AN1506 - APPLICATION NOTE

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through the MOSFET (forward conduction, positive current) or through the intrinsic diode (dead time, and

reverse current), or through the MOSFET in reverse conduction and gate biased.

Figure 9. Sinusoidal-shaped current through the upper device and the lower device (first half

period), and vice-versa in the second half period

The behavior of the MOSFET while it is in such a reverse conduction, via the intrinsic body diode or via

the channel, is clearly shown in figure 10, where the time interval adopted as dead time of the inverter is

also evident.

Accordingly, the conduction power loss can be calculated by:

Finally the total power losses can be evaluated by:

Vd (+24V)

T

D

I

T

D

I

I

L

I

I

L

I

P

con

j

1

f

s

∑

R

on

0

i

con j

⋅

∫

i

2

Dj

R

on

1

T

1

-----

2

π

T

1

------

sin

t





0

T

12

⁄

∫

dt=

≅

=

P

con

0.5R

2

rms

=8

()

P

tot

P

on

P

off

0.5

++

R

2

rms

=9

()