hi,
without any tweaking for driving circuit (like IR4427 or BJT buffer stage between mosfets and SG3525 outputs), you've to change only gate resistors according the mosfet gate capacitance.
Original 25n06 had about 1200pF.If capacitance is similar to 1200pF, or less, you could not change the original 470ohm gate resistor.
My experience said that 470ohm is too high. It works..but not well for me. you could use 100ohm for that gate capacitance.
Other mosfet with Vds>55V but with higher capacitance can be driven directly from SG3525. I think that until 3000pF each, SG3525 can drives
(500mA max output current).
Obviously, you've to reduce the gate resistor, for example to 47ohm for 2500pF mosfets.
If you don't change gate resistor, the mosfet cannot turn on fast..and the circuit won't work.
For me, another substitution is the pull-down resistor from gate to source. There are 2 of them, one each bank of mosfet (2150AM has 2 bank of 5 mosfets).
It provides fast discharge for the gate capacitance. I suggest to substitute original value (i don't remember) to 1-10k resistor. 1k for high capacitance mosfet (3000pF) and 10k for less capacitance.
That because if the gate capacitance isn't fully discharged..the next turn on makes damages the circuit won't work.
I usually use 1k resistor. It's not efficent in general, but provides good performance especially if you use SG3525 directly to drive mosfets.
In my SMPS designs i always use a BJT buffet between SG3525 and mosfets. Sometimes, for huge banks (high power), i use IR4427 that is an integrated mosfet buffer (max output current of 2A!!)
without any tweaking for driving circuit (like IR4427 or BJT buffer stage between mosfets and SG3525 outputs), you've to change only gate resistors according the mosfet gate capacitance.
Original 25n06 had about 1200pF.If capacitance is similar to 1200pF, or less, you could not change the original 470ohm gate resistor.
My experience said that 470ohm is too high. It works..but not well for me. you could use 100ohm for that gate capacitance.
Other mosfet with Vds>55V but with higher capacitance can be driven directly from SG3525. I think that until 3000pF each, SG3525 can drives
(500mA max output current).Obviously, you've to reduce the gate resistor, for example to 47ohm for 2500pF mosfets.
If you don't change gate resistor, the mosfet cannot turn on fast..and the circuit won't work.
For me, another substitution is the pull-down resistor from gate to source. There are 2 of them, one each bank of mosfet (2150AM has 2 bank of 5 mosfets).
It provides fast discharge for the gate capacitance. I suggest to substitute original value (i don't remember) to 1-10k resistor. 1k for high capacitance mosfet (3000pF) and 10k for less capacitance.
That because if the gate capacitance isn't fully discharged..the next turn on makes damages
the circuit won't work.I usually use 1k resistor. It's not efficent in general, but provides good performance especially if you use SG3525 directly to drive mosfets.
In my SMPS designs i always use a BJT buffet between SG3525 and mosfets. Sometimes, for huge banks (high power), i use IR4427 that is an integrated mosfet buffer (max output current of 2A!!)
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