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Calculate Inductor/MOSFET Power Dissipation

in buck DCDC converters

$Inductor$ $MOSFETs$ $L 0.33 ←$ $uH$ $RdsONupper 0.0035 ←$ $switching_MOSFET ($ $I_L_AV 18 ←$ $Amps$ $I_out ($ $RdsONlower 0.0025 ←$ $switching_MOSFET ($ $R_DC 0.003 ←$ $Ohms$

Parallel combination of the resistance of

$k_factor 2 ←$

multiple MOSFETs, if more than 1 used.

The k-factor is given by

$t_rise_upper 50 ←$ $ns$

Wurth Electronic for the

$t_rise_lower 38 ←$ $ns$

equation : P = k*f^1.274*(dIL/Imax)^1.9

$Gatecharge_upper 40 ←$ $nC$

For WE-PD shielded inductors: XXL - 13, XL

$Gatecharge_lower 58 ←$ $nC$

- 12, L - 7.2, M - 2, S - 1.6, XS - 1.1

$V_GS 10 ←$ $V$ $DCDC$ $f_SW 300 ←$ $kHz$ $V_in 3.3 ←$ $Volts$ $V_out 1 ←$ $Volts$ $T_per 1 f_SW 1000 * / ←$ $D V_out RdsONupper I_L_AV * + R_DC I_L_AV * + V_in R_DC I_L_AV * - RdsONlower I_L_AV * ( + RdsONupper I_L_AV * ( - / ←$ $T_per 3.3333 10 6 - ^ * =$ $D 0.346 =$ $T_on D T_per * ←$ $T_off 1 D - ( T_per * ←$ $T_on 1.1534 10 6 - ^ * =$ $T_off 2.1799 10 6 - ^ * =$ $dI_L V_in V_out - ( T_on * L 0.000001 * / ←$ $I_max I_L_AV dI_L 2 / + ←$ $dI_L 8.0392 =$ $P_d_on R_DC T_on / I_L_AV dI_L 2 / ( - dI_L t T_on / * ( + ( 2 ^ t 0 T_on int * ←$ $P_d_off R_DC T_off / I_L_AV dI_L 2 / ( + dI_L t 1 D - ( T_off * / * ( - ( 2 ^ t 0 T_off int * ←$

DC resistive dissipation:

$P_d_on 0.9882 =$ $P_ddc D P_d_on * 1 D - ( P_d_off * ( + ←$ $P_d_off 0.7936 =$ $P_ddc 0.861 =$

AC magnetic core dissipation:

$Pcore 0.001 k_factor * f_SW 1.274 ^ * dI_L I_max / ( 1.9 ^ * ←$ $Pcore 0.4221 =$ $P_d D P_d_on * 1 D - ( P_d_off * ( + Pcore + ←$

The Inductor dissipation is

Inductor Currents

$P_d 1.2831 =$ $Watts$ $dI_L 8.0392 =$ $I_max 22.0196 =$

DC power

$PdFETupperDC RdsONupper D * T_on / I_L_AV dI_L 2 / ( - dI_L t T_on / * ( + ( 2 ^ t 0 T_on int * ←$ $PdFETlowerDC RdsONlower 1 D - ( * T_off / I_L_AV dI_L 2 / ( + dI_L t 1 D - ( T_off * / * ( - ( 2 ^ t 0 T_off int * ←$ $PdFETupperDC 0.3989 =$ $PdFETlowerDC 0.4325 =$

Dynamic power

$Pdynupper V_out I_L_AV RdsONupper * ( - ( I_L_AV * t_rise_upper 0.000000002 * ( 2 T_per * / * ←$ $Pdynupper 0.253 =$ $Pdynlower V_out I_L_AV RdsONlower * ( - ( I_L_AV * t_rise_lower 0.000000002 * ( 2 T_per * / * ←$ $Pdynlower 0.196 =$ $PdFETupper PdFETupperDC Pdynupper + ←$ $PdFETlower PdFETlowerDC Pdynlower + ←$

The MOSFET. dissipation is

$PdFETupper 0.6519 =$ $Watts$ $PdFETlower 0.6285 =$ $Watts$

Gate driver Power dissipation

$Pgatedrive Gatecharge_upper V_GS * f_SW * 1000 * Gatecharge_lower V_GS * f_SW * 1000 * + 1000000000 / ←$

Gate driver Power dissipation, in DCDC controller

$Pgatedrive 0.294 =$ $Watts$