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assuming the power comes in the middle top and goes out the middle right, then the lower fet is the buck diode, but energised when conducting to lower overall losses - hence synchronous buck circuit .... easy to look up - tons of info on the web ...
in this case there are two buck ckts, usually operated out of phase to reduce input current ripple .... and to increase o/p freq of ripple, allow the use of smaller chokes, as each handles half the ave current, size proportional to L . I^2 for chokes ....
so the low side diode is doing the job of freewheel diode. I had a misunderstanding that an n-channel mosfet conducts from drain-> source (and not other way around). and then how the body diode acts?
It can go backwards as easily as forwards - don't forget to click "helped" above and here - thank you
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Also you have to turn the bottom fet OFF just before the top fet turns ON - a dead time of about 100nS is usually adeqate - the current flows in the internal parasitic diode inherent on the N fet for this short time ( on a scope you can see the volts jump up to 1V or so ... )
Presume the solar charge controller is only feeding forward power. Then it can work with diodes in place of the low side transistors, but with higher voltage drop. The synchronous (transistor-transistor) buck topology is used for higher efficiency.
In this specific circuit, the bootstrap gate drivers for the high side transistor even require low-side switch transistors to precharge the bootstrap capacitors.
so enery can go either direction in all types of mosfet??.. same with BJT also?
unlike in the above design, if i ignore the lowside mosfet and replace it with a diode and also use an high side only driver like IR2117 , is it possible to drive multiple mosfet ? And also with the bootstrap setup ,, what will be the upper duty cycle limit?
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