Hi Team,
My customer Preh has a question about the UCC5350-Q1:
How to calculate the RMS current for gate drivers.
4x Gate Driver UCC5530 for H-bridge control are in use and a Gate Driver will each drive an IGBT, which each IGBT 650nC gate charge has.
The switching frequency with approx. 50% duty cycle is f_sw=60kHz.
The 15V_supply supplies VCC2 at the gate driver. A transformer inductance must be dimensioned at the input of the 15V_supply and for this I need the RMS current.
1) is the RMS current calculated like this?
t_on=1/(f_sw/2)=8,3µs
I_RMS_per_driver= Q/t_on =650nC*8,3µs=78mA
I_RMS_total:= I_RMS_per_driver*2 = 156mA (2x gate drivers activated simultaneously)
2) or so?
Charge is converted as a capacitor.
C=Q/V=650nC/15V=43,3nF
Calculate Tau:
=1.365ohm+3.75ohm+2.5ohm=7.6ohm
Tau_on_nom=Ron_total_nom*C=310,2ns
The current curve during capacitor charging:
Peak current I_OH_nom is calculated as in the data sheet=15V/7.6ohm=1.97Ampere
Then the RMS current is calculated for the t_on duration:
I_RMS_total=IG_on_nom_RMS*2 = 537mA (2x gate drivers activated simultaneously)
Thanks and best regards
David
