Electronics > Beginners
Understanding P Mosfet drive
Zero999:
--- Quote from: magic on March 25, 2019, 06:50:59 pm ---Zero999's circuit is roughly what I wanted to suggest.
With the Q4/Q2 totem pole, I think it might even be feasible to increase R2 and R3 10x to reduce power dissipation on Q3 which is currently 1W at 100V.
--- End quote ---
Yes, the resistor values can be increased to save power, but bear in mind it will start to slow it down, especially if you go too high. A low value capacitor in parallel with R2, say 47pF, can also help with the turn-on time. However it won't improve the off time. To help with that, more current gain is required. A Sziklai pair can be used for the upper transistor.
langwadt:
--- Quote from: ZeroResistance on March 25, 2019, 04:38:23 pm ---@Zero999 and @Ian.M
Thanks for the awesome circuits and sim's.
Are discretes the only way to go here? I mean aren't there any single chip driver for the P-channel fets?
--- End quote ---
https://www.mouser.dk/datasheet/2/609/LTC7001-1504282.pdf
Zero999:
--- Quote from: langwadt on March 25, 2019, 11:02:44 pm ---
--- Quote from: ZeroResistance on March 25, 2019, 04:38:23 pm ---@Zero999 and @Ian.M
Thanks for the awesome circuits and sim's.
Are discretes the only way to go here? I mean aren't there any single chip driver for the P-channel fets?
--- End quote ---
https://www.mouser.dk/datasheet/2/609/LTC7001-1504282.pdf
--- End quote ---
That's an N-MOSFET driver, not P-channel, but is a good idea and can do 100% duty cycle.
If the duty cycle is always under 100%, then a much cheaper MOSFET drive IC can be used. They're normally sold as half bridge drivers, but if only the high side is needed, the low side can be unused.
https://www.mouser.com/datasheet/2/268/mic4103-4-778767.pdf
https://www.onsemi.com/pub/Collateral/NCV51511-D.PDF
http://wiki.icub.org/misc/datasheets/LM5100A.pdf
https://www.maximintegrated.com/en/products/power/mosfet-drivers-controllers/MAX5063A.html
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