Existing solutions

AN3276

4/22

Doc ID 17975 Rev 1

Figure 2.

Switch-on losses in SiC or GaN diode behavior

Unlike PN diodes, SiC diodes allow the turn-on dI/dt to be increased without increasing the

diode recovery current. Thus, switching time decreases and switch-on losses decrease too,

but they are not removed entirely. Today, in PFC designs, the turn-on dI/dt with the SiC diode

is around 1000 A/µs maximum to respect EMI standards, whereas the PN diode is used with

a dI/dt of 300 A/µs.

1.2

Soft switch-on method

Another way to reduce these losses is to use a soft switching method by adding a small

inductor L to control the dI/dt slope. This solution removes the current/voltage crossing area

and the PN diode recovery current effect during the turn-on of the transistor as shown in

Figure 3.

Figure 3.

Switch-on losses in current soft switching behavior

t

I

0

V

DS

Losses are due to area

between I and V

0DS

t

Small losses:

Zero current switching

I+I

RM

0

I

0

V

DS