MOSFET Power Loss Calculator

This MOSFET power loss calculator is used to estimate the power dissipation (losses) of a Metal Oxide Semiconductor Field Effect Transistor (MOSFET). The calculator computes the:

• Conduction losses due to the flow of current I_DS when the MOSFET is in the "on" state
• Switching losses which occur during the transistion between the "on" and "off" states of the MOSFET
• Gate charge losses which are incurred during the charging of the gate.

Reference the article Introduction to MOSFET Switching Losses for a further explaination of these losses and the equations used in the calculator.

This calculator will also determine the heat sink thermal resistance required to achieve a specified MOSFET junction temperature based on the total MOSFET power losses calculated.

Power Losses

Heat Sink

Calculate

I_DS: Amps

R_DS(on): mOhms

D: %

f_SW: Hz

Include Switching Losses

V_IN: V

t_r: sec

t_f: sec

Include Gate Charge Losses

Q_G: C

V_GS: V

Equations used for MOSFET power loss calculations

Conduction Losses

$$P_{on}=I_{DS}^2\times R_{DS(on)}\times D$$

where:

Pon	is the conduction power losses
IDS	is the RMS current through the MOSFET when it's on
RDS(on)	is the drain to source resistance
D	is the duty cycle of the MOSFET with a value greater than 0 and less or equal to 100%. The duty cycle is 100% if the MOSFET is always on.

Switching Losses

$$P_{sw}=\frac{1}{2}\times V_{IN}\times I_{DS}\times \left( t_{r}+t_{f} \right)\times f_{sw}$$

where:

Psw	is the switching power losses
VIN	is the voltage used to drive the current through the MOSFET
Iout	is the current through the MOSFET
tr	is the rise time
tf	is the fall time
fsw	is the switching frequency

Gate Charge Losses

$$P_{GC}=Q_{G}\times V_{GS}\times f_{sw}$$

where:

PGC	is the gate-charge power losses
VGS	is the gate-source voltage
QG	is the total gate charge required by the MOSFET

Calculate required heat sink thermal resistance

T_amb: °C

T_j(max): °C

R_{th jc}: °C/W

Thermal interface material

t_int: mm

k_int: W/(m·K)

W_M: mm

L_M: mm

Results

Oops....An error occured during the calculations. Check your inputs.

W

Total MOSFET Power Losses

Conduction Power Loss

W

Switching Power Loss

W

Gate Charge Power Loss

W

°C/W

Required Heat Sink Thermal Resistance

T_ambient

°C

T_junction

°C