# Blog

## Online MOSFET Power Loss/Dissipation Calculator and Guide for Engineers

In the dynamic world of power electronics, understanding and minimizing power losses in Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) is crucial for optimizing efficiency and performance. This guide explains the basics of calculating various types of power losses in MOSFETs, including conduction, switching, reverse recovery, deadtime, and gate charge losses.

### MOSFET Power Loss Calculator

Parameter Value Units Description
Vbus Volts Bus voltage
Current Amps Current
f_sw Switching frequency
Vgate_drive Volts Gate drive voltage
Rds(on) Drain-to-source on resistance
Qg Gate charge total
Td(on) Turnon delay time
Tr Rise time
Td(off) Turn-off delay
Tf Fall time
Qrr Reverse recovery charge
Vsd Volts Body diode Forward Voltage
Conduction Loss (P_cond)   Watts Power loss due to conduction
Switching Loss (P_sw)   Watts Power loss during switching
Reverse Recovery Loss (P_rr)   Watts Power loss due to reverse recovery of the body diode
Gate Charge Loss (P_gate)   Watts Power loss due to gate charge
Total MOSFET Power Loss   Watts Total power loss in MOSFET

## 1. Conduction Loss (P_cond)

Conduction loss occurs when the MOSFET is in the 'on' state and current flows through its channel. It's calculated using the formula:
`P_cond = Current^2 × Rds(on)`
where `Current` is the drain-source current and `Rds(on)` is the on-resistance of the MOSFET.

## 2. Switching Loss (P_sw)

Switching loss happens during the transition between the 'on' and 'off' states. The energy dissipated in each switching event is proportional to the bus voltage `Vbus`, current `Current`, and the sum of rise and fall times `(Tr + Tf)`. The formula is:
`P_sw = 0.5 × Vbus × Current × (Tr + Tf) × f_sw`

## 3. Reverse Recovery Loss (P_rr)

This loss is associated with the reverse recovery charge `Qrr` of the internal diode in the MOSFET and is significant in high-frequency applications. It's calculated as:
`P_rr = Qrr × Vbus × f_sw`

Deadtime loss occurs due to the body diode conduction during the interval when both the high-side and low-side MOSFETs are off. It's a function of the body diode forward voltage drop `Vsd`, current `Current`, and the sum of turn-on and turn-off delays `(Td(on) + Td(off))`. The calculation is:
`P_dt = 2 × Vsd × Current × (Td(on) + Td(off)) × f_sw`

## 5. Gate Charge Loss (P_gate)

Gate charge loss accounts for the energy required to charge and discharge the gate capacitance of the MOSFET. The total energy for one complete cycle of operation is double the energy required for a single charge or discharge. The formula for calculating this loss is:
`P_gate = 2 × (Qg × Vgate_drive) × f_sw`

## Summary

This guide provides an introduction to the power dissipation characteristics in MOSFETs under various operating conditions. These calculations are helpful for anyone looking to understand the efficiency and performance of MOSFET-based power electronic systems.

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