i want to build induction furnace
i parallel 16 power mosfet(irfp460) 8 fet for high side and 8 fet for low side for half bridge
i use ir2104s and bd139 and bd140 totem pole for drive mosfet.
According to irfp460 datasheet, Total Gate Charge=210 nc and td(on)=18 and tr=59
td(on)+tr=77ns then 210/77=2.7 amp. V=IR then R=6.6 and i use 6.8 ohm resistor for each gate and use 10 ohm for bd139 and bd140 bias.
i see the output of totem pole with oscop and its nice and clean square wave without any noise or ringing. like this
but when i connect output of totem pole to high side mosfet the output is ringing and have Too much noise with 12 volt switching power supply without any load for test.
freq is 20khz
why this is happen?
how to reduce or Eliminate this ringing and noise?