Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Why is my homebrew controller blowing mosfets? [Solved]

electrowizard · 07-09-2010, 12:45 PM

Hi saand, thank you for the reply

I will do both! Here are some images to feast on.
I haven't been able to post them due to my low post count.

The first is from my last failure. Ch1 is Vgs and Ch2 is current as measured by hall effect sensor. Conversion is (CH2-2.59)/0.0015625

The second is an earlier gate drive. Shows input and output of my 6A MIC4420 driver chip. This iteration had no gate resistor or TVS.

Third picture is the current state of the controller with some annotations.
I wish I could have made the image larger, it is tough to read. My apologies.

I was the one who said the case may not get hot; I said it because of the huge copper heatsink it is sitting on; if the thermal resistance is low enough it may be difficult to detect a temperature increase. Or so my train of thought goes

In the past I have driven a 1A motor and my 42 ohm precharge resistor simultaneously. Nothing got hot, I'm sure I could have run that load indefinitely.
I will try the light load again first, then move to something larger as you suggest.
Yep, inductive spike is accounted for and the pair of diodes work at last test.

As for having my mosfet backwards... please check the third picture and confirm my sanity

Yep, parts are correct. All the screwups are mine :P

Thanks again saand!

I will post back later this afternoon with the new results, hopefully a little success.

07-09-2010, 12:45 PM	#9 (permalink)
electrowizard EcoModding Lurker Join Date: Jun 2010 Location: Fort Erie, Canada Posts: 19 Thanks: 1 Thanked 1 Time in 1 Post	Hi saand, thank you for the reply I will do both! Here are some images to feast on. I haven't been able to post them due to my low post count. The first is from my last failure. Ch1 is Vgs and Ch2 is current as measured by hall effect sensor. Conversion is (CH2-2.59)/0.0015625 The second is an earlier gate drive. Shows input and output of my 6A MIC4420 driver chip. This iteration had no gate resistor or TVS. Third picture is the current state of the controller with some annotations. I wish I could have made the image larger, it is tough to read. My apologies. I was the one who said the case may not get hot; I said it because of the huge copper heatsink it is sitting on; if the thermal resistance is low enough it may be difficult to detect a temperature increase. Or so my train of thought goes In the past I have driven a 1A motor and my 42 ohm precharge resistor simultaneously. Nothing got hot, I'm sure I could have run that load indefinitely. I will try the light load again first, then move to something larger as you suggest. Yep, inductive spike is accounted for and the pair of diodes work at last test. As for having my mosfet backwards... please check the third picture and confirm my sanity Yep, parts are correct. All the screwups are mine :P Thanks again saand! I will post back later this afternoon with the new results, hopefully a little success. Attached Thumbnails Last edited by electrowizard; 07-09-2010 at 04:09 PM..