| Electronics > Projects, Designs, and Technical Stuff |
| Run into a wall (3180 fet drive circuit) |
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| zap!:
Hello Everyone! Long time browser first time posting. I've in the very green hobby category so please have patience :) I'm attempting to build an Arduino controlled buck converter and ordered up some parts. The first step which is where i'm stuck on is testing the fet drive chip (hcpl-3180). I've built the attached schematic but am having no luck having the test point switch between the 12v rail and Vee(gnd). The test point remains locked to Vee. I've tried several different 3180s to see if it was a defect. Tried Arduino duty at different amounts (0% 25% 50% 75% 100%), no luck. What am I doing wrong here - I'm sure it's obvious and elementary but I'm stuck. Thanks for any help |
| MasterT:
Can you switch it on/off w/o arduino, jumping a wire to pin 2 & +5V? |
| zap!:
--- Quote from: MasterT on September 03, 2019, 06:44:49 pm ---Can you switch it on/off w/o arduino, jumping a wire to pin 2 & +5V? --- End quote --- Thanks for the suggestion! I figured it out! The issue was with the 12v rail and the data sheet misleading me. I turned the 12v rail up to 13v and it works now so clearly the stated "UVLO+ of 7.9v" and "UVLO- of 7.4" are not true or i'm testing it at radically different conditions. With that kinda figured out is there a way to have that supply voltage be closer to 10v without cutting out (UVLO)? |
| T3sl4co1l:
What's the 330 ohm for? Tim |
| zap!:
--- Quote from: T3sl4co1l on September 03, 2019, 08:00:59 pm ---What's the 330 ohm for? Tim --- End quote --- I guess it was to limit current... i took it out. I have the whole circuit working but am not sure if the fet is being driven properly - it's getting quite warm (70ÂșC) with no heatsink. is this a reasonable temp? it's being run at 90% duty with an output of 14.2v I've been reading and there seems to be a fair amount of gate drive messing around to get the fet to stay cool/efficient. any pointers as to where to start? edit: to add info i'm using the IRF4905 p channel fet and the low side is a .213Vf diode which is staying totally cool |
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