Conduction losses: basic equations

AN604

6/12

Doc ID 3607 Rev 3

2

Conduction losses: basic equations

Conduction losses are the average dissipated power in the diode during the forward

conduction phase given in Equation 10:

Equation 10

Equation 10 can also be written as follows:

Equation 11

current flowing through the diode.

Note:

In case of a square waveform, a short formula can be used to calculate conduction losses:

Equation 12

2.1

Application parameters: average and rms currents

The average and rms currents are different for each application condition. They can be

calculated using Equations 12 (average current) and 13 (rms current).

Equation 13

Equation 14

Figure 4 presents simplified expression of average and rms currents of commonly observed

waveforms in a power rectifier. In most cases, these waveforms can be used for a rough

estimation.

()

dt

(t)

I

T

,

I

V

T

1

)

(T

P

sw

T

0

F

j

F

F

sw

j

COND

⋅

⋅

=

∫

2

F(rms)

j

D

F(av)

j

T0

j

COND

I

)

(T

R

I

)

(T

V

)

(T

P

⋅

+

⋅

=

δ

I

)

T

,

(I

V

)

(T

P

F(AV)

j

F

F

j

COND

⋅

⋅

=

()

∫

⋅

=

sw

T

0

F

sw

AV

F

dt

t

I

T

1

I

)

(

()

∫

⋅

=

sw

T

0

2

F

sw

RMS

F

dt

t

I

T

1

I

)

(