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How to drive a mosfet for buck-boost converter

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nirza

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Hi, I am working on a simple project to design a basic Buck-Boost Converter by using a 8051-based microcontroller. But, I have a very low knowledge about the hardware implementation. Can i directly drive a mosfet from AT89S52? What is mosfet driver actually? Can anyone help me on how to connect the microcontroller to the mosfet on a breadboard? I am very grateful if anyone can reply me soon. Thank you very much in advance :)
 

Hi,

I am working on a project to design a basic Buck-Boost Converter by using a 8051-based microcontroller.

However, I have a very little knowlegde on the hardware implementation especially on driving the mosfet by PWM generated on AT89S52.

Can i drive a mosfet directly from the AT89S52?

Do I need a gate driver?

I am using an n-channel NTD12N50 mosfet.

I am very grateful if anyone can help me on this.
 

Hi,

From what I know: You need to know output current capability of AT89S52, then calculate MOSFET gate current needed, see if it's enough. Most of these circuits seem to need a gate driver IC rather than a discrete solution. Probably, you'd need to provide some figures for others to provide useful advice, e.g. voltages in and out, current/load, etc., and a schematic of the whole design would help.
 
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    nirza

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You must use a driver to drive the MOSFET. There are lot of driver IC's available in the market. If your circuit does not require isolation you can use transistors also.
 
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    nirza

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Thank you for your response. It means that i do really need a driver, isn't it? so, the hardware connection would be AT89S52 to DRIVER IC to MOSFET? sorry, this part is really confusing ? The input voltage will be 12V from battery source and the B-B circuit will step down the voltage to 5V.

- - - Updated - - -

Thank you for your response. May I know what is the considerations to be made in choosing the correct driver IC? :thinker:
 

Hi,

Again, not something I know much about, but going on basic points, driver IC needs operating voltage (not absolute maximum ratings, but recommended operating range) and current capability at or preferably a little above circuit requirements, also power dissipation would be a "must know." If you are using an NMOS I think avoiding open collector type drivers would be a good idea. Maybe looking for a driver IC that can be interfaced directly to 3.3V output, if that's what AT89S52 does, but a transistor or logic level mosfet can do the level-shifting in that respect if the AT isn't a 5V output.
 

Hi,
Its always recommended to use the gate driver instead of using the microcontroller to use the N-Mosfet Gate driver.Make sure that,adding the series resistor(~1K) between the gate and microcontroller output.

Simply follow the rule of thumb for N-Channel MOS low side driver:

VGS>2.5V.If the source terminal is connected to GND then minimum gate voltage is 2.5V.Micro output voltage (min) is 2V for high.Hence gate driver is required.

Simply follow the rule of thumb for N-Channel MOS High side driver:
Gate voltage =Source voltage+Gate threshold voltage(VGS).

By the way how are you planning for feedback control and compensation ?.

Thanks
 

Drivers are selected depending on the switching current rating, switching speed, voltage etc.
TLP250 is a commonly used isolated driver.
 

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