Power Electronics

Diode Loss & Thermal Calculator

Diodes generate heat from two sources: Conduction Loss (due to forward voltage drop) and Switching Loss (due to reverse recovery charge).

This calculator computes the total power dissipation and the resulting Junction Temperature (TJ). It helps you determine if a heatsink or a faster diode (like Schottky/SiC) is required.

Forward Conduction

Static
V
A
0–1

Switching & Recovery

Dynamic
V

Thermal Specs

°C/W
°C

Power Analysis

Result
Total Dissipation (Ptot)
— W
Cond: — Sw: —
Junction Temp (TJ)
— °C
Enter parameters

Formulas Explained

Conduction Loss (Pcond)

Pcond = VF × IF × D

Energy lost while the diode is conducting current. D is duty cycle.

Switching Loss (Psw)

Psw ≈ Qrr × VR × fsw

Energy lost recovering from reverse bias. Critical at high frequencies.

Total Power (Ptot)

Ptot = Pcond + Psw

Sum of all losses.

Junction Temp (TJ)

TJ = Tamb + (Ptot × RθJA)

Must remain below max rating (usually 150°C or 175°C).

How to Use

Analyze diode efficiency in 3 steps.

1

Set Conduction Params

Enter VF (Forward Voltage) and IF (Current). Check the Duty Cycle if the diode isn’t always on.

2

Add Switching Info

If switching at high speed, enter the Frequency and Reverse Recovery Charge (Qrr) from the datasheet.

3

Check Thermal Safety

Input the Thermal Resistance. If the Diode turns RED, it’s overheating. Try a lower Qrr diode (like Schottky).