Power Electronics

Diode Power Loss Calculator

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

This calculator computes total power dissipation and the resulting Junction Temperature (TJ). It helps you determine if you need a heatsink or should switch to a faster diode (like Schottky or SiC) to prevent overheating.

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
Visual representation of a diode package heating up based on calculated power loss

Diode Type Comparison

Choosing the right diode depends on the switching speed and voltage requirements.

Diode TypeVF (Drop)Qrr (Recovery)Best For
Standard Rectifier~1.0 VHigh (Slow)50/60Hz Mains
Fast Recovery~1.2 VMediumLow Freq SMPS
Schottky~0.4 – 0.7 VNear ZeroHigh Eff. SMPS
Silicon Carbide (SiC)~1.5 VZeroHigh Voltage SMPS

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 (Qrr dominates).

Total Power (Ptot)

Ptot = Pcond + Psw

Sum of all losses. This determines the heat.

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).