Really excellent explanations and insights! The engineering challenge of managing parallel MOSFETs was fascinating, I think I understand now why some cheap offshore inverter welding boxes with parallel MOSFETs are prone to blowing MOSFET chips.
Best explanation. I am only starting to use Power Mosfets now after a 40 year break from this hobby ( started with OC71 and OC45 transistors ) so thank you.
Lewis - Thanks for sharing your insightful experience! I did all the odd problems in six electrical engineering text books, but it helps to hear someone else's perspective. Fun fact: The video pace was perfect first time through. The second time I was able to soak it in at almost 2x speed! :) Good stuff!!
Maybe I missed it, but the beauty of parallel MOSFET is the positive temp coefficient which keeps one from hogging all the current. BJT transistors require negative feedback to keep one from hogging the current and going into thermal runaway. Here’s the trick, use drive voltage at least double the gate threshold, now your tc doesn’t matter. Use appropriate sized gate drive resistor for each MOSFET. First this is placed close to the gate to nullify gate inductance, and has to be small in value the faster you switch, but big enough not to overvdrive the driver. This is why a drive chip is recommended, especially to drive the parallel gate capacitance. Keep Rb resistor in to help pull gates low. If you are switching real fast go to GaN Fets.
Really good!! Thanks for sharing knowledge! Something I was thinking... It's usually done with N-Mosfets, because of the negative thermal associated resistence, ie, the more it heats up, the more resistivity it gets. It's the opposite for P-MOSFETs, correct me if I'm wrong.
Really excellent explanations and insights! The engineering challenge of managing parallel MOSFETs was fascinating, I think I understand now why some cheap offshore inverter welding boxes with parallel MOSFETs are prone to blowing MOSFET chips.
Very clear discussion of this tricky, misunderstood and often ignored issue. Spot on!
Best explanation. I am only starting to use Power Mosfets now after a 40 year break from this hobby ( started with OC71 and OC45 transistors ) so thank you.
I would like to like this video every time I see it. Now 4th time. Very clear explanations and solutions. Thank you Lewis.
Very good explanation, rapid switching and shunt of the gate capacitor charge is critical in maintaining even power sharing.
This is awesome, I love the clear explanation and strategies.
Excellent explanation. Much improved my understanding of MOSFETS. Thanks
Hi Lewis,
Nice and very useful video but its good that you could drawn out my thought in particular. Thx a lot.
Thank you for this tutorial on parallelling mosfets my application is to build a quarter bridge induction heater
Lewis - Thanks for sharing your insightful experience! I did all the odd problems in six electrical engineering text books, but it helps to hear someone else's perspective. Fun fact: The video pace was perfect first time through. The second time I was able to soak it in at almost 2x speed! :) Good stuff!!
Great job man. Thank you for sharing.
Excellent video. Very professional.
Very good and solid information ! Thanks !
In the circuit at
Maybe I missed it, but the beauty of parallel MOSFET is the positive temp coefficient which keeps one from hogging all the current. BJT transistors require negative feedback to keep one from hogging the current and going into thermal runaway. Here’s the trick, use drive voltage at least double the gate threshold, now your tc doesn’t matter. Use appropriate sized gate drive resistor for each MOSFET. First this is placed close to the gate to nullify gate inductance, and has to be small in value the faster you switch, but big enough not to overvdrive the driver. This is why a drive chip is recommended, especially to drive the parallel gate capacitance. Keep Rb resistor in to help pull gates low. If you are switching real fast go to GaN Fets.
excellent , i am myself an electtronics engeneer building an inverter , but i learned something , thank you
Really good!! Thanks for sharing knowledge! Something I was thinking... It's usually done with N-Mosfets, because of the negative thermal associated resistence, ie, the more it heats up, the more resistivity it gets. It's the opposite for P-MOSFETs, correct me if I'm wrong.
muy bien analisis y explicacion , gracias
Dear Lewis