Hi there.
As the title says, I am having trouble with some mosfets getting really hot, like 115 C.
I am using a picaxe (14m) with the pwmout command to drive the mosfets. The mosfet that I am using is a STP35NF10 from STmicroelectronics. The digikey part # is 497-2645-5-ND. The datasheet can be found here:
http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=497&M=STP35NF10
The mosfets are rated at 100V and 40A.
I am using 2 of these mosfets to power a blower motor in an automobile. The max current draw is about 10A.
I use the pwmout command with a period of 49 and the duty varies from 180- 200. This allows for operation at 20000 hz so that there is no audible whining from the motor.
The tabs of the mosfets are connected to an aluminum sheet as a heat sink (3x5 inches). When the motor is running, the sheet gets very hot and will boil water in the vicinity of the mosfets.
I originally used only one of these mosfets, but it got so hot that it desoldered itself from my circuit board, so I added the second one. I have also run the pwmout command at a lower frequency (12000hz) but there was an audible whine at lower speeds and the mosfets still got just as hot.
So after that longwinded explanation, does anyone have any suggestions on what I can do to get cooler temps. Am I using the wrong mosfet for my application?
Thanks in advance for your assistance!
As the title says, I am having trouble with some mosfets getting really hot, like 115 C.
I am using a picaxe (14m) with the pwmout command to drive the mosfets. The mosfet that I am using is a STP35NF10 from STmicroelectronics. The digikey part # is 497-2645-5-ND. The datasheet can be found here:
http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=497&M=STP35NF10
The mosfets are rated at 100V and 40A.
I am using 2 of these mosfets to power a blower motor in an automobile. The max current draw is about 10A.
I use the pwmout command with a period of 49 and the duty varies from 180- 200. This allows for operation at 20000 hz so that there is no audible whining from the motor.
The tabs of the mosfets are connected to an aluminum sheet as a heat sink (3x5 inches). When the motor is running, the sheet gets very hot and will boil water in the vicinity of the mosfets.
I originally used only one of these mosfets, but it got so hot that it desoldered itself from my circuit board, so I added the second one. I have also run the pwmout command at a lower frequency (12000hz) but there was an audible whine at lower speeds and the mosfets still got just as hot.
So after that longwinded explanation, does anyone have any suggestions on what I can do to get cooler temps. Am I using the wrong mosfet for my application?
Thanks in advance for your assistance!