AN4043 datasheet(45/60 Pages) STMICROELECTRONICS

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AN4043

Power losses and dissipation

Doc ID 022726 Rev 2

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and therefore, the conduction power losses of one device (IGBT and diode) are:

Equation 25

Of course, the total conduction losses per inverter are six times this value.

4.2

Switching power losses

The switching loss is the power consumption during the turn-on and turn-off transients. As

already shown in

Figure 26, it is given by the pulse of power dissipated during the turn-on

(ton) and turn-off (toff). Experimentally, it can be calculated by the time integral of product of

the collector current and collector-emitter voltage for the switching period. However, the

dynamic performance is strictly related to many parameters such as voltage, current and

temperature, so it is necessary to use the same assumptions of conduction power losses

(

Section 4.1: Conduction power losses) to simplify the calculations.

Under these conditions, the switching energy losses are given by:

Equation 26

Equation 27

where Êon and Êoff are the maximum values taken at Tjmax and Îc, θ stands for ωt and φ is

the phase angle between output voltage and current.

Finally, the switching power losses per device depend on the switching frequency (fsw) and

they are calculated as follows:

Equation 28

where EIGBT and EDiode are the total switching energy for the IGBT and the freewheeling

diode, respectively. Also in this case, the total switching losses per inverter are six times this

value.

Figure 28 shows the real turn-on and turn-off waveforms of the STGIPN3H60 under the

following conditions:

●

VPN = 300 V, IC = 0.5 A, Tj = 100 °C with inductive load on full bridge topology, taken on

the low-side IGBT.

The green plots represent instantaneous power as a result of IC (in red) and VCE (in yellow)

waveforms multiplication, during the switching transitions. The areas under these plots are

the switching energies computed by graphic integration thanks to the digital oscilloscope.

cond_Diode

cond_IGBT

cond

()φ

cos

Eˆ

)

(

()φ

cos

Eˆ

)

(

off

∫

⋅

Diode

IGBT

Diode

IGBT

)

(

)

(

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