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I want to create dc boost convertro based on microcontroller. If I only use low-side switch, can I just use logiclevel NFET instead of using gate-driver? I've planed to replace ir2110 + IRF540 with IRLZ44NPBF with 5V 64kHz 8-bit PWM.

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  • \$\begingroup\$ No, as switching at 64Khz needs 1A peak current to the MOSFET gate. But microcontrollers can only deliver a few mA, so the Mosfet gate voltage rise time will be huge and it will heat a lot. \$\endgroup\$
    – Deepak
    Commented Oct 5, 2020 at 17:20
  • \$\begingroup\$ To drive it you can use any low-side Mosfet driver available online. \$\endgroup\$
    – Deepak
    Commented Oct 5, 2020 at 17:20

3 Answers 3

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Controlled directly from the CPU, the latency and switching loss will also be high. driver1

A simple Gate driver solves the problem and it can work from 5V: driver2

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  • \$\begingroup\$ Can I use bjt totempole instead? \$\endgroup\$
    – M lab
    Commented Oct 5, 2020 at 16:18
  • \$\begingroup\$ Yes, you can. It will be a little more complicated and high current transistors are needed for high speed. \$\endgroup\$
    – csabahu
    Commented Oct 5, 2020 at 16:25
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You still need some sort of gate driver for high switching speed and low switching losses/heat. They aren't just to drive a floating MOSFET. Very powerful low side only gate driver ICs exist.

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  • \$\begingroup\$ Then, can I just use bjt as totem-pole driver instead? \$\endgroup\$
    – M lab
    Commented Oct 5, 2020 at 14:33
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    \$\begingroup\$ Yes, you can... \$\endgroup\$
    – DKNguyen
    Commented Oct 5, 2020 at 14:34
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It would be possible to use a N-Channel mosfet to drive a low side switch for a boost converter. The issue you may run into is the pull up resistor on the high side of the driver mosfet could be too high which may take too long to turn the switch on. The turn off time won't be affected since the gate resistance is only equal to the gate resistor. The turn on will be equal to the gate resistor + the pull up resistor. If the pull up resistor is low enough, then you may not have any problems turning on fast enough. But you can only go so low with the pull up resistor before there's too much current going through the driver mosfet.

I would recommend a totem-pole type driver. Which I would use a gate driver for this instead of individual components. The gate driver won't take up very much room and is very simple to implement.

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