MOSFET Driver

280

03:09:38

I used this circuit to control a MOSFET via PWM with a microcontroler, but the output of 5 volts and max current isn't enough for high power loads, so i used two transistors to be able to use a higher voltage, but the MOSFET can't handle over 20 volts... So using a resistor voltage divider and storing in a capacitor to be able to deliver a high enough current peak so the MOSFET can turn on fast enough and stay on.
If you have sugestions to beef up this circuit, leave it on comments.

published 8 years ago

hurz

8 years ago

Only thing is, your mosfet model does not fit well the reality. Depends on which mosfet you have used. But in sim you drop to much voltage across drain and source while it source 3A. Which results to about 6W power loss across the Fet and would burn it without heatsink, even the biggest mosfet! The divider voltage is a little to high in impedance and especialy in 100% pwm on it will drop below 10V. I made some little changes http://everycircuit.com/circuit/4713199926771712

zanini007

8 years ago

I made a few changes and tested on a protoboard using an osciloscope and a motor. Changing only the voltage divider still drops the voltage when the MOSFET turn on, i had no choice but add a transistor as a voltage follower and works fine even up to 1KHz. By the way, MOSFETs are very confusing on this app..

hurz

8 years ago

If you lower the impedance of the gate voltage divider by use of an extra transistor, you can also increase the resistors of the reference voltage divider by factor 10 or more, to lower idle power. Keep it up!

nikisalli

8 years ago

Isn't a push pull better then this?

hurz

8 years ago

No, cuz for push you need a higher voltage then 5V

nikisalli

8 years ago

You put another transistor with a pullup resistor to drive the push pull?

hurz

8 years ago

Right, but then its a different circuit then this and would need an extra transistor.

hurz

8 years ago

Stop, you probably mean this way http://everycircuit.com/circuit/4651739506802688

zanini007

8 years ago

With this settings of push and pull hurz suggested, the gate voltage drops to under 5 volts...

zanini007

8 years ago

I changed the circuit a little, seems to work fine, going to test under high freq...

zanini007

8 years ago

Nevermind... i was using a motor that draws too much current at startup and my powersupply couldn't handle it, so in the end, both worked very well for my aplications, also i'm keeping this one as it is, for future reference. I also add a RG in order to reduce reverse peak voltage (using inductive loads) The new one: http://everycircuit.com/circuit/4820068376772608

hurz

8 years ago

Set the sim-evironment to the correct time domain to see how your circut really behaves. http://everycircuit.com/circuit/4734998227976192 And keep it up!

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