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LM2577 external mosfet

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yoosefheidari

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Hi everyone
i want to add a mosfet to lm2577 to achive high current about 15 amper ,is that possible?how can i add mosfet and what is need?
 

I do not think you can add an external switch to the LM2577

Page 14 Figure 32 shows the operation of the LM2577.
The current sense resistor, that provides a feedback into the control loop, is internal.
Adding an external switch would require access to the current sense resistor to maintain the integrity of the control loop.
 
Thank you
so i going to use UC3845
is this schematic ok?has it any problem?
BOOST.jpg
 

There's probably room for improvements.

I would expect a PI rather than P controller for good output regulation.

Above duty cycle of 0.5, a current mode controller needs slope compensation, otherwise it exposes subharmonic oscillations. Review 3845 datasheet and application notes in this regard.

The 600V MOSFET has relative large rdson and respective conduction losses.
 
FvM said:
There's probably room for improvements.

I would expect a PI rather than P controller for good output regulation.

Above duty cycle of 0.5, a current mode controller needs slope compensation, otherwise it exposes subharmonic oscillations. Review 3845 datasheet and application notes in this regard.

The 600V MOSFET has relative large rdson and respective conduction losses.
Click to expand...

in datasheet there is a slope resistor.but there is any value for that?i don't know the value of this resistor.adding this resistor solve the subharmonic oscillation problem?
another question is feedback section.is that correct?
slope.jpg
 

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