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arnolde · 06-05-2009, 08:28 AM

I was just working through this paper http://powerelectronics.com/mag/606PET25.pdf and writing an Excel sheet for all the calculations. It seems that the lower the gate current is, the higher the switching power loss of the MOSFET? (See Page 52, Eq.12) In my case, if I did everything right, the loss is 60W with 100mA gate current and only 6W with 1A gate current! Now the NE555 probably cant serve with 1A can it? Maybe thats why most people use special MOSFET driver chips, which take a TTL input and whomps the MOSFET up and down at 1A...

Another interesting thing I noticed, is that my output caps were way overdimensioned. Since my voltage difference Vin-Vout is only max 100V and the current is <6A, and I can allow several volts of ripple, the formulas only call for 17µF! That will make a nice snug design :-)

06-05-2009, 08:28 AM	#84 (permalink)
arnolde EcoModding Lurker Join Date: May 2009 Location: Germany Posts: 21 Thanks: 0 Thanked 0 Times in 0 Posts	I was just working through this paper http://powerelectronics.com/mag/606PET25.pdf and writing an Excel sheet for all the calculations. It seems that the lower the gate current is, the higher the switching power loss of the MOSFET? (See Page 52, Eq.12) In my case, if I did everything right, the loss is 60W with 100mA gate current and only 6W with 1A gate current! Now the NE555 probably cant serve with 1A can it? Maybe thats why most people use special MOSFET driver chips, which take a TTL input and whomps the MOSFET up and down at 1A... Another interesting thing I noticed, is that my output caps were way overdimensioned. Since my voltage difference Vin-Vout is only max 100V and the current is <6A, and I can allow several volts of ripple, the formulas only call for 17µF! That will make a nice snug design :-) Last edited by arnolde; 06-05-2009 at 08:53 AM..