75nf75 MOSFET to drive a DC motor

[Pheetuz]

Hi folks.

Im using a 75nf75 MOSFET to drive a DC motor, this motor can draw anywhere up to 60A when under load but should only draw between 2A and 6A when at steady state, basically i have a circuit for switching the direction of the motor - using relays but i am trying to use pulse width modulation to control the amount of power being fed to the motor, I have been successful in doing so.

The main problem that i am having is that my MOSFET drivers keep going kaput and giving out a constant voltage or sometimes even no voltage at all - usually the previous of the two.

I have two, voltage levels on this circuit, 18V and 5V that i can draw power from to supply the MOSFET driver and managed to make it work off the 5V supply earlier but the regulator i was using got rather hot so would prefer to supply it from the 18V line.

Basically, i was wondering if anyone knew any ICs that i could use to drive the MOSFET - relaible ones that arent going to fail on me, or a way of stopping the drivers from failing???

The driver i am using atm is a TC427.

Many thanks.

/Pete

 

[kabiru]

Re: MOSFET Drivers - please help me!

Hi. pls can you post your circute diagram pl's .

 

[siongboon]

Re: MOSFET Drivers - please help me!

Hi,

I check out on the datasheet for TC427 and realised that it is only supporting 1.5A.
Perhaps you should measure your motor rating again.
I hope that you are not running your motor from a regulated voltage source.

Best Regards,
Siong Boon

MODERATOR - SIGNATURE LINKS ARE NOT ALLOWED

 

[FvM]

Re: MOSFET Drivers - please help me!

75nf75's input capcitance isn't very high (3.8 nF) and can be driven by a TC427 without problems. A possible explanation for TC427
failure is, that you have high overvoltage spikes at the supply (is it the motor power supply?) that damage the driver. You may
want to add a protective zener diode near the driver with a current limiting resistance, or an additional 15V linear regulator to
supply the driver. You also risk to damage the MOSFET by feeding spikes exceeding 20V to the gate, by the way.

Before putting a new driver into the circuit, you should also verify, that the MOSFET is still operational and has no gate short.

 

[Pheetuz]

Re: MOSFET Drivers - please help me!

Cheers peeps.

Im running the motor from a battery with no current limiter on it so dont think thats the problem

I have got the circuit working again today, by putting a new TC427 in the circuit and running off of the 5V line that i am using for my PIC and it seems to be working ok atm, think it may be a problem when i connect the actual motor to the MOSFET and its drawing some serious current, think ill need more than 5V on the gate.

Makes sense that it could have been voltage spikes that have damaged the TC427 as i was running it from the motor drive line before when it stopped working, and now that im running it off of the regulated 5V line it works fine.

/Pete

 

[kabiru]

Re: MOSFET Drivers - please help me!

Hi, i think that what you need to control your motor the H-bridge arrangment using HI and LOW side gate drivers.