Motor Driver

[shero2010]

Dear all

i want to design motor driver speed and direction using power mosfet, 24v and 14 amp.
mosfet used irf530, how i can select Rg. "Resistor on gate".
when i put 1k ohm and V input 24 from gate side the mosfet was damaged.

 

[3v0]

After you left chat Dark2012 suggested
Build an H-Bridge Motor Control with Power MOSFETS (Tutorial)

 

[misterT]

What kind of gate driver did you use? Show us some schematics.

- If you are building an H-bridge the important thing is that the MOSFET is turning fully on and off fast.
- Big gate resistor slows down the switching time. Use a small resistor 10...100 ohms.
- Check that your gate voltage (Vgs) is high enough to turn the mosfet fully on. It should be 10...15 volts.
- Check that your mosfet can take the 14 amps. Use a big heat sink to cool the mosfet.

 

[shero2010]

thank, i will try to upload my sch.

 

[shero2010]

attached sch. "first design" but when i connected the motor the driver was damaged

 

[misterT]

Uh, there is so much wrong in that design. Most severe problem are the high side N-channel mosfets (Q1 and Q2). Think of the gate voltage that is needed to turn the mosfet ON.. you need the gate voltage to be at least 10 volts above the source and that is not happening in your circuit. When Q1 or Q2 is ON, the source voltage is 24V. That means you need the gate voltage to be at least 34V relative to ground. Easiest way to fix that is to use P-channel mosfets (IRF9540) on the high side and redesign the gate driver.

Also a software error in your PIC can easily burn the h-bridge. If you accidentally turn Q1 and Q3 ON at the same time.. actually I can't see how you could avoid that. At least you should turn the Q5 OFF every time you switch direction and make sure the Q5 is also OFF when the microcontroller resets.

Using the Q5 as PWM switcher is a bad design also. When Q5 is OFF, the source voltage at Q3 and Q4 can go up to 24V and if your gate voltage is at 0V when that happens you are exceeding the ±20V Vgs limit. Actually you are exceeding that limit also when the Q5 is ON.