Gonna pwm-control a 12v dc motor with 2.3Ohm resistance between pins at pwm frequency of 500Hz (actually, it's an electronic throttle).
is it viable at all without special drivers, just that IRF540N fet connected directly to arduino? why should I add a driver to that circuit? Should I be using an optocoupler? What are the benefits/disadvantages of using/not using a driver?
Hy kokoko,
Welcome to ETO. I see you are from Russia; which part? Russia is a big country. Also care to put your location in your user window on the left of your posts.
One of the problems with driving a MOSFET gate with an Arduino is that the maximum current allowed from each Arduino input/output pin is 40mA and the total output current of all pins combined is limited to 200mA. As MOSFET gates have a very high effective input capacitance of 1nF to 20nF, there is a problem when you drive MOSFET gates directly; because the edges of the Arduino output are very fast, the drive current will be very high to charge and discharge the MOSFET gate capacitance. You will normally get away with directly turning a MOSFET on and off occasionally, but the trouble is that PWM is continuous so you will be stressing the Arduino microcontroller chip.
So for PWM you need a gate driver circuit between the Arduino and the MOSFET gate. This can either be a discrete circuit or an integrated circuit
Gate drivers have other advantages:
(1) Gate drivers have a high current capability, typically 1A to 4A, to charge and discharge MOSFET gate capacitances fast. This reduces MOSFET switching times and thus reduces the MOSFET power dissipation which in turn gives the MOSFETs an easier time and increases efficiency.
(2) Gate drivers can also generate a high gate drive voltage which gives you the option of using a wider range of MOSFETs, rather than just logic-level MOSFETs. This advantage is especially important with the Arduino Due which, although a far superior microcontroller in all other respects, has less drive current (10mA I think) and only 3.3V drive voltage.
In your case, a gate driver could generate a gate drive voltage of 12V simply without any complex additional circuitry. This would allow an IRF540N NMOSFET to be used.
(3) The other major advantage of gate drivers is that they are designed to handle the difficult conditions present at MOSFET gates when MOSFETs are driving nasty loads: noisy, inductive, capacitive. This is especially relevant in an industrial, automobile, and motorcycle environment.
Isolation: opto, capacitive, inductive, between the Arduino and the MOSFET, in the same way as (3) above, isolates the Arduino supplies from what may be a nasty 12V supply with loads of noise and hash, especially on the critical ground line.
You can get direct coupled and isolated gate driver chips; both are freely available, easy to use, and reasonably priced.
By the way, I would advise dropping your PWM frequency from 500Hz to 50Hz to minimize switching losses and maximize efficiency.
spec