April 2012

Doc ID 022588 Rev 1

1/10

AN4021

Application note

Calculation of reverse losses in a power diode

Introduction

This application note explains how to calculate reverse losses in a power diode by taking

the leakage current.

The ideal current and voltage waveforms of an ultrafast diode in a power supply system

during a switching cycle are illustrated in Figure 1.

Figure 1.

Ideal current and voltage waveforms of a diode in a switch mode power

supply

The reverse losses in a diode are the result of a reverse bias applied on the diode. They are

temperature. Most of time, the reverse losses are negligible for bipolar and silicon carbide

diodes. For silicon Schottky structured diodes, these losses should be accurately estimated

as they are the main origin of the thermal runaway risk phenomenon (See AN1542).

t

t

0

0

F

Switching frequency

T

Switching period

Duty cycle

T

Duration of diode conduction

Maximum forward current

Minimum forward current

Forward voltage

Reverse voltage

sw

sw

sw

δ

δ·

V

D(t)

I

D(t)

I

D(t)

I

Max

I

Min

V

F

I

Min

V

D(t)

I

Max

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