tune to high efficiency.


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    Re: High Efficiency buck topologies

    Thanks asdf44
    What should be the switching frequency that should be targeted in case of PSFB with Synchronous rectification. I am thinking of 50khz as a start. Also is there any tool to evaluate efficiency of converter at various frequencies (analytical or simulation)



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