Dear friends. I bought VNH3SP30 a few years a go from pololu and recently used them in my self design board.
I want to drive it by 3~5 KHz PWM freq. based on its spec. (Up to 10KHz as mentioned in its Datasheet). but when apply upper 1KHz PWM freq. to this chip, it get hot as if its solder melts.(by the way i also install a heatsink).
as you know driving motor under 1KHz freq. make a bad sound.
Please help me kindly what should i do?
thank you
Hi.
If your driver got hot enough to melt solder, I suspect it is probably damaged. Could you post picture of the driver in your setup that show how it was connected? Also, could you post close up pictures that show the melted solder and any other damage?
Why do you think the PWM frequency is linked to your driver overheating? Did you test the driver with other PWM frequencies? Did the driver ever work for you?
-Claire
Dear Claire,
Thanks for your response, here is our driver schematic:
We connect INA to +5V and INB to GND (for CW direction) and PWM pin to PWM output of a microcontroller, also connect +5V pin to five regulated voltage to enable VNH.
We have tested the driver in 6 below frequencies:
245, 488, 978, 1.96K, 3.9K, 7.8K Hz. Our observation is as follows:
- Power dissipation (VNH Chip temperature) depends on two parameters:
– PWM frequency: by increasing the frequency of PWM signal from 245Hz to 7.8KHz, power dissipation increased (increasing switching dissipation).
– Duty cycle of PWM signal (Motor Speed): in each frequency when we decrease duty cycle of PWM, the power dissipation (VNH Chip temperature) increased significantly. The effect of this parameter is very high but we don’t have any reasonable cause for that.
- In 7.8KHz PWM freq. and low duty cycle (10%) the chip temperature increased terribly in a way that the soldering of VNH pad is melt so that we pick it up from PCB!!! and after that we solder it again and VNH doesn’t damage!!!
Finally, we decide to drive VNH in 245Hz freq. (despite of its mentioned frequency capability in its datasheet- up to 10KHz) because in other freq. at the low duty cycles (below 10%) the VNH temperature isn’t reasonable.
As you know 245Hz PWM freq. isn’t a good freq. for driving motor because of mechanical resonations and producing annoying sounds. Our experimental work shows that the minimum best freq. is up to 20KHz, so what could we do to solve our problem?
Thanks a lot.
I agree that the heat increasing with lower duty cycles seems strange. If that is the case, the board should get hottest when PWM is just constantly held low, though with PWM held low the motor should not be driven at all so normally this would take almost no power. Could you try connecting PWM directly to ground (with the rest of your setup the same and at 245Hz) and see if the driver still heats up? If so, does it get hotter than 50% duty cycle and is that hotter than connecting PWM directly to 5V?
Were your tests done with a motor connected? If so, could you post a link to its datasheet or product page? What input voltage are you using? Could you post pictures of your actual setup that show all connections and both sides of the board?
-Claire