Alright, so today I’m gonna walk you through my little adventure with infineon MOSFETs. It was a bit of a rollercoaster, but hey, that’s how we learn, right?
It all started when I was trying to build this beefy power supply for my, uh, let’s just say “ambitious” project. I needed a MOSFET that could handle some serious current and voltage, and after digging around, the Infineon stuff seemed to be the way to go. They’ve got a good reputation, and the datasheets looked promising.
First things first, I hopped online and ordered a bunch of different Infineon MOSFETs. I figured I’d experiment a bit and see what worked best. I grabbed a couple of different voltage and current ratings, different packages (TO-220, TO-247 – you know, the usual suspects), and a few with different on-resistances (Rds(on)).
Once the parts arrived, I started breadboarding things. Yeah, I know, breadboarding high-power stuff isn’t the smartest idea, but I was just testing the waters, seeing if I could even get the basic circuit working. I started with a simple boost converter topology, just to get a feel for the MOSFET’s switching characteristics.
Now, here’s where things got interesting. I hooked everything up, turned on the power, and… nothing. Well, not nothing, but the MOSFET was getting HOT. Like, “burn your finger” hot. I immediately shut it down.
Okay, first thought: gate drive. Was I driving the MOSFET gate hard enough? I checked my gate drive circuit, made sure the voltage was sufficient (around 10V), and that the gate resistor wasn’t too big. Nope, everything seemed fine. I even swapped out the gate driver IC just to be sure. Still getting hot.
Next, I started suspecting shoot-through. This happens when both the high-side and low-side MOSFETs in a bridge are on at the same time, creating a dead short across the power supply. But I only had one MOSFET in my boost converter, so that wasn’t it.
Then it hit me: switching losses. The MOSFET was switching too slowly, spending too much time in the linear region, and dissipating a ton of power as heat. I looked back at the datasheet and realized I’d overlooked the gate charge (Qg) parameter. This tells you how much charge you need to pump into the gate to turn the MOSFET on and off. If you don’t provide enough current to quickly charge and discharge the gate capacitance, you’re gonna have a bad time.
I decreased the gate resistor value to provide more current to charge and discharge the gate. This helped a little, but the MOSFET was still running hotter than I liked.
So, I tried a different MOSFET with a lower gate charge. This made a huge difference! The switching losses went down significantly, and the MOSFET ran much cooler. Lesson learned: pay attention to the gate charge!
After that, I moved from the breadboard to a proper PCB. I designed a small board with good thermal management (big copper pours, heatsink mounting holes, the works). This helped even more. I also added a snubber circuit (a resistor and capacitor in series across the MOSFET) to damp out voltage ringing during switching, which further reduced stress on the MOSFET.
Finally, after a lot of trial and error, I got the Infineon MOSFET running nice and cool in my power supply. It’s been humming along for weeks now, powering my “ambitious” project without any issues.
Key Takeaways:
- Read the datasheet carefully, especially the gate charge (Qg) parameter.
- Make sure your gate drive circuit can provide enough current to quickly charge and discharge the gate capacitance.
- Use good thermal management practices (heatsinks, copper pours) to keep the MOSFET cool.
- Consider using a snubber circuit to damp out voltage ringing.
It was a fun learning experience. Infineon MOSFETs are great devices, but you gotta treat ’em right!