Project: MOSFET Driver v1 (Product?)

Today I received the first of a couple batches of PCBs from OSH Park. This set is a simple MOSFET w/ driver. The MOSFET can be logic level driven and all my testing was done at 5VDC however the driver had a wide voltage range so running this at 9V or 12V should present no issues (16V max! VGS). I do have a few minor adjustments I want to add (silk screen additions and adjustments). I built this board as an electric scooter motor drive and I tested it with the motor I was interested in using and thankfully all testing worked out well including loading my power supply at max load for over an hour straight 🙂 This board can be used for an assortment of load control applications.

MOSFET Driver v1

The build was easy enough, next board I think I’ll just skip the chipquik and stick to straight soldering iron… and I think I also “figured out” the trick to solder the heat sink without making too much of a mess.

MOSFET Driver v1

I tested the load for 60 minutes at 66% duty cycle and 1.5KHz PWM with total load at 140watts (45Volts 3.1 Amps)..  the heat sink temperature on the MOSFET raised from ambient (78 deg F) to 90.7 deg F (32.3 deg C) steady for an hour.  The MOSFET is rated for 55V (max) at 30 amps but the board isn’t designed to handle that load. I used 50mil power traces which is roughly 3 amp handling according to the google machine; 5A if you don’t mind a 40 deg C rise (though there is a fan) so I’ll call this a 140W MOSFET board (47×3). I personally feel I could squeeze more current out of this in short bursts but I would need to do more testing.. and I can’t promise anything along those lines. The PWM signal was generated and directly fed from a PIC 18F16K22 microcontroller running @ 5V. You’re NOT going to be able to drive this at 3.3V.

 

Fresh off the soldering iron!
Fresh off the soldering iron!
Driving an electric scooter motor. Note the diode for flyback near the bottom of the photo just hanging out. The flyback is a must in this application.
Driving an electric scooter motor. Note the diode for flyback near the bottom of the photo just hanging out. The flyback diode is a must in this application.
MOSFET PWM signal vs VDSS
MOSFET PWM signal vs VDSS

 

I will likely stick a 75VDSS MOSFET in the next revision…

.. I’m considering selling these on Tindie. If you’re interested in getting on of these “BETA” boards at cost let me know before they’re gone.

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