12v led driver circuit using irfz44n

Thread Starter

jimit5

Joined Sep 26, 2016
19
I'm trying to control an 12v rgb led strip with an nodemcu and irfz44n from what I read online and checked the nodemcu is not capable of driving the irfz44n directly so to solve this im using an pnp transistor (bc557) that controls the mosfet everything seems to be working just wanted to know if its the right way to do it or is there a better way to do the same
 

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Sensacell

Joined Jun 19, 2012
2,903
You don't specify if the MCU is 5V or 3.3 V- or if this is static switching or PWM control?

You are generally on the right track, but the 10K gate pullup will result in a very slow turn-on time and high power dissipation if the switching frequency is high.
You could make that resistor much smaller to speed things up, try 220 ohms.

A simpler approach is to use a MOSFET with a lower gate threshold and run it directly from the IO pin with a small series resistor ~ 100 ohms.
 

Thread Starter

jimit5

Joined Sep 26, 2016
19
You don't specify if the MCU is 5V or 3.3 V- or if this is static switching or PWM control?

You are generally on the right track, but the 10K gate pullup will result in a very slow turn-on time and high power dissipation if the switching frequency is high.
You could make that resistor much smaller to speed things up, try 220 ohms.

A simpler approach is to use a MOSFET with a lower gate threshold and run it directly from the IO pin with a small series resistor ~ 100 ohms.
the mcu is 3.3v and im using pwm control will try 220ohms thanks
 

crutschow

Joined Mar 14, 2008
27,894
The voltage from the mcu and Vcc must be the same for your circuit to work properly, since your circuit applies the Vcc voltage to the mcu through the base resistor and the emitter-base junction (which looks like a diode) .

If Vcc is higher, then you need to use an NPN driver, not a PNP.

Depending upon the frequency of the PWM you may also need to reduce the value of the resistor.
 

Audioguru again

Joined Oct 21, 2019
3,632
The datasheet for the IRFZ44 shows that some of them will barely turn on when the Vgs (threshold voltage) is 4V but all of them will fully turn on when Vgs is 10V.

An IRLZ44 has some of them barely turned on when Vgs (threshold voltage) is 2V and all of them are almost fully turned on when Vgs is 4V.

With your Vgs of only 3.3V then you must teat many Mosfets to find one that turns on with such a low Vgs.
 
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