How to get microcontroller to drive gate of mosfet for SMPS

you may consider TLP250 MOSFET driver.

BradtheRad said:

An op amp can work as a simple controller.



I have tested this concept in hardware, at very low volt and Ampere levels.

The op amp is powered by the 18V supply. Its output voltage must go high enough to turn off the P-mosfet.

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My only issue with this is where would I get the 18V supply? I don't want to have a completely separate power supply to just power up this part. I'm trying to keep it to one wall supply for the input.

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FvM said:

TPS2811 is a low side driver and does not work (or more exactly, doesn't achieve correct switching) with a buck converter and NMOSFET switch. I believe you'll see this if you review the simulation results thoroughly.

The problem of controlling the power switch with a suitable circuit isn't directly related to the intended usage of a microcontroller. It also arises if you use a conventional PWM controller IC or any other switched mode regulator control design.

The microcontroller adds a digital controller design problem. If you feel that designing the power stage is demanding enough, changing to conventional analog control might be wise.

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You're correct, when I looked at the oscope the wave looked to fluctuate. Is there a mosfet driver in multisim that would work for my circuit? I don't have to use a microcontroller in my project but don't know what to do for analog circuitry. I think it would involve using op amps and one that I've used is the LM741 but if I remember correctly I need to supply it with + and - 15V for the rail voltage.

Is there any IC that I can use that will take of my issues with the pwm of my buck converter? Like a gate driver I would imagine that I would need and maybe some sort of feedback IC. I'm not very familiar with what's available as I don't order parts very often or at all. They would have to be through hole so I could test them on my breadboard so my professor can check me off.

My only issue with this is where would I get the 18V supply?

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The 18V in this schematic is your rectifier output voltage. The circuit solves the driver voltage problem by using a PMOS instead of a NMOS transistor and inverting the gate voltage.