UM0969 datasheet(37/46 Pages) STMICROELECTRONICS

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UM0969

Power losses and dissipation

Doc ID 17665 Rev 2

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Equation 14

and ma is the PWM modulation index (defined as the peak phase voltage divided by the half

of dc link voltage). Finally, the integration of Equation 12 and Equation 13 gives:

Equation 15

It should be noted that the total IPM conduction losses are six times the calculated Pcon.

8.3

Switching loss

Switching losses can be divided into: turn-on power dissipation and turn-off power

dissipation. The dynamic performances of the IGBT are strictly related to many parameters

(voltage, current, temperature, etc.) so it is possible to make some assumptions to simplify

the calculations. If the output current is sinusoidal, it is true if the switching frequency is high

enough, also the switching power losses are sinusoidal:

Equation 16

where Eon_peak and Eoff_peak are the maximum value @ Tjmax and Icpeak.

Using Equation 16, the switching losses can be obtained as follows:

Equation 17

8.4

Thermal impedance overview

Semiconductor devices are very sensitive to junction temperature. This makes the thermal

performances analysis of the IPM a very important factor during the application

development stage. To start the analysis of the device's thermal behavior, the basic (and

[

] 2

)

cos(

)

cos(

)

(

peak

−

)

cos(

)

(

peak

off

−

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